14. Customizing and Extending GPS — GPS 6.0.1 documentation

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# 14. Customizing and Extending GPS

GPS provides several levels of customization, from simple preferences dialog to powerful scripting capability through the python language. This chapters describes each of these capabilities.

## 14.1. The Preferences Dialog

This dialog, available through the menu Edit->Preferences, allows you to modify the global preferences of GPS. To enable the new preferences, you simply need to confirm by pressing the OK button. To test your changes, you can use the Apply button. Pressing the Cancel button will undo all your changes.

Each preference is composed of a label displaying the name of the preference, and an editing area to modify its value. If you leave to mouse over the label, a tool tip will be displayed giving an on-line help on the preference.

The preferences dialog is composed of several areas, accessible through the tabs at the left of the dialog. Each page corresponds to a set of preferences.

- Themes

  This page allows you to quickly change the current settings for GPS, including preferences, key bindings, menus...; See GPS Themes for more information on themes. It is only displayed when there are themes registered.

- General

  Default font

    The default font used in GPS. The background color you select for this preference will set the background color for all consoles and most views (the ones that display their data as trees, mostly). To change the background color of editors, see the preference Edit/Fonts&Colors/Default.

  Fixed view font

    The fixed (monospace) font used in views like the outline view, the bookmark view, ...; As much as possible, this font should use a fixed width for characters, for a better rendering

  Character set

    Name of character set to use when reading or writting text files. GPS uses UTF-8 and Unicode internally, which can handle any character in any language. However, your system will generally not support Unicode natively, and thus the contents of the files should be translated from the file system encoding to unicode.

    This preference indicates the file system encoding in use. It defaults to ISO-8859-1, which corresponds to western european characters.

  Display splash screen

    Whether a splash screen should be displayed when starting GPS.

  Display welcome window

    Whether GPS should display the welcome window for the selection of the project to use.

  Show text in tool bar

    Whether the tool bar should show both text and icons, or only icons.

  Auto save

    Whether unsaved files and projects should be saved automatically before calling external tools (e.g. before a build).

  Save desktop on exit

    Whether the desktop (size and positions of all windows) should be saved when exiting. If you are working with a project created automatically by GPS, the desktop will not be saved.

  Save editor in desktop

    Determines when source editors should be saved in the desktop: Never, Always, or when a source file is associated with the current project (From_Project).

  Default builder

    The default builder to be used by GPS.

    - Auto to use gnatmake for Ada-only projects and gprbuild otherwise (for multi-language and non Ada projects).
    - Gnatmake to always use gnatmake for builds, even for projects that contain other sources. This will disable support for building non Ada projects.
    - Gprbuild to always use gprbuild for builds, even for Ada only projects.
  Hyper links

    Whether to display hyper links in the editors when the Control key is pressed. Navigating with hyperlinks.

  Clipboard size

    This controls the size of the list where all the entries copied into the clipboard through Edit->Copy and Edit->Cut are saved. This list is navigated through the menu Edit->Paste and Edit->Paste Previous, as described earlier in this guide.

  Show status bar

    Whether the status bar at the bottom of the GPS window should be displayed. This status bar contains one or more progress bars while GPS is executing long actions like a build or a search. These progress bars can be used to monitor the progress of those actions.

    If you wish to save vertical screen space, you can hide this status bar. The progress bars will no longer be visible. Instead, you can display the Task Manager through the Tools->Views->Tasks menu, to get similar information. This manager can then be put on the right or left side of the GPS window, for instance just below the Project View.

  Remove policy when fixing code

    Prefered way to fix code when parts have to be removed. Always_Remove means that the code will be removed by GPS. Always_Comment means that the code will always be commented out. Propose_Both_Choices will propose a menu with both choices.

  Tip of the Day

    Whether GPS will display a Tip of the Day dialog at start up.

- Windows

  This section specifies preferences that apply to the Multiple Document Interface described in Multiple Document Interface.

  Opaque

    If True, items will be resized or moved opaquely when not maximized.

  Destroy floats

    If False, closing the window associated with a floating item will put the item back in the main GPS window, but will not destroy it. If True, the item is destroyed.

  All floating

    If True, then all the windows will be floating by default, i.e. be under the control of your system (Windows) or your window manager (Unix machines). This replaces the MDI.

  Short titles for floats

    If True, all floating windows will have a short title. In particular, base file names will be used for editors instead of full names.

  Background color

    Color to use for the background of the MDI.

  Title bar color

    Color to use for the title bar of unselected items.

  Selected title bar color

    Color to use for the title bar of selected items.

  Show title bars

  > If Always, each window in GPS will have its own title bars, showing some particular information (like the name of the file edited for editors), and some buttons to iconify, maximize or close the window. This title bar is highlighted when the window is the one currently selected.

  > If Never, the title bar is not displayed, to save space on the screen. The tabs of the notebooks will then be highlighted.

  > If Central Only, then only the windows in the central area (ie the part that gets preserved when switching perspective, mostly editors) will have a title bar. All other windows will not show the title bar. This is often a good way to save space on the screen: the title bar is useful for editors since it gives the full name of the file as well as provide an easy handle for drag and drop operations, whereas the other views do not change position as much and it is better to save space on the screen by not displaying their title.

Notebook tabs policy

> > Indicates when the notebook tabs should be displayed. If set to “Never”, you will have to select the window in the Window menu, or through the keyboard. If set to “Automatic”, then the tabs will be shown when two or more windows are stacked.

> Notebook tabs position

> > Indicates where the notebook tabs should be displayed by default. It is possible to select the position of tabs individually for each notebook by right-clicking in any of their tabs and chosing a new position in the contextual menu. This position will be saved as part of the desktop and restored the next time you restart GPS. However, if you change the value of this preference, all notebooks will reset the position of their tabs to match the new value of the preference.

- Editor .. index:: editor

  General

  > Strip blanks

  >   Whether the editor should remove trailing blanks when saving a file.

  > Line terminator

  >   Choose between Unix, Windows and Unchanged line terminators when saving files. Choosing Unchanged will use the original line terminator when saving the file; Unix will use LF line terminators; Windows will use CRLF line terminators.

  > Display line numbers

  >   Whether the line numbers should be displayed in file editors.

  > Display subprogram names

  >   Whether the subprogram name should be displayed in the editor’s status bar.

  > Tooltips

  >   Whether tool tips should be displayed automatically.

  > Tooltips timeout

  >   Time (in milliseconds) before displaying tooltips.

  > Highlight delimiters

  >   Determine whether the delimiter matching the character following the cursor should be highlighted. The list of delimiters includes: {}[]()

  > Autosave delay

  >   The period (in seconds) after which an editor is automatically saved, 0 if none.

  >   Each modified file is saved under a file called .#filename#, which is removed on the next explicit save operation.

  > Right margin

  >   The right margin to highlight. 0 if none. This value is also used to implement the Edit->Refill command.

  > Block highlighting

  >   Whether the editor should highlight the current block. The current block depends on the programming language, and will include e.g. procedures, loops, if statements, ...

  > Block folding

  >   Whether the editor should provide the ability to fold/unfold blocks.

  > Speed Column Policy

  >   When the Speed Column should be shown on the side of the editors:

  >   Never

  >     The Speed Column is never displayed.

  >   Automatic

  >     The Speed Column is shown whenever lines are highlighted in the editor, for example to show the current execution point, or lines containing compilation errors, ...; It disappears when no lines are highlighted.

  >   Always

  >     The Speed Column is always displayed.

  > Use Windows ACL

  >   This is a Windows specific preference which is disabled by default. When enabled GPS will use the ACL to change the file’s write permission. Note that ACL can’t be used on network drives.

  > External editor

  >   The default external editor to use.

  > Custom editor command

  >   Specify the command line for launching a custom editor. It is assumed that the command will create a new window/terminal as needed. If the editor itself does not provide this capability (such as vi or pico under Unix systems), you can use an external terminal command, e.g:

  >       xterm -geo 80x50 -exe vi +%l %f

  >   The following substitutions are provided:

  >   %l

  >     line to display

  >   %c

  >     column to display

  >   %f

  >     full pathname of file to edit

  >   %e

  >     extended lisp inline command

  >   %p

  >     top level project file name

  >   %%

  >     percent sign (‘%’)

  > Always use external editor

  >   True if all editions should be done with the external editor. This will deactivate completely the internal editor. False if the external editor needs to be explicitly called by the user.

  > Smart completion

  >   When enabled, GPS loads on startup all the information needed for the Smart completion to work.

  > Smart completion timeout

  >   The timeout, expressed in milliseconds, after which the Smart completion window appears automatically after entering a triggering character, such as ‘.’

  Fonts & Colors
    Default

      The default font, default foreground and default background colors used in the source editor.

    Blocks

      Font variant and colors used to highlight blocks (subprograms, task, entries, ...) in declarations.

    Types

      Font variant and colors used to highlight types in declarations.

    Keywords

      Font variant and colors used to highlight keywords.

    Comments

      Font variant and colors used to highlight comments. Setting the color to white will set a transparent color.

    SPARK Annotations

      Font variant and colors used to highlight SPARK annotations within Ada comments (Starting with –#). Setting the color to white will set a transparent color.

    Ada/SPARK Aspects

      Font variant and colors used to highlight Ada 2012 and SPARK 2014 aspects. Setting the color to white will set a transparent color.

    Strings

      Font variant and colors used to highlight strings. Setting the color to white will set a transparent color.

    Numbers

      Font variant and colors used to highlight numbers. Setting the color to white will set a transparent color.

    Current line color

      Color for highlighting the current line. Leave it to blank for no highlighting. Setting the color to white will set a transparent color.

    Draw current line as a thin line

      Whether to use a thin line rather than full background highlighting on the current line.

    Current block color

      Color for highlighting the current source block.

    Delimiter highlighting color

      Color for highlighting delimiters.

    Search results highlighting

      Color for highlighting the search results in the text of source editors.

  Ada

    > Auto indentation

    >   How the editor should indent Ada sources. None means no indentation; Simple means that indentation from the previous line is used for the next line; Extended means that a language specific parser is used for indenting sources.

    > Use tabulations

    >   Whether the editor should use tabulations when indenting. Note that this preference does not modify the `Tab` key which will still insert Tab characters. Consider also the /Edit/Insert Tab With Spaces key shortcut which can be mapped (to e.g. `Tab`) via The Key Manager Dialog. Finally, another alternative is to reconfigure the default key binding for the automatic indentation action: by default, it is mapped to `Tab` and can be changed to `Tab` by modifying the /Edit/Format Selection action from The Key Manager Dialog.

    > Default indentation

    >   The number of spaces for the default Ada indentation.

    > Continuation lines

    >   The number of extra spaces for continuation lines.

    > Declaration lines

    >   The number of extra spaces for multiple line declarations. For example, using a value of 4, here is how the following code would be indented:

    >       variable1,
    >           variable2,
    >           variable3 : Integer;

    > Conditional continuation lines

    >   The number of extra spaces used to indent multiple lines conditionals within parentheses.

    >   For example, when this preference is set to 1 (the default), continuation lines are indented based on the previous parenthesis plus one space:

    >       if (Condition1
    >           and then Condition2)
    >       then

    >   When this preference is set to 3, this gives:

    >       if (Condition1
    >             and then Condition2)
    >       then

    > Record indentation

    >   The number of extra spaces for record definitions, when the record keyword is on its own line.

    >   For example, when this preference is set to 3 (the default), the following sample will be indented as:

    >       type T is
    >          record
    >             F : Integer;
    >          end record;

    >   When this preference is set to 1, this gives:

    >       type T is
    >        record
    >           F : Integer;
    >        end record;

    > Case indentation

    >   Whether GPS should indent case statements with an extra level, as used in the Ada Reference Manual, e.g:

    >       case Value is
    >          when others =>
    >             null;
    >       end case;

    >   If this preference is set to Non_Rm_Style, this would be indented as:

    >       case Value is
    >       when others =>
    >          null;
    >       end case;

    >   By default (Automatic), GPS will choose to indent with an extra level or not based on the first when construct: if the first when is indented by an extra level, the whole case statement will be indented following the RM style.

    > Casing policy

    >   The way the editor will handle the case settings below. Disabled no auto-casing will be done; End_Of_Line auto-casing will be done when hitting `Enter` key; End_Of_Word auto-casing will be done word-by-word while typing; On_The_Fly auto-casing will be done character-by-character while typing. For the End_Of_Line, End_Of_Word and On_The_Fly policies it is always possible to force the casing of the current line by pressing the indentation key (`Tab` by default).

    >   It is also possible to disable the casing for a single character (action No Casing/indentation on Next Key, default `Ctrl-Q`) or temporarily (action Toggle Auto Casing/indentation, default `Alt-Q`).

    > Reserved word casing

    >   How the editor should handle reserved words casing. Unchanged will keep the casing as-is; Upper will change the casing of all reserved words to upper case; Lower will change the casing to lower case; Mixed will change the casing to mixed case (all characters to lower case except first character and characters after an underscore which are set to upper case); Smart_Mixed As above but do not force upper case characters to lower case.

    > Identifier casing

    >   How the editor should handle identifiers casing. The values are the same as for the Reserved word casing preference.

    > Format operators/delimiters

    >   Whether the editor should add extra spaces around operators and delimiters if needed. If enabled, an extra space will be added when needed in the following cases: before an opening parenthesis; after a closing parenthesis, comma, semicolon; around all Ada operators (e.g. <=, :=, =>, ...)

    > Align colons in declarations

    >   Whether the editor should automatically align colons in declarations and parameter lists. Note that the alignment is computed by taking into account the current buffer up to the current line (or end of the current selection), so if declarations continue after the current line, you can select the declarations lines and hit the reformat key.

    > Align associations on arrows

    >   Whether the editor should automatically align arrows in associations (e.g. aggregates or function calls). See also previous preference.

    Align declarations after colon

      > Whether the editor should align continuation lines in variable declarations based on the colon character.

      > Consider the following code:

      >     Variable : constant String :=
      >       "a string";

      > If this preference is enabled, it will be indented as follows:

      >     Variable : constant String :=
      >                  "a string";

      Indent comments

        Whether to indent lines containing only comments and blanks, or to keep these lines unchanged.

      Align comments on keywords

        Whether to align comment lines following record and is keywords immediately with no extra space.

        When enabled, the following code will be indented as:

            package P is
            --  Comment

               [...]
            end P;

        When disabled, the indentation will be:

            package P is
               --  Comment

               [...]
            end P;

  C & C++
    Auto indentation

      How the editor should indent C/C++ sources. None means no indentation; Simple means that indentation from the previous line is used for the next line; Extended means that a language specific parser is used for indenting sources.

    Use tabulations

      Whether the editor should use tabulations when indenting. If True, the editor will replace each occurrence of eight characters by a tabulation character.

    Default indentation

      The number of spaces for the default indentation.

    Extra indentation

      Whether to indent loops, if and switch statements an extra level. if this preference is enabled, the following layout will be chosen:

          if (condition)
            {
              int x;
            }

      If disabled, the same code will be indented as:

          if (condition)
          {
            int x;
          }

    Indent comments

      Whether to indent lines containing only comments and blanks, or to keep these lines unchanged.

- Debugger .. index:: debugger

  Preserve State on Exit

    If this preference is enabled, the debugger will automatically save breakpoints when it exists, and restore them the next time the same executable is debugged. This is a convenient way to work on an executable, where the typical usage looks like compile, debug, compile, debug, ...

    When the preference is enabled, the debugger will also preserve the contents of the data window whenever it is closed. Reopening the window either during the same debugger session, or automatically when a new debugger is started on the same executable, will recreate the same boxes within the data window.

  Debugger Windows

    > This preference controls what happens to debugger-related windows, like the call stack, the data window, the tasks view,..., when the debugger is terminated. There are three possible behavior:

    > Close Windows

    >   In this case, all these windows are closed. This saves memory and space on the screen, but you will need to explicitly reopen them and put them in the right location on the desktop the next time you start a debugger session.

    Keep Windows

      In this case, the windows are cleared, but kept on the desktop. When you start a new debugger session, the windows will be automatically reused. This ensures that you won’t have to reopen and reposition them, but takes space on your screen

    Hide Windows

      The windows are cleared, and hidden. When you start a new debugger session, they are automatically made visible again and reused. This also ensures you will not have to reopen and reposition them, but requires a bit of memory. If you move some windows around while these windows are hidden, they might reappear in unexpected location the next time, although you then just have to move them.

  Break on exceptions

    Specifies whether a breakpoint on all exceptions should be set by default when loading a program. This setup is only taken into account when a new debugger is initialized, and will not modify a running debugger (use the breakpoint editor for running debuggers).

  Execution window

    Specifies whether the debugger should create a separate execution window for the program being debugged.

    Note that this preference cannot be taken into account for the current debug session: you need to terminate the current debug session and restart a new one.

    If true, a separate console will be created. Under Unix systems, this console is another window in the bottom part of the main window; under Windows, this is a separate window created by the underlying gdb, since Windows does not have the notion of separate terminals (aka ttys).

    Note that in this mode under Windows, the Debug->Interrupt menu will only interrupt the debugged program with recent versions of gdb. If you are using older versions of gdb, you need to hit `Ctrl-C` in the separate execution window to interrupt it while it is running. Note also that this separate execution window uses the default system-wide console properties (the size of the window, the colors...). It is possible to change those properties using e.g. the default console menu (top-left of the console) on Windows XP.

    If false, no execution window will be created. The debugger assumes that the program being debugged does not require input, or that if it does, input is handled outside GPS. For example, when you attach to a running process, this process already has a separate associated terminal.

  Show lines with code

    Specifies whether the source editor should display blue dots for lines that contain code. If set to False, gray dots will be displayed instead on each line, allowing breakpoint on any line. Disabling this option provides a faster feedback, since GPS does not need to query the debugger about which lines contain code.

  Detect aliases

    If enabled, do not create new items when an item with the same address is already present on the canvas.

  Assembly range size

    Number of assembly lines to display in the initial display of the assembly window. If the size is 0, then the whole subprogram is displayed, but this can take a very long time on slow machines.

  Current assembly line

    Color used to highlight the assembly code for the current line.

  Color highlighting

    Color used for highlighting in the debugger console.

  Clickable item

    Indicates color to be used for the items that are click-able (e.g pointers).

  Changed data

    Indicates color to be used to highlight fields in the data window that have changed since the last update.

  Memory color

    Color used by default in the memory view window.

  Memory highlighting

    Color used for highlighted items in the memory view.

  Memory selection

    Color used for selected items in the memory view.

  Item name

    Indicates the font to be used for the name of the item in the data window.

  Item type

    Indicates font to be used to display the type of the item in the data window.

  Max item width

    The maximum width an item can have.

  Max item height

    The maximum height an item can have.

- External Commands .. index:: helper .. index:: external commands

  List processes

    Command used to list processes running on the machine.

  Remote shell

    Program used to run a process on a remote machine. You can specify arguments, e.g. rsh -l user

  Remote copy

    Program used to copy a file from a remote machine. You can specify arguments, e.g. rcp -l user

  Execute command

    Program used to execute commands externally.

  HTML Browser

    Only used under Unix, not relevant under Windows where the default HTML browser is used. Program used to execute view HTML files, for instance the documentation. Empty by default, which means that GPS will try to find a suitable HTML browser automatically. Only change the value if GPS cannot find a HTML browser, or if the browser found is not your preferred one.

  Print command

    External program used to print files.

    This program is required under Unix systems in order to print, and is set to a2ps by default. If a2ps is not installed on your system, you can download it from ftp://ftp.enst.fr/pub/unix/a2ps/, although other printing programs such as lp can be specified instead.

    Under Windows systems, this program is optional and is empty by default, since a built-in printing is provided. An external tool will be used if specified, such as the PrintFile freeware utility available from http://www.lerup.com/printfile/descr.html

- Search .. index:: search

  Confirmation for “Replace all”

    Enable or disable the confirmation popup for the replace all action.

  Close on Match

    If this option is enabled, the search window will be closed when a match is found.

  Select on Match

    If this option is enabled, the focus will be given to the editor when a match is found.

  Preserve Search Context

    If this option is enabled, the contents of the “Look in:” field will be preserved between consecutive searches in files.

- Browsers .. index:: browsers

  General

  > Selected item color

  >   Color to use to draw the selected item.

  > Background color

  >   Color used to draw the background of the browsers.

  > Hyper link color

  >   Color used to draw the hyper links in the items.

  > Selected link color

  >   Color to use for links between selected items.

  > Default link color

  >   Color used to draw the links between unselected items.

  > Ancestor items color

  >   Color to use for the background of the items linked to the selected item.

  > Offspring items color

  >   Color to use for the background of the items linked from the selected item.

  > Vertical layout

  >   Whether the layout of the graph should be vertical (True) or horizontal (False). This setting applies to most browsers (call graph for instance), but does not apply to the entities browsers.

  > Show elaboration cycles

  >   Whether GPS should display an elaboration graph after each compilation showing an elaboration cycle.

- VCS .. index:: vcs

  Implicit status

    Whether a status action can be launched as part of another action. For example to get the revision numbers of new files after an update command. If the network connection with the repository is slow disabling this command can speed-up the VCS actions.

  Default VCS

    The default VCS to use when the project does not define a VCS.

- Visual diff .. index:: visual diff .. index:: file comparison

  Note that in order to perform visual comparison between files, GPS needs to call external tool (not distributed with GPS) such as diff or patch. These tools are usually found on most unix systems, and may not be available by default on other OSes. Under Windows, you can download them from one of the unix toolsets available, such as msys (http://www.mingw.org) or cygwin (http://www.cygwin.com).

  mode

    How GPS displays visual diffs between two files:

    Side_By_Side

      Editors are displayed side-by-side; new editors are created as needed

    Unified

      No new editor is created, and changes are displayed directly in the reference editor.

  Diff command

    Command used to compute differences between two files. Arguments can also be specified. The visual diff expects a standard diff output with no context (that is, no -c nor -u switch). Arguments of interest may include (this will depend on the version of diff used):

    -b

      Ignore changes in amount of white space.

    -B

      Ignore changes that just insert or delete blank lines.

    -i

      Ignore changes in case; consider upper and lower case letters equivalent.

    -w

      Ignore white space when comparing lines.

  Patch command

    Command used to apply a patch. Arguments can also be specified. This command is used internally by GPS to perform the visual comparison on versioned files (e.g. when performing a comparison with a version control system).

    This command should be compatible with the GNU patch utility.

  Use old diff

    Use the old version of the visual comparison.

  Diff3 command

    This item is only displayed if the preference Use old diff is disabled. Command used to query a 3-way diff. See Diff command for a description of the parameters.

  Default color

    This item is only displayed if the preference Use old diff is disabled. The color used to indicate lines on which there is a difference, in the “reference” editor.

  Old color

    This item is only displayed if the preference Use old diff is disabled. The color used to indicate spaces used by lines not present in one of the editors in a 3-way diff and present in the other editors.

  Append color

    This item is only displayed if the preference Use old diff is disabled. The color used to display the lines that are present in an editor but not in the reference editor.

  Remove color

    This item is only displayed if the preference Use old diff is disabled. The color used to display the lines that are present in the reference editor but not in other editors.

  Change color

    This item is only displayed if the preference Use old diff is disabled. The color used to display the lines that have changed between the reference editor and the other editors.

  Fine change color

    This item is only displayed if the preference Use old diff is disabled. The color used to highlight fine differences within a modified line.

  Context length

    This item is only displayed if the preference Use old diff is enabled. The number of lines displayed before and after each chunk of differences. Specifying -1 will display the whole file.

- Messages .. index:: messages

  Color highlighting

    Color used to highlight text in the messages window.

  Errors highlighting

    Color used to highlight lines causing compilation errors, in the source editors. When this color is set to white, the errors are not highlighted. (Compilation/Build)

  Warnings highlighting

    Color used to highlight lines causing compilation warnings, in the source editors. When this color is set to white, the warnings are not highlighted.

  Style errors highlighting

    Color used to highlight lines containing style errors, in the source editors. When this color is set to white, the errors are not highlighted.

  Compiler info highlighting

    Color used to highlight lines containing compiler information, in the source editors. When this color is set to white, the information is not highlighted.

  File pattern

    Pattern used to detect file locations and the type of the output from the messages window. This is particularly useful when using an external tool such as a compiler or a search tool, so that GPS will highlight and allow navigation through source locations. This is a standard system V regular expression containing from two to five parenthesized subexpressions corresponding to the file, line, column, warnings or style error patterns.

  File index

    Index of filename in the file pattern.

  Line index

    Index of the line number in the file pattern.

  Column index

    Index of the column number in the file pattern.

  Warning index

    Index of the warning identifier in the file pattern.

  Style index

    Index of the style error identifier in the file pattern.

  Info index

    Index of the compiler info identifier in the file pattern.

  Secondary File pattern

    Pattern used to detect additional file locations from the messages window. This is a standard system V regular expression containing from two to three parenthesized subexpressions corresponding to the file, line, and column patterns.

  Secondary File index

    Index of filename in the file pattern.

  Secondary Line index

    Index of the line number in the file pattern.

  Secondary Column index

    Index of the column number in the file pattern.

  Alternate Secondary File pattern

    Pattern used to detect additional file locations in alternate form from the messages window. This is a standard system V regular expression containing one parenthesized subexpressions corresponding to the line patterns.

  Alternate Secondary Line index

    Index of the line number in the file pattern.

- Project

  Relative project paths

    Whether paths should be absolute or relative when the projects are modified.

  Fast Project Loading

    If the project respects a number of restrictions, activating the preference will provide major speed up when GPS parses the project. This is especially noticeable if the source files are on a network drive.

    GPS assumes that the following restricitions are true when the preference is activated. If this isn’t the case, no error is reported, and only minor drawacks will be visible in GPS (no detection that two files are the same if one of them is a symbolic link for instance, although GPS will still warn you if you are trying to overwrite a file modified on the disk).

    The restrictions are the following:

    Symbolic links shouldn’t be used in the project.

      More precisely, you can only have symbolic links that point to files outside of the project, but not to another file in the project

    Directories can’t have source names.

      No directory name should match the naming scheme defined in the project. For instance, if you are using the default GNAT naming scheme, you cannot have directories with names ending with ”.ads” or ”.adb”

  Hidden directories pattern

    A regular expression used to match hidden directories. Such directories are not displayed by default in the project view, and are not taken into account for VCS operations working on directories.

- Documentation .. _Documention_Preferences:

  This section specifies preferences that apply to the Documentation Generator. Documentation Generation for more information.

  Process body files

    If this preference is enabled, implementation files will be processed. Otherwise, only the specification files will.

  Show private entities

    By default, no documentation is generated for private entities. Enabling this preference will change this behavior.

  Call graph

    If enabled, the documentation tool will compute and take advantage of source references to e.g generate call graph information. Activating this option will slow down the documentation generation process.

  Up-to-date files only

    If enabled, only files having up-to-date cross references information will be documented.

  Comments filter regexp

    A regular expression used to filter to comments found in the source code before using them for generating documentation. For example “^!.*” will remove all comments starting with ‘!’.

  Spawn a browser

    If enabled, a browser is spawned after each documentation generation to view the generated files. This browser is not spawned if disabled.

  Find xrefs in comments

    If enabled, GPS will try to find references to entities in comments, and generate links to them when generating the documentation.

- Coverage Analysis .. _Coverage_Analysis_Preferences:

  Coverage toolchain

    Select which coverage toolchain (gcov or xcov) to use from the Tools->Coverage menu.

## 14.2. GPS Themes

GPS provides an extensive support for themes. Themes are predefined set of value for the preferences, for the key bindings, or any other configurable aspect of GPS.

For instance, color themes are a convenient way to change all colors in GPS at once, according to predefined choices (strongly contrasted colors, monochrome,...). It is also possible to have key themes, defining a set of key bindings to emulate e.g. other editors.

Any number of themes can be activated at the same time through the preferences dialog (Edit->Preferences). This dialog contains a list of all themes that GPS knows about, organized into categories for convenient handling. Just click on the buttons on the left of each theme name to activate that theme.

Note that this will immediately change the current preferences settings. For instance, if the theme you just selected changes the colors in the editor, these are changed immediately in the Editor->Fonts & Colors. You can of course still press Cancel to keep your previous settings

If multiple themes are active at the same time and try to override the same preferences, the last theme which is loaded by GPS will override all previously loaded themes. However, there is no predefined order in which the themes are loaded.

## 14.3. The Key Manager Dialog

The key manager is accessible through the menu Edit->Key Shortcuts. This dialog provides an easy way to associate key shortcuts with actions. These actions are either predefined in GPS, or defined in your own customization files, as documented in Customizing through XML and Python files. It also provides an easy way to redefine the menu shortcuts.

Actions are referenced by their name, and are grouped into categories. These categories indicate when the action applies. For instance, the indentation command only applies in source editors, whereas the command to change the current window applies anywhere in GPS. The categories can be explicitly specified when you created your own actions through XML files (Defining Actions).

Through the key manager, you can define key bindings similar to what Emacs uses (`control-x` followed by `control-k` for instance). To register such key bindings, you need to press the Grab button as usual, and then type the shortcut. The recording of the key binding will stop a short while after the last key stroke.

If you define complex shortcuts for menus, they will not appear next to the menu name when you select it with the mouse. This is expected, and is due to technical limitations in the graphical toolkit that GPS uses.

When you assign a new shortcut to an action, the following happens:

- All actions and menus currently associated with the same key will no longer be executed when the key is pressed.
- All key shortcuts defined for this action are replaced by the new one. As a result, the action is only executable through this new shortcut.

## 14.4. The Plug-ins Editor

GPS can be extensively customized through external plug-ins. You can write your own plug-ins (Customization files and plugins), but GPS also comes with its own collection of plug-ins.

Some of them are loaded by default when GPS starts (for instance the support for the CVS version management system or support for highlighting in various programming languages); others are available for any user but not loaded automatically by GPS, for instance an Emacs emulation mode.

Among the plug-ins that are provided with GPS, you will find:

- Emacs emulation .. index:: Emacs

  Several plug-ins emulate some of the functions provided by Emacs, such as the interactive search, manipulation of rectangles, navigation in the editor, and of course the usual Emacs key shortcuts

  This emacs mode used to be activated in the preferences dialog, on the Themes page, but you should now activate it by loading the `emacs.xml` plug-in.

- Makefile support .. index:: Makefile

  A plug-in is provided that parses a Makefile and creates menus for each of its possible targets, so that you can easily start a make command.

- Cross-references enhancements

  Various plug-ins take advantage of GPS’s cross-references information to create additional menus to navigate (for instance to jump to the primitive operations of Ada tagged types, to the body of Ada separate entities, ...)

- Text manipulation

  Several plug-ins provide support for advanced text manipulation in the editors, for instance to be able to align a set of lines based on various criteria, or to manipulate a rectangular selection of text.

You can choose graphically which plug-ins should or should not be loaded on startup. To do so, select the menu /Tools/Plug-ins. This brings up a new window, containing two parts:

- On the left is the list of all known plug-ins.

  As described in Customization files and plugins, GPS will search for candidates in various directories, and based on these directories decide whether to automatically load the plug-in or not.

  This list indicates the name of the plug-in, and whether it has been loaded in this GPS session (when the toggle button is checked).

- On the right are the details for the selected plug-in.

  This window is displayed as a notebook with two pages: on the first one you will see the exact location of the plug-in, the reason why it was loaded or not, and, more importantly, the source of the plug-in. By convention, each plug-in starts with a general comment that indicates the purpose of this plug-in, and some more detailed documentation on its usage.

  For those interested, this also contains the plug-in itself, so that this can act as an example to create your own customization script.

  Technically, the list of plug-ins to load or not to load are stored in the file `HOME/.gps/startup.xml`.

  If you have modified anything through this dialog (the list of plug-ins to load or unload), you will need to restart GPS. GPS cannot unload a module, since it can have too many possible effects on GPS (adding menus, overriding key shortcuts, ...).

  A dialog is displayed asking you whether you would like to exit GPS now. This will properly save all your files.

## 14.5. Customizing through XML and Python files

### 14.5.1. Customization files and plugins

You can customize lots of capabilities in GPS using files that are loaded by GPS at start up.

For example, you can add items in the menu and tool bars, as well as defining new key bindings, new languages, new tools, ...; Using Python as a programming language, you can also add brand new facilities and integrate your own tools in the GPS platform.

These customization files are searched for at startup in several different places. Depending on the location where they are found, these files will either be automatically loaded by GPS (and thus can immediately modify things in GPS), or will simply be made visible in the Plug-ins Editor (The Plug-ins Editor).

These directories are searched for in the order given below. Any script loaded latter can override setups done by previously loaded scripts. For instance, they could override a key shortcut, remove a menu, redefine a GPS action, ...

In the directory names below, `INSTALL` is the name of the directory in which you have installed GPS. `HOME` is the user’s home directory, either by default or as overriden by the GPS_HOME environment variable. If none of these exists, GPS will use the USERPROFILE environment variable.

In all these directories, only the files with `.xml` or `.py` extensions are taken into account. Other files are ignored, although for compatibility with future versions of GPS it is recommended not to keep other files in the same directory.

- Automatically loaded system wide modules

  The `INSTALL/share/gps/plug-ins` directory should contain the files that GPS will automatically load by default (unless overriden by the user through the Plug-ins Editor). These plug-ins are visible to any user on the system that uses the same GPS installation. This directory should be reserved for critical plug-ins that almost everyone should use.

- Not automatically loaded system wide modules

  The `INSTALL/share/gps/library` directory should contain the files that GPS should show in the Plug-ins Editor, but not load automatically. Typically, these would be files that add optional capabilities to GPS, for instance an emacs emulation mode, or additional editor capabilities that a lot of users would not generally use.

- GPS_CUSTOM_PATH

  This environment variable can be set before launching GPS. It should contain a list of directories, separated by semicolons (‘;’) on Windows systems and colons (‘:’) on Unix systems. All the files in these directories with the appropriate extensions will be automatically loaded by default by GPS, unless overriden by the user through the Plug-ins Editor.

  This is a convenient way to have project-specific customization files. You can for instance create scripts, or icons, that set the appropriate value for the variable and then start GPS. Depending on your project, this allows you to load specific aliases which do not make sense for other projects.

- Automatically loaded user directory

  The directory `HOME/.gps/plug-ins` is searched last. Any script found in there will be automatically loaded unless overriden in the Plug-ins Editor.

  This is a convenient way for users to create their own plug-ins, or test them before they are made available to the whole system by copying them to one of the other directories.

Any script loaded by GPS can contain customization for various aspects of GPS, mixing aliases, new languages or menus, ... in a single file. This is a convenient way to distribute your plug-ins to other users.

#### 14.5.1.1. Python files

Although the format of the python plug-ins is free (as long as it can be executed by Python), the following organization is suggested. These plug-ins will be visible in the Plug-ins Editor, and therefore having a common format makes it easier for users to understand the goal of the plug-ins:

- Comment

  The first part of the script should be a general comment on the goal and usage of the script. This comment should use python’s triple-quote convention, rather than start-of-line hash (‘#’) signs.

  The first line of the comment should be a one liner explaining the goal of the script. It is separated by a blank line from the rest of the comment.

  The rest of the comment is free-form.

- Customization variables

  If your script can be configured by the user by changing some global variables, they should be listed in their own section, and fully documented. The user can then, through the /Tools/Plug-ins editor change the value of these variables

- Implementation

  The implementation should be separated from the initial comment by a form-feed (control-L) character. The startup scripts editor will know not to display the rest of the script on the first page of the editor.

  Generally speaking, scripts should avoid executing code as soon as they are loaded. This gives a chance to the user to change the value of global variables or even override functions before the script is actually launched.

  The solution is to connect to the “gps_started” hook, as in:

      ^L
      ###########################################################
      ## No user customization below this line
      ###########################################################

      import GPS

      def on_gps_started (hook_name):
         ... launch the script

      GPS.Hook ("gps_started").add (on_gps_started)

#### 14.5.1.2. XML files

XML files must be utf8-encoded by default. In addition, you can specify any specific encoding through the standard <?xml encoding=”...” ?> declaration, as in the following example:

    <?xml version="1.0" encoding="iso-8859-1"?>
    <!--  general description -->
    <submenu>
      <title>encoded text</title>
    </submenu>

These files must be valid XML files, i.e. must start with the <?xml?> tag, and contain a single root XML node, the name of which is left to your consideration. The general format is therefore:

    <?xml version="1.0" ?>
    <root_node>
       ...
    </root_node>

It is also recommended that the first line after the <?xml?> tag contains a general comment describing the purpose and usage of the script. This comment will be made visible in the Plug-ins editor.

The list of valid XML nodes that can be specified under <root> is described in later sections. It includes:

<action>
  (Defining Actions)
<key>
  (Binding actions to keys)
<submenu>
  (Adding new menus)
<pref>
  (Preferences support in custom files)
<preference>
  (Preferences support in custom files)
<alias>
  (Defining text aliases)
<language>
  (Adding support for new languages)
<button>
  (Adding tool bar buttons)
<entry>
  (Adding tool bar buttons)
<vsearch-pattern>
  (Defining new search patterns)
<tool>
  (Adding support for new tools)
<filter>
  (Filtering actions)
<contextual>
  (Adding contextual menus)
<case_exceptions>
  (Adding casing exceptions)
<documentation_file>
  (Adding documentation)
<doc_path>
  (Adding documentation)
<stock>
  (Adding stock icons)
<project_attribute>
  (Defining project attributes)
<remote_machine_descriptor>
  (Defining a remote server)
<remote_path_config>
  (Defining a remote path translation)
<remote_connection_config>
  (Defining a remote connection tool)
<rsync_configuration>
  (Configuring rsync usage)

### 14.5.2. Defining Actions

This facility distinguishes the actions from their associated menus or key bindings. Actions can take several forms: external commands, shell commands and predefined commands, as will be explained in more details below.

The general form to define new actions is to use the <action> tag. This tag accepts the following attributes:

name (mandatory)
  This tag must be specified. It provides the name by which the action is referenced in other parts of the customization files, for instance when it is associated with a menu or a toolbar button. The name can contain any character, although it is recommended to avoid XML special characters. It mustn’t start with a ‘/’.
output (optional)
  If specified, this attribute indicates where the output of the commands will be sent by default. This can be overridden by each command, using the same attribute for <shell> and <external> tags, Redirecting the command output.
show-command (optional, default true)
  If specified, this attribute indicates whether the text of the command itself should be displayed at the same location as its output. Neither will be displayed if the output is hidden. The default is to show the command along with its output. This attribute can be overridden for each command.
show-task-manager (optional, default false)
  This attribute indicates whether an entry should be created in the task manager to show this command. Associated with this entry is the progress bar indicator, so if you hide the entry, no progress will be shown. On the other hand, several progress bars might be displayed for your action if you show the progress bar here, which might be an issue depending on the context. This attribute can be overriden for each external command.
category (optional, default “General”)
  The category in the keybindings editor (menu Edit/Key bindings) in which the action should be shown to the user. If you specify an empty string, the action is considered as an implementation detail, and not displayed in the editor. The user will thus not be able to assign it a keybinding through the graphical user interface (although this is still doable through XML commands).

If you are defining the same action multiple times, the last definition will be kept. However, existing menus, buttons, ... that already reference that action will keep their existing semantic. The new definition will only be used for all new menus created from that point on.

The <action> can have one or several children, all of which define a particular command to execute. All of these commands are executed one after the other, unless one of them fails in which case the following commands are not executed.

The following XML tags are valid children for <action>.

<external>

  This defines a command to execute through the system (i.e. a standard Unix or Windows command)

  Note for Windows users: like under UNIX, scripts can be called from custom menu. In order to do that, you need to write your script in a `.bat` or `.cmd` file, and call this file as usual. The external tag would e.g. look like:

      <?xml version="1.0" ?>
      <external_example>
        <action name="my_command">
          <external>c:\\.gps\\my_scripts\\my_cmd.cmd</external>
        </action>
      </external_example>

  This tag accepts the following attributes:

  server (optional)
    This attribute can be used to execute the external command on a remote server. The accepted values are “gps_server” (default), “build_server”, “execution_server”, “debug_server” and “tools_server”. Remote operations, for explanation of what these servers are.
  check-password (optional)

    This attribute can be used to tell GPS to check and handle password prompts from the external command. The accepted values are “false” (default) and “true”.

  show-command (optional)
    This attribute can be used to override the homonym attribute specified for the <action> tag.
  output (optional)
    This attribute can be used to override the homonym attribute specified for the <action> tag.
  progress-regexp (optional)

    This attribute specifies a regular expression that the output of the command will be checked against. Every time the regular expression matches, it should provide two numeric values that are used to display the usual progress indicators at the bottom-right corner of the GPS window, as happens during regular compilations.

    The name of the action is printed in the progress bar while the action is executing:

        <?xml version="1.0" ?>
        <progress_action>
          <action name="progress" >
            <external
              progress-regexp="(\\d+) out of (\\d+).*$"
              progress-current="1"
              progress-final="2"
              progress-hide="true">gnatmake foo.adb
            </external>
          </action>
        </progress_action>

  progress-current (optional, default is 1)
    This is the opening parenthesis count index in progress-regexp that contains the current step.
  progress-final (optional, default is 2)
    This is the opening parenthesis count index in progress-regexp that contains the current last step. This last index can grow as needed. For example, gnatmake will output the number of the file it is currently examining, and the total number of files to be examined. However, that last number may grow up, since parsing a new file might generate a list of additional files to parse later on.
  progress-hide (optional, default is true)
    If this attribute is set to the value “true”, then all the lines that match progress-regexp and are used to compute the progress will not be displayed in the output console. For any other value of this attribute, these lines are displayed along will the rest of the output.
  show-task-manager (optional, default inherited from `<action>`)

    This attribute indicates whether an entry should be created in the task manager to show this command. Associated with this entry is the progress bar indicator, so if you hide the entry, no progress will be shown. On the other hand, several progress bars might be displayed for your action if you show the progress bar here, which might be an issue depending on the context.

    If you have set a value for progress-regexp, this will automatically be set to true by default so that the progress bar is indeed displayed in the task manager. You can still override it explicitly for that <external> element to force hiding the progress bar.

<on-failure>

  This tag specifies a group of command to be executed if the previous external command fails. Typically, this is used to parse the output of the command and fill the location window appropriately (Processing the tool output).

  For instance, the following action spawns an external tool, and parses its output to the location window and the automatic fixing tool if the external tool happens to fail.

  In this group of commands the %... and $... macros can be used (Macro arguments):

      <?xml version="1.0" ?>
      <action_launch_to_location>
        <action name="launch tool to location" >
          <external>tool-path</external>
          <on-failure>
            <shell>Locations.parse "%1" category<shell>
            <external>echo the error message is "%2"</external>
          </on-failure>
          <external>echo the tool succeeded with message %1</external>
        </action>
      </action_launch_to_location>

<shell>

  As well as external commands, you can use custom menu items to invoke GPS commands using the shell tag. These are command written in one of the shell scripts supported by GPS.

  This tag supports the same show-command and output attributes as the <action> tag.

  The following example shows how to create two actions to invoke the help interactive command and to open the file `main.c`:

      <?xml version="1.0" ?>
      <help>
        <action name="help">
          <shell>help</shell>
        </action>
        <action name="edit">
          <shell>edit main.c</shell>
        </action>
      </help>

  By default, commands are expected to be written in the GPS shell language. However, you can specify the language through the lang attribute. Its default value is “shell”.

  The value of this attribute could also be “python”.

  When programming with the GPS shell, you can execute multiple commands by separating them with semicolons. Therefore, the following example adds a menu which lists all the files used by the current file, in a project browser:

      <?xml version="1.0" ?>
      <current_file_uses>
        <action name="current file uses">
          <shell lang="shell">File %f</shell>
          <shell lang="shell">File.uses %1</shell>
        </action>
      </current_file_uses>

<description>

  This tag contains a description for the command, which is used in the graphical editor for the key manager. The Key Manager Dialog.

<filter>, <filter_and>, <filter_or>

  This is the context in which the action can be executed, Filtering actions.

It is possible to mix both shell commands and external commands. For instance, the following command opens an xterm (on Unix systems only) in the current directory, which depends on the context:

    <?xml version="1.0" ?>
    <xterm_directory>
      <action "xterm in current directory">
        <shell lang="shell">cd %d</shell>
        <external>xterm</external>
      </action>
    </xterm_directory>

As seen in some of the examples above, some special strings are expanded by GPS just prior to executing the command. These are the “%f”, “%d”,.. See below for a full list.

More information on chaining commands is provided in Chaining commands.

Some actions are also predefined in GPS itself. This include for instance aliases expansion, manipulating MDI windows, ...; All known actions (predefined and the ones you have defined in your own customization files) can be discovered by opening the key shortcut editor (Edit->Key shortcuts menu).

### 14.5.3. Macro arguments

When an action is defined, you can use macro arguments to pass to your shell or external commands. Macro arguments are special parameters that are transformed every time the command is executed. The following macro arguments are provided.

The equivalent python command is given for all tests. These commands are useful when you are writing a full python script, and want to test for yourself whether the context is properly defined.

%a
  If the user clicked within the Locations Window, this is the name of the category to which the current line belongs
%builder
  Replaced by the default builder configured in GPS. This can be e.g. gnatmake if your project contains only Ada code, or gprbuild for non Ada or multi-language projects. Note: this macro is only available in the commands defined in the Build Manager and the Build Launcher dialogs.
%c

  This is the column number on which the user clicked. Python equivalent:

      GPS.current_context().column()

%d

  The current directory. Python equivalent:

      GPS.current_context().directory()

%dk
  The krunched name of the current directory.
%e

  Name of the entity the user clicked on. Python equivalent:

      GPS.current_context().entity().name()

%ef
  Name of the entity the user clicked on, possibly followed by “(best guess)” if there is an ambiguity on which entity it really, for instance because the cross-reference information is not up-to-date.
%E
  The full path to the executable name corresponding to the target.
%ek
  Krunched name of the entity the user clicked on. This is the same as %e, except long names are shorted as in %fk.
%eL
  Replaced by either an empty string, or -eL, depending on whether the Fast Project Loading preference if set or not. -eL is used by GNAT tools to specify whether symbolink links should be followed or not when parsing projects. Note: this macro is only available in the commands defined in the Build Manager and the Build Launcher dialogs.
%external
  Replaced by the command line specified in the preference External Commands->Execute command.
%f

  Base name of the currently selected file. Python equivalent:

      import os.path
      os.path.basename (GPS.current_context().file().name())

%F

  Absolute name of the currently opened file. Python equivalent:

      GPS.current_context().file().name()

%fk
  Krunched base name of the currently selected file. This is the same as %f, except that long names are shortened, and their middle letters are replaced by “[...]”. This should be used in particular in menu labels, to keep the menus narrow.
%fp
  Base name of the currently selected file. If the file is not part of the project tree, or no file is selected, generate an error on the Messages window. Note: this macro is only available in the commands defined in the Build Manager and the Build Launcher dialogs.
%gnatmake
  Replaced by the gnatmake executable configured in your project file.
%gprbuild
  Replaced by the gprbuild command line configured in your project file.
%gprclean
  Replaced by the default cleaner configured in GPS. This can be e.g. gnat clean, or gprclean. Note: this macro is only available in the commands defined in the Build Manager and the Build Launcher dialogs.
%GPS
  Replaced by the home directory for GPS (ie the .gps directory in which GPS stores its own configuration files).
%i
  If the user clicked within the Project View, this is the name of the parent project, ie the one that is importing the one the user clicked on. Note that with this definition of parent project, a given project might have multiple parents. The one that is returned is read from the Project View itself.
%l

  This is the line number on which the user clicked. Python equivalent:

      GPS.current_context().line()

%o
  The object directory of the current project.
%O
  The object directory of the root project.
%p

  The current project. This is the name of the project, not the project file, ie the `.gpr` extension is not included in this name, and the casing is the one found inside the project file, not the one of the file name itself. If the current context is an editor, this is the name of the project to which the source file belongs. Python equivalent:

      GPS.current_context().project().name()

%P

  The root project. This is the name of the project, not the project file. Python equivalent:

      GPS.Project.root().name()

%Pb
  The basename of the root project file.
%Pl
  The name of the root project, all lower case.
%pp

  The current project file pathname. If a file is selected, this is the project file to which the source file belongs. Python equivalent:

      GPS.current_context().project().file().name()

%PP

  The root project pathname. Python equivalent:

      GPS.Project.root().file().name()

%pps

  This is similar to %pp, except it returns the project name prepended with -P, or an empty string if there is no project file selected and the current source file doesn’t belong to any project. This is mostly for use with the GNAT command line tools. The project name is quoted if it contains spaces. Python equivalent:

      if GPS.current_context().project():
         return "-P" & GPS.current_context().project().file().name()

%PPs
  This is similar to %PP, except it returns the project name prepended with -P, or an empty string if the root project is the default project. This is mostly for use with the GNAT command line tools.
%(p|P)[r](d|s)[f]

  Substituted by the list of sources or directories of a given project. This list is a list of space-separated, quoted names (all names are surrounded by double quotes, for proper handling of spaces in directories or file names).

  P
    the root project.
  p
    the selected project, or the root project if there is no project selected.
  r
    recurse through the projects: sub projects will be listed as well as their sub projects, etc...
  d

    list the source directories.

    Python equivalent:

        GPS.current_context().project().source_dirs()

  s

    list the source files.

    Python equivalent:

        GPS.current_context().project().sources()

  f
    output the list into a file and substitute the parameter with the name of that file. This file is never deleted by GPS, it is your responsibility to do so.
%s
  This is the text selected by the user, if a single line was selected. When multiple lines were selected, this returns the empty string
%S
  This is either the text selected by the user, of the current entity if there is no selection. If the entity is part of an expression (“A.B.C”), then the whole expression is used instead of the entity name.
%switches(tool)

  Replaced by IDE’Default_Switches (tool), in other words, if you have a tool whose switches are defined via an xml file in GPS, they are stored as Default_Switches (xxx) in the IDE package and can be retrieved using this macro. The value returned is a list of switches, or an empty list if not set.

  Note: This macro is only available in the commands defined in the Build Manager and Build Launcher dialogs.

%T
  Replaced by the subtarget being considered for building. Depending on the context, this can correspond to e.g. the base filename of a Main source, or makefile targets. Note: this macro is only available in the commands defined in the Build Manager and the Build Launcher dialogs.
%TT
  Same as %TT, but returns the full path to main sources rather than the base filename.
%attr(Package’Name[,default])

  Replaced by the project attribute Package’Name, in other words, the attribute Name from the package Package. Package’ is optional if Name is a top level attribute (e.g. Object_Dir).

  If the attribute is not defined in the project, an optional default value is returned, or an empty string if not.

  Note: This macro is only available in the commands defined in the Build Manager and Build Launcher dialogs, and only supports single string attributes, not lists.

%dirattr(Package’Name[,default])
  Replaced by the directory part of an attribute. The attribute is specified as in %attr above.
%baseattr(Package’Name[,default])
  Replaced by the base name of an attribute. The attribute is specified as in %attr above.
%vars
  Replaced by a list of switches of the form <variable>=<value>, where <variable> is the name of a scenario variable and <value> its current value, as configured in the Scenario View. All the scenario variables defined in the current project tree will be listed. Alternatively, you can also use %vars(-D) to generate a list of switches of the form -D<variable>=<value>. Note: this macro is only available in the commands defined in the Build Manager and the Build Launcher dialogs.
%X
  Replaced by a list of switches of the form -X<variable>=<value>, where <variable> is the name of a scenario variable and <value> its current value, as configured in the Scenario View. All the scenario variables defined in the current project tree will be listed. Note: this macro is only available in the commands defined in the Build Manager and the Build Launcher dialogs.
%target
  Replaced by –target=<t> where <t> is the build target detected by the toolchain being used.
%%
  Replaced by the % sign.

Examples:

%Ps
  Replaced by a list of source files in the root project.
%prs
  Replaced by a list of files in the current project, and all imported sub projects, recursively.
%prdf
  Replaced by the name of a file that contains a list of source directories in the current project, and all imported sub projects, recursively.

Another type of macros are expanded before commands are executed: These all start with the $ character, and represent parameters passed to the action by its caller. Depending on the context, GPS will give zero, one or more arguments to the action. This is in particular used when you define your own VCS system. See also the shell function execute_action, which you can use yourself to execute an action and pass it some arguments.

These arguments are the following

$1, $2, ... $n
  Where n is a number. These are each argument passed to the action
$1-, $2-, ... $n-
  This represents a string concatenating the specified argument and all arguments after it
$*
  This represents a string concatenating all arguments passed to the action
$repeat

  This is the number of times the action has been repeated in a row. It will in general be 1 (ie this is the first execution of the action), unless the user has first executed the action “Repeat Next”, which allows automatic repetition of an action.

  By default, when the action “Repeat Next” is invoked by the user, it will repeat the following action as many times as the user specified. However, in some cases, either for efficiency reasons or simply for technical reasons, you might want to handle yourself the repeat. This can be done with the following action declaration:

      <action name="my_action">
         <shell lang="python">if $repeat==1: my_function($remaining + 1)</shell>
      </action>

      def my_function (count):
         """Perform an action count times"""
         ...

  Basically, the technique here is to only perform something the first time the action is called (hence the if statement), but pass your shell function the number of times that it should repeat (hence the $remaining parameter).

$remaining
  This is similar to $repeat, and indicates the number of times that the action remains to be executed. This will generally be 0, unless the user has chosen to automatically repeat the action a number of times.

### 14.5.4. Filtering actions

By default, an action will execute in any context in GPS. The user just selects the menu or key, and GPS tries to execute the action.

It is possible to restrict when an action should be considered as valid. If the current context is incorrect for the action, GPS will not attempt to run anything, and will display an error message for the user.

Actions can be restricted in several ways:

- Using macro arguments (Macro arguments). If you are using one of the macro arguments defined in the previous section, anywhere in the chain of commands for that action, GPS will first check that the information is available, and if not will not start running any of the shell commands or external commands for that action.

  For instance, if you have specified %F as a parameter to one of the commands, GPS will check prior to running the action that there is a current file. This can be either a currently selected file editor, or for instance that the project view is selected, and a file node inside it is also selected.

  You do not have to specify anything else, this filtering is automatic

  Note however that the current context might contain more information than you expect. For instance, if you click on a file name in the Project View, then the current context contains a file (thus satisfies %F), but also contains a project (and thus satisfies %p and similar macros).

- Defining explicit filters Explicit restrictions can be specified in the customization files. These are specified through the <filter>, <filter_and> and <filter_or> tags, see below.

  These tags can be used to further restrict when the command is valid. For instance, you can use them to specify that the command only applies to Ada files, or only if a source editor is currently selected.

#### 14.5.4.1. The filters tags

Such filters can be defined in one of two places in the customization files:

- At the toplevel. At the same level as other tags such as <action>, <menu> or <button> tags, you can define named filters. These are general filters, that can be referenced elsewhere without requiring code duplication.
- As a child of the <action> tag. Such filters are anonymous, although they provide exactly the same capabilities as the ones above. These are mostly meant for simple filters, or filters that you use only once.

There are three different kinds of tags:

<filter>
  This defines a simple filter. This tag takes no child tag.
<filter_and>
  All the children of this tag are composed together to form a compound filter. They are evaluated in turn, and as soon as one of them fails, the whole filter fails. Children of this tag can be of type <filter>, <filter_and> and <filter_or>.
<filter_or>
  All the children of this tag are composed together to form a compound filter. They are evaluated in turn, and as soon as one of them succeeds, the whole filter succeeds. Children of this tag can be of type <filter>, <filter_and> and <filter_or>.

If several such tags are found following one another under an <action> tag, they are combined through “or”, i.e. any of the filters may match for the action to be executed.

The <filter>, <filter_and> and <filter_or> tags accept the following set of common attributes:

name (optional)
  This attribute is used to create named filters, that can be reused elsewhere in actions or compound filters through the id attribute. The name can take any form.
error (optional)
  This is the error message printed in the GPS console if the filter doesn’t match, and thus the action cannot be executed. If you are composing filters through <filter_and> and <filter_or>, only the error message of the top-level filter will be printed.

In addition, the <filter> has the following specific attributes:

id (optional)

> If this attribute is specified, all other attributes are ignored. This is used to reference a named filter previously defined. Here is for instance how you can make an action depend on a named filter:

>     <?xml version="1.0" ?>
>     <test_filter>
>       <filter name="Test filter" language="ada" />
>       <action name="Test action" >
>          <filter id="Test filter" />
>          <shell>pwd</shell>
>       </action>
>     </test_filter>

> A number of filters are predefined by GPS itself.

> Source editor
>   This filter will only match if the currently selected window in GPS is an editor.
> Explorer_Project_Node
>   Matches when clicking on a project node in the Project View
> Explorer_Directory_Node
>   Matches when clicking on a directory node in the Project View
> Explorer_File_Node
>   Matches when clicking on a file node in the Project View
> Explorer_Entity_Node
>   Matches when clicking on an entity node in the Project View
> File
>   Matches when the current context contains a file (for instance the focus is on a source editor, or the focus is on the Project view and the currently selected line contains file information).

language (optional)
  This attribute specifies the name of the language that must be associated with the current file to match. For instance, if you specify ada, you must have an Ada file selected, or the action won’t execute. The language for a file is found by GPS following several algorithms (file extensions, and via the naming scheme defined in the project files).
shell_cmd (optional)

  This attribute specifies a shell command to execute. The output value of this command is used to find whether the filter matches: if it returns “1” or “true”, the filter matches. In any other case, the filter fails.

  Macro arguments (%f, %p, ...) are fully supported in the text of the command to execute.

shell_lang (optional)
  This attribute specifies in which language the shell command above is written. Its default value indicates that the command is written using the GPS shell.
module (optional)

  This attribute specifies that the filter only matches if the current window was setup by this specific GPS module. For instance, if you specify “Source_Editor”, this filter will only match when the active window is a source editor.

  The list of module names can be obtained by typing lsmod in the shell console at the bottom of the GPS window.

  This attribute is mostly useful when creating new contextual menus.

When several attributes are specified for a <filter> node (which is not possible with id), they must all match for the action to be executed:

    <?xml version="1.0" ?>
    <!-- The following filter will only match if the currently selected
         window is a text editor editing an Ada source file -->
    <ada_editor>
      <filter_and name="Source editor in Ada" >
        <filter language="ada" />
        <filter id="Source editor" />
      </filter_and>

      <!-- The following action will only be executed for such an editor -->

      <action name="Test Ada action" >
         <filter id="Source editor in Ada" />
         <shell>pwd</shell>
      </action>

      <!--  An action with an anonymous filter. It will be executed if the
            selected file is in Ada, even if the file was selected through
            the project view  -->

      <action name="Test for Ada files" >
          <filter language="ada" />
          <shell>pwd</shell>
      </action>
    </ada_editor>

### 14.5.5. Adding new menus

These commands can be associated with menus, tool bar buttons and keys. All of these use similar syntax.

Binding a menu to an action is done through the <menu> and <submenu> tags.

The <menu> tag takes the following attributes:

action (mandatory)

  This attribute specifies which action to execute when the menu is selected by the user. If no action by this name was defined, no new menu is added. The action name can start with a ‘/’, in which case it represents the absolute path to a menu to execute instead.

  This attribute can be omitted only when no title is specified for the menu to make it a separator (see below).

  If a filter is associated with the action through the <filter> tag, then the menu will be greyed out when the filter doesn’t match. As a result, users will not be able to click on it.

before (optional)
  It specifies the name of another menu item before which the new menu should be inserted. The reference menu must have been created before, otherwise the new menu is inserted at the end. This attribute can be used to control where precisely the new menu should be made visible.
after (optional)
  This attribute is similar to before, but has a lower priority. If it is specified, and there is no before attribute, it specifies a reference menu after which the new menu should be inserted.

It should also have one XML child called <title> which specifies the label of the menu. This is really a path to a menu, and thus you can define submenus by specifying something like “/Parent1/Parent2/Menu” in the title to automatically create the parent menus if they don’t exist yet.

You can define the accelerator keys for your menus, using underscores in the titles. Thus, if you want an accelerator on the first letter in a menu named File, set its title as _File.

The tag <submenu> accepts the following attributes:

before (optional)
  See description above, same as for <menu>
after (optional)
  See description above, same as for <menu>

It accepts several children, among <title> (which must be specified at most once), <submenu> (for nested menus), and <menu>.

Since <submenu> doesn’t accept the action attribute, you should use <menu> for clickable items that should result in an action, and <submenu> if you want to define several menus with the same path.

You can specify which menu the new item is added to in one of two ways:

- Specify a path in the title attribute of <menu>
- Put the <menu> as a child of a <submenu> node This requires slightly more typing, but it allows you to specify the exact location, at each level, of the parent menu (before or after an existing menu).

For example, this adds an item named mymenu to the standard Edit menu:

    <?xml version="1.0" ?>
    <test>
      <submenu>
        <title>Edit</title>
        <menu action="current file uses">
           <title>mymenu</title>
        </menu>
      </submenu>
    </test>

The following has exactly the same effect:

    <?xml version="1.0" ?>
    <test>
      <menu action="current file uses">
        <title>Edit/mymenu</title>
      </menu>
    </test>

The following adds a new item “stats” to the “unit testing” submenu in “my_tools”:

    <?xml version="1.0" ?>
    <test>
      <menu action="execute my stats">
         <title>/My_Tools/unit testing/stats</title>
      </menu>
    </test>

The previous syntax is shorter, but less flexible than the following, where we also force the My_Tools menu, if it doesn’t exist yet, to appear after the File menu. This is not doable by using only <menu> tags. We also insert several items in that new menu:

    <?xml version="1.0" ?>
    <test>
      <submenu after="File">
        <title>My_Tools</title>
        <menu action="execute my stats">
           <title>unit testing/stats</title>
        </menu>
        <menu action="execute my stats2">
           <title>unit testing/stats2</title>
        </menu>
      </submenu>
    </test>

Adding an item with an empty title or no title at all inserts a menu separator. For instance, the following example will insert a separator followed by a File/Custom menu:

    <?xml version="1.0" ?>
    <menus>
      <action name="execute my stats" />
      <submenu>
         <title>File</title>
         <menu><title/></menu>
         <menu action="execute my stats">
             <title>Custom</title>
         </menu>
      </submenu>
    </menus>

### 14.5.6. Adding contextual menus

The actions can also be used to contribute new entries in the contextual menus everywhere in GPS. These menus are displayed when the user presses the right mouse button, and should only show actions relevant to the current context.

Such contributions are done through the <contextual> tag, which takes the following attributes:

“action” (mandatory)

  Name of the action to execute, and must be defined elsewhere in one of the customization files.

  If this attribute is set to an empty string, a separator will be inserted in the contextual menu instead. If you specify a reference item with one of the “before” or “after” attribute, the separator will be visible only when the reference item is visible.

“before” (optional, default=””)

  If it is specified, this attribute should be the name of another contextual, before which the new menu should appear. The name of predefined contextual menus can be found by looking at the output of “Contextual.list” in the shell console. The name of the contextual menus you define yourself is the value of the <title> child.

  There is no guarantee that the new menu will appear just before the referenced menu. In particular, it won’t be the case if the new menu is created before the reference menu was created, or if another later contextual menu indicates that it must be displayed before the same reference item.

“after” (optional, default=””)

  Same as “before”, except it indicates the new menu should appear after the reference item.

  If both “after” and “before” are specified, only the latter is taken into account.

“group” (optional, default=”0”)
  Group attribute allows you to create groups of contextual menus that will be put together. Items of the same group appear before all items with a greater group number.

It accepts one child tag, <Title> which specifies the name of the menu entry. If this child is not specified, the menu entry will use the name of the action itself. The title is in fact the full path to the new menu entry. Therefore, you can create submenus by using a title of the form “Parent1/Parent2/Menu”.

Special characters can be used in the title, and will be automatically expended based on the current context. These are exactly the ones described in the section for macros arguments, Macro arguments.

The new contextual menu will only be shown if the filters associated with the action match the current context.

For instance, the following example inserts a new contextual menu which prints the name of the current file in the GPS console. This contextual menu is only displayed in source editors. This contextual menu entry is followed by a separator line, visible when the menu is visible:

    <?xml version="1.0" ?>
    <print>
      <action name="print current file name" >
        <filter module="Source_Editor" />
        <shell>echo %f</shell>
      </action>

      <contextual action="print current file name" >
        <Title>Print Current File Name</Title>
      </contextual>
      <contextual action="" after="Print Current File Name" />
    </print>

### 14.5.7. Adding tool bar buttons

As an alternative to creating new menu items, you can create new buttons on the tool bar, with a similar syntax, by using the <button> tag. As for the <menu> tag, it requires an action attribute which specifies what should be done when the button is pressed. The button is not created if no such action was created.

Within this tag, the tag <pixmap> can be used to indicate the location of an image file (of the type jpeg, png, gif or xpm) to be used as icon for the button. An empty <button> tag indicates a separator in the tool bar.

A title can also be specified with <title>. This will be visible only if the user choses to see both text and icons (or text only) in the tool bar. This title also acts as a tooltip (popup help message) when the button is displayed as an icon only.

The following example defines a new button:

    <?xml version="1.0" ?>
    <stats>
      <button action="execute my stats">
        <title>stats</title>
        <pixmap>/my_pixmaps/button.jpg</pixmap>
      </button>
    </stats>

The <button> tag allows you to create a simple button that the user can press to start an action. GPS also supports another type of button, a combo box, from which the user can choose among a list of choices. Such a combo box can be created with the <entry> tag.

This tag accepts the following arguments:

id (mandatory)
  This should be a unique id for this combo box, and will be used later on to refer it, in particular from the scripting languages. It can be any string
label (default is “”)
  The text of a label to display on the left of the combo box. If this isn’t specified, no text will be displayed
on-changed (default is “”)
  The name of a GPS action to execute whenever the user selects a new value in the combo box. This action is called with two parameters, the unique id of the combo box and the newly selected text respectively.

It also accepts any number of <choice> tags, each of which defines one of the values the user can choose from. These tags accepts one optional attribute, “on-selected”, which is the name of a GPS action to call when that particular value is selected:

    <action name="animal_changed">
       <shell>echo A new animal was selected in combo $1: animal is $2</shell>
    </action>
    <action name="gnu-selected">
       <shell>echo Congratulations on choosing a Gnu</shell>
    </action>
    <entry id="foo" label="Animal" on-changed="animal_changed">
       <choice>Elephant</choice>
       <choice on-selected="gnu-selected">Gnu</choice>
    </entry>

A more convenient interface exists for Python, the GPS.Toolbar class, which gives you the same flexibility as above, but also gives you dynamic control over the entry, and allows placement of buttons at arbitrary positions in the toolbar. See the python documentation.

### 14.5.8. Binding actions to keys

All the actions defined above can be bound to specific key shortcuts through the <key> attribute. As usual, it requires one <action> attribute to specify what to do when the key is pressed. The name of the action can start with a ‘/’ to indicate that a menu should be executed instead of a user-defined action.

If the action is the empty string, then instead the key will no longer be bound to any action.

This tag doesn’t contain any child tag. Instead, its text contents specified the keyboard shortcut. The name of the key can be prefixed by control-, alt-, shift- or any combination of these to specify the key modifiers to apply.

You can also define multiple key bindings similar to Emacs’s by separating them by a space. For instance, control-x control-k means that the user should press `control-x`, followed by a `control-k` to activate the corresponding action. This is only possible if the prefix key is not already bound to an action. If it is, you should first unbound it by passing an empty action to <key>.

Use an empty string to describe the key binding if you wish to deactivate a preexisting binding. The second example below deactivates the standard binding:

    <?xml version="1.0" ?>
    <keys>
      <key action="expand alias">control-o</key>
      <key action="Jump to matching delimiter" />

      <!--  Bind a key to a menu -->
      <key action="/Window/Close">control-x control-w</key>
    </key>

Multiple actions can be bound to the same key binding. They will all be executed in turn, followed by any menu for which this key is an accelerator.

When GPS processes a <key> tag, it does the following:

- Removes all actions bound to that key. This ensures that if you press the key, any action associated with it by default in GPS or in some other XML file will no longer be executed, and only the last one will be executed.
- Adds the new key to the list of shortcuts that can execute the action. Any existing shortcut on the action is preserved, and therefore there are multiple possible shortcuts for this action.

### 14.5.9. Preferences support in custom files

#### 14.5.9.1. Creating new preferences

GPS has a number of predefined preferences to configure its behavior and its appearance. They are all customizable through the Edit->Preferences menu.

However, you might wish to add your own kind of preferences for your extension modules. This can easily be done through the usual GPS customization files. Preferences are different from project attributes (Defining project attributes), in that the latter will vary depending on which project is loaded by the user, whereas preferences are always set to the same value no matter what project is loaded.

Such preferences are created with the <preference> tag, which takes a number of attributes.

name (mandatory)
  This is the name of the preference, used when the preference is saved by GPS in the `$HOME/.gps/preferences` file, and to query the value of a preference interactively through the GPS.Preference class in the GPS shell or python. There are a few limitation to the form of these names: they cannot contain space or underscore characters. You should replace the latter with minus signs for instance.
page (optional, default is “General”)

  The name of the page in the preferences editor where the preference can be edited. If this is the name of a non-existing page, GPS will automatically create it. If this is the empty string (“”), the preference will not be editable interactively. This could be used to save a value from one session of GPS to the next, without allowing the user to alter it.

  Subpages are references by separating pages name with colons (‘:’).

default (optional, default depends on the type of the preference)
  The default value of the preference, when not set by the user. This is 0 for integer preferences, the empty string for string preferences, True for boolean values, and the first possible choice for choice preferences.
tip (optional, default is “”)
  This is the text of the tooltip that appears in the preferences editor dialog.
label (mandatory)
  This is the name of the preference as it appears in the preferences editor dialog
type (mandatory)

  This is the type of the preference, and should be one of:

  “boolean”
    The preference can be True or False.
  “integer”
    The preference is an integer. Two optional attributes can be specified for <preference>, “minimum” and “maximum”, which define the range of valid values for that integer. Default values are 0 and 10 respectively.
  “string”
    The preference is a string, which might contain any value
  “color”
    The preference is a color name, in the format of a named color such as “yellow”, or a string similar to “#RRGGBB”, where RR is the red component, GG is the green component, and BB is the blue component
  “font”
    The preference is a font
  “choices”
    The preference is a string, whose value is chosen among a static list of possible values. Each possible value is defined in a <choice> child of the <preference> node.

Here is an example that defines a few new preferences:

    <?xml version="1.0"?>
    <custom>
       <preference name="my-int"
                   page="Editor"
                   label="My Integer"
                   default="30"
                   minimum="20"
                   maximum="35"
                   page="Manu"
                   type="integer" />

       <preference name="my-enum"
                   page="Editor:Fonts &amp; Colors"
                   label="My Enum"
                   default="1"
                   type="choices" >
         <choice>Choice1</choice>
         <choice>Choice2</choice>  <!--  The default choice -->
         <choice>Choice3</choice>
       </preference>
    </custom>

The values of the above preferences can be queries in the scripting languages:

- GPS shell:

      Preference "my-enum"
      Preference.get %1

- Python:

      val = GPS.Preference ("my-enum").get ()
      val2 = GPS.Preference ("my-int").get ()

#### 14.5.9.2. Setting preferences values

You can force specific default values for the preferences in the customization files through the <pref> tag. This is the same tag that is used by GPS itself when it saves the preferences edited through the preferences dialog.

This tag requires on attribute:

name
  This is the name of the preference of which you are setting a default value. Such names are predefined when the preference is registered in GPS, and can be found by looking at the `$HOME/.gps/preferences` file for each user, or by looking at one of the predefined GPS themes.

It accepts no child tag, but the value of the <pref> tag defines the default value of the preference, which will be used unless the user has overridden it in his own preferences file.

Any setting that you have defined in the customization files will be overridden by the user’s preferences file itself, unless the user was still using the default value of that preference.

This <pref> tag is mostly intended for use through the themes (Creating themes).

### 14.5.10. Creating themes

You can create your own themes and share them between users. You can then selectively chose which themes they want to activate through the preferences dialog (GPS Themes).

Creating new themes is done in the customization files through the <theme> tag.

This tag accepts a number of attributes:

name (mandatory)
  This is the name of the theme, as it will appear in the preferences dialog
description (optional)
  This text should explain what the text does. It appears in the preferences dialog when the user selects that theme.
category (optional, default is General)
  This is the name of the category in which the theme should be presented in the preferences dialog. Categories are currently only used to organize themes graphically. New categories are created automatically if you chose one that doesn’t exist yet.

This tag accepts any other customization tag that can be put in the customization files. This includes setting preferences (<pref>, defining key bindings (<key), defining menus (<menu>), ...

If the same theme is defined in multiple locations (multiple times in the same customization file or in different files), their effects will be cumulated. The first definition of the theme seen by GPS will set the description and category for this theme.

All the children tags of the theme will be executed when the theme is activated through the preferences dialog. Although there is no strict ordering in which order the children will be executed, the global order is the same as for the customization files themselves: first the predefined themes of GPS, then the ones defined in customization files found through the GPS_CUSTOM_PATH directories, and finally the ones defined in files found in the user’s own GPS directory:

    <?xml version="1.0" ?>
    <my-plug-in>
       <theme name="my theme" description="Create a new menu">
           <menu action="my action"><title>/Edit/My Theme Menu</title></menu>
       </theme>
    </my-plug-in>

### 14.5.11. Defining new search patterns

The search dialog contains a number of predefined search patterns for Ada, C and C++. These are generally complex regular expressions, presented in the dialog with a more descriptive name. This includes for instance “Ada assignment”, which will match all such assignments.

You can define your own search patterns in the customization files. This is done through the <vsearch-pattern> tag. This tag can have a number of children tags:

<name>
  This tag is the string that is displayed in the search dialog to represent the new pattern. This is the text that the user will effectively see, instead of the often hard to understand regular expression.
<regexp>

  This tag provides the regular expression to use when the pattern has been selected by the user. Be careful that you must protect reserved XML characters such as ‘<’ and replace them by their equivalent expansion (“&lt;” for this character).

  This accepts one optional attribute, named case-sensitive. This attribute accepts one of two possible values (“true” or “false”) which indicates whether the search should distinguish lower case and upper case letters. Its default value is “false”.

<string>

  This tag provides a constant string that should be searched. Only one of <regexp> and <string> should be provided. If both exists, the first <regexp> child found is used. If there is none, the first <string> child is used.

  The tag accepts the same optional attribute case-sensitive as above

Here is a small example on how the “Ada assignment” pattern was defined:

    <?xml version="1.0" ?>
    <search>
      <vsearch-pattern>
        <name>Ada: assignment</name>
        <regexp case-sensitive="false">\\b(\\w+)\\s*:=</regexp>
      </vsearch-pattern>
    </search>

### 14.5.12. Adding support for new languages

You can define new languages in a custom file by using the Language tag. Defining languages gives GPS the ability to highlight the syntax of a file, explore a file (using e.g. the project view), find files associated with a given language, ...

As described previously for menu items, any file in the `plug-ins` directory will be loaded by GPS at start up. Therefore, you can either define new languages in a separate file, or reuse a file where you already define actions and menus.

The following tags are available in a Language section:

Name
  A short string describing the name of the language.
Parent
  If set to the name of an existing language (e.g. Ada, C++) or another custom language, this language will inherit by default all its properties from this language. Any field explicitly defined for this language will override the inherited settings.
Spec_Suffix
  A string describing the suffix of spec/definition files for this language. If the language does not have the notion of spec or definition file, you can ignore this value, and consider using the Extension tag instead. This tag must be unique.
Body_Suffix
  A string describing the suffix of body/implementation files for this language. This tag works in coordination with the Spec_Suffix, so that the user can choose to easily go from one file to the other. This tag must be unique.
Extension
  A string describing one of the valid extensions for this language. There can be several such children. The extension must start with a ‘.’ character
Keywords

  A V7 style regular expression for recognizing and highlighting keywords. Multiple Keywords tags can be specified, and will be concatenated into a single regular expression. If the regular expression needs to match characters other than letters and underscore, you must also edit the Wordchars node. If a parent language has been specified for the current language definition it is possible to append to the parent Keywords by setting the mode attribute to append, the default value is override meaning that the keywords definition will replace the parent’s one.

  The full grammar of the regular expression can be found in the spec of the file `g-regpat.ads` in the GNAT run time.

Wordchars
  Most languages have keywords that only contain letters, digits and underscore characters. However, if you want to also include other special characters (for instance ‘<’ and ‘>’ in XML), you need to use this tag to let GPS know. The value of this node is a string made of all the special word characters. You do not need to include letters, digits or underscores.
Engine

  The name of a dynamic library providing one or several of the functions described below.

  The name can be a full pathname, or a short name. E.g. under most Unix systems if you specify custom, GPS will look for libcustom.so in the LD_LIBRARY_PATH run time search path. You can also specify explicitly e.g. libcustom.so or /usr/lib/libcustom.so.

  For each of the following five items, GPS will look for the corresponding symbol in Engine and if found, will call this symbol when needed. Otherwise, it will default to the static behavior, as defined by the other language-related items describing a language.

  You will find the required specification for the C and Ada languages to implement the following functions in the directory `<prefix>/share/examples/gps/language` of your GPS installation. `language_custom.ads` is the Ada spec file; `language_custom.h` is the C spec file; `gpr_custom.ad?` are example files showing a possible Ada implementation of the function Comment_Line for the GPS project files (`.gpr` files), or any other Ada-like language; `gprcustom.c` is the C version of gpr_custom.adb.

Comment_Line
  Name of a symbol in the specified shared library corresponding to a function that will comment or uncomment a line (used to implement the menu Edit->Un/Comment Lines).
Parse_Constructs

  Name of a symbol in the specified shared library corresponding to a function that will parse constructs of a given buffer.

  This procedure is used by GPS to implement several capabilities such as listing constructs in the project view, highlighting the current block of code, going to the next or previous procedure, ...

Format_Buffer

  Name of a symbol in the specified shared library corresponding to a function that will indent and format a given buffer.

  This procedure is used to implement the auto indentation when hitting the `enter` key, or when using the format key on the current selection or the current line.

Parse_Entities
  Name of a symbol in the specified shared library corresponding to a function that will parse entities (e.g. comments, keywords, ...) of a given buffer. This procedure is used to highlight the syntax of a file, and overrides the Context node described below.
Context

  Describes the context used to highlight the syntax of a file.

  Comment_Start
    A string defining the beginning of a multiple-line comment.
  Comment_End
    A string defining the end of a multiple-line comment.
  New_Line_Comment_Start
    A regular expression defining the beginning of a single line comment (ended at the next end of line). This regular expression may contain multiple possible line starts, such as ;|# for comments starting after a semicolon or after the hash sign. If a parent language has been specified for the current language definition it is possible to append to the parent New_Line_Comment_Start by setting the mode attribute to append, the default value is override meaning that the New_Line_Comment_Start definition will replace the parent’s one.
  String_Delimiter
    A character defining the string delimiter.
  Quote_Character
    A character defining the quote character, used for e.g. canceling the meaning of a string delimiter (\ in C).
  Constant_Character
    A character defining the beginning of a character literal.
  Can_Indent
    A boolean indicating whether indentation should be enabled for this language. The indentation mechanism used will be the same for all languages: the number of spaces at the beginning of the current line is used when indenting the next line.
  Syntax_Highlighting
    A boolean indicating whether the syntax should be highlighted/colorized.
  Case_Sensitive
    A boolean indicating whether the language (and in particular the identifiers and keywords) is case sensitive.
  Accurate_Xref
    A boolean indicating wwhether cross reference information for this language is supposed to be fully accurate or not (e.g. approximate, or none). Default to False.
  Use_Semicolon
    A boolean indicating whether semicolons are expected in sources and may be used as a delimiter for syntax highlighting purposes. Default to False.
Categories

  Optional node to describe the categories supported by the project view for the current language. This node contains a list of Category nodes, each describing the characteristics of a given category, with the following nodes:

  Name
    Name of the category, which can be either one of the following predefined categories: package, namespace, procedure, function, task, method, constructor, destructor, protected, entry, class, structure, union, type, subtype, variable, local_variable, representation_clause, with, use, include, loop_statement, case_statement, if_statement, select_statement, accept_statement, declare_block, simple_block, exception_handler, or any arbitrary name, which will create a new category.
  Pattern
    Regular expression used to detect a language category. As for the Keywords node, multiple Pattern tags can be specified and will be concatenated into a single regular expression.
  Index
    Index in the pattern used to extract the name of the entity contained in this category.
  End_Index
    Optional attribute that indicates the index in the pattern used to start the next search. Default value is the end of the pattern.
  Icon
    Name of a stock icon that should be used for that category (Adding stock icons). This attribute is currently ignored, and is reserved for future uses.
Project_Field

  This tag describes the tools that are used to support this language. The name of these tools is stored in the project files, and therefore only a limited number of tools can be specified. Note that this tag is currently only used by the project properties and wizard, and is not taken into account by other components.

  This node has two attributes:

  Name
    Name of the attribute in the project file. Currently, only “compiler_command” can be specified.
  Index

    If present, this attributes indicates the index to use for the attribute in the project file. The line defining this attribute would therefore look like:

        for Name ("Index") use "value";

    e.g:

        for Compiler_Command ("my_language") use "my_compiler";

    The value of the index should be either the empty string or the name of the language.

  The value of this tag is the string to use in the project properties editor when editing this project field.

Here is an example of a possible language definition for the GPS project files:

    <?xml version="1.0"?>
    <Custom>
      <Language>
        <Name>Project File</Name>
        <Spec_Suffix>.gpr</Spec_Suffix>
        <Keywords>^(case|e(nd|xte(nds|rnal))|for|is|</Keywords>
        <Keywords>limited|null|others|</Keywords>
        <Keywords>p(ackage|roject)|renames|type|use|w(hen|ith))\\b</Keywords>

        <Context>
          <New_Line_Comment_Start>--</New_Line_Comment_Start>
          <String_Delimiter>&quot;</String_Delimiter>
          <Constant_Character>&apos;</Constant_Character>
          <Can_Indent>True</Can_Indent>
          <Syntax_Highlighting>True</Syntax_Highlighting>
          <Case_Sensitive>False</Case_Sensitive>
        </Context>

        <Categories>
          <Category>
            <Name>package</Name>
            <Pattern>^[ \\t]*package[ \\t]+((\\w|\\.)+)</Pattern>
            <Index>1</Index>
          </Category>
          <Category>
            <Name>type</Name>
            <Pattern>^[ \\t]*type[ \\t]+(\\w+)</Pattern>
            <Index>1</Index>
          </Category>
        </Categories>

        <Engine>gpr</Engine>
        <Comment_Line>gpr_comment_line</Comment_Line>
      </Language>
    </Custom>

### 14.5.13. Defining text aliases

GPS provides a mechanism known as aliases. These are defined through the menu Edit->Aliases.

Each alias has a name, which is generally a short string of characters. When you type them in any textual entry in GPS (generally a source editor, but also entry fields for instance in the file selector), and then press the special activation key (by default `control-o`, controlled by a preference), this name is removed from the source editor, and replaced by the text you have associated with it.

Alias names may be composed of any character except newlines, but must start with a letter. GPS will jump to the start of each word before the current cursor position, and if the characters between this word start and the cursor position is an alias name (the comparison is case insensitive), this alias is expanded.

The alias editor is divided into three main parts: on the left side, the list of currently defined aliases is shown. Clicking on any of them will display the replacement text for this alias. If you click again the selected alias, GPS displays a text entry which you can use to rename an existing alias. Alias names must start with a letter. A check button at the bottom selects whether the read-only aliases (i.e. system-wide aliases) should be displayed.

The second part is the expansion text for the alias, at the bottom right corner. This replacement text can used multiple lines, and contain some special text that act as a special replacement. These special texts are highlighted in a different color. You can insert these special entities either by typing them, or by right-clicking in the editor, and select the entity in the contextual menu.

The following special entities are currently defined:

%_
  This is the position where the cursor should be put once the replacement text has been inserted in the editor.
%(name)
  This is the name of a parameter. name can be any string you want, excluding closing parenthesis. See below for more information on parameters.
%D
  This is the current date, in ISO format. The year is displayed first, then the month and the day
%H
  This is the current time (hour, minutes and seconds)
%l
  If the expansion of the alias is done in a source editor, this is the line on which the cursor is when pressing `control-o`.
%c
  This is similar to %l, except it returns the current column.
%f
  If the expansion is done in a source editor, this is the name of the current file (its base name only, this doesn’t include the directory)
%d
  If the expansion is done in a source editor, this is the directory in which the current file is
%p
  If the expansion is done in a source editor, this is the base name of the project file to which the file belongs.
%P
  If the expansion is done in a source editor, this is the full path name to the project file (directory and base name).
%O
  Used for recursive aliases expansion. This special character will expand the text seen before it in the current alias, after replacement of the parameters and possibly other recursive expansions. This is similar to pressing `control-o` (or any key you have defined for alias expansion) in the expanded form of the alias.
%%

  Inserts a percent sign as part of the expanded text

  You cannot expand an alias recursively when already expanding that alias. For instance, if the alias expansion for procedure contains procedure%O, the inner procedure will not be expanded.

The indentation as set in the expansion of the alias is preserved when the alias is expanded. All the lines will be indented the same amount to the right as the alias name. You can override this default behavior by selecting the check button Indent source editor after expansion. In this case, GPS will replace the name of the alias by its expansion, and then automatically recompute the position of each line with its internal indentation engine, as if the text had been inserted manually.

The third part of the aliases editor, at the top right corner, lists the parameters for the currently selected alias. Any time you insert a %(name) string in the expansion text, GPS automatically detects there is a new parameter reference (or an old reference has changed name or was removed); the list of parameters is automatically updated to show the current list.

Each parameters has three attributes:

name
  This is the name you use in the expansion text of the alias in the %(name) special entity.
Environment
  This specifies whether the default value of the parameter comes from the list of environment variables set before GPS was started.
default value
  Instead of getting the default value from the environment variable, you can also specify a fixed text. Clicking on the initial value of the currently selected variable opens a text entry which you can use to edit this default value.

When an alias that contains parameters is expanded, GPS will first display a dialog to ask for the value of the parameters. You can interactively enter this value, which replaces all the %(name) entities in the expansion text.

### 14.5.14. Aliases files

The customization files described earlier can also contain aliases definition. This can be used for instance to create project or system wide aliases. All the customization files will be parsed to look for aliases definition.

All these customization files are considered as read-only by GPS, and therefore cannot be edited through the graphical interface. It is possible to override some of the aliases in your own custom files.

There is one specific files, which must contain only aliases definition. This is the file `$HOME/.gps/aliases`. Whenever you edit aliases graphically, or create new ones, they are stored in this file, which is the only one that GPS will ever modify automatically.

The system files are loaded first, and aliases defined there can be overridden by the user-defined file.

These files are standard XML customization files. The specific XML tag to use is <alias>, one per new alias. The following example contains a standalone customization file, but you might wish to merge the <alias> tag in any other customization file.

The following tags are available:

alias
  This indicates the start of a new alias. It has one mandatory attribute, name, which the text to type in the source editor before pressing `control-o`. It has one optional attribute, indent, which, if set to true, indicate that GPS should recompute the indentation of the newly inserted paragraph after the expansion.
param

  These are children of the alias node. There is one per parameter of the alias. They have one mandatory attribute, name, which is the name to type between %(name) in the alias expansion text.

  They have one optional attribute, environment, which indicates the default value must be read from the environment variables if it is set to true.

  These tags contain text, which is the default value for the parameter.

text
  This is a child of the alias node, whose value is the replacement text for the alias.

Here is an example of an alias file:

    <?xml version="1.0"?>
    <Aliases>
      <alias name="proc" >
        <param name="p" >Proc1</param>
        <param environment="true" name="env" />
        <text>procedure %(p) is
    %(env)%_
    end %(p);</text>
      </alias>
    </Aliases>

### 14.5.15. Defining project attributes

The project files are required by GPS, and are used to store various pieces of information related to the current set of source files. This includes how to find the source files, how the files should be compiled, or manipulated through various tools, ....

However, the default set of attributes that are usable in a project file is limited to the attributes needed by the tool packaged with GPS or GNAT.

If you are delivering your own tools, you might want to store similar information in the project files themselves, since these are a very convenient place to associate some specific settings with a given set of source files.

GPS lets manipulate the contents of projects through XML customization files and script commands. You can therefore add you own typed attributes into the projects, so that they are saved automatically when the user saves the project, and reloaded automatically the next time GPS is started.

#### 14.5.15.1. Declaring the new attributes

New project attributes can be declared in two ways: either using the advanced XML tags below, or using the <tool> tag (Defining tool switches).

The customization files support the <project_attribute> tag, which is used to declare all the new attributes that GPS should expect in a project. Attributes that have not been declared explictly will not be accessible through the GPS scripting languagues, and will generate warnings in the Messages window.

Project attributes are typed: they can either have a single value, or have a set of such values (a list). The values can in turn be a free-form string, a file name, a directory name, or a value extracted from a list of preset values.

Attributes that have been declared in these customization files will also be graphically editable through the project properties dialog, or the project wizard. Therefore, you should specify when an attribute is defined how it should be presented to the GPS user.

The <project_attribute> tag accepts the following attributes:

- package (a string, default value: “”)

  This is the package in the project file in which the attribute is stored. Common practice suggests that one such package should be used for each tool. These packages provide namespaces, so that attributes with the same name, but for different tools, do not conflict with each other.

- name (a string, mandatory)

  This is the name of the attribute. This should be a string with no space, and that represents a valid Ada identifier (typically, it should start with a letter and be followed by a set of letters, digits or underscore characters). This is an internal name that is used when saving the attribute in a project file.

- editor_page (a string, default value: “General”)

  This is the name of the page in the Project Properties editor dialog in which the attribute is presented. If no such page already exists, a new one will be created as needed. If the page already exists, the attribute will be appended at its bottom.

- editor_section (a string, default value: “”)

  This is the name of the section, inside editor page, in which the attribute is displayed. These sections are surrounded by frames, the title of which is given by the editor_section attribute. If this attribute is not specified, the attribute is put in an untitled section.

- label (a string, default value: the name of the attribute)

  If this attribute is set to a value other than the empty string “”, a textual label is displayed to the left of the attribute in the graphical editor. This should be used to identify the attribute. However, it can be left to the empty string if the attribute is in a named section of its own, since the title of the section might be a good enough indication.

- description (a string, default value: “”)

  This is the help message that describes the role of the attribute. It is displayed in a tooltip if the user leaves the mouse on top of the attribute for a while.

- list (a boolean, default value: “false”)

  If this is set to “true”, the project attribute will in fact contains a list of values, as opposed to a single value. This is used for instance for the list of source directories in standard projects.

- ordered (a boolean, default value: “false”)

  This is only relevant if the project attribute contains a list of values. This indicates whether the order of the values is relevant. In most cases, it will not matter. However, for instance, the order of source directories matters, since this also indicates where the source files will be searched, stopping at the first match.

- omit_if_default (a boolean, default value: “true”)

  This indicates whether the project attribute should be set explicitly in the project if the user has left it to its default value. This can be used to keep the project files a simple as possible, if all the tools that will use this project attribute know about the default value. If this isn’t the case, set omit_if_default to “false” to force the generation of the project attribute.

- base_name_only (a boolean, default value: “false”)

  If the attribute contains a file name or a directory name, this indicates whether the full path should be stored, or only the base name. In most cases, the full path should be used. However, since GPS automatically looks for source files in the list of directories, for instance, the list of source files should only contain base names. This also increases the portability of project files.

- case_sensitive_index (a string (“true”, “false” or “file”), default: “false”)

  This XML attribute is only relevant for project attributes that are indexed on another one (see below for more information on indexed attributes). It indicates whether two indexes that differ only by their casing should be considered the same. For instance, if the index is the name of one of the languages supported by GPS, the index is case insensitive since “Ada” is the same as “C”.

  As a special case, the value “file” can be passed to indicate that the case sensitivity is the same as on the filesystem of the local host. This should be used when the index is the name of a file.

- hide_in (a string, default value: “”)

  This XML attribute defines the various context in which this attribute should not be editable graphically. Currently, GPS provides three such contexts (“wizard”, “library_wizard” and “properties”, corresponding to the project creation wizards and the project properties editor). If any of those context is specified in hide_in, then the widget to edit this attribute will not be shown. The goal is to keep the graphical interface simple.

- disable_if_not_set (a boolean, default value: “false”)

  If this attribute is set to “true”, the editor for this attribute will be greyed out if the attribute is not explicitly set in the project. In most cases, this is not needed, since the default value of the attribute can be used to leave the editor active at all time. However, when the value of the attribute is automatically computed depending on other attributes, the default value cannot be easily specified in the XML file, and in this case it might be easier to grey out the editor. An extra check box is displayed next to the attribute so that the user can choose to activate the editor and add the attribute to the project.

- disable (a space-separated list of attribute names, default: “”)

  This is a list of attribute whose editor should be greyed out if the current attribute is specified. This only works if both the current attribute and the referenced attributes have their disable_if_not_set attribute set to “true”. This can be used to have mutually exclusive attributes present in the editor

#### 14.5.15.2. Declaring the type of the new attributes

The type of the project attribute is specified through one or several child tags of <project_attribute>. The following tags are recognized.

- <string>

  This tag indicates that the attribute is made of one (or more if it is a list) strings. This tag accepts the following XML attributes:

  - default (a string, default value: “”)

    This gives the default value to be used for the string (and therefore the project attribute), in case the user hasn’t overridden it.

    If the attribute’s type is a file or a directory, the default value will be normalized (ie an absolute path will be generated from it, based on the project’s location, where ”.” will represent the project’s directory). As a special case, if default is surrounded by parenthesis, no normalization takes place, so that you can later on test whether the user is still using the default value or not).

    A special case if when default is set to “project source files”. In this case, this is automatically replaced by the known list of source files for the project. This doesn’t work from the project wizard, since the list of source files hasn’t been computed at that stage.

  - type (one of “” (default), “file”, “directory” or “unit”)

    This indicates what the string represents. In the first case, any value can be used. In the second case, it should represent a file name, although no check is done to make sure the file actually exists on the disk. But GPS will be able to do some special marshalling with the file name. The third case indicates that GPS should expect a directory. The fourth case indicates the GPS should expect the name of one of the project’s units.

  - filter (one of “none”, “project”, “extending_project”)

    This attribute is ignored for all types except “file”. In this case, it further specifies what kind of files can be used in this attribute. If the filter is “none”, then any file anywhere on the system is valid. If the filter is “project”, then only files from the selected project can be specified. If the filter is “extended_project”, then only the files from the project extended by the current project can be specified. The attribute will not be shown if the current project is not an extending project.

  - allow_empty (one of “True” or “False, default “True”)

    This attribute indicates whether the value for this attribute can be an empty string. If not, the user must specify a value or an error message will be displayed in the project properties editor and project wizard.

- <choice>

  This tag can be repeated several times. It indicates one of the valid values for the attribute, and can be used to provide a static list of such values. If it is combined with a <string> tag, this indicates that the attribute can be any string, although a set of possible values is provided to the user for ease of use. This tag accepts one optional attribute, “default”, which is a boolean. It indicates whether this value is the default to use for the project attribute.

  If several <choice> tags are used, it is possible that several of them are part of the default value if the project attribute is a list, as opposed to a single value.

- <shell>

  This tag is a GPS scripting command to execute to get a list of valid values for the attribute. The command should return a list. As for the <choice> tag, the <shell> tag can be combined with a <string> tag to indicate that the list of values returned by the scripting command is only a set of possible values, but that the project attribute can in fact take any value.

  The <shell> tag accepts two attributes:

  - lang (a string, default value: “shell”)

    The scripting language in which the command is written. Currently, the only other possible value is “python”.

  - default (a string, default value: “”)

    The default value that the project attribute takes if the user hasn’t overridden it.

In some cases, the type of the project attribute, or at least its default value, depends on what the attribute applies to. The project file support this in the form of indexed project attribute. This is for instance used to specify what should be the name of the executable generated when compiling each of the main files in the project (ie the executable name for gps.adb should be gps.exe, the one for main.c should be myapp.exe, and so on).

Such attributes can also be declared through XML files. In such cases, the <project_attribute> tag should have one <index> child, and zero or more <specialized_index> children. Each of these two tags in turn take one of the already mentioned <string>, <choice> or <shell> tag.

The <index> tag indicates what other project attribute is used to index the current one. In the example given above for the executable names, the index is the attribute that contains the list of main files for the project.

It accepts the following XML attributes:

- attribute (a string, mandatory)

  The name of the other attribute. This other attribute must be declared elsewhere in the customization files, and must be a list of values, not a single value.

- package (a string, default value: “”)

  The package in which the index project attribute is defined. This is used to uniquely identify homonym attributes.

The <specialized_index> is used to override the default type of the attribute for specific values of the index. For instance, the project files contains an attribute that specify what the name of the compiler is for each language. It is indexed on the project attribute that list the languages used for the source files of the project. Its default value depends on the language (“gnatmake” for Ada, “gcc” for C, and so on). This attribute accepts requires one XML attribute:

- value (a string, mandatory)

  This is the value of the attribute for which the type is overriden.

Note that almost all the standard project attributes are defined through an XML file, `projects.xml`, which is part of the GPS installation. Check this file to get advanced examples on how to declare project attributes.

#### 14.5.15.3. Examples

The following example declares three attributes, with a single string as their value. This string represents a file or a directory in the last two cases. You can simply copy this into a `.xml` file in your `$HOME/.gps/plug-ins` directory, as usual:

    <?xml version="1.0"?>
    <custom>
      <project_attribute
          name="Single1"
          package="Test"
          editor_page="Tests single"
          editor_section="Single"
          description="Any string">

         <string default="Default value" />
      </project_attribute>

      <project_attribute
          name="File1"
          package="Test"
          editor_page="Tests single"
          editor_section="Single"
          description="Any file" >

          <string type="file" default="/my/file" />
      </project_attribute>

      <project_attribute
          name="Directory1"
          package="Test"
          editor_page="Tests single"
          editor_section="Single"
          description="Any directory" >

          <string type="directory" default="/my/directory/" />
      </project_attribute>
    </custom>

The following example declares an attribute whose value is a string. However, a list of predefined possible values is also provided, as an help for interactive edition for the user. If the <string> tag wasn’t given, the attribute’s value would have two be one of the three possible choices:

    <?xml version="1.0" ?>
    <custom>
      <project_attribute
          name="Static2"
          package="Test"
          editor_page="Tests single"
          editor_section="Single"
          description="Choice from static list (or any string)" >

          <choice>Choice1</choice>
          <choice default="true" >Choice2</choice>
          <choice>Choice3</choice>
          <string />
      </project_attribute>
    </custom>

The following example declares an attribute whose value is one of the languages currently supported by GPS. Since this list of languages is only know when GPS is executed, a script command is used to query this list:

    <?xml version="1.0" ?>
    <custom>
     <project_attribute
          name="Dynamic1"
          package="Test"
          editor_page="Tests single"
          editor_section="Single"
          description="Choice from dynamic list" >

          <shell default="C" >supported_languages</shell>
      </project_attribute>
    </custom>

The following example declares an attribute whose value is a set of file names. The order of files in this list matters to the tools that are using this project attribute:

    <?xml version="1.0" ?>
    <custom>
     <project_attribute
          name="File_List1"
          package="Test"
          editor_page="Tests list"
          editor_section="Lists"
          list="true"
          ordered="true"
          description="List of any file" >

          <string type="file" default="Default file" />
      </project_attribute>
    </custom>

The following example declares an attribute whose value is a set of predefined possible values. By default, two such values are selected, unless the user overrides this default setting:

    <?xml version="1.0" ?>
    <custom>
      <project_attribute
          name="Static_List1"
          package="Test"
          editor_page="Tests list"
          editor_section="Lists"
          list="true"
          description="Any set of values from a static list" >

          <choice>Choice1</choice>
          <choice default="true">Choice2</choice>
          <choice default="true">Choice3</choice>
      </project_attribute>
    </custom>

The following example declares an attribute whose value is a string. However, the value is specific to each language (this could for instance be used for the name of the compiler to use for a given language). This is an indexed project attribute. It has two default values, one for Ada, one for C. All other languages have no default value:

    <?xml version="1.0" ?>
    <custom>
      <project_attribute
          name="Compiler_Name"
          package="Test"
          editor_page="Tests indexed"
          editor_section="Single"
          <index attribute="languages" package="">
             <string default="" />
          </index>
          <specialized_index value="Ada" >
             <string default="gnatmake" />
          </specialized_index>
          <specialized_index value="C" >
             <string default="gcc" />
          </specialized_index>
      </project_attribute>
    </custom>

#### 14.5.15.4. Accessing the project attributes

The new attributes that were defined are accessible from the GPS scripting languages, like all the standard attributes, Querying project switches.

You can for instance access the Compiler_Name attribute we created above with a python command similar to:

    GPS.Project.root().get_attribute_as_string ("Compiler_Name", "Test", "Ada")

You can also access the list of main files for the project, for instance, by calling:

    GPS.Project.root().get_attribute_as_list ("main")

### 14.5.16. Adding casing exceptions

A set of case exceptions can be declared in this file. Each case exception is put inside the tag <word> or <substring>. These exceptions are used by GPS to set identifiers or keywords case when editing case insensitive languages (except if corresponding case is set to Unchanged). The Preferences Dialog:

    <?xml version="1.0" ?>
    <exceptions>
      <case_exceptions>
         <word>GNAT</word>
         <word>OS_Lib</word>
         <substring>IO</substring>
      </case_exceptions>
    </exceptions>

### 14.5.17. Adding documentation

New documentation can be added in GPS in various ways. This is useful if you want to point to your own project documentation for instance.

The first possibility is to create a new menu, through a <menu> tag in an XML file, associated with an action that either spawn an external web browser or calls the internal GPS.Help.browse() shell command.

However, this will not show the documentation in the Help->Contents menu, which you also might want to do.

To have both results, you should use the <documentation_file> tag in an XML file. These tags are generally found in a `gps_index.xml` files but you can in fact add them in any of your customization files.

The documentation files you display can contain the usual type of html links. In addition, GPS will treat specially links starting with ‘%’, and consider them as script commands to execute instead of file to display. The following example show how to insert a link that will in effect open a file in GPS when clicked by the user:

    <a href="%shell:Editor.editor g-os_lib.ads">Open runtime file</a>

The first word after ‘%’ is the name of the language, and the command to execute is found after the ‘:’ character.

The <documentation_file> accepts a number of child nodes:

name

  This is the name of the file. It can be either an absolute file name, or a file name relative to one of the directories in GPS_DOC_PATH. If this child is omitted, you must specify a <shell> child.

  This name can contain a reference to a specific anchor in the html file, using the standard HTML syntax:

      <name>file#anchor</name>

shell
  This child specifies the name of a shell command to execute to get the name of the HTML file. This command can for instance create the HTML file dynamically, or download it locally using some special mechanism. This child accepts one attribute, “lang”, which is the name of the language in which the command is written
descr
  This is the description for this help file. It appears in a tool tip for the menu item.
category
  This is used in the Help->Contents menu to organize all the documentation files.
menu

  This is the full path to the menu. It behaves like a UNIX path, except it reference the various menus, starting from the menu bar itself. The first character of this path must be “/”. The last part of the path is the name of the new menu item. If not set, no menu is displayed for this file, although it will still appear in the Help->Contents menu

  The <menu> child tag accepts two attributes.

  before (optional, default=””)
    The name of the menu before which the new entry should be inserted. If the new menu is inserted in some submenus, this tag controls the deeper nesting. Parent menus are created as needed, but if you wish to control their specific order, you should create them first with a <menu> tag.
  after (optional, default=””)
    The name of the menu after which the new entry should be inserted.

The following example shows how to create a new entry “item” in the Help menu, that will display `file.html`. The latter is searched in the GPS_DOC_PATH list of directories:

    <?xml version="1.0"?>
    <index>
       <documentation_file>
          <name>file.html</name>
          <descr>Tooltip text</descr>
          <category>name</category>
          <menu>/Help/item</menu>
       </documentation_file>
    </index>

As mentioned above, HTML files are looked for through the GPS_DOC_PATH environment variable. However, you can also use the <doc_path> XML node to defined additional directories to be searched.

Such a directory is relative to the installation directory of GPS:

    <?xml version="1.0"?>
    <GPS>
       <doc_path>doc/application/</doc_path>
    </GPS>

will add the directory `<prefix>/doc/application` to the search path for the documentation.

Such a directory can also be added through Python, as in:

    GPS.HTML.add_doc_directory ('doc/application')

### 14.5.18. Adding stock icons

XML files can be used to define ‘stock icons’. Stock icons are pictures that are identified by their label, and which are used through GPS in various places, such as buttons, menus, toolbars, and so on.

The stock icons must be declared using the tag <icon>, within the global tag <stock>. The attribute id indicates the label used to identify the stock icon, and the attribute file points to the file which contains the actual picture, either in absolute format, or relative to the GPS icons directory. If you would like to read the icons from a directory relative to the location of the plug-in, you should use a python script like:

    XML = r"""<GPS><stock>
        <icon id="gtk-new" file="${icons}/file.svg"/>
      </stock></GPS>"""

    icons = os.path.normpath(
       os.path.join(os.path.dirname(__file__), "../dir"))
    XML = XML.replace("${icons}", icons)
    GPS.parse_xml(XML)

If the stock icon is to be used in a toolbar, use the attribute label to specify the text to display in the toolbar, under the button, when the toolbar is configured to show text.

For icons that are intended to be displayed at multiple sizes, you can specify multiple files corresponding to these multiple sizes. This is done by adding children to the main icon node, with the tag alternate, containing a file attribute and a size attribute which correspond to the size for which this alternate source should be used.

Possible sizes are:

1
  Menu item (ideal size: 16x16 pixels)
2
  Button in a small toolbar (ideal size: 18x18 pixels)
3
  Button in a large toolbar (ideal size: 24x24 pixels)
4
  Image for a standard button (ideal size: 20x20 pixels)
5
  Image used during drag-and-drop operation (ideal size: 32x32 pixels)
6
  Main image in a dialog (ideal size: 48x48 pixels)

Here is an example:

    <?xml version="1.0"?>
    <my_visual_preferences>
      <stock>
        <icon id="myproject-my-picture" file="icons/my-picture.png" />

        <icon id="myproject-multipurpose-image"
               label="do something"
               file="icons/icon_default.png">
           <alternate file"icons/icon_16.png" size="menu" />
           <alternate file"icons/icon_24.png" size="large_toolbar" />
           <alternate file"icons/icon_20.png" size="button" />
        </icon>

      </stock>
    </my_visual_preferences>

Note: as shown in the example above, it is a good practice to prefix the label by a unique name (e.g. myproject-), in order to make sure that predefined stock icons will not get overridden by your icons.

### 14.5.19. Remote programming customization

The configuration of the remote programming functionality has two separate parts: the tools configuration (remote connection tools, shells, and rsync parameters) and the servers configuration.

The first part (see Defining a remote connection tool, Defining a shell and Configuring rsync usage) is handled by a pre-installed file in the plug-ins directory called `protocols.xml`.

The second part (see Defining a remote server and Defining a remote path translation), when configured via the user interface (see Setup the remote servers), will create a remote.xml file in the user’s gps directory. System-wide servers can be also installed.

#### 14.5.19.1. Defining a remote connection tool

Several remote access tools are already defined in GPS: ssh, rsh, telnet and plink. It is possible to add other tools, using the node remote_connection_config.

The attributes for this node are:

name (string) (mandatory)
  The name of the tool. This name does not necessarilly correspond to the command used to launch the tool.

The following children are defined:

start_command (mandatory)

  The command used to launch the tool. This tag supports the use_pipes attribute. This attribute selects on Windows the way GPS will launch the remote tools, and can take the following values:

  true
    use pipes to launch the tool.
  false (default)
    use a tty emulation, which is a bit slower but allow password prompts retrieval with some tools.

  Note that this argument has effects only on Windows platforms.

start_command_common_args (optional)

  The arguments that are provided to the tool. This string can contain the following replacement macros:

  %C
    is replaced by the command executed on the remote host (e.g. the shell command)
  %h
    is replaced by the remote host name
  %U
    is replaced by the start_command_user_args, if a user is specified
  %u
    is replaced by the user name

  Note that if neither %u nor %U is found, and a user is specified in the remote connection configuration, then the start_command_user_args is placed at the beginning of the arguments.

start_command_user_args (optional)
  The arguments used to define a specific user during connection. %u is replaced by the user name
send_interrupt (optional)
  The characters sequence to send to the remote tool to interrupt the remote application. If unset, then an Interrupt signal is sent directly to the remote tool.
user_prompt_ptrn (optional)
  A regular expression, used to catch user name prompts from the connection tool. If undefined, a default regular expression is used.
password_prompt_ptrn (optional)

  A regular expression, used to catch password prompts from the connection tool. If undefined, a default regular expression is used.

passphrase_prompt_ptrn (optional)
  A regular expression, used to catch passphrase prompts from the connection tool. If undefined, a default regular expression is used.
extra_ptrn (optional)
  Complex child. Used to catch extra prompts from the connection tool, other than password, passphrase or usename prompts. This tag has an attribute auto_answer telling if GPS automatically answers to this prompt, or ask the user. If auto_answer is true, then this tag needs an answer child, whose value is used for the answer. If auto_answer is false, then this tag needs a question child, whose value is used as question to the end user.

#### 14.5.19.2. Defining a shell

Several shells are already defined in GPS: sh, bash, csh, tcsh and cmd.exe (Windows). It is possible to add other shells, using the node remote_shell_config.

The attributes for this node are:

name (string) (mandatory)
  The name of the shell. This name does not necessarilly correspond to the command used to launch the shell.

The following children are defined:

start_command (mandatory)
  The command used to launch the shell. If arguments are required, they should be put here, separated with spaces.
generic_prompt (optional)
  The regular expression used to identify a prompt after the initial connection. If not set, a default value is used.
gps_prompt (mandatory)
  The regular expression used to identify a prompt after the initial setup is performed. If not set, a default value is used.
filesystem (mandatory)
  Takes the following values: unix or windows. This is the filesystem used by the shell.
init_commands (optional)
  Complex child. Each cmd child contains a command used to initialise a new session.
exit_commands (optional)
  Complex child. Each cmd child contains a command used to exit a session.
no_echo_command (optional)
  Command used to suppress the echo of the remote shell.
cd_command (mandatory)
  Command used to go to a directory. %d is replaced by the directory’s full name.
get_status_command (mandatory)
  Command used to retrieve the status of the last command launched.
get_status_ptrn (mandatory)
  Regular expression used to retrieve the status returned by get_status_command. A pair of parenthesis is required, and identifies the status.

#### 14.5.19.3. Configuring rsync usage

GPS has native support for the rsync tool, for paths synchronization during remote programming operations.

By default, GPS will use –rsh=ssh option if ssh is the main connection tool for the concerned server. It will also define the -L switch when transfering files to a Windows local host.

It is possible to define additional arguments to rsync using the rsync_configuration tag.

This tag accepts the child tagged arguments, and containing additional arguments to pass to rsync.

#### 14.5.19.4. Defining a remote server

Remote servers can be defined via the user interface, as described in Setup the remote servers. This user interface will create a remote.xml file in the user’s gps directory, which in turn can be installed in any plug-ins directory to set the values system-wide. This file will define for each server the node remote_machine_descriptor.

The attributes for this node are:

nickname (mandatory)
  Identifies uniquely the server in GPS.
network_name (mandatory)
  The server’s network name or IP address.
remote_access (mandatory)
  The tool’s name used to access the server. Shall point to one of the tools defined in Defining a remote connection tool.
remote_shell (mandatory)
  The shell’s name used to access the server. Shall point to one of the shells defined in Defining a shell.
remote_sync (mandatory)
  The remote file synchronisation tool used to synchronize files between the local host and the server. Only rsync is recognized currently.
debug_console (optional)
  Can take the value True or False. Tells if a debug console should be displayed during connection with a remote host. False by default.

The children for this node are:

extra_init_commands (optional)
  Complex child. Can contain cmd children whose values are used to set server specific initialization commands.
max_nb_connections (optional)
  Positive number representing the maximum number of simultaneous connections GPS can launch.
timeout (optional)
  Positive number representing a timeout value (in ms) used for every action performed on the remote host.

#### 14.5.19.5. Defining a remote path translation

Remote path translation can also be defined via the user interface, as described in Setup the remote servers. The remote paths translation are defined with the node remote_path_config.

The attributes for this node are:

server_name (mandatory)
  The server name concerned by the paths translation.

The remote_path_config node contains mirror_path children.

The attributes for the node mirror_path are:

local_path (mandatory)
  The absolute local path, expressed using the local filesystem standards.
remote_path (mandatory)
  The absolute remote path, expressed using the remote filesystem standards.
sync (mandatory)
  Specify the synchronization mechanism used for the paths (see Paths settings). Possible values are NEVER, ONCE_TO_LOCAL, ONCE_TO_REMOTE and ALWAYS.

### 14.5.20. Customizing build Targets and Models

The information displayed in The Target Configuration Dialog and in the Mode selection can be customized through XML.

#### 14.5.20.1. Defining new Target Models

Models are defined in a target-model node which has one attributes, name, which contains the name of the model, and which supports the following sub-nodes:

<icon>
  The stock name of the icon to associate by default with targets of this model.
<description>
  A one-line description of what the Model supports
<server>
  Optional, defaulting to Build_Server. Indicates the server used for launching Targets of this model. Remote operations.
<is-run>
  Optional, defaulting to False. A boolean indicating whether this target corresponds to the launching of an executable rather than a build. Targets with such a model are launched through an interactive console in GPS, and their output is not parsed for errors.
<uses-shell>
  Optional, defaulting to False. A boolean indicating whether Targets of this model should be launched via the shell pointed to by the SHELL environment variable.
<command-line>
  Contains a number of <arg> nodes, each containing an argument of the default command line for this model, starting with the executable.

<switches command=”executable_name”>

  The graphical description of the switches. (Defining tool switches):

      <?xml version="1.0" ?>
         <my_model>
         <target-model name="gprclean" category="">
            <description>Clean compilation artefacts with gprclean</description>
            <command-line>
               <arg>gprclean</arg>
               <arg>-P%PP</arg>
               <arg>%X</arg>
            </command-line>
            <icon>gps-clean</icon>
            <switches command="%(tool_name)s" columns="1">
               <check label="Clean recursively" switch="-r"
                      tip="Clean all projects recursively" />
            </switches>
         </target-model>
      </my_model>

#### 14.5.20.2. Defining new Targets

Targets are defined in a target node which has three attributes:

name
  Contains the name of the Target. It must be a unique name. Underscores are interpreted as menu mnemonics. To represent an actual underscore, use a double underscore.
category
  The category which contains the Target, for purposes of ordering the tree in the Target Configuration Dialog, and for ordering in the Build menu.Underscores are interpreted as menu mnemonics. To represent an actual underscore, use a double underscore. If category begins and ends with an underscore, the menu for the Target is placed in the toplevel Build menu.
messages_category
  The name of the category to be used to organize messages in Locations window.
model
  The name of the Model of which this Target inherits initially.
<icon>
  The stock name of the icon to associate by default with the Target.
<in-toolbar>
  Optional, defaulting to False. A boolean indicating whether the Target should have an associated icon in the Toolbar.
<in-menu>
  Optional, defaulting to True. A boolean indicating whether the Target should have an associated entry in the Build menu.
<in-contextual-menus-for-projects>
  Optional, defaulting to False. A boolean indicating whether the Target should have an associated entry in the contextual menu for projects.
<in-contextual-menus-for-files>
  Optional, defaulting to False. A boolean indicating whether the Target should have an associated entry in the contextual menu for files.
<visible>
  Optional, defaulting to True. A boolean indicating whether the Target should initially be visible in GPS.
<read-only>
  Optional, defaulting to False. A boolean indicating whether the Target can be removed by the user.
<target-type>
  Optional, defaulting to an empty string. A string indicating whether the Target represents a simple target (if empty), or a family of Targets. The name represents a parameter passed to the compute_build_targets hook. If set to main, a new subtarget will be create for each Main source defined in the project.
<launch-mode>
  Optional, defaulting to MANUALLY. Indicates how the Target should be launched. Possible values are MANUALLY, MANUALLY_WITH_DIALOG, MANUALLY_WITH_NO_DIALOG, and ON_FILE_SAVE.
<server>
  Optional, defaulting to Build_Server. Indicates the server used for launching Target. Remote operations.
<command-line>

  Contains a number of <arg> nodes, each containing an argument of the default command line for this Target, starting with the executable:

      <?xml version="1.0" ?>
      <my_target>
         <target model="gprclean" category="C_lean" name="Clean _All">
             <in-toolbar>TRUE</in-toolbar>
             <icon>gps-clean</icon>
             <launch-mode>MANUALLY_WITH_DIALOG</launch-mode>
             <read-only>TRUE</read-only>
             <command-line>
                <arg>%gprclean</arg>
                <arg>-r</arg>
                <arg>%eL</arg>
                <arg>-P%PP</arg>
                <arg>%X</arg>
             </command-line>
        </target>
      </my_target>

#### 14.5.20.3. Defining new Modes

Modes are defined in a builder-mode node which has one attributes, name, which contains the name of the model, and which supports the following sub-nodes:

<description>
  A one-line description of what the Mode does
<subdir>
  Optional. The base name of the subdirectory to create for this Mode. The macro argument %subdir in the extra-args nodes will be substituted with this.
<supported-model>
  The name of a model supported by this Mode. There can be multiple supported-model nodes, each corresponding to a supported Model. Optionally, you can specify a filter attribute for this node, corresponding to the switches that are relevant for this mode. By default, all switches will be taken into account. The extra-args of the Mode that match filter will be passed to commands of the supported Models.
<extra-args>

  Contains a list of <arg> nodes, each containing one extra argument to append to the command line when launching Targets while this Mode is active. Macros are supported in the <arg> nodes:

      <?xml version="1.0" ?>
      <my_mode>
       <builder-mode name="optimization">
        <description>Build with code optimization activated</description>
        <subdir>optimized_objects</subdir>
        <supported-model>builder</supported-model>
        <supported-model>gnatmake</supported-model>
        <supported-model filter="--subdirs=">gprclean</supported-model>
        <extra-args>
           <arg>--subdirs=%subdir</arg>
           <arg>-cargs</arg>
           <arg>-O2</arg>
        </extra-args>
       </builder-mode>
      </my_mode>

### 14.5.21. Toolchains customization

The list of toolchains and their values presented in the project editor (The Project Wizard) can be customized through XML. The GPS default list is contained in toolchains.xml. You can add your own toolchain by providing an xml description following the below described structure:

<toolchain_default>
  Contains the default names for the different tools used by all toolchains. The final name used will be toolchain_name-default_name.
<toolchain name=”name”>
  Defines a toolchain using name “name”. This toolchain can override the default values defined in the toolchain_default above.

Each of the above tags can have the following chilren

<gnat_driver>
  Defines the gnat driver to use.
<gnat_list>
  Defines the gnat list tool to use.
<debugger>
  Defines the debugger to use.
<cpp_filt>
  Not used by GPS.
<compiler lang=”lang”>
  Defines the compiler to use to compile language “lang”

The toolchain_default values can either be overriden or nullified by just providing the same tab with an empty value in a toolchain definition.

## 14.6. Adding support for new tools

GPS has built-in support for external tools. This feature can be used to support a wide variety of tools (in particular, to specify different compilers). Regular enhancements are done in this area, so if you are planning to use the external tool support in GPS, check for the latest GPS version available.

Typically, the following things need to be achieved to successfully use a tool:

- Specify its command line switches
- Pass it the appropriate arguments depending on the current context, or on user input
- Spawn the tool
- Optionally parse its result and act accordingly

Each of these points is discussed in further sections. In all these cases, most of the work can be done statically through XML customization files. These files have the same format as other XML customization files (Customizing through XML and Python files), and the tool descriptions are found in <tool> tags.

This tag accepts the following attributes:

name (mandatory)
  This is the name of the tool. This is purely descriptive, and will appear throughout the GPS interface whenever this tool is referenced. This includes for instances the tabs of the switches editor.
package (Default value is ide)

  This optional attribute specifies which package should be used in the project to store information about this tool, in particular its switches. Most of the time the default value should be used, unless you are working with one of the predefined packages.

  See also Defining project attributes, for more information on defining your own project attributes. Using the “package”, “attribute” or “index” XML attributes of <tool> will implicitly create new project attributes as needed.

  If this attribute is set to “ide”, then the switches cannot be set for a specific file, only at the project level. Support for file-specific switches currently requires modification of the GPS sources themselves.

attribute (Default value is default_switches)
  This optional attribute specifies the name of the attribute in the project which is used to store the switches for that tool.
index (Default value is the tool name)
  This optional attribute specifies what index is used in the project. This is mostly for internal use by GPS, and describes what index of the project attribute is used to store the switches for that tool.
override (Default value is ‘false’)
  This optional attribute specifies whether the tool definition can be redefined. The accepted values are ‘true’ or ‘false’. If override is not set, and the tool is defined several times, then a Warning will be displayed.

This tag accepts the following children, described in separate sections:

<switches>
  (Defining tool switches)
<language>
  (Defining supported languages)
<initial-cmd-line>
  (Defining default command line)

### 14.6.1. Defining supported languages

This is the language to which the tool applies. There can be from no to any number of such nodes for one <tool> tag.

If no language is specified, the tool applies to all languages. In particular, the switches editor page will be displayed for all languages, no matter what languages they support.

If at least one language is specified, the switches editor page will only be displayed if that language is supported by the project:

    <?xml version="1.0" ?>
    <my_tool>
      <tool name="My Tool" >
        <language>Ada</language>
        <language>C</language>
      </tool>
    </my_tool>

### 14.6.2. Defining default command line

It is possible to define the command line that should be used for a tool when the user is using the default project, or hasn’t overridden this command line in the project.

This is done through the <initial-cmd-line> tag, as a child of the <tool> tag. Its value is the command line that would be passed to the tool. This command line is parsed as usual, e.g. quotes are taken into account to avoid splitting switches each time a space is encountered:

    <?xml version="1.0" ?>
    <my_tool>
      <tool name="My tool" >
         <initial-cmd-line>-a -b -c</initial-cmd-line>
      </tool>
    </my_tool>

### 14.6.3. Defining tool switches

The user has to be able to specify which switches to use with the tool. If the tool is simply called through custom menus, you might want to hard code some or all of the switches. However, in the general case it is better to use the project properties editor, so that project-specific switches can be specified.

This is what GPS does by default for Ada, C and C++. You can find in the GPS installation directory how the switches for these languages are defined in an XML file. These provide extended examples of the use of customization files.

The switches editor in the project properties editor provides a powerful interface to the command line, where the user can edit the command line both as text and through GUI widgets.

The switches are declared through the <switches> tag in the customization file, which must be a child of a <tool> tag as described above.

This <switches> tag accepts the following attributes:

lines (default value is 1)
  The switches in the project properties editor are organized into boxes, each surrounded by a frame, optionally with a title. This attribute specifies the number of rows of such frames.
columns (default value is 1)
  This attribute specifies the number of columns of frames in the project properties page.
separator (default value is “”)
  This attribute specifies the default character that should go between a switch and its value, to distinguishes cases like “-a 1”, “-a1” and “-a=1”. This can be overridden separately for each switch. Note that if you want the separator to be a space, you must use the value “&#32;” rather than ” “, since XML parser must normalize the latter to the empty string when reading the XML file.
use_scrolled_window (Default value is false)
  This optional attribute specifies if the boxes of the project editor are placed into scrolled window. This is particularily useful if the number of displayed switches if important.
show_command_line (Default value is true)
  If this attribute is set to “false”, the command line will not be displayed in the project properties editor. This can be used for instance if you only want users to edit it through the buttons and other widgets, and not directly.
switch_char (Default value is “-”)
  This is the leading character of command line arguments that indicate they are considered as switches. Arguments not starting with this character will be kept as is, and cannot have graphical widgets associated with them
sections (Default value is empty)
  This is a space separated list of switches delimiting a section (such as “-bargs -cargs -largs”). A section of switches is a set of switches that need to be grouped together and preceded by a specific switch. Sections are always placed at the end of the command line, after regular switches.

This <switches> tag can have any number of child tag, among the following. They can be repeated multiple times if you need several check boxes. For consistency, most of these child tags accept attributes among the following:

line (default value is 1)
  This indicates the row of the frame that should contain the switch. See the description of lines above.
column (default value is 1)
  This indicates the column of the frame that should contain the switch. See the description of columns above.
label (mandatory)
  This is the label which is displayed in the graphical interface
switch (mandatory)
  This is the text that should be put on the command line if that switch is selected. Depending on its type, a variant of the text might be put instead, see the description of combo and spin below. This switch shouldn’t contain any space.
switch-off (default value is empty)
  This attribute is used for <check> tags, and indicates the switch used for deactivating the concerned feature. This is useful for features that are on by default on certain occasions, but can be individually deactivated.
section (default value is empty)
  This is the switch section delimiter (such as “-cargs”). See the ‘sections’ attribute of the tag ‘switches’ for more information.
tip (default value is empty)
  This is the tooltip which describes that switch more extensively. It is displayed in a small popup window if the user leaves the mouse on top of the widget. Note that tags accepting the tip attribute also accept a single child <tip> whose value will contain the text to be displayed. The advantage of the latter is that the text formatting is then kept.
before (default value is “false”)
  This attribute is used to indicate that a switch needs to be always inserted at the begining of the command line.
min (default value is 1)
  This attribute is used for <spin> tags, and indicates the minimum value authorized for that switch.
max (default value is 1)
  This attribute is used for <spin> tags, and indicates the maximum value authorized for that switch.
default (default value is 1)
  This attribute is used for <check> and <spin> tags. See the description below.
noswitch (default is empty)
  This attribute is only valid for <combo> tags, and described below.
nodigit (default is empty)
  This attribute is only valid for <combo> tags, and described below.
value (mandatory)
  This attribute is only valid for <combo-entry> tags.
separator (default is the value given to `<switches>`
  This attribute specifies the separator to use between the switch and its value. See the description of this attribute for <switches>.

Here are the valid children for <switches>:

<title>

  This tag, which accepts the line and column attributes, is used to give a name to a specific frame. The value of the tag is the title itself. You do not have to specify a name, and this can be left to an empty value.

  Extra attributes for <title> are:

  line-span (default value is 1)
    This indicates how many rows the frame should span. If this is set to 0, then the frame is hidden from the user. See for instance the Ada or C switches editor.
  column-span (default value is 1)
    This indicates how many columns the frame should span. If this is set to 0, then the frame is hidden from the user. See for instance the Ada or C switches editor.
<check>

  This tag accepts the line, column, label, switch, switch-off, section, default, before and tip attributes.

  This tag doesn’t have any value. An optional <tip> child can be present.

  It creates a toggle button. When the latter is active, the text defined in the switch attribute is added as is to the command line. The switch can be also activated by default (default attribute is “on” or “true”). In this case, deactivating the switch will add switch-off to the command line.

<spin>

  This tag accepts the line, column, label, switch, section, tip, min, max, separator and default attributes.

  This tag doesn’t have any value. An optional <tip> child can be present.

  This switch will add the contents of the switch attribute followed by the current numeric value of the widget to the command line. This is typically used to indicate indentation length for instance. If the current value of the widget is equal to the default attribute, then nothing is added to the command line.

<radio>

  This tag accepts the line and column attributes. It groups any number of children, each of which is associated with its own switch. However, only one of the children can be selected at any given time.

  The children must have the tag radio-entry. This tag accepts the attributes label, switch, section, before and tip. As a special case, the switch attribute can have an empty value (“”) to indicate this is the default switch to use in this group of radio buttons.

  This tag doesn’t have any value. An optional <tip> child can also be present.

<field>

  This tag accepts the line, column, label, switch, section, separator, before and tip attributes.

  This tag doesn’t have any value. An optional <tip> child can be present.

  This tag describes a text edition field, which can contain any text the user types. This text will be prefixed by the value of the switch attribute, and the separator (by default nothing). If no text is entered in the field by the user, nothing is put on the command line.

  This tag accepts two extra attributes:

  as-directory (optional)

    If this attribute is specified and set to “true”, then an extra “Browse” button is displayed, so that the user can easily select a directory.

  as-file (optional)

    This attribute is similar to as-directory, but opens a dialog to select a file instead of a directory. If both attributes are set to “true”, the user will select a file.

<combo>

  This tag accepts the line, column, label, switch, section, before, tip, noswitch, separator and nodigit attributes.

  The tag <combo> accepts any number of combo-entry children tags, each of which accepts the label and value attribute. An optional <tip> child can also be present.

  The text inserted in the command line is the text from the switch attribute, concatenated with the text of the value attribute for the currently selected entry. If the value of the current entry is the same as that of the nodigit attribute, then only the text of the switch attribute is put on the command line. This is in fact necessary to interpret the gcc switch “-O” as “-O1”.

  If the value of the current entry is that of the noswitch attribute, then nothing is put in the command line.

<popup>

  This tag accepts the line, column, label, lines and columns attributes. This displays a simply button that, when clicked, displays a dialog with some extra switches. This dialog, just as the switches editor itself, is organizes into lines and columns of frames, the number of which is provided by the lines and columns attributes.

  This tag accepts any number of children, which are the same as the <switches> attribute itself.

<dependency>

  This tag is used to describe a relationship between two switches. It is used for instance when the “Debug Information” switch is selected for “Make”, which forces it for the Ada compiler as well.

  It has its own set of attributes:

  master-page master-switch master-section
    These two attributes define the switch that possibly forces a specific setting on the slave switch. In our example, they would have the values “Make” and “-g”. The switch referenced by these attributes must be of type <check> or <field>. If it is part of a section, then ‘master-section’ needs to be defined. If the check button is selected, it forces the selection of the slave check button. Likewise, if the field is set to any value, it forces the selection of the slave.
  slave-page slave-switch slave-section
    These two attributes define the switch which is acted upon by the master switch. In our example, they would have the values “Ada” and “-g”. The switch referenced by these attributes must be of type <check>.
  master-status slave-status
    These two switches indicate which state of the master switch forces which state of the slave-status. In our example, they would have the values “on” and “on”, so that when the make debug information is activated, the compiler debug information is also activated. However, if the make debug information is not activated, no specific setup is forced for the compiler debug information. if master-status is “off” and the master switch is a field, then the status of the slave will be changed when no value is set in the field.
<default-value-dependency>

  This tag is used to describe a relationship between two switches. It is slightly different from the <dependency> tag in that the relationship concerns only the default activation states. It is used for instance when the “-gnatwa” switch is selected for the “Ada” Compiler, which imply that the default values for “-gnatwc”, “-gnatwd”, etc. become activated by default. They can however still be deactivated with respectively “-gnatwC” and “-gnatwD”.

  It has its own set of attributes:

  master-switch
    This is the switch that triggers the dependency. If master-switch is present in the command line, then the switch’s default status of slave-switch is modified accordingly.
  slave-switch
    This is the switch whose default value depends on master-switch. This needs to be a switch already defined in a <switch> tag. It can match its ‘switch’ or ‘switch-off’ attributes. In the latter case, the slave-switch default value is deactivated if master-switch is present.
<expansion>

  This tag is used to describe how switches can be grouped together on the command line to keep it shorter. It is also used to define aliases between switches.

  It is easier to explain it through an example. Specifying the GNAT switch “-gnatyy” is equivalent to specifying “-gnaty3abcefhiklmnprst”. This is in fact a style check switch, with a number of default values. But it is also equivalent to decomposing it into several switches, as in “-gnatya”, “-gnatyb”, ...; With this information, GPS will try to keep the command line length as short as possible, to keep it readable.

  Both these aspects are defined in a unique <expansion> tag, which accepts two attributes: switch is mandatory, and alias is optional. Alias contains the text “-gnatyabcefhiklmnprst” in our example.

  There are two possible uses for this tag:

  - If the “alias” attribute is not specified, then the “switch” attribute indicates that all switches starting with that prefix should be grouped. For instance, if you pass “-gnatw” as the value for the “switch” attribute, then a command line with “-gnatwa -gnatw.b” will in fact result in “-gnatwa.b”.
  - If the “alias” attribute is specified, then the “switch” attribute is considered as a shorter way of writting “alias”. For instance, if “switch” is “-gnatyy” and “alias” is “-gnaty3abcefhiklmnprst”, then the user can simply type “-gnatyy” to mean the whole set of options.

  The same “switch” attribute can be used in two expansion nodes if you want to combine the behavior.

  For historical reasons, this tag accepts <entry> children, but these are no longer used.

### 14.6.4. Executing external tools

The user has now specified the default switches he wants to use for the external tool. Spawning the external tool can be done either from a menu item, or as a result of a key press.

Both cases are described in an XML customization file, as described previously, and both are setup to execute what GPS calls an action, i.e. a set of commands defined by the <action> tag.

#### 14.6.4.1. Chaining commands

This action tag, as described previously, executes one or more commands, which can either be internal GPS commands (written in any of the scripting language supported by GPS), or external commands provided by executables found on the PATH.

The command line for each of these commands can either be hard-coded in the customization file, or be the result of previous commands executed as part of the same action. As GPS executes each command from the action in turn, it saves its output on a stack as needed. If a command line contains a special construct %1, %2... then these constructs will be replaced by the result of respectively the last command executed, the previous from last command, and so on. They are replaced by the returned value of the command, not by any output it might have done to some of the consoles in GPS.

Every time you execute a new command, it pushes the previous %1, %2... parameters one step further on the stack, so that they become respectively %2, %3... and the output of that command becomes %1.

The result value of the previous commands is substituted exactly as is. However, if the output is surrounded by quotes, they are ignored when a substitution takes place, so you need to put them back if they are needed. The reason for this behavior is so that for scripting languages that systematically protect their output with quotes (simple or double), these quotes are sometimes in the way when calling external commands:

    <?xml version="1.0" ?>
    <quotes>
      <action name="test quotes">
        <shell lang="python">'-a -b -c'</shell>
        <external> echo with quotes: "%1"</external>
        <external> echo without quotes: %2</external/>
      </action>
    </quotes>

If one of the commands in the action raises an error, the execution of the action is stopped immediately, and no further command is performed.

#### 14.6.4.2. Saving open windows

Before launching the external tool, you might want to force GPS to save all open files, the project...; This is done using the same command GPS itself uses before starting a compilation. This command is called MDI.save_all, and takes one optional boolean argument which specifies whether an interactive dialog should be displayed for the user.

Since this command aborts when the user presses cancel, you can simply put it in its own <shell> command, as in:

    <?xml version="1.0" ?>
    <save_children>
      <action name="test save children">
        <shell>MDI.save_all 0</shell>
        <external>echo Run unless Cancel was pressed</external>
      </action>
    </save_children>

#### 14.6.4.3. Querying project switches

Some GPS shell commands can be used to query the default switches set by the user in the project file. These are get_tool_switches_as_string, get_tool_switches_as_list, or, more generally, get_attribute_as_string and get_attribute_as_list. The first two require a unique parameter which is the name of the tool as specified in the <tool> tag. This name is case-sensitive. The last two commands are more general and can be used to query the status of any attribute from the project. See their description by typing the following in the GPS shell console window:

    help Project.get_attribute_as_string
    help Project.get_attribute_as_list

The following is a short example on how to query the switches for the tool “Find” from the project, Tool example. It first creates an object representing the current project, then passes this object as the first argument of the get_tool_switches_as_string command. The last external command is a simple output of these switches:

    <?xml version="1.0" ?>
    <find_switches>
      <action name="Get switches for Find">
        <shell>Project %p</shell>
        <shell>Project.get_tool_switches_as_string %1 Find </shell>
        <external>echo %1</external>
      </action>
    </find_switches>

The following example shows how something similar can be done from Python, in a simpler manner. For a change, this function queries the Ada compiler switches for the current project, and prints them out in the messages window. The:

    <?xml version="1.0" ?>
    <query_switches>
      <action name="Query compiler switches">
        <shell lang="python">GPS.Project("%p").get_attribute_as_list
          (package="compiler",
           attribute="default_switches",
           index="ada")</shell>
        <external>echo compiler switches= %1</external>
      </action>
    </query_switches>

#### 14.6.4.4. Querying switches interactively

Another solution to query the arguments for the tool is to ask the user interactively. The scripting languages provides a number of solutions for these.

They generally have their own native way to read input, possibly by creating a dialog.

In addition, the simplest solution is to use the predefined GPS commands for this. These are the two functions:

yes_no_dialog
  This function takes a single argument, which is a question to display. Two buttons are then available to the user, “Yes” and “No”. The result of this function is the button the user has selected, as a boolean value.
input_dialog

  This function is more general. It takes a minimum of two arguments, with no upper limit. The first argument is a message describing what input is expected from the user. The second, third and following arguments each correspond to an entry line in the dialog, to query one specific value (as a string). The result of this function is a list of strings, each corresponding to these arguments.

  From the GPS shell, it is only convenient to query one value at a time, since it doesn’t have support for lists, and would return a concatenation of the values. However, this function is especially useful with other scripting languages.

The following is a short example that queries the name of a directory and a file name, and displays each in the Messages window:

    <?xml version="1.0" ?>
    <query_file>
      <action name="query file and dir">
        <shell lang="python">list=GPS.MDI.input_dialog \\
          ("Please enter directory and file name", "Directory", "File")</shell>
        <shell lang="python">print ("Dir=" + list[0], "File=" + list[1])</shell>
        </shell>
      </action>
    </query_file>

#### 14.6.4.5. Redirecting the command output

The output of external commands is send by default to the GPS console window. In addition, finer control can be exercised using the output attribute of the <external> and <shell> tags.

This attribute is a string that may take any value. Two values have specific meanings:

“none”
  The output of the command, as well as the text of the command itself, will not be shown to the user at all.
“”
  The output of the command is sent to the GPS console window, entitled “Messages”.
other values
  A new window is created, with the title given by the attribute. If such a window already exists, it is cleared up before any of the command in the chain is executed. The output of the command, as well as the text of the command itself, are sent to this new window.

This attribute can also be specified at the <action> tag level, in which case it defines the default value for all <shell> and <external> tags underneath. If it isn’t specified for the action itself, its default value will always be the empty string, i.e. output is sent to the GPS console:

    <?xml version="1.0" ?>
    <ls>
      <action name="ls current directory" output="default output" >
         <shell output="Current directory" >pwd</shell>
         <external output="Current directory contents" >/bin/ls</external>
      </action>
    </ls>

#### 14.6.4.6. Processing the tool output

The output of the tool has now either been hidden or made visible to the user in one or more windows.

There are several additional things that can be done with this output, for further integration of the tool in GPS.

- Parsing error messages .. index:: Locations.parse

  External tools can usually display error messages for the user that are associated with specific files and locations in these files. This is for instance the way the GPS builder itself analyzes the output of make.

  This can be done for your own tools using the shell command Locations.parse. This command takes several arguments, so that you can specify your own regular expression to find the file name, line number and so on in the error message. By default, it is configured to work seamlessly with error message of the forms:

      file:line: message
      file:line:column: message

  Please refer to the online help for this command to get more information (by e.g. typing help Locations.parse in the GPS Shell).

  Here is a small example on how to run a make command and send the errors to the location window afterward.

  For languages that support it, it is also recommended that you quote the argument with triple quotes, so that any special character (newlines, quotes, ...) in the output of the tool are not specially interpreted by GPS. Note also that you should leave a space at the end, in case the output itself ends with a quote:

      <?xml version="1.0" ?>
      <make>
        <action name="make example" >
           <external>make</external>
           <on-failure>
              <shell>Locations.parse """%1 """ make_example</shell>
           </on-failure>
        </action>
      </make>

- Auto-correcting errors .. index:: Codefix.parse

  GPS has support for automatically correcting errors for some of the languages. You can get access to this auto-fixing feature through the Codefix.parse shell command, which takes the same arguments as for Locations.parse.

  This will automatically add pixmaps to the relevant entries in the location window, and therefore Locations.parse should be called first prior to calling this command.

  Errors can also be fixed automatically by calling the methods of the Codefix class. Several codefix sessions can be active at the same time, each of which is associated with a specific category. The list of currently active sessions can be retrieved through the Codefix.sessions() command.

  If support for python is enabled, you can also manipulate the fixable errors for a given session. To do so, you must first get a handle on that section, as shown in the example below. You can then get the list of fixable errors through the errors command.

  Each error is of the class CodefixError, which has one important method fix which allows you to perform an automatic fixing for that error. The list of possible fixes is retrieved through possible_fixes:

      print GPS.Codefix.sessions ()
      session = GPS.Codefix ("category")
      errors  = session.errors ()
      print errors [0].possible_fixes ()
      errors [0].fix ()

## 14.7. Customization examples

### 14.7.1. Menu example

This section provides a full example of a customization file. It creates a top-level menu named custom menu. This menu contains a menu item named item 1, which is associated to the external command external-command 1, a sub menu named other menu, etc...:

    <?xml version="1.0"?>
    <menu-example>
      <action name="action1">
        <external>external-command 1</external>
      </action>

      <action name="action2">
        <shell>edit %f</shell>
      </action>

      <submenu>
        <title>custom menu</title>
        <menu action="action1">
          <title>item 1</title>
        </menu>

        <submenu>
          <title>other menu</title>
          <menu action="action2">
            <title>item 2</title>
          </menu>
        </submenu>
      </submenu>
    </menu-example>

### 14.7.2. Tool example

This section provides an example that defines a new tool. This is only a short example, since Ada, C and C++ support themselves are provided through such a file, available in the GPS installation.

This example adds support for the “find” Unix utility, with a few switches. All these switches are editable through the project properties editor.

It also adds a new action and menu. The action associated with this menu gets the default switches from the currently selected project, and then ask the user interactively for the name of the file to search:

    <?xml version="1.0" ?>
    <toolexample>
      <tool name="Find" >
        <switches columns="2" >
          <title column="1" >Filters</title>
          <title column="2" >Actions</title>

          <spin label="Modified less than n days ago" switch="-mtime-"
                min="0" max="365" default="0" />
          <check label="Follow symbolic links" switch="-follow" />

          <check label="Print matching files" switch="-print" column="2" />
        </switches>
      </tool>

      <action name="action find">
        <shell>Project %p</shell>
        <shell>Project.get_tool_switches_as_string %1 Find </shell>
        <shell>MDI.input_dialog "Name of file to search" Filename</shell>
        <external>find . -name %1 %2</external>
      </action>

      <Submenu>
        <Title>External</Title>
         <menu action="action find">
           <Title>Launch find</Title>
        </menu>
      </Submenu>
    </toolexample>

## 14.8. Scripting GPS

### 14.8.1. Scripts

Scripts are small programs that interact with GPS and allow you to perform complex tasks repetitively and easily. GPS includes support for two scripting languages currently, although additional languages might be added in the future. These two languages are described in the following section.

Support for scripting is currently work in progress in GPS. As a result, not many commands are currently exported by GPS, although their number is increasing daily. These commands are similar to what is available to people who extend GPS directly in Ada, but with a strong advantage: they do not require any recompilation of the GPS core, and can be tested and executed interactively.

The goal of such scripts is to be able to help automate processes such as builds, automatic generation of graphs, ...

These languages all have a separate console associated with them, which you can open from the Tools menu. In each of these console, GPS will display a prompt, at which you can type interactive commands. These console provide completion of the command names through the `tab` key.

For instance, in the GPS shell console you can start typing:

    GPS> File

then press the `tab` key, which will list all the functions whose name starts with “File”.

A similar feature is available in the python console, which also provides completion for all the standard python commands and modules.

All the scripting languages share the same set of commands exported by GPS, thanks to an abstract interface defined in the GPS core. As a result, GPS modules do not have to be modified when new scripting languages are added.

Scripts can be executed immediately upon startup of GPS by using the command line switch –load. Specifying the following command line:

    gps --load=shell:mytest.gps

will force the gps script `mytest.gps` to be executed immediately, before GPS starts reacting to user’s requests. This is useful if you want to do some special initializations of the environment. It can also be used as a command line interface to GPS, if you script’s last command is to exit GPS.

In-line commands can also be given directly on the command line through –eval command line switch.

For instance, if you want to analyze an entity in the entity browser from the command line, you would pass the following command switches:

    gps --eval=shell:'Entity entity_name file_name; Entity.show %1'

See the section Customizing through XML and Python files on how to bind key shortcuts to shell commands.

### 14.8.2. Scripts and GPS actions

There is a strong relationship between GPS actions, as defined in the customization files (Defining Actions), and scripting languages

Actions can be bound to menus and keys through the customization files or the Edit->Key shortcuts dialog.

These actions can execute any script command, Defining Actions. This is done through the <shell> XML tag.

But the opposite is also true. From a script, you can execute any action registered in GPS. This can for instance be used to split windows, highlight lines in the editor, ... when no equivalent shell function exists. This can also be used to execute external commands, if the scripting language doesn’t support this in an easy manner.

Such calls are made through a call to execute_action, as in the following example:

    execute_action "Split horizontally"

    GPS.execute_action (action="Split horizontally")

The list of actions known to GPS can be found through the Edit->Key shortcuts dialog. Action names are case sensitive.

Some of the shell commands take subprograms as parameters. If you are using the GPS shell, this means you have to pass the name of a GPS action. If you are using Python, this means that you pass a subprogram, Subprogram parameters.

### 14.8.3. The GPS Shell

The GPS shell is a very simple-minded, line-oriented language. It is accessible through the Shell window at the bottom of the GPS window. It is similar to a Unix shell, or a command window on Windows systems.

Type help at the prompt to get the list of available commands, or help followed by the name of a command to get more information on that specific command.

The following example shows how to get some information on a source entity, and find all references to this entity in the application. It searches for the entity “entity_name”, which has at least one reference anywhere in the file “file_name.adb”. After the first command, GPS returns an identifier for this entity, which can be used for all commands that need an entity as a parameter, as is the case for the second command. When run, the second command will automatically display all matching references in the location window:

    GPS> Entity my_entity file_name.adb
    <Entity_0x09055790>
    GPS> Entity.find_all_refs <Entity_0x09055790>

Since the GPS shell is very simple, it doesn’t provide any reference counting for the result types. As a result, all the values returned by a command, such as <Entity_0x09055790> in the example above, are kept in memory.

The GPS shell provides the command clear_cache which removes all such values from the memory. After this command is run, you can no longer use references obtained from previous commands, although of course you can run these commands again to get a new reference.

The return value of the 9 previous commands can easily be recalled by passing %1, %2, ... on the command line. For instance, the previous example could be rewritten as:

    GPS> Entity my_entity file_name.adb
    <Entity_0x09055790>
    GPS> Entity.find_all_refs %1

These return values will be modified also for internal commands sent by GPS, so you should really only use this when you emit multiple commands at the same time, and don’t do any other action in GPS. This is mostly useful when used for command-line scripts (see –eval and –load), or for custom files, Customizing through XML and Python files.

Arguments to commands can, but need not, be quoted. If they don’t contain any space, double-quote (‘”’) or newline characters, you do not need to quote them. Otherwise, you should surround them with double-quotes, and protect any double-quote part of the argument by preceding it with a backslash.

There is another way to quote a command: use three double-quotes characters in a row. Any character loses its special meaning until the next three double-quotes characters set. This is useful if you do not know in advance the contents of the string you are quoting:

    Locations.parse """%1 """ category_name

### 14.8.4. The Python Interpreter

Python is an interpreted object-oriented language, created by Guido Van Rossum. It is similar in its capabilities to languages such as Perl, Tcl or Lisp. This section is not a tutorial on python programming. See http://docs.python.org/ to access the documentation for the current version of python.

If python support has been enabled, the python shell is accessible through the Python window at the bottom of the GPS window. You can also display it by using the menu `Tools->Consoles->Python`.

The full documentation on what GPS makes visible through python is available through the /Help/Python extensions.

The same example that was used to show the GPS shell follows, now using python. As you can notice, the name of the commands is similar, although they are not run exactly in the same way. Specifically, GPS benefits from the object-oriented aspects of python to create classes and instances of these classes.

In the first line, a new instance of the class Entity is created through the create_entity function. Various methods can then be applied to that instance, including find_all_refs, which lists all references to that entity in the location window:

    >>> e=GPS.Entity ("entity_name", GPS.File ("file_name.adb"))
    >>> e.find_all_refs()

The screen representation of the classes exported by GPS to python has been modified, so that most GPS functions will return an instance of a class, but still display their output in a user-readable manner.

Python has extensive introspection capabilities. Continuing the previous example, you can find what class e is an instance of with the following command:

    >>> help(e)
    Help on instance of Entity:

    <GPS.Entity instance>

It is also possible to find all attributes and methods that can be applied to e, as in the following example:

    >>> dir (e)
    ['__doc__', '__gps_data__', '__module__', 'called_by', 'calls',
    'find_all_refs']

Note that the list of methods may vary depending on what modules were loaded in GPS, since each module can add its own methods to any class.

In addition, the list of all existing modules and objects currently known in the interpreter can be found with the following command:

    >>> dir ()
    ['GPS', 'GPSStdout', '__builtins__', '__doc__', '__name__', 'e', 'sys']

You can also load and execute python scripts with the execfile command, as in the following example:

    >>> execfile ("test.py")

Python supports named parameters. Most functions exported by GPS define names for their parameters, so that you can use this Python feature, and make your scripts more readable. A notable exception to this rule are the functions that take a variable number of parameters. Using named parameters allows you to specify the parameters in any order you wish, e.g:

    >>> e=GPS.Entity (name="foo", file=GPS.File("file.adb"))

### 14.8.5. Python modules

On startup, GPS will automatically import (with python’s import command) all the files with the extension `.py` found in the directory `$HOME/.gps/plug-ins`, the directory `$prefix/share/gps/plug-ins` or in the directories pointed to by `GPS_CUSTOM_PATH`. These files are loaded only after all standard GPS modules have been loaded, as well as the custom files, and before the script file or batch commands specified on the command lines with the –eval or –load switches.

As a result, one can use the usual GPS functions exported to python in these startup scripts. Likewise, the script run from the command line can use functions defined in the startup files.

Since the import command is used, the functions defined in this modules will only be accessible by prefixing their name by the name of the file in which they are defined. For instance if a file `mystartup.py` is copied to the startup directory, and defines the function func, then the latter will be accessible in GPS through mystartup.func.

Python’s own mechanism for loading files at startup (the environment variable PYTHONSTARTUP) is not suitable for use within the context of GPS. When python is loaded by GPS, the GPS module itself is not yet available, and thus any script that depends on that module will fail to load correctly. Instead, copy your script to one of the plug-ins directories, as documented above.

If you are writing a set of python scripts that other people will use, you need to provide the python files themselves. This is a set of `.py` files, which the user should install in the `plug-ins` directory.

To make the Python function accessible through GPS, this can be done:

- Either by exporting the APIs directly through Python, under the form of Actions (see the Action class), Menus (see the Contextual and Menu classes) or toolbar buttons (see the ToolButton and Toolbar classes);
- Or by writing an XML file with the format described in the customization section of this documentation. This XML file should create a set of actions, through the <action> tag, exported to the user. This allows him to either create menus to execute these commands or to bind them to special key shortcuts. The menus can be created directly in python, with the GPS.Menu class. The same XML can in fact be directly embedded in the python file itself and executed through GPS.parse_xml.

The following example defines a python command that inserts a line full of dashes (‘-‘) at the current cursor location. This command is associated with the key binding `control-c n`, and can be distributed as a single Python file:

    # This code can be stored in a file test.py in $HOME/.gps/plug-ins
    from GPS import *

    def add_dashes_line():
       Editor.replace_text (current_context().file().name(),
                            current_context().location().line(),
                            current_context().location().column(),
                            "--------------------------------", 0, 0)
    GPS.parse_xml ("""
       <action name="dashes line">
          <shell lang="python">test.add_dashes_line()</shell>
          <context>Source editor</context>
       </action>
       <key action="dashes line">control-c n</key>
    """)

Several complex examples are provided in the GPS distribution, in the directory `examples/python`. These are modules that you might want to use for your own GPS, but more important that will show how GPS can be extended from Python.

If your script doesn’t do what you expect it to do, there are several ways to debug it, among which the easiest is probably to add some “print” statements. Since some output of the scripts is sometimes hidden by GPS (for instance for interactive commands), you might not see this output.

In this case, you can reuse the tracing facility embedded in GPS itself. Modify the file `$HOME/.gps/traces.cfg`, and add the following line:

    PYTHON.OUT=yes

This will include the python traces as part of the general traces available in the file `$HOME/.gps/log`. Note that it may slow down GPS if there is a lot of output to process.

### 14.8.6. Subprogram parameters

A few of the functions exported by GPS in the GPS shell or in python expect a subprogram as a parameter.

This is handled in different ways depending on what language your are using:

- GPS shell

  It isn’t possible to define new functions in the GPS shell. However, this concept is similar to the GPS actions (Defining Actions), which allow you to execute a set of commands and launch external processes.

  Therefore, a subprogram parameter in the GPS shell is a string, which is the name of the action to execute.

  For instance, the following code defines the action “on_edition”, which is called every time a new file is edited. The action is defined in the shell itself, although this could be more conveniently done in a separate customization file:

      parse_xml """<action name="on_edition">
                   <shell>echo "File edited"</shell></action>"""
      Hook "file_edited"
      Hook.add %1 "on_edition"

- Python

  Python of course has its own notion of subprogram, and GPS is fully compatible with it. As a result, the syntax is much more natural than in the GPS shell. The following example has the same result as above:

      import GPS
      def on_edition(self, *arg):
        print "File edited"
      GPS.Hook ("file_edited").add (on_edition)

  Things are in fact slightly more complex if you want to pass methods as arguments. Python has basically three notions of callable subprograms, detailed below. The following examples all create a combo box in the toolbar, which calls a subprogram whenever its value is changed. The documentation for the combo box indicates that the callback in this case takes two parameters:

  - The instance of the combo
  - The current selection in the combo box

  The first parameter is the instance of the combo box associated with the toolbar widget, and, as always in python, you can store your own data in the instance, as shown in the examples below.

  Here is the description of the various subprograms:

  - Global subprograms

    These are standard subprograms, found outside class definitions. There is no implicit parameter in this case. However, if you need to pass data to such a subprogram, you need to use global variables:

        import GPS

        my_var = "global data"

        def on_changed (combo, choice):
           global my_var
           print "on_changed called: " + \\
              my_var + " " + combo.data + " " + choice

        combo = GPS.Combo \\
          ("name", label="name", on_changed=on_changed)
        GPS.Toolbar().append (combo)
        combo.data = "My own data"

  - Unbound methods

    These are methods of a class. You do not specify, when you pass the method in parameter to the combo box, what instance should be passed as its first parameter. Therefore, there is no extra parameter either.

    Note however than whatever class the method is defined in, the first parameter is always an instance of the class documented in the GPS documentation (in this case a GPS.Combo instance), not an instance of the current class.

    In this first example, since we do not have access to the instance of MyClass, we also need to store the global data as a class component. This is a problem if multiple instances of the class can be created:

        import GPS
        class MyClass:
           my_var = "global data"
           def __init__ (self):
              self.combo = GPS.Combo \\
                 ("name", label="name", on_changed=MyClass.on_changed)
              GPS.Toolbar().append (self.combo)
              self.combo.data = "My own data"

           def on_changed (combo, choice):
              ## No direct access to the instance of MyClass.
              print "on_changed called: " + \\
                 MyClass.my_var + " " + combo.data + " " + choice

        MyClass()

    As the example above explains, there is no direct access to MyClass when executing on_changed. An easy workaround is the following, in which the global data can be stored in the instance of MyClass, and thus be different for each instance of MyClass:

        import GPS
        class MyClass:
           def __init__ (self):
              self.combo = GPS.Combo \\
                 ("name", label="name", on_changed=MyClass.on_changed)
              GPS.Toolbar().append (self.combo)
              self.combo.data = "My own data"
              self.combo.myclass = self   ## Save the instance
              self.my_var = "global data"

           def on_changed (combo, choice):
              print "on_changed called: " + \\
                 combo.myclass.my_var + " " + combo.data + " " + choice

        MyClass()

  - Bound methods

    The last example works as expected, but is not convenient to use. The solution here is to use a bound method, which is a method for a specific instance of a class. Such a method always has an extra first parameter, set implicitly by Python or GPS, which is the instance of the class the method is defined in.

    Notice the way we pass the method in parameter to append(), and the extra third argument to on_changed in the example below:

        import GPS
        class MyClass:
           def __init__ (self):
              self.combo = GPS.Combo \\
                 ("name", label="name", on_changed=self.on_changed)
              GPS.Toolbar().append (self.combo)
              self.combo.data = "My own data"
              self.my_var = "global data"

           def on_changed (self, combo, choice):
              # self is the instance of MyClass specified in call to append()
              print "on_changed called: " + \\
                 self.my_var + " " + combo.data + " " + choice

        MyClass()

    It is often convenient to use the object-oriented approach when writing python scripts. If for instance you want to spawn an external process, GPS provides the GPS.Process class. When you create an instance, you specify a callback to be called when some input is made available by the process. Matching the above example, the code would look something like:

        class MyClass:
          def __init__ (self):
             self.process = GPS.Process
                 ("command_line", on_match = self.on_match)

          def on_match (self, process, matched, unmatched);
             print "Process output: " + unmatched + matched + "\\n"

    A more natural approach, rather than having a class that has a process field, is to directly extend the GPS.Process class, as in:

        class MyClass (GPS.Process):
          def __init__ (self):
             GPS.Process.__init__ \\
                (self, "command_line", on_match = self.on_match)

          def on_match (self, matched, unmatched);
             print "Process output: " + unmatched + matched + "\\n"

    Any command that can be used on a process (such as send) can then directly be used on instances of MyClass.

    There is one non-obvious improvement in the code above: the on_match callback has one less parameter. What happens is the following: as per the documentation of GPS.Process.__init__, GPS gives three arguments to its on_match callback: the instance of the process (process in the first example above), the string that matched the regular expression, and the string before that match.

    In the first example above, we are passing self.on_match, ie a bound method, as a callback. That tells python that it should automatically, and transparently, add an extra first parameter when calling MyClass.on_match, which is self. This is why the first example has four parameters to on_match.

    However, the second example only has three parameters, because GPS has detected that self (the instance of MyClass) and the instance of GPS.Process are the same in this case. Thus it doesn’t add an extra parameter (self and process would have been the same).

### 14.8.7. Python FAQ

This section lists some of the problems that have been encountered while using Python inside GPS. This is not a general Python discussion.

#### 14.8.7.1. Hello World! in python

Writing a python script to interact with GPS is very simple. Here we show how to create a new menu in GPS that when clicked, diplays a dialog saying the famous ‘Hello World!’.

Here is the code that you need to put in hello_world.py:

    import GPS

    def hello_world (self):
       GPS.MDI.dialog ("Hello World!")

    GPS.Menu.create ("/Help/Hello World!", on_activate=hello_world)

In order to use this plug-in, you can launch GPS with the following command line:

    $ gps --load=python:hello_world.py

If would want the plug-in to be loaded every time you launch GPS without having to specify it on the command line, you should copy hello_world.py to your $HOME/.gps/plug-ins/ directory or %USERPROFILE%\.gps\ under Windows.

Alternatively, you can add the directory in which you plug-in is located to you GPS_CUSTOM_PATH environment variable. For a description of the various environment variables used by GPS, Environment Variables.

#### 14.8.7.2. Spawning external processes

There exist various solutions to spawn external processes from a script:

- Use the functionalities provided by the GPS.Process class

- Execute a GPS action through GPS.execute_action.

  This action should have an <external> XML node indicating how to launch the process

- Create a pipe and execute the process with os.popen() calls

  This solution doesn’t provide a full interaction with the process, though.

- Use a standard expect library of Python

  The use of an expect library may be a good solution. There are various python expect libraries that already exist.

  These libraries generally try to copy the parameters of the standard file class. They may fail doing so, as GPS’s consoles do not fully emulate all the primitive functions of that class (there is no file descriptor for instance).

  When possible, it is recommended to use one of the methods above instead.

#### 14.8.7.3. Redirecting the output of spawned processes

In general, it is possible to redirect the output of any Python script to any GPS window (either an already existing one, or creating one automatically), through the “output” attribute of XML configuration files.

However, there is a limitation in python that the output of processes spawned through os.exec() or os.spawn() is redirected to the standard output, and not to the usual python output that GPS has overriden.

There are two solutions for this:

- Execute the external process through a pipe

  The output of the pipe is then redirected to Python’s output, as in:

      import os, sys
      def my_external():
         f = os.popen ('ls')
         console = GPS.Console ("ls")
         for l in f.readlines():
            console.write ('   ' + l)

  This solution allows you, at the same time, to modify the output, for instance to indent it as in the example above.

- Execute the process through GPS

  You can go through the process of defining an XML customization string for GPS, and execute your process this way, as in:

      GPS.parse_xml ("""
         <action name="ls">
           <external output="output of ls">ls</external>
         </action>""")

      def my_external():
         GPS.execute_action ("ls")

  This solution also allows you to send the output to a different window than the rest of your script. But you cannot filter or modify the output as in the first solution.

#### 14.8.7.4. Contextual menus on object directories only

The following filter can be used for actions that can only execute in the Project View, and only when the user clicks on an object directory. The contextual menu entry will not be visible in other contexts:

    <?xml version="1.0" ?>
    <root>
       <filter name="object directory"
               shell_cmd="import os.path; os.path.samefile (GPS.current_context().project().object_dirs()[0],GPS.current_context().directory())"
               shell_lang="python"
               module="Explorer" />

       <action name="Test on object directory">
          <filter id="object directory" />
          <shell>echo "Success"</shell>
       </action>

       <contextual action="Test on object directory" >
          <Title>Test on object directory</Title>
       </contextual>
    </root>

Another example would be to have a filter so that the contextual menu only appears when on a project node in the Project View. Using %P in your command is not enough, since the current context when you click on a file or directory also contain information about the project this file or directory belongs to. Thus this implicit filter will not be enough to hide your contextual menu.

As a result, you need to do a slightly more complex test, where you check that the current context doesn’t contains information on directories (which will disable the contextual menu for directories, files and entities). Since the command uses %P, GPS garantees that a project is available.

We’ll implement this contextual menu in a Python file, called `filters.py`:

    import GPS
    def on_project():
       try:
          GPS.current_context().directory()
          return False
       except:
          return True

    GPS.parse_xml ("""
    <action name="test_filter">
    <filter module="Explorer"
         shell_lang="python"
         shell_cmd="filters.on_project()" />
    <shell>echo current project is %P</shell>
    </action>
    <contextual action="test_filter">
    <title>Print current project</title>
    </contextual>""")

The example above shows the flexibility of filters, since you can pretty much do anything you wish through the shell commands. However, it is complex to write for such a simple filter. Luckily, GPS provides a predefined filter just for that purpose, so that you can write instead, in an XML file:

    <action name="test_filter" >
    <filter id="Explorer_Project_Node" />
    <shell>echo current project is %P</shell>
    </action>

#### 14.8.7.5. Redirecting the output to specific windows

By default, the output of all python commands is displayed in the Python console. However, you might want in some cases to create other windows in GPS for this output. This can be done in one of two ways:

- Define a new action

  If the whole output of your script should be redirected to the same window, or if the script will only be used interactively through a menu or a key binding, the easiest way is to create a new XML action, and redirect the output, as in:

      <?xml version="1.0" ?>
      <root>
        <action name="redirect output" output="New Window">
           <shell lang="python">print "a"</shell>
        </action>
      </root>

  All the various shell commands in your action can be output in a different window, and this also applies for the output of external commands.

- Explicit redirection

  If, however, you want to control in your script where the output should be sent, for instance if you can’t know that statically when you write your commands, you can use the following code:

      sys.stdin = sys.stdout = GPS.Console ("New window")
      print "foo"
      print (sys.stdin.read ())
      sys.stdin = sys.stdout = GPS.Console ("Python")

  The first line redirect all input and output to a new window, which is created if it doesn’t exist yet. Note however that the output of stderr is not redirected, and you need to explicitely do it for sys.stderr.

  The last line restore the default Python console. You must do this at the end of your script, or all scripts will continue to use the new consoles.

  You can alternatively create separate objects for the output, and use them in turn:

      my_out  = GPS.Console ("New Window")
      my_out2 = GPS.Console ("New Window2")

      sys.stdout=my_out
      print "a"
      sys.stdout=my_out2
      print "b"
      sys.stdout=GPS.Console ("Python")

  The parameter to the constructor GPS.Console indicates whether any output sent to that console should be saved by GPS, and reused for the %1, %2, ... parameters if the command is executed in a GPS action. That should generally be 1, except for stderr where it should be 0.

#### 14.8.7.6. Reloading a python file in GPS

After you have made modification to a python file, you might want to reload it in GPS. This requires careful use of python commands.

Here is an example. Lets assume you have a python file (`"mymod.py"`) which contains the following:

    GPS.parse_xml ("""
       <action name="my_action">
          <shell lang="python">mymod.myfunc()</shell>
       </action>""")

    def myfunc():
       print "In myfunc\\n"

As you can guess from this file, it defines an action “my_action”, that you can for instance associate with a keybinding through the Edit->Key shortcuts menu.

If this file has been copied in one of the `plug-ins` directories, it will be automatically loaded at startup.

Notice that the function myfunc is thus found in a separate namespace, with the name mymod, same as the file.

If you decide, during your GPS session, to edit this file and have the function print “In myfunc2” instead, you then have to reload the file by typing the following command in the Python console:

    > execfile ("HOME/.gps/plug-ins/mymod.py", mymod.__dict__)

The first parameter is the full path to the file that you want to reload. The second argument is less obvious, but indicates that the file should be reloaded in the namespace mymod.

If you omit the optional second parameter, Python will load the file, but the function myfunc will be defined in the global namespace, and thus the new definition is accessible through:

    > myfunc()

Thus, the key shortcut you had set, which still executes mymod.myfunc() will keep executing the old definition.

By default, GPS provides a contextual menu when you are editing a Python file. This contextual menu (Python->Reload module) will take care of all the above details.

#### 14.8.7.7. Printing the GPS Python documentation

The python extension provided by GPS is fully documentation in this manual and a separate manual accessible through the Help menu in GPS.

However, this documentation is provided in HTML, and might not be the best suitable for printing, if you wish to do so.

The following paragraph explains how you can generate your own documentation for any python module, including GPS, and print the result:

    import pydoc
    pydoc.writedoc (GPS)

In the last comamnd, GPS is the name of the module that you want to print the documentation for.

These commands generate a `.html` file in the current directory.

Alternatively, you can generate a simple text file with:

    e=file("./python_doc", "w")
    e.write (pydoc.text.document (GPS))
    e.flush()

This text file includes bold characters by default. Such bold characters are correctly interpreted by tools such as `a2ps` which can be used to convert the text file into a postscript document.

#### 14.8.7.8. Automatically loading python files at startup

At startup, GPS will automatically load all python files found in the directories `share/gps/plug-ins` and `$HOME/.gps/plug-ins`.

In addition, python files located under `<prefix>/share/gps/python` can be imported (using the import command) by any python script.

You can also set the PYTHONPATH environment variable to add other directories to the python search path.

#### 14.8.7.9. Hiding contextual menus

GPS provides most of its tools through contextual menus, accessed by right clicking in various parts of GPS. Due to the number of tools provided by GPS, these contextual menus tend to be big, and you might want to control what should be displayed in them. There are several ways to control this:

- Define appropriate filters for your actions

  If you are creating your own contextual menus through customization files and XML, these menus are associated with actions (<action>) that you have created yourself most of the time. In this case, you need to define filters appropriately, through the <filter> tag, to decide when the action is relevant, and therefore when the contextual menu should be displayed.

- Use shell commands to hide the menus

  If you want to control the visibility of predefined contextual menus, or for menus where you cannot easily modify the associated filter, you can use shell and python commands to hide the menu entry. For this, you will need to find out the name of the menu, which can be done by checking the list returned by GPS.Contextual.list() and using the most likely entry. This name is also the value of the <title> tag for contextual menus that you have created yourself. Using this name, you can then disable the contextual menu by executing:

      GPS.Contextual ("name").hide()

  in the python console

#### 14.8.7.10. Creating custom graphical interfaces

GPS is based on the Gtk+ graphical toolkit, which is available under many platforms and for many programming languages.

In particular, GPS comes with pygobject, a python binding to Gtk+. Using pygobject, you will be able to create your own dialogs and graphical windows using the python capabilities provided by GPS.

See the menu Help->Python Extensions, in particular the GPS.MDI documentation, for a sample of code on how to create your own graphical interfaces and integrate them in GPS.

### 14.8.8. Hooks

A hook is a named set of commands to be executed on particular occasions as a result of user actions in GPS.

GPS and its various modules define a number of standard hooks, which are called for instance when a new project is loaded, when a file is edited, and so on. You can define your own commands to be executed in such cases.

You can find out the list of hooks that GPS currently knows about by calling the Hook.list function, which takes no argument, and returns a list of hook names that you can use. More advanced description for each hook is available through the Help->Python Extensions:

    GPS> Hook.list
    project_changed
    open_file_action_hook
    preferences_changed
    [...]

    Python> GPS.Hook.list()

The description of each hooks includes a pointer to the type of the hook, that is what parameters the subprograms in this hook will receive. For instance:

The list of all known hook types can be found through the Hook.list_types command. This takes no argument and returns a list of all known types of hooks. As before, you can more information for each of these type through a call to Hook.describe_type.

#### 14.8.8.1. Adding commands to hooks

You can add your own command to existing hooks through a call to the Hook.add command. Whenever the hook is executed by GPS or another script, your command will also be executed, and will be given the parameters that were specified when the hook is run. The first parameter is always the name of the hook being executed.

This Hook.add applies to an instance of the hook class, and takes one parameter, the command to be executed. This is a subprogram parameter (Subprogram parameters).

- GPS shell

  The command can be any GPS action (Defining Actions). The arguments for the hook will be passed to the action, and are available as $1, $2, ...; In the following example, the message “Just executed the hook: project_changed” will be printed in the Shell console. Note that we are defining the action to be executed inline, but this could in fact be defined in a separate XML customization file for convenience:

      GPS> parse_xml """<action name="my_action"><shell>echo "Just executed the hook"</shell></action_name>"""
      GPS> Hook project_changed
      GPS> Hook.add %1 "my_action"

- Python

  The command must be a subprogram to execute. The arguments for the hook will be passed to this subprogram. In the following example, the message “The hook project_changed was executed by GPS” will be displayed in the Python console whenever the project changes:

      def my_callback (name):
          print "The hook " + name + " was executed by GPS"
      GPS.Hook ("project_changed").add (my_callback)

The example above shows the simplest type of hook, which doesn’t take any argument. However, most hooks receive several parameters. For instance, the hook “file_edited” receives the file name as a parameter.

- GPS shell

  The following code will print the name of the hook (“file_edited”) and the name of the file in the shell console every time a file is open by GPS:

      GPS> parse_xml """<action name="my_action"><shell>echo name=$1 file=$2</shell></action>"""
      GPS> Hook "file_edited"
      GPS> Hook.add %1 "my_action"

- Python

  The following code prints the name of the file being edited by GPS in the python console whenever a new editor is opened. The second argument is of type GPS.File:

      def my_file_callback (name, file):
          print "Editing " + file.name()
      GPS.Hook ("file_edited").add (my_file_callback)

#### 14.8.8.2. Action hooks

Some hooks have a special use in GPS. Their name always ends with “_action_hook”.

As opposed to the standard hooks described in the previous section, the execution of the action hooks stops as soon as one of the subprograms returns a True value (“1” or “true”). The subprograms associated with that hook are executed one after the other. If any such subprogram knows how to act for that hook, it should do the appropriate action and return “1”.

Other action hooks expect a string as a return value instead of a boolean. The execution will stop when a subprogram returns a non-empty string.

This mechanism is used extensively by GPS internally. For instance, whenever a file needs to be opened in an editor, GPS executes the “open_file_action_hook” hook to request its editing. Several modules are connected to that hook.

One of the first modules to be executed is the external editor module. If the user has chosen to use an external editor, this module will simply spawn Emacs or the external editor that the user has selected, and return 1. This immediately stops the execution of the “open_file_action_hook”.

However, if the user doesn’t want to use external editors, this module will return 0. This will keep executing the hook, and in particular will execute the source editor module, which will always act and open an editor internally in GPS.

This is a very flexible mechanism. In your own script, you could choose to have some special handling for files with a ”.foo” extension for instance. If the user wants to open such a file, you would spawn for instance an external command (say “my_editor”) on this file, instead of opening it in GPS.

This is done with a code similar to the following:

    from os.path import *
    import os
    def my_foo_handler(name, file, line, column,
                       column_end, enable_nav, new_file, reload):
        if splitext(file.name())[1] == ".foo":
            os.spawnv(
               os.P_NOWAIT, "/usr/bin/emacs", ("emacs", file.name()))
            return 1   ## Prevent further execution of the hook
        return 0  ## Let other subprograms in the hook do their job

    GPS.Hook("open_file_action_hook").add(my_foo_handler)

#### 14.8.8.3. Running hooks

Any module in GPS is responsible for running the hooks when appropriate. Most of the time, the subprograms exported by GPS to the scripting languages will properly run the hook. But you might also need to run them in your own scripts.

As usual, this will result in the execution of all the functions bound to that hook, whether they are defined in Ada or in any of the scripting languages.

This is done through the Hook.run command. This applies to an instance of the Hook class, and a variable number of arguments These must be in the right order and of the right type for that specific type of hook.

If you are running an action hook, the execution will stop as usual as soon as one of the subprograms return a True value.

The following example shows how to run a simple hook with no parameter, and a more complex hook with several parameters. The latter will in fact request the opening of an editor for the file in GPS, and thus has an immediately visible effect on the interface. The file is opened at line 100. See the description of the hook for more information on the other parameters:

    GPS.Hook ("project_changed").run()
    GPS.Hook ("open_file_action_hook").run \\
                  (GPS.File ("test.adb"), 100, 1, 0, 1, 1, 1)

#### 14.8.8.4. Creating new hooks

The list of hooks known to GPS is fully dynamic. GPS itself declares a number of hooks, mostly for its internal use although of course you can also connect to them.

But you can also create your own hooks to report events happening in your own modules and programs. This way, any other script or GPS module can react to these events.

Such hooks can either be of a type exported by GPS, which constraints the list of parameters for the callbacks, but make such hooks more portable and secure; or they can be of a general type, which allows basically any kind of parameters. In the latter case, checks are done at runtime to ensure that the subprogram that is called as a result of running the hook has the right number of parameters. If this isn’t the case, GPS will complain and display error messages. Such general hooks will also not pass their parameters to other scripting languages.

Creating new hooks is done through a call to Hook.register. This function takes two arguments: the name of the hook you are creating, and the type of the hook.

The name of the hook is left to you. Any character is allowed in that name, although using only alphanumerical characters is recommended.

The type of the hook must be one of the following:

- “” (the empty string)

  This indicates that the hook doesn’t take any argument. None should be given to Hook.run, and none should be expected by the various commands connected to that hook, apart from the hook name itself.

- one of the values returned by Hook.list_types

  This indicates that the hook is of one of the types exported by GPS itself. The advantage of using such explicit types as opposed to “general” is that GPS is able to make more tests for the validity of the parameters. Such hooks can also be connected to from other scripting languages.

- “general”

  This indicates that the hook is of the general type that allows any number of parameter, of any type. Other scripts will be able to connect to it, but will not be executed when the hook is run if they do not expect the same number of parameters that was given to Hook.run. Other scripts in other language will only receive the hook name in parameter, not the full list of parameters.

A small trick worth noting: if the command bound to a hook doesn’t have the right number of parameters that this hook provides, the command will not be executed and GPS will report an error. You can make sure that your command will always be executed by either giving default values for its parameter, or by using python’s syntax to indicate a variable number of arguments.

This is especially useful if you are connecting to a “general” hook, since you do not really know in advance how many parameters the call of Hook.run will provide:

    ## This callback can be connected to any type of hook
    def trace (name, *args):
       print "hook=" + name

    ## This callback can be connected to hooks with one or two parameters
    def trace2 (name, arg1, arg2=100):
       print "hook=" + str (arg1) + str (arg2)

    Hook.register ("my_custom_hook", "general")
    Hook ("my_custom_hook").add (trace2)
    Hook ("my_custom_hook").run (1, 2) ## Prints 1 2
    Hook ("my_custom_hook").run (1)    ## Prints 1 100

## 14.9. Adding support for new Version Control Systems

### 14.9.1. Custom VCS interfaces

The Version Control interface in GPS can be customized, either to refine the behavior of the existing system and adapt it to specific needs, or to add support for other Version Control systems.

Custom VCS interfaces are defined through XML files and Python plugins. Those files are read in the same location as all the other XML and Python customizations that GPS offers. See Customizing through XML and Python files for a complete description.

There are three steps to follow when creating a custom VCS interface. The first step is to describe the VCS itself, the second step is to implement actions corresponding to all the operations that this VCS can perform, and the third step is to define the layout of the menus. The following three sections (Describing a VCS, Implementing VCS actions, and Implementing VCS menus) describe those steps.

GPS is distributed with XML/Python files describing the interfaces to ClearCase, CVS, Subversion, Git and Mercurial (experimental support). These XML/Python files are located in the directory share/gps/plug-ins in the GPS installation, and can be used as a reference for implementing new custom VCS interfaces.

### 14.9.2. Describing a VCS

#### 14.9.2.1. The VCS node

The vcs node is the toplevel node which contains the description of the general behavior expected from the VCS. It has the following attributes:

name
  The attribute name indicates the identifier of the VCS. The casing of this name is important, and the same casing must be used in the project files.
absolute_names
  The attribute absolute_names indicates the behavior of the VCS relative to file names, and can take the values TRUE or FALSE. If it is set to TRUE, it means that all commands in the VCS will work on absolute file names. If it set to FALSE, it means that all actions work on base file names, and that GPS will move to the appropriate directory before executing an action.
group_queries_by_directory
  The attribute group_queries_by_directory indicates that, when querying status for all the source files in a directory, a query for the directory should be launched, instead of launching a query for multiple files. This operation is faster on some Version Control systems. By default, this is set to FALSE.
ignore_file
  The attribute ignore_file specifies the name of the file used by the VCS Explorer to get the list of files to ignore. By default for the CVS mode this is set to `.cvsignore`.
atomic_commands
  The attribute atomic_commands specifies if the VCS supports atomicity and can take the values TRUE or FALSE. If it is set to TRUE it means that the VCS supports atomic commands. It is FALSE by default. This attribute is important to trigger the activities group commit feature. See The VCS Activities.
path_style
  The attribute path_style specifies which kind of directory separator is supported by the VCS and can take the values UNIX, DOS, Cygwin or System_Default. The later value is the default value. With this attribute it is possible to control the directory separator to use when specifying files to the VCS. For the Cygwin case the drive is specified as /cygdrive/<drive>.
dir_sep
  Alias for path_style, obsolescent.
commit_directory
  The attribute commit_directory specifies if the VCS supports commit on directories and can take the values TRUE or FALSE. If it is set to TRUE it means that the VCS supports commit on directories this is the case for Subversion for example.
administrative_directory
  The attribute administrative_directory specifies the name of the directory where the external VCS stores the local repository information. For example for Subversion this is `.svn`. This information is used when the project is setup to select automatically the external VCS. Version Control System.
prev_revision
  A string which can be used when querying revisions to indicate the previous revision of a file, for instance “PREV” for subversion.
head_revision
  A string which can be used when querying revisions to indicate the latest revision of a file, for instance “HEAD” for subversion.
require_log
  The attribute require_log specifies if the VCS require a log for the commit/add/delete actions. It can take the values TRUE or FALSE. If it is set to TRUE GPS will ensure that a log is created for each file. If it is set to FALSE GPS will not ask for log, it is expected to be handled by the external VCS.

Note that to support group commit with shared log on GPS both absolute_name and atomic_commands must be true. This is the case for the Subversion VCS for example.

Here is an example, adapted to the use of CVS:

    <vcs name="Custom CVS" absolute_names="FALSE">

       (... description of action associations ...)
       (... description of supported status ...)
       (... description of output parsers ...)

    </vcs>

#### 14.9.2.2. Associating actions to operations

GPS knows about a certain set of predefined ‘operations’ that a VCS can perform. The user can decide to implement some of them - not necessarily all of them - in this section.

The following node is used to associate a predefined operation to an action:

    <OPERATION  action="ACTION_LABEL" label="NAME OF OPERATION" />

Where:

OPERATION
  is the name of the predefined action. The list of predefined actions is described in Implementing VCS actions,
ACTION_LABEL
  is the name of the corresponding gps Action that will be launched when GPS wants to ask the VCS to perform OPERATION,
NAME OF OPERATION
  is the name that will appear in the GPS menus when working on a file under the control of the defined VCS.

#### 14.9.2.3. Defining revision information

Some VCS reports revisions number from which it is possible to deduce the related branches. This is the case in CVS for example where a revision number for a branch uses as prefix the branch point revision number. For such VCS it is possible to specify two regular expressions:

`parent_revision`

  Parse the revision number and report as first match the parent revision:

      <parent_revision regexp="..." />

  For CVS on 1.2.4.5 it must match 1.2.

`branch_root_revision`

  Parse the revision number and report as first match the branch root revision:

      <branch_root_revision regexp="..." />

  For CVS on 1.2.4.5 it must match 1.2.4.

#### 14.9.2.4. Defining status

All VCS have the notion of ‘status’ or ‘state’ to describe the relationship between the local file and the repository. The XML node status is used to describe the status that are known to a custom VCS, and the icons associated to it:

    <status label="STATUS_LABEL" stock="STOCK_LABEL" />

Where:

STATUS_LABEL
  is the name of the status, for example ‘Up to date’ or ‘Needs update’ in the context of CVS.
STOCK_LABEL
  is the stock identifier of the icon associated to this status, that will be used, for example, in the VCS Explorer. See section Adding stock icons for more details on how to define stock icons.

Note that the order in which status are defined in the XML file is important: the first status to be displayed must correspond to the status ‘Up-to-date’ or equivalent.

#### 14.9.2.5. Output parsers

There are cases in which GPS needs to parse the output of the VCS commands: when querying the status, or when ‘annotating’ a file.

The following parsers can be implemented in the vcs node.

`<status_parser>`, `<local_status_parser>` and `<update_parser>`

  These parsers are used by the command VCS.status_parse, to parse a string for the status of files controlled by a VCS.

  They accept the following child nodes:

  `<regexp>` (mandatory)
    Indicates the regular expression to match.
  `<file_index>`
    An index of a parenthesized expression in regexp that contains the name of a file.
  `<status_index>`
    An index of a parenthesized expression in regexp that contains the file status. This status is passed through the regular expressions defined in the status_matcher nodes, see below.
  `<local_revision_index>`
    An index of a parenthesized expression in regexp that contains the name of the local revision (the version of the file that was checked out).
  `<repository_revision_index>`
    An index of a parenthesized expression in regexp that contains the name of the repository revision (the latest version of the file in the VCS).
  `<status_matcher>`
    A regular expression which, when matching an expressions, identifies the status passed in the node attribute label.
`<annotations_parser>`

  This parser is used by the command VCS.annotations_parse, to parse a string for annotations in a file controlled by a VCS.

  It accepts the following child nodes:

  `<regexp>` (mandatory)
    Indicates the regular expression to match.
  `<repository_revision_index>` (mandatory)
    An index of a parenthesized expression in regexp that contains the repository revision of the line.
  `<author_index>`
    An index of a parenthesized expression in regexp that contains the author of the line.
  `<date_index>`
    An index of a parenthesized expression in regexp that contains the date of the line.
  `<file_index>`
    An index of a parenthesized expression in regexp that indicates the part of the line that belongs to the file.
  `<tooltip_pattern>`
    A template pattern that will be used to format the tooltip information. It can contain text and reference parenthesized expressions in regexp using \`n` (where n represents the nth expression in regexp).
`<log_parser>`

  This parser is used by the command VCS.log_parse, to parse a string for revision histories in a file controlled by a VCS.

  It accepts the following child nodes:

  `<regexp>` (mandatory)
    Indicates the regular expression to match.
  `<repository_revision_index>` (mandatory)
    An index of a parenthesized expression in regexp that contains the repository revision of the log.
  `<author_index>`
    An index of a parenthesized expression in regexp that contains the author of the log.
  `<date_index>`
    An index of a parenthesized expression in regexp that contains the date of the log.
  `<log_index>`
    An index of a parenthesized expression in regexp that contains the actual text of the log.
`<revision_parser>`

  This parser is used by the command VCS.revision_parse, to parse a string for revision tags and branches in a file controlled by a VCS.

  It accepts the following child nodes:

  `<regexp>` (mandatory)
    Indicates the regular expression to match.
  `<sym_index>` (mandatory)
    An index of a parenthesized expression in regexp that contains the tags or branches symbolic name of the revision.
  `<repository_revision_index>` (mandatory)
    An index of a parenthesized expression in regexp that contains the repository revision number of the revision.

### 14.9.3. Implementing VCS actions

A number of ‘standard’ VCS operations are known to GPS. Each of these operations can be implemented, using Actions. See Defining Actions) for a complete description of how to implement actions.

Here is a list of all the defined VCS operations, and their parameters:

status_files

> - $1 = whether the log files should be cleared when obtaining up-to-date status
> - $2- = the list of files to query status for.

> Query the status for a list of files. This should perform a complete VCS query and return results as complete as possible.

status_dir

> - $1 = the directory.

> Same as above, but works on all the files in one directory.

status_dir_recursive

> - $1 = the directory.

> Same as above, but works on all the files in one directory and all subdirectories, recursively.

local_status_files

> - $* = list of files

> Query the local status for specified files. This query should be as fast as possible, not connecting to any remote VCS. The results need not be complete, but it is not useful to implement this command if the output does not contain at least the working revision.

open

> - $* = list of files

> Open files or directories for editing. This command should be implemented on any VCS that require an explicit check-out/open/edit action before being able to edit a file.

update

> - $* = list of files

> Bring the specified files in sync with the latest repository revision.

resolved

> - $* = list of files

> Mark files’ merge conflics as resolved. Some version control systems (like Subversion) will block any commit until this action is called.

commit

> - $1 = log file
> - $2- = list of files

> Commit/submit/check-in files or directories with provided log. The log is passed in a file.

commit_dir

> - $1 = log
> - $2 = directory

> Commit/submit one directory with provided log. The log is passed in a file.

history_text

> - $1 = file

> Query the entire changelog history for the specified file. The result is expected to be placed into an editor as plain text.

history

> - $1 = file

> Query the entire changelog history for the specified file. The result is expected to be placed into a Revision View.

history_revision

> - $1 = revision
> - $2 = file

> Query the history for corresponding revision of the specified file.

annotate

> - $1 = file

> Query the annotations for a file.

add

> - $1 = log
> - $2- = list of files or dirs

> Add files/dirs to the repository, with the provided revision log. The added files/dirs are commited.

add_no_commit

> - $1 = log
> - $2- = list of files or dirs

> Add files/dirs to the repository, with the provided revision log. The added files/dirs are not commited.

remove

> - $1 = log
> - $2 = file or dir

> Remove file/dir from the repository, with the provided revision log.

remove_no_commit

> - $1 = log
> - $2 = file or dir

> Remove file/dir from the repository, with the provided revision log. The removed files/dirs are not commited.

revert

> - $* = files

> Revert the local file to repository revision, cancelling all local changes, and close the file for editing if it was open.

diff_patch

> - $1 = file

> Create a textual diff for the given file. This command is used to build the activity patch file.

diff_head

> - $1 = file

> Display a visual comparison between the local file and the latest repository revision. The diff command must report a normal diff as opposed to context or unified ones.

diff_base_head

> - $1 = file

> Display a visual comparison between the revision from which the file has been checked-out and the latest revision. The diff command must report a normal diff as opposed to context or unified ones.

diff_working

> - $1 = file

> Display a visual comparison between the local file and the revision from which it was obtained. The diff command must report a normal diff as opposed to context or unified ones.

diff

> - $1 = rev
> - $2 = file

> Display a visual comparison between the local file and the specified revision. The diff command must report a normal diff as opposed to context or unified ones.

diff2

> - $1 = revision 1
> - $2 = revision 2
> - $3 = file

> Display a visual comparison between the two specified revisions of the file. The diff command must report a normal diff as opposed to context or unified ones.

### 14.9.4. Implementing VCS menus

GPS defines a standard set of Actions to interact with Version Control Systems. All these actions can be viewed, for instance, in the “VCS” of the Key Shortcuts dialog (see The Key Manager Dialog).

A Python facility exists in plugin vcs.py to associate menu items to VCS actions. This facility defines in one place the VCS menus that are to be displayed in the global VCS menu, in the contextual menus on contexts that contain files, and on the menus in the VCS explorer.

To use this facility, you must first define a list of associations in Python, and then register this list through a call to vcs.register_vcs_actions.

This function takes as parameter:

the name of the version control system
  as defined in the name attribute of the vcs node in the XML definition.
a list of dictionaries
  of the form ACTION : <name of the vcs action>, LABEL: <menu label>. The predefined SEPARATOR dictionary can be used to indicate a separator which will be displayed in the contextual menus on file and on the VCS Explorer.

If you have defined a custom VCS in a previous version of GPS, you will need to define your menus through this facility. The easiest is to simply copy one of the existing plugins (for instance subversion.py or clearcase.py) and simply change the first parameter in the call to register_vcs_actions.

## 14.10. The Server Mode

In order to give access to the GPS capabilities from external processes (e.g. Emacs), GPS can be launched in server mode.

The two relevant command line switches are –server and –hide.

–server will open a socket on the given port, allowing multiple clients to connect to a running GPS, and sending GPS shell or python commands.

–hide tells GPS not to display its main window when starting. note that under unix systems, you still need to have access to the current screen (as determined by the DISPLAY environment variable) in this mode.

Using the two switches together provides a way to launch GPS as a background process with no initial user interface.

Clients connecting through a standard socket have access to a simple shell using GPS>> as the separating prompt between each command. This is needed in order to determine when the output (result) of a command is terminated.

All the GPS shell commands (as defined in The GPS Shell) are available from this shell. In addition, the python interpreter, if enabled, is also available through the use of the python prefix before a python command.

For example, sending pwd through the socket will send the pwd command through the GPS shell and display the result on the socket; similarly, sending python GPS.pwd() will send the GPS.help() command through the python interpreter (see The Python Interpreter for more details).

The socket shell provides also additional commands:

- logout This command will inform the GPS server that the connection should now be closed.
- id <string> This command will register the current session with a given string. This string can then be used within GPS itself (for example via a .xml or python plug-in) to display extra information to the client via the socket, using the command GPS.Socket().send.

For example, let suppose that we start gps with the –server=1234 command: this will bring up GPS as usual.

Now, on a separate terminal, create a simple client by typing the following:

    telnet localhost 1234
    Trying 127.0.0.1...
    Connected to localhost.
    Escape character is '^]'.
    GPS>> id test-1
    id set to 'test-1'
    GPS>> pwd
    c:\\working-dir\\
    GPS>>

Then in the GPS Python Console:

    >>> GPS.Socket ("test-1").send ("hello, it's time to logout\\n");

At this point, the following is received on the client (telnet) side:

    GPS>> hello, it's time to logout

We can then close the client:

    logout
    Connection closed by foreign host.

## 14.11. Adding project templates

The Project template wizard lists a selection of templates. The default set is found automatically by GPS in the share/gps/templates directory of your GPS installation.

It is possible to register new directories in which GPS will look for templates, by using the Shell/Python command GPS.ProjectTemplate.add_templates_dir.

To create a new project template, first create a subdirectory in the share/gps/templates/ directory, or in one of the directories which has been registered through GPS.ProjectTemplate.add_templates_dir. Then, in this directory, create one template description file.

A template description file is a text file with the .gpt extension, with the following syntax:

    Name: <name>
    Category: <category>
    Project: <project file>
    <optional_hook_line>

    <variable_1>: <variable_1_default_value>: <variable_1_description>
    <variable_2>: <variable_2_default_value>: <variable_3_description>
    <etc>

    [Description]
    <the description>

Where the following should be defined:

- <name> The name of the template as it will appear in the template tree in the project template wizard.
- <category> The category in which the template will be inserted in the template tree. There can be multiple levels of categories, separated with /.
- <variable_1> A name which will be substituted in the template files when deploying the template, see below.
- <variable_1_default_value> The default value for variable 1, which will appear in the project template wizard.
- <variable_1_description> The description of variable 1.
- <optional_hook_line> An optional line of the form post_hook: <python_file> where <python_file> is the name of a Python file present in the same directory as the template description file. This Python file will be run by GPS once, right after the project template is deployed
- <description> A short paragraph describing the project template. This paragraph will be displayed in the project template wizard when the template is selected in the tree.

When deploying templates, GPS will copy in the destination directory chosen by the use all files and directories present in the directory that contains the template description file, except the Python file indicated as post_hook, and the template description file itself.

As it deploys templates, GPS will replace strings of the form @code{@_<variable_name>_} with the value of the variable. If <variable_name> is all lower case, the substitution will be transformed to lower-case. If <variable_name> is in Mixed_Case, the substitution will be transformed into Mixed_Case as well. If it is in upper case, then the substitution will contain the original value specified by the user.

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