Author: Csaba Nemethi
Keywords: scrollarea, scrollsync, mouse wheel event, binding, event handling, scrolling, scrollable widget container, focus

# Scrollutil Programmer's Guide

## For Scrollutil Version 1.5

### by

## Csaba Nemethi

## Contents

#### Overview

- What Is Scrollutil?
- How to Get It?
- How to Install It?
- How to Use It?

#### Examples

- The Helper Script `styleUtil.tcl`
- A Scrolled tablelist Widget
- A Scrolled text Widget
- Synchronizing Two listbox Widgets
- Synchronizing Three tablelist Widgets
- A Script Using a scrollutil::scrollableframe Widget
- A Script Using a BWidget ScrollableFrame Widget
- A Script Using an iwidgets::scrolledframe Widget
- A Script Using Two scrollutil::scrollableframe Widgets
- A Script Using Two BWidget ScrollableFrame Widgets
- A Script Using Two iwidgets::scrolledframe Widgets

Start page

## Overview

### What Is Scrollutil?

Scrollutil is a library package for Tcl/Tk versions 8.0 or higher, written in pure Tcl/Tk code. It contains:

- the implementation of the scrollarea, scrollsync, and scrollableframe mega-widgets, including a general utility module for mega-widgets;
- the command `scrollutil::addMouseWheelSupport`, which creates mouse wheel event bindings for a given binding tag. This command requires Tcl/Tk 8.4 or later;
- commands for user-friendly mouse wheel event handling in scrollable widget containers like scrollutil::scrollableframe, BWidget ScrollableFrame, and iwidgets::scrolledframe. These commands require Tcl/Tk versions 8.4 or higher on X11 and Mac OS X and Tk 8.6b2 or later on Windows;
- demo scripts illustrating the use of the Scrollutil package in connection with various scrollable widgets and the above-mentioned scrollable widget containers;
- this tutorial;
- reference pages in HTML format.

The scrollutil::scrollarea mega-widget greatly simplifies the creation of arbitrary scrolled widgets. It consists of a scrollable widget and two scrollbars connected with that widget. The display mode of each scrollbar can be `static`, `dynamic`, or `none`. This scrolled window implementation also supports the widgets that are scrollable in one direction only (e.g., entry and ttk::entry) and respects the header component and title columns of tablelist widgets (this is freely configurable).

The scrollutil::scrollarea widget is similar to BWidget ScrolledWindow and its snit-based equivalent widget::scrolledwindow, contributed by Jeffrey Hobbs and contained in tklib. The snit-based scrodget package by Aldo Buratti and its TclOO-based equivalent scrolledwidget contributed by Johann Oberdorfer are further scrolled window implementations. However, full tablelist support is only provided by the scrollarea widget, which is free from external dependencies like BWidget, snit, or (for Tcl 8.5) TclOO. It is also free from the shimmering problem in connection with text widgets, which the above-mentioned scrolled window implementations either share with the autoscroll package (contained in tklib) or circumvent in a suboptimal way.

The scrollutil::scrollsync mega-widget is designed for scrolling several widgets simultaneously. Whenever the horizontal/vertical position of the view in the window of one of its widgets changes, the view in the windows of all the other widgets is automatically adjusted accordingly, thus making sure that the view's position in these windows is kept in sync. This mega-widget is horizontally and vertically scrollable, hence it can be embedded into a scrollutil::scrollarea widget via the latter's `setwidget` subcommand.

The scrollutil::scrollableframe mega-widget is a scrollable widget container. It contains a content frame, whose dimensions are typically larger than those of the widget itself. Arbitrary regions of this frame can be brought into view by scrolling, and the widget also provides a command for making individual widgets contained in the content frame visible in the scrollableframe window.

The scrollutil::scrollableframe widget is similar to BWidget ScrollableFrame and iwidgets::scrolledframe. However, unlike these widgets, which use a canvas for scrolling the content frame, it adjusts the view with the aid of the `place` geometry manager, just like the `scrolledframe::scrolledframe` command of the Scrolledframe package by Maurice Bredelet (ulis) and its optimized and enhanced version contributed by Keith Nash. For details on these commands see the wiki page

Scrollutil's canvas-free approach is more lightweight and integrates better in applications that use tile widgets.

From the point of view of the commands related to mouse wheel event handling provided by the Scrollutil package, the scrollability of a widget or widget container window means that the associated Tcl command supports the `xview scroll number units` and `yview scroll number units` subcommands. The reason for requiring at least Tk version 8.6b2 on Windows for the commands related to scrollable widget containers is that in earlier Tk versions on this platform the mouse wheel events were sent to the widget having the focus rather than to the one under the pointer.

To make use of the user-friendly mouse wheel event handling via the Scrollutil package, follow the steps below:

- Create mouse wheel event bindings for the binding tag `"all"` or for the toplevel widgets (including `"."`) having scrollable widget containers, by invoking the `scrollutil::createWheelEventBindings` command. In addition, register your scrollable widget containers for scrolling via these bindings with the aid of the `scrollutil::enableScrollingByWheel` command. The above-mentioned bindings handle the mouse wheel events by scrolling the (innermost) registered scrollable widget container that is an ascendant of the widget under the pointer and is contained in the latter's toplevel.
- Invoke the `scrollutil::adaptWheelEventHandling` command for those widgets contained in registered scrollable widget containers that have mouse wheel event (class) bindings. This step eliminates the annoying and often dangerous double-handling effect, by modifying the mouse wheel event handling as follows: If the focus is on the widget under the pointer then the mouse wheel events will be handled by the (class bindings of the) widget only, otherwise by the bindings created with the `scrollutil::createWheelEventBindings` command. Without this step the mouse wheel events would scroll both the listbox, text, ttk::treeview, or tablelist widget under the pointer and the widget container to whose descendants the latter belongs, or they would select the next/previous value in the ttk::combobox or ttk::spinbox under the pointer in addition to scrolling the widget container.
- For some widgets it can be desirable to make the focus check within this modified event handling less restrictive. For example, if the widget under the pointer is an entry component of a mentry of type `"Date"`, `"Time"`, `"DateTime"`, `"IPAddr"`, or `"IPv6Addr"` and the focus is on any of its siblings, then the mouse wheel events sent to this entry should be handled by the entry widget itself rather than scrolling the widget container that is an ascendant of the mentry. The `scrollutil::setFocusCheckWindow` command covers exactly cases like this.

The mouse wheel event handling with the aid of the Scrollutil package was also tested to work with the `scrolledframe::scrolledframe` command of the Scrolledframe package by Maurice Bredelet (ulis) and its optimized and enhanced version contributed by Keith Nash, as well as with the `sframe` command implemented by Paul Walton. For details on these commands (which provide further implementations of scrollable widget containers) see the above-mentioned wiki page.

### How to Get It?

Scrollutil is available for free download from the Web page

The distribution file is `scrollutil1.5.tar.gz` for UNIX and `scrollutil1_5.zip` for Windows. These files contain the same information, except for the additional carriage return character preceding the linefeed at the end of each line in the text files for Windows.

Scrollutil is also included in tklib, which has the address

### How to Install It?

Install the package as a subdirectory of one of the directories given by the `auto_path` variable. For example, you can install it as a directory at the same level as the Tcl and Tk script libraries. The locations of these library directories are given by the `tcl_library` and `tk_library` variables, respectively.

To install Scrollutil on UNIX, `cd` to the desired directory and unpack the distribution file `scrollutil1.5.tar.gz`:

>     gunzip -c scrollutil1.5.tar.gz | tar -xf -

On most UNIX systems this can be replaced with

>     tar -zxf scrollutil1.5.tar.gz

Both commands will create a directory named `scrollutil1.5`, with the subdirectories `demos`, `doc`, and `scripts`.

On Windows, use WinZip or some other program capable of unpacking the distribution file `scrollutil1_5.zip` into the directory `scrollutil1.5`, with the subdirectories `demos`, `doc`, and `scripts`.

Notice that in tklib the Scrollutil `demos` directory is replaced with the subdirectory `scrollutil` of the `examples` directory. Please take this into account when reading the examples below.

### How to Use It?

The Scrollutil distribution provides two packages, called Scrollutil and Scrollutil_tile. The main difference between the two is that Scrollutil_tile enables the tile-based, theme-specific appearance of scrollarea, scrollsync, and scrollableframe widgets; this package requires Tcl/Tk 8.4 or higher and tile 0.6 or higher. It is not possible to use both packages in one and the same application, because both are implemented in the same `scrollutil` namespace and provide identical commands.

To be able to access the commands and variables defined in the package Scrollutil, your scripts must contain one of the lines

>     package require scrollutil ?version?
>     package require Scrollutil ?version?

You can use either one of the two statements above because the file `scrollutil.tcl` contains both lines

>     package provide scrollutil ...
>     package provide Scrollutil ...

Likewise, to be able to access the commands and variables defined in the package Scrollutil_tile, your scripts must contain one of the lines

>     package require scrollutil_tile ?version?
>     package require Scrollutil_tile ?version?

Again, you can use either one of the two statements above because the file `scrollutil_tile.tcl` contains both lines

>     package provide scrollutil_tile ...
>     package provide Scrollutil_tile ...

You are free to remove one of these two lines from `scrollutil.tcl` and `scrollutil_tile.tcl`, respectively, if you want to prevent the corresponding packages from making themselves known under two different names each. Of course, by doing so you restrict the argument of `package require` to a single name.

Since the packages Scrollutil and Scrollutil_tile are implemented in the `scrollutil` namespace, you must either invoke the

>     namespace import scrollutil::pattern ?scrollutil::pattern ...?

command to import the procedures you need, or use qualified names like `scrollutil::scrollarea`. In the examples below we have chosen the latter approach.

To access Scrollutil variables, you must use qualified names. There are only three Scrollutil variables that are designed to be accessed outside the namespace `scrollutil`:

- The variable `scrollutil::version` holds the current version number of the Scrollutil package.
- The variable `scrollutil::library` holds the location of the Scrollutil installation directory.
- The read-only variable `scrollutil::usingTile` has the value `0` in the package Scrollutil and the value `1` in Scrollutil_tile.

The Scrollutil_tile package checks whether the required Tk and tile versions are present, by executing the commands

>     package require Tk 8.4
>     if {$::tk_version < 8.5 || [regexp {^8\.5a[1-5]$} $::tk_patchLevel]} {
>         package require tile 0.6
>     }

The second command above reflects the fact that, beginning with Tk 8.5a6, tile is integrated into the Tk core and therefore it should only be loaded explicitly when using an earlier Tk version.

Contents Start page

## Examples

### The Helper Script `styleUtil.tcl`

All the examples in the `demos` directory use tile (ttk) widgets and contain the line

>     source styleUtil.tcl

The script `styleUtil.tcl` patches a few ttk widget styles and defines the style `Small.Toolbutton`. In addition, on X11 it sets the theme to a slightly patched variant of the `clam` theme (having smaller ttk::button widgets as well as ttk::treeview and tablelist headers).

The patch for the style `TCombobox` makes sure that the (readonly) ttk::combobox widgets of the themes `alt`, `clam`, and `default` will show whether they have the focus. This basic requirement, which makes the keyboard navigation more user-friendly, is already fulfilled by the themes `vista`, `xpnative`, and `aqua`.

The ttk::button widgets of the style `Small.Toolbutton` created by the procedure `createToolbutton`, implemented in this helper script, will appear raised when they have the focus. Again, this makes the keyboard navigation more user-friendly.

### A Scrolled tablelist Widget

This example shows how you can greatly simplify the creation of a scrolled tablelist by using a scrollarea widget.

The file `ScrolledTablelist1.tcl` in the `demos` directory creates a horizontally and vertically scrolled tablelist widget having two header rows and one title column, and manages the two scrollbars in such a way that the vertical scrollbar appears below the tablelist's header and the horizontal one starts to the right of the widget's title column area:

The script achieves these requirements using traditional scrollbar management, which is shown below in red color:

>     package require Tk 8.5
>     package require tablelist_tile 6.3
>     source styleUtil.tcl

>     wm title . "Scrolled Tablelist"

>     #
>     # Create the tablelist and the scrollbars as children
>     # of a frame having -borderwidth 1 and -relief sunken
>     #
>     set f   [ttk::frame .f]
>     set frm [ttk::frame $f.frm -borderwidth 1 -relief sunken]
>     set tbl $frm.tbl
>     set vsb $frm.vsb
>     set hsb $frm.hsb
>     tablelist::tablelist $tbl ... -borderwidth 0 \
>         -xscrollcommand [list $hsb set] -yscrollcommand [list $vsb set]
>     . . .
>     ttk::scrollbar $vsb -orient vertical   -command [list $tbl yview]
>     ttk::scrollbar $hsb -orient horizontal -command [list $tbl xview]

>     . . .

>     #
>     # Manage the widgets within the frame
>     #
>     grid $tbl -row 0 -rowspan 2 -column 0 -columnspan 2 -sticky news
>     if {[tk windowingsystem] eq "win32"} {
>         grid $vsb -row 0 -rowspan 2 -column 2 -sticky ns
>     } else {
>         grid [$tbl cornerpath] -row 0 -column 2 -sticky ew
>         grid $vsb              -row 1 -column 2 -sticky ns
>     }
>     grid [$tbl cornerpath -sw] -row 2 -column 0 -sticky ns
>     grid $hsb                  -row 2 -column 1 -sticky ew
>     grid rowconfigure    $frm 1 -weight 1
>     grid columnconfigure $frm 1 -weight 1

>     #
>     # Manage the frame
>     #
>     pack $frm -expand yes -fill both -padx 10 -pady 10
>     pack $f   -expand yes -fill both

The file `ScrolledTablelist2.tcl` in the `demos` directory replaces the rather technical code above with just a few lines (shown below in red color), by embedding the tablelist into a scrollarea widget. It requires Tablelist version 6.5, which is needed so the `-respectheader` and `-respecttitlecolumns` scrollarea options can work as expected (for earlier Tablelist versions these options are silently ignored). As a further benefit, the scrollbars created with this method will have the default display mode `dynamic`.

>     package require Tk 8.5
>     package require tablelist_tile 6.5
>     package require scrollutil_tile
>     source styleUtil.tcl

>     wm title . "Scrolled Tablelist"

>     #
>     # Create the tablelist within a scrollarea
>     #
>     set f  [ttk::frame .f]
>     set sa [scrollutil::scrollarea $f.sa]
>     set tbl $sa.tbl
>     tablelist::tablelist $tbl ...
>     . . .
>     $sa setwidget $tbl

>     . . .

>     #
>     # Manage the scrollarea
>     #
>     pack $sa -expand yes -fill both -padx 10 -pady 10
>     pack $f  -expand yes -fill both

### A Scrolled text Widget

The file `ScrolledText.tcl` in the `demos` directory shows how the scrollarea widget circumvents the potential shimmering effect in connection with text widgets.

Here is the relevant code, in which the lines related to the scrollarea widget are shown in red color:

>     package require scrollutil_tile
>     source styleUtil.tcl

>     wm title . "Scrolled Text"

>     #
>     # Create a text widget within a scrollarea
>     #
>     set f  [ttk::frame .f]
>     set sa [scrollutil::scrollarea $f.sa -lockinterval 10]
>     set txt [text $sa.txt -font TkFixedFont -width 49 -height 12 \
>              -spacing1 2 -spacing3 2 -wrap none]
>     $sa setwidget $txt

>     #
>     # Populate the text widget and set the background color of line #25 to red
>     #
>     for {set i 1} {$i <= 30} {incr i} {
>         set j [expr {2*$i}]
>         $txt insert end [string repeat x $j]\n
>     }
>     $txt delete 30.end
>     $txt tag configure bgRed -background red
>     $txt tag add bgRed 25.0 25.end

>     . . .

>     #
>     # Manage the scrollarea
>     #
>     pack $sa -expand yes -fill both -padx 10 -pady 10
>     pack $f  -expand yes -fill both

>     #
>     # Adjust the vertical view in the text window
>     # so that line #25 becomes the bottom line
>     #
>     tkwait visibility $txt
>     after 100 [list $txt yview 14.0]

The script creates a text widget `$txt` embedded into a scrollarea, populates it with 30 lines, and adjusts the vertical view in the text window so that line #25 becomes the bottom line. This line has 50 characters, hence it doesn't fit completely into the window, whose width is 49 characters. Consequently, the command `$txt xview` will return the list `{0.0 0.98}`, hence the scrollarea's horizontal scrollbar will be mapped and will obscure most part of the bottom line. Since this line has `red` background, it is easy to see how much of it sticks out above the upper edge of the scrollbar.

Let's analyze what happens if the text widget's height is decreased by dragging the main window's upper or lower edge, just until the red pixels get obscured by the horizontal scrollbar. After performing this action, line #25 is completely out of view and the new bottom line is line #24, which has 48 characters, hence the command `$txt xview` will return `{0.0 1.0}`. Normally, this would cause the horizontal scrollbar to be unmapped. However, that would make line #25 to the bottom line, thus causing the horizontal scrollbar to be mapped again. This time the scrollbar would completely obscure this line, which would result in line #24 to become the bottom line, which would cause the scrollbar to be unmapped again, and so on. In other words, the horizontal scrollbar would get mapped and unmapped in an endless loop, giving rise to an annoying flickering effect. The built-in locking mechanism of the scrollarea widget guards against such potential endless loops. To make sure that the locking will work as expected, we have set the `-lockinterval` scrollarea option to `10` (recall that the default value is `1`).

### Synchronizing Two listbox Widgets

The file `SyncListboxes.tcl` in the `demos` directory creates two listboxes within a scrollsync widget, which in turn is embedded into a scrollarea.

Here is the relevant code, in which the lines related to the scrollarea and scrollsync widgets are shown in red color:

>     package require scrollutil_tile
>     source styleUtil.tcl

>     wm title . "European Countries"

>     . . .

>     set f  [ttk::frame .f]

>     . . .

>     #
>     # Create a scrollsync widget within a scrollarea
>     #
>     set sa [scrollutil::scrollarea $f.sa]
>     set ss [scrollutil::scrollsync $sa.ss]
>     $sa setwidget $ss

>     #
>     # Populate the scrollsync widget with two listboxes
>     #

>     . . .

>     set lb1 [listbox $ss.lb1 -activestyle none -highlightthickness 0 -width 16]
>     set lb2 [listbox $ss.lb2 -activestyle none -highlightthickness 0 -width 16]
>     $ss setwidgets [list $lb1 $lb2]

>     . . .

>     grid $lb1 $lb2 -sticky news -padx {0 2}
>     grid rowconfigure    $ss 0 -weight 1
>     grid columnconfigure $ss 0 -weight 1
>     grid columnconfigure $ss 1 -weight 1

>     . . .

>     pack $sa -side top -expand yes -fill both -padx 10 -pady {2 10}
>     pack $f  -expand yes -fill both

>     . . .

### Synchronizing Three tablelist Widgets

The file `SyncTablelists.tcl` in the `demos` directory creates three tablelists within a scrollsync widget, which in turn is embedded into a scrollarea.

The relevant code is similar to the one shown in the previous example:

>     package require tablelist_tile
>     package require scrollutil_tile
>     source styleUtil.tcl

>     wm title . "Synchronized Tablelists"

>     . . .

>     set f  [ttk::frame .f]

>     . . .

>     #
>     # Create a scrollsync widget within a scrollarea
>     #
>     set sa [scrollutil::scrollarea $f.sa]
>     set ss [scrollutil::scrollsync $sa.ss]
>     $sa setwidget $ss

>     #
>     # Populate the scrollsync widget with three tablelists
>     #

>     option add *Tablelist.stripeBackground  #f0f0f0

>     for {set n 1; set colWidth 40} {$n <= 3} {incr n; incr colWidth 20} {
>         set tbl [tablelist::tablelist $ss.tbl$n \
>                  -columns [list 0 "Column 0" left  $colWidth "Column 1" left]]
>         set tbl$n $tbl

>         for {set i 0} {$i < 40} {incr i} {
>             $tbl insert end [list "cell $i,0" "cell $i,1"]
>         }
>     }
>     $ss setwidgets [list $tbl1 $tbl2 $tbl3]

>     grid $tbl1 $tbl2 $tbl3 -sticky news -padx {0 2}
>     grid rowconfigure    $ss 0 -weight 1
>     grid columnconfigure $ss 0 -weight 1
>     grid columnconfigure $ss 1 -weight 1
>     grid columnconfigure $ss 2 -weight 1

>     . . .

>     pack $sa -side top -expand yes -fill both -padx 10 -pady {2 10}
>     pack $f  -expand yes -fill both

>     . . .

Notice that column #1 of the three tablelist widgets is 40, 60, and 80 characters wide, respectively. For this reason, when scrolling horizontally to the right, the left table's view will reach its horizontal end position first, then that of the midde table, and as last one the view of the right table.

### A Script Using a scrollutil::scrollableframe Widget

The file `SuScrollableFrmDemo1.tcl` in the `demos` directory creates a scrollutil::scrollableframe widget embedded into a scrollarea, creates mouse wheel event bindings for the binding tag `"all"` with the aid of the `scrollutil::createWheelEventBindings` command, and invokes the `scrollutil::enableScrollingByWheel` command for this scrollableframe, thus registering the latter for scrolling by these bindings. After that it populates the content frame of the scrollableframe with ttk::label widgets displaying the names of the European countries, ttk::combobox widgets for selecting the corresponding capital cities, and ttk::button widgets of the style `Small.Toolbutton` (created by using the procedure `createToolbutton`, implemented in the file `styleUtil.tcl`) for the less patient users, displaying the text "Resolve".

Here is the relevant code:

>     package require scrollutil_tile
>     source styleUtil.tcl

>     wm title . "European Capitals Quiz"

>     #
>     # Create a scrollableframe within a scrollarea
>     #
>     set f  [ttk::frame .f]
>     set sa [scrollutil::scrollarea $f.sa]
>     set sf [scrollutil::scrollableframe $sa.sf]
>     $sa setwidget $sf

>     #
>     # Create mouse wheel event bindings for the binding tag "all" and
>     # register the scrollableframe for scrolling by these bindings
>     #
>     scrollutil::createWheelEventBindings all
>     scrollutil::enableScrollingByWheel $sf

>     #
>     # Get the content frame and populate it
>     #

>     set cf [$sf contentframe]

>     set countryList {
>         Albania Andorra Austria Belarus Belgium "Bosnia and Herzegovina" Bulgaria
>         . . .
>     }
>     set capitalList {
>         Tirana "Andorra la Vella" Vienna Minsk Brussels Sarajevo Sofia
>         . . .
>     }

>     . . .

>     set capitalList [lsort $capitalList]

>     . . .

>     set row 0
>     foreach country $countryList {
>         . . .

>         set w [ttk::combobox $cf.cb$row -state readonly -width 14 \
>                -values $capitalList]
>         . . .

>         #
>         # Make the keyboard navigation more user-friendly
>         #
>         bind $w <<TraverseIn>> [list $sf see %W]

>         #
>         # Adapt the handling of the mouse wheel events for the ttk::combobox widget
>         #
>         scrollutil::adaptWheelEventHandling $w

>         . . .

>         incr row
>     }

>     . . .

We make the keyboard navigation more user-friendly with the aid of the `see` subcommand of the scrollableframe widget when handling the `<<TraverseIn>>` virtual event for the ttk::combobox and (not shown above) ttk::button widgets. In addition, we invoke the `scrollutil::adaptWheelEventHandling` command for every ttk::combobox widget, which is needed for a user-friendly event handling, being that this widget has built-in bindings for the mouse wheel events. Due to this command, the mouse wheel events over one of the ttk::combobox widgets will only select the next/previous capital city if the widget has the focus, otherwise they will scroll the scrollableframe.

With this script you can also test the scanning in the scrollableframe: If you press mouse button 1 over a free space of the scrollableframe window then the cursor will take on the shape of a pointing hand, and by draggging the mouse, the content frame will drag at high speed through the window, in the direction the mouse moves.

### A Script Using a BWidget ScrollableFrame Widget

The file `BwScrollableFrmDemo1.tcl` in the `demos` directory creates a BWidget ScrollableFrame embedded into a scrollarea widget, creates mouse wheel event bindings for the binding tag `"all"` with the aid of the `scrollutil::createWheelEventBindings` command, and invokes the `scrollutil::enableScrollingByWheel` command for this ScrollableFrame, thus registering the latter for scrolling by these bindings. After that it populates the content frame of the ScrollableFrame with the same widgets as `SuScrollableFrmDemo1.tcl` in the previous example.

Here is the relevant code:

>     package require BWidget
>     Widget::theme yes
>     package require scrollutil_tile
>     source styleUtil.tcl

>     wm title . "European Capitals Quiz"

>     #
>     # Create a ScrollableFrame within a scrollarea
>     #
>     set f  [ttk::frame .f]
>     set sa [scrollutil::scrollarea $f.sa]
>     set sf [ScrollableFrame $sa.sf]
>     $sa setwidget $sf

>     . . .

>     #
>     # Create mouse wheel event bindings for the binding tag "all" and
>     # register the ScrollableFrame for scrolling by these bindings
>     #
>     scrollutil::createWheelEventBindings all
>     scrollutil::enableScrollingByWheel $sf

>     #
>     # Get the content frame and populate it
>     #

>     set cf [$sf getframe]

>     set countryList {
>         Albania Andorra Austria Belarus Belgium "Bosnia and Herzegovina" Bulgaria
>         . . .
>     }
>     set capitalList {
>         Tirana "Andorra la Vella" Vienna Minsk Brussels Sarajevo Sofia
>         . . .
>     }

>     . . .

>     set capitalList [lsort $capitalList]

>     . . .

>     set row 0
>     foreach country $countryList {
>         . . .

>         set w [ttk::combobox $cf.cb$row -state readonly -width 14 \
>                -values $capitalList]
>         . . .

>         #
>         # Make the keyboard navigation more user-friendly
>         #
>         bind $w <<TraverseIn>> [list $sf see %W]

>         #
>         # Adapt the handling of the mouse wheel events for the ttk::combobox widget
>         #
>         scrollutil::adaptWheelEventHandling $w

>         . . .

>         incr row
>     }

>     . . .

### A Script Using an iwidgets::scrolledframe Widget

The file `ScrolledFrmDemo1.tcl` in the `demos` directory creates an iwidgets::scrolledframe widget, creates mouse wheel event bindings for the binding tag `"all"` with the aid of the `scrollutil::createWheelEventBindings` command, and invokes the `scrollutil::enableScrollingByWheel` command for this scrolledframe, thus registering the latter for scrolling by these bindings. After that it populates the content frame of the scrolledframe with the same widgets as `SuScrollableFrmDemo1.tcl` and `BwScrollableFrmDemo1.tcl` in the two previous examples.

Here is the relevant code:

>     if {[catch {package require iwidgets} result1] != 0 &&
>         [catch {package require Iwidgets} result2] != 0} {
>         error "$result1; $result2"
>     }
>     source scrolledwidgetPatch.itk                  ;# adds ttk::scrollbar widgets
>     package require scrollutil_tile
>     source styleUtil.tcl

>     wm title . "European Capitals Quiz"

>     . . .

>     #
>     # Create a scrolledframe
>     #
>     set f  [ttk::frame .f]
>     set sf [iwidgets::scrolledframe $f.sf -borderwidth 1 -relief sunken \
>             -scrollmargin 0]
>     . . .

>     #
>     # Create mouse wheel event bindings for the binding tag "all"
>     # and register the scrolledframe for scrolling by these bindings
>     #
>     scrollutil::createWheelEventBindings all
>     scrollutil::enableScrollingByWheel $sf

>     #
>     # Get the content frame and populate it
>     #

>     set cf [$sf childsite]
>     . . .

>     <exactly as in the two previous examples, except the stuff related to keyboard navigation>

>     . . .

The code related to keyboard navigation is not present in this example, because the iwidgets::scrolledframe widget doesn't provide a `see` subcommand.

### A Script Using Two scrollutil::scrollableframe Widgets

The script `SuScrollableFrmDemo2.tcl` in the `demos` directory creates a scrollutil::scrollableframe widget embedded into a scrollarea and then `source`s the script `SuScrollableFrmContent.tcl`, which populates the content frame of the scrollableframe with the following widgets:

- a series of ttk::label widgets;
- a scrolled text widget `$txt` within a scrollarea;
- a scrolled listbox widget `$lb` within a scrollarea;
- a ttk::combobox widget `$cb`;
- a ttk::spinbox widget `$sb`;
- a ttk::entry widget `$e`;
- a ttk::separator widget;
- a mentry widget `$me` of type `"Date"`;
- a scrolled tablelist widget `$tbl` within a scrollarea;
- a scrolled ttk::treeview widget `$tv` within a scrollarea.

With the exception of ttk::label, ttk::entry, and ttk::separator, all these widgets have bult-in mouse wheel event bindings.

Here is the relevant code:

>     package require Tk 8.5.9                        ;# for ttk::spinbox
>     package require mentry_tile 3.2                 ;# for mouse wheel support
>     package require tablelist_tile 6.5              ;# for -(x|y)mousewheelwindow
>                                                     ;# and scrollutil::scrollarea
>     package require scrollutil_tile
>     source styleUtil.tcl

>     wm title . "Scrollutil Demo"

>     #
>     # Create a scrollableframe within a scrollarea
>     #
>     set tf [ttk::frame .tf]
>     set sa [scrollutil::scrollarea $tf.sa]
>     set sf [scrollutil::scrollableframe $sa.sf]
>     $sa setwidget $sf

>     #
>     # Get the content frame and populate it
>     #
>     set cf [$sf contentframe]
>     source SuScrollableFrmContent.tcl

>     #
>     # Make the keyboard navigation more user-friendly
>     #
>     foreach w [list $cb $sb $e $me] {
>         bind $w <<TraverseIn>> [list $sf see %W]
>     }
>     foreach w [list $txt $lb $tbl $tv] {
>         bind $w <<TraverseIn>> [list seeScrollarea $sf %W]
>     }
>     proc seeScrollarea {sf w} { $sf see [scrollutil::getscrollarea $w] }

Whenever the `<<TraverseIn>>` virtual event is sent to one of the four widgets created within scrollareas, we query the path name of the corresponding scrollarea via `scrollutil::getscrollarea` and bring that scrollarea (including the scrollbars and the border) into view rather than just the widget in question. While in this script we could have used `[winfo parent]` instead, the command `scrollutil::getscrollarea` is the recommended one, being that it works also for widgets that are no children of the corresponding scrollareas.

Here is the additional stuff related to the mouse wheel events, using the Scrollutil commands described in the What Is Scrollutil? section:

>     #
>     # Create mouse wheel event bindings for the binding tag "all" and
>     # register the scrollableframe for scrolling by these bindings
>     #
>     scrollutil::createWheelEventBindings all
>     scrollutil::enableScrollingByWheel $sf

>     #
>     # Adapt the handling of the mouse wheel events for the text, listbox,
>     # ttk::combobox, ttk::spinbox, tablelist, and ttk::treeview widgets, as
>     # well as for the entry components of the mentry widget of type "Date"
>     #
>     set entryList [$me entries]
>     scrollutil::adaptWheelEventHandling $txt $lb $cb $sb $tbl $tv {*}$entryList

>     #
>     # For the entry components of the mentry widget
>     # set the "focus check window" to the mentry
>     #
>     scrollutil::setFocusCheckWindow {*}$entryList $me

Notice that we have passed, among others, the tablelist widget to the `scrollutil::adaptWheelEventHandling` command. This will only work for Tablelist versions 6.4 and later, because the command handles tablelist widgets by setting their `-xmousewheelwindow` and `-ymousewheelwindow` options to the path name of the containing toplevel window, and these options were introduced in Tablelist version 6.4. (For earlier Tablelist versions the command silently ignores any tablelist widget passed to it as argument.)

As already mentioned, in the file `SuScrollableFrmContent.tcl` the scrolled text, listbox, tablelist, and ttk::treeview widgets are created within scrollarea widgets:

>     set _sa [scrollutil::scrollarea ...]
>     set txt [text $_sa.txt -font TkFixedFont -width 73]
>     scrollutil::addMouseWheelSupport $txt
>     $_sa setwidget $txt
>     grid $_sa ...

>     . . .

>     set _sa [scrollutil::scrollarea ...]
>     set lb [listbox $_sa.lb -width 0]
>     $_sa setwidget $lb
>     grid $_sa ...

>     . . .

>     set _sa [scrollutil::scrollarea ...]
>     set tbl [tablelist::tablelist $_sa.tbl ...]
>     . . .
>     $_sa setwidget $tbl
>     grid $_sa ...

>     . . .

>     set _sa [scrollutil::scrollarea ... -borderwidth 0]
>     set tv [ttk::treeview $_sa.tv ...]
>     . . .
>     $_sa setwidget $tv
>     grid $_sa ...

In the case of the text, listbox, and tablelist widgets we use scrollarea widgets with their default `-borderwidth 1 -relief sunken` settings, which will cause the `setwidget` subcommand of the associated Tcl commands to set the `-borderwidth` option of the text, listbox, and tablelist widgets to `0`. On the other hand, for the ttk::treeview we use a scrollarea widget with `-borderwidth 0`, because the ttk::treeview has a border of width `1` and doesn't support the `-borderwidth` configuration option.

For our text widget we prefer a mouse wheel event handling that scrolls the widget by lines rather than pixels, as done by the `Text` class bindings in Tk 8.5 and later; we achieve this by passing the path name `$txt` to the `scrollutil::addMouseWeelSupport` command.

The file `SuScrollableFrmContent.tcl` contains also the implementation of the procedure `configTablelist`, associated with the "Configure Tablelist Widget" button as the value of its `-command` option. This procedure opens a toplevel window that contains a scrollutil::scrollableframe widget created with the `-fitcontentwidth yes` setting within a scrollarea and invokes the `scrollutil::enableScrollingByWheel` command for this scrollableframe, thus registering the latter for scrolling by the already created mouse wheel event bindings for the binding tag `"all"`. After that it populates the content frame of the scrollableframe with ttk::label, ttk::combobox, ttk::spinbox, ttk::entry, and ttk::checkbutton widgets used to display and edit the configuration options of the tablelist widget. The procedure handles the `<<TraverseIn>>` virtual event sent to one of these widgets with the aid of the scrollableframe's `see` subcommand. Whenever a ttk::combobox or ttk::spinbox is created, the `scrollutil::adaptWheelEventHandling` command is invoked for it, being that these widgets have built-in bindings for the mouse wheel events.

The widgets populating the content frame are managed using `grid`. In case of the ttk::entry widgets we invoke `grid` with `-sticky we`. Due to this and the `-fitcontentwidth yes` scrollableframe setting, the ttk::entry widgets will stretch or shrink whenever the width of the scrollableframe changes as a result of resizing the toplevel window.

### A Script Using Two BWidget ScrollableFrame Widgets

The script `BwScrollableFrmDemo2.tcl` in the `demos` directory creates a BWidget ScrollableFrame embedded into a scrollarea widget and then `source`s the script `BwScrollableFrmContent.tcl`, which populates the content frame of the ScrollableFrame with the same widgets as `SuScrollableFrmContent.tcl` in the previous example.

Here is the relevant code:

>     package require Tk 8.5.9                        ;# for ttk::spinbox
>     package require BWidget
>     Widget::theme yes
>     package require mentry_tile 3.2                 ;# for mouse wheel support
>     package require tablelist_tile 6.5              ;# for -(x|y)mousewheelwindow
>                                                     ;# and scrollutil::scrollarea
>     package require scrollutil_tile
>     source styleUtil.tcl

>     wm title . "Scrollutil Demo"

>     #
>     # Create a ScrollableFrame within a scrollarea
>     #
>     set tf [ttk::frame .tf]
>     set sa [scrollutil::scrollarea $tf.sa]
>     set sf [ScrollableFrame $sa.sf]
>     $sa setwidget $sf

>     . . .

>     #
>     # Get the content frame and populate it
>     #
>     set cf [$sf getframe]
>     source BwScrollableFrmContent.tcl

>     #
>     # Make the keyboard navigation more user-friendly
>     #
>     foreach w [list $cb $sb $e $me] {
>         bind $w <<TraverseIn>> [list $sf see %W]
>     }
>     foreach w [list $txt $lb $tbl $tv] {
>         bind $w <<TraverseIn>> [list seeScrollarea $sf %W]
>     }
>     proc seeScrollarea {sf w} { $sf see [scrollutil::getscrollarea $w] }

The additional stuff related to the mouse wheel events contains exactly the same Scrollutil command invocations as the one in the previous example.

The file `BwScrollableFrmContent.tcl` contains also the implementation of the procedure `configTablelist`, associated with the "Configure Tablelist Widget" button as the value of its `-command` option. This procedure opens a toplevel window that contains a BWidget ScrollableFrame created with the `-constrainedwidth yes` setting within a scrollarea widget and invokes the `scrollutil::enableScrollingByWheel` command for this ScrollableFrame, thus registering the latter for scrolling by the already created mouse wheel event bindings for the binding tag `"all"`. After that it populates the content frame of the ScrollableFrame with ttk::label, ttk::combobox, ttk::spinbox, ttk::entry, and ttk::checkbutton widgets used to display and edit the configuration options of the tablelist widget. The procedure handles the `<<TraverseIn>>` virtual event sent to one of these widgets with the aid of the ScrollableFrame's `see` subcommand. Whenever a ttk::combobox or ttk::spinbox is created, the `scrollutil::adaptWheelEventHandling` command is invoked for it, being that these widgets have built-in bindings for the mouse wheel events.

Again, all this is nearly identical to what we did in the previous example.

### A Script Using Two iwidgets::scrolledframe Widgets

The script `ScrolledFrmDemo2.tcl` in the `demos` directory creates an iwidgets::scrolledframe widget and then `source`s the file `ScrolledFrmContent.tcl`, which populates the content frame of the scrolledframe with the same widgets as `SuScrollableFrmContent.tcl` and `BwScrollableFrmContent.tcl` in the two previous examples.

Here is the relevant code:

>     package require Tk 8.5.9                        ;# for ttk::spinbox
>     if {[catch {package require iwidgets} result1] != 0 &&
>         [catch {package require Iwidgets} result2] != 0} {
>         error "$result1; $result2"
>     }
>     source scrolledwidgetPatch.itk                  ;# adds ttk::scrollbar widgets
>     package require mentry_tile 3.2                 ;# for mouse wheel support
>     package require tablelist_tile 6.5              ;# for -(x|y)mousewheelwindow
>                                                     ;# and scrollutil::scrollarea
>     package require scrollutil_tile
>     source styleUtil.tcl

>     wm title . "Scrollutil Demo"

>     . . .

>     #
>     # Create a scrolledframe
>     #
>     set tf [ttk::frame .tf]
>     set sf [iwidgets::scrolledframe $tf.sf -borderwidth 1 -relief sunken \
>             -scrollmargin 0]
>     . . .

>     #
>     # Get the content frame and populate it
>     #
>     set cf [$sf childsite]
>     . . .
>     source ScrolledFrmContent.tcl

The additional stuff related to the mouse wheel events contains exactly the same Scrollutil command invocations as the one in the two previous examples.

The file `ScrolledFrmContent.tcl` contains also the implementation of the procedure `configTablelist`, associated with the "Configure Tablelist Widget" button as the value of its `-command` option. This procedure opens a toplevel window that contains an iwidgets::scrolledframe widget with a manually implemented equivalent of the `-fitcontentwidth yes` scrollutil::scrollableframe and `-constrainedwidth yes` BWidget ScrollableFrame settings and invokes the `scrollutil::enableScrollingByWheel` command for this scrolledframe, thus registering the latter for scrolling by the already created mouse wheel event bindings for the binding tag `"all"`. After that it populates the content frame of the scrolledframe with ttk::label, ttk::combobox, ttk::spinbox, ttk::entry, and ttk::checkbutton widgets used to display and edit the configuration options of the tablelist widget. Whenever a ttk::combobox or ttk::spinbox is created, the `scrollutil::adaptWheelEventHandling` command is invoked for it, being that these widgets have built-in bindings for the mouse wheel events.

Again, all this is nearly identical to what we did in the two previous examples.

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