- Qt 6.8
- Qt GUI
- C++ Classes
- QPolygonF
- Qt 6.8.2 Reference Documentation

# QPolygonF Class

The QPolygonF class provides a list of points using floating point precision. More...

Header: | `#include <QPolygonF>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS Gui)` `target_link_libraries(mytarget PRIVATE Qt6::Gui)`
qmake: | `QT += gui`
Inherits: | QList

- List of all members, including inherited members
- QPolygonF is part of Painting Classes and Implicitly Shared Classes.

Note: All functions in this class are reentrant.

## Public Functions

| QPolygonF()
| QPolygonF(const QList<QPointF> &points)
| QPolygonF(const QPolygon &polygon)
| QPolygonF(const QRectF &rectangle)
QRectF | boundingRect() const
bool | containsPoint(const QPointF &point, Qt::FillRule fillRule) const
QPolygonF | intersected(const QPolygonF &r) const
bool | intersects(const QPolygonF &p) const
bool | isClosed() const
QPolygonF | subtracted(const QPolygonF &r) const
void | swap(QPolygonF &other)
QPolygon | toPolygon() const
void | translate(const QPointF &offset)
void | translate(qreal dx, qreal dy)
QPolygonF | translated(const QPointF &offset) const
QPolygonF | translated(qreal dx, qreal dy) const
QPolygonF | united(const QPolygonF &r) const
QVariant | operator QVariant() const

## Related Non-Members

QDataStream & | operator<<(QDataStream &stream, const QPolygonF &polygon)
QDataStream & | operator>>(QDataStream &stream, QPolygonF &polygon)

## Detailed Description

A QPolygonF is a QList<QPointF>. The easiest way to add points to a QPolygonF is to use its streaming operator, as illustrated below:

     QPolygonF polygon;
     polygon << QPointF(10.4, 20.5) << QPointF(20.2, 30.2);

In addition to the functions provided by QList, QPolygonF provides the boundingRect() and translate() functions for geometry operations. Use the QTransform::map() function for more general transformations of QPolygonFs.

QPolygonF also provides the isClosed() function to determine whether a polygon's start and end points are the same, and the toPolygon() function returning an integer precision copy of this polygon.

The QPolygonF class is implicitly shared.

See also QList, QPolygon, and QLineF.

## Member Function Documentation

### `[constexpr noexcept]` QPolygonF::QPolygonF()

Constructs a polygon with no points.

See also QList::isEmpty().

### QPolygonF::QPolygonF(const QList<QPointF> &points)

Constructs a polygon containing the specified points.

### QPolygonF::QPolygonF(const QPolygon &polygon)

Constructs a float based polygon from the specified integer based polygon.

See also toPolygon().

### QPolygonF::QPolygonF(const QRectF &rectangle)

Constructs a closed polygon from the specified rectangle.

The polygon contains the four vertices of the rectangle in clockwise order starting and ending with the top-left vertex.

See also isClosed().

### QRectF QPolygonF::boundingRect() const

Returns the bounding rectangle of the polygon, or QRectF(0,0,0,0) if the polygon is empty.

See also QList::isEmpty().

### bool QPolygonF::containsPoint(const QPointF &point, Qt::FillRule fillRule) const

Returns `true` if the given point is inside the polygon according to the specified fillRule; otherwise returns `false`.

### QPolygonF QPolygonF::intersected(const QPolygonF &r) const

Returns a polygon which is the intersection of this polygon and r.

Set operations on polygons will treat the polygons as areas. Non-closed polygons will be treated as implicitly closed.

See also intersects().

### bool QPolygonF::intersects(const QPolygonF &p) const

Returns `true` if the current polygon intersects at any point the given polygon p. Also returns `true` if the current polygon contains or is contained by any part of p.

Set operations on polygons will treat the polygons as areas. Non-closed polygons will be treated as implicitly closed.

See also intersected().

### bool QPolygonF::isClosed() const

Returns `true` if the polygon is closed; otherwise returns `false`.

A polygon is said to be closed if its start point and end point are equal.

See also QList::first() and QList::last().

### QPolygonF QPolygonF::subtracted(const QPolygonF &r) const

Returns a polygon which is r subtracted from this polygon.

Set operations on polygons will treat the polygons as areas. Non-closed polygons will be treated as implicitly closed.

### void QPolygonF::swap(QPolygonF &other)

Swaps this polygon with other. This operation is very fast and never fails.

### QPolygon QPolygonF::toPolygon() const

Creates and returns a QPolygon by converting each QPointF to a QPoint.

See also QPointF::toPoint().

### void QPolygonF::translate(const QPointF &offset)

Translate all points in the polygon by the given offset.

See also translated().

### void QPolygonF::translate(qreal dx, qreal dy)

This is an overloaded function.

Translates all points in the polygon by (dx, dy).

See also translated().

### QPolygonF QPolygonF::translated(const QPointF &offset) const

Returns a copy of the polygon that is translated by the given offset.

See also translate().

### QPolygonF QPolygonF::translated(qreal dx, qreal dy) const

This is an overloaded function.

Returns a copy of the polygon that is translated by (dx, dy).

See also translate().

### QPolygonF QPolygonF::united(const QPolygonF &r) const

Returns a polygon which is the union of this polygon and r.

Set operations on polygons will treat the polygons as areas. Non-closed polygons will be treated as implicitly closed.

See also intersected() and subtracted().

### QVariant QPolygonF::operator QVariant() const

Returns the polygon as a QVariant.

## Related Non-Members

### QDataStream &operator<<(QDataStream &stream, const QPolygonF &polygon)

Writes the given polygon to the given stream, and returns a reference to the stream.

See also Serializing Qt Data Types.

### QDataStream &operator>>(QDataStream &stream, QPolygonF &polygon)

Reads a polygon from the given stream into the given polygon, and returns a reference to the stream.

See also Serializing Qt Data Types.