The QRegion class specifies a clip region for a painter. More...

#include <QRegion>

enum | RegionType { Rectangle, Ellipse } |

QRegion () | |

QRegion ( int x, int y, int w, int h, RegionType t = Rectangle ) | |

QRegion ( const QPolygon & a, Qt::FillRule fillRule = Qt::OddEvenFill ) | |

QRegion ( const QRegion & r ) | |

QRegion ( const QBitmap & bm ) | |

QRegion ( const QRect & r, RegionType t = Rectangle ) | |

QRect | boundingRect () const |

bool | contains ( const QPoint & p ) const |

bool | contains ( const QRect & r ) const |

Handle | handle () const |

QRegion | intersected ( const QRegion & r ) const |

QRegion | intersected ( const QRect & rect ) const |

bool | intersects ( const QRegion & region ) const |

bool | intersects ( const QRect & rect ) const |

bool | isEmpty () const |

int | rectCount () const |

QVector<QRect> | rects () const |

void | setRects ( const QRect * rects, int number ) |

QRegion | subtracted ( const QRegion & r ) const |

void | translate ( int dx, int dy ) |

void | translate ( const QPoint & point ) |

QRegion | translated ( int dx, int dy ) const |

QRegion | translated ( const QPoint & p ) const |

QRegion | united ( const QRegion & r ) const |

QRegion | united ( const QRect & rect ) const |

QRegion | xored ( const QRegion & r ) const |

operator QVariant () const | |

bool | operator!= ( const QRegion & other ) const |

const QRegion | operator& ( const QRegion & r ) const |

const QRegion | operator& ( const QRect & r ) const |

QRegion & | operator&= ( const QRegion & r ) |

QRegion & | operator&= ( const QRect & r ) |

const QRegion | operator+ ( const QRegion & r ) const |

const QRegion | operator+ ( const QRect & r ) const |

QRegion & | operator+= ( const QRegion & r ) |

QRegion & | operator+= ( const QRect & rect ) |

const QRegion | operator- ( const QRegion & r ) const |

QRegion & | operator-= ( const QRegion & r ) |

QRegion & | operator= ( const QRegion & r ) |

bool | operator== ( const QRegion & r ) const |

const QRegion | operator^ ( const QRegion & r ) const |

QRegion & | operator^= ( const QRegion & r ) |

const QRegion | operator| ( const QRegion & r ) const |

QRegion & | operator|= ( const QRegion & r ) |

QDataStream & | operator<< ( QDataStream & s, const QRegion & r ) |

QDataStream & | operator>> ( QDataStream & s, QRegion & r ) |

The QRegion class specifies a clip region for a painter.

QRegion is used with QPainter::setClipRegion() to limit the paint area to what needs to be painted. There is also a QWidget::repaint() function that takes a QRegion parameter. QRegion is the best tool for minimizing the amount of screen area to be updated by a repaint.

This class is not suitable for constructing shapes for rendering, especially as outlines. Use QPainterPath to create paths and shapes for use with QPainter.

QRegion is an implicitly shared class.

A region can be created from a rectangle, an ellipse, a polygon or a bitmap. Complex regions may be created by combining simple regions using united(), intersected(), subtracted(), or xored() (exclusive or). You can move a region using translate().

You can test whether a region isEmpty() or if it contains() a QPoint or QRect. The bounding rectangle can be found with boundingRect().

The function rects() gives a decomposition of the region into rectangles.

Example of using complex regions:

void MyWidget::paintEvent(QPaintEvent *) { QRegion r1(QRect(100, 100, 200, 80), // r1: elliptic region QRegion::Ellipse); QRegion r2(QRect(100, 120, 90, 30)); // r2: rectangular region QRegion r3 = r1.intersected(r2); // r3: intersection QPainter painter(this); painter.setClipRegion(r3); ... // paint clipped graphics }

On Embedded Linux, Windows CE and X11 platforms, parts of this class rely on code obtained under the following licenses:

Copyright (c) 1987 X Consortium

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE X CONSORTIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Except as contained in this notice, the name of the X Consortium shall not be used in advertising or otherwise to promote the sale, use or other dealings in this Software without prior written authorization from the X Consortium.

Copyright 1987 by Digital Equipment Corporation, Maynard, Massachusetts.

All Rights Reserved

Permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation, and that the name of Digital not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission.

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See also QPainter::setClipRegion(), QPainter::setClipRect(), and QPainterPath.

Specifies the shape of the region to be created.

Constant | Value | Description |
---|---|---|

QRegion::Rectangle | 0 | the region covers the entire rectangle. |

QRegion::Ellipse | 1 | the region is an ellipse inside the rectangle. |

Constructs an empty region.

See also isEmpty().

Constructs a rectangular or elliptic region.

If *t* is `Rectangle`, the region is the filled rectangle (*x*, *y*, *w*, *h*). If *t* is `Ellipse`, the region is the filled ellipse with center at (*x* + *w* / 2, *y* + *h* / 2) and size (*w* ,*h*).

Constructs a polygon region from the point array *a* with the fill rule specified by *fillRule*.

If *fillRule* is Qt::WindingFill, the polygon region is defined using the winding algorithm; if it is Qt::OddEvenFill, the odd-even fill algorithm is used.

**Warning:** This constructor can be used to create complex regions that will slow down painting when used.

Constructs a new region which is equal to region *r*.

Constructs a region from the bitmap *bm*.

The resulting region consists of the pixels in bitmap *bm* that are Qt::color1, as if each pixel was a 1 by 1 rectangle.

This constructor may create complex regions that will slow down painting when used. Note that drawing masked pixmaps can be done much faster using QPixmap::setMask().

This is an overloaded function.

Create a region based on the rectange *r* with region type *t*.

If the rectangle is invalid a null region will be created.

See also QRegion::RegionType.

Returns the bounding rectangle of this region. An empty region gives a rectangle that is QRect::isNull().

Returns true if the region contains the point *p*; otherwise returns false.

This is an overloaded function.

Returns true if the region overlaps the rectangle *r*; otherwise returns false.

Returns a platform-specific region handle. The `Handle` type is `HRGN` on Windows, `Region` on X11, and `RgnHandle` on Mac OS X. On Qt for Embedded Linux it is `void *`.

**Warning:** This function is not portable.

Returns a region which is the intersection of this region and *r*.

The figure shows the intersection of two elliptical regions.

This function was introduced in Qt 4.2.

See also subtracted(), united(), and xored().

Returns a region which is the intersection of this region and the given *rect*.

This function was introduced in Qt 4.4.

See also subtracted(), united(), and xored().

Returns true if this region intersects with *region*, otherwise returns false.

This function was introduced in Qt 4.2.

Returns true if this region intersects with *rect*, otherwise returns false.

This function was introduced in Qt 4.2.

Returns true if the region is empty; otherwise returns false. An empty region is a region that contains no points.

Example:

QRegion r1(10, 10, 20, 20); r1.isEmpty(); // false QRegion r3; r3.isEmpty(); // true QRegion r2(40, 40, 20, 20); r3 = r1.intersected(r2); // r3: intersection of r1 and r2 r3.isEmpty(); // true r3 = r1.united(r2); // r3: union of r1 and r2 r3.isEmpty(); // false

Returns the number of rectangles that will be returned in rects().

This function was introduced in Qt 4.6.

Returns an array of non-overlapping rectangles that make up the region.

The union of all the rectangles is equal to the original region.

See also setRects().

Sets the region using the array of rectangles specified by *rects* and *number*. The rectangles *must* be optimally Y-X sorted and follow these restrictions:

- The rectangles must not intersect.
- All rectangles with a given top coordinate must have the same height.
- No two rectangles may abut horizontally (they should be combined into a single wider rectangle in that case).
- The rectangles must be sorted in ascending order, with Y as the major sort key and X as the minor sort key.

See also rects().

Returns a region which is *r* subtracted from this region.

The figure shows the result when the ellipse on the right is subtracted from the ellipse on the left (`left - right`).

This function was introduced in Qt 4.2.

See also intersected(), united(), and xored().

Translates (moves) the region *dx* along the X axis and *dy* along the Y axis.

This is an overloaded function.

Translates the region *point**.x()* along the x axis and *point**.y()* along the y axis, relative to the current position. Positive values move the region to the right and down.

Translates to the given *point*.

Returns a copy of the region that is translated *dx* along the x axis and *dy* along the y axis, relative to the current position. Positive values move the region to the right and down.

This function was introduced in Qt 4.1.

See also translate().

This is an overloaded function.

Returns a copy of the regtion that is translated *p**.x()* along the x axis and *p**.y()* along the y axis, relative to the current position. Positive values move the rectangle to the right and down.

This function was introduced in Qt 4.1.

See also translate().

Returns a region which is the union of this region and *r*.

The figure shows the union of two elliptical regions.

This function was introduced in Qt 4.2.

See also intersected(), subtracted(), and xored().

Returns a region which is the union of this region and the given *rect*.

This function was introduced in Qt 4.4.

See also intersected(), subtracted(), and xored().

Returns a region which is the exclusive or (XOR) of this region and *r*.

The figure shows the exclusive or of two elliptical regions.

This function was introduced in Qt 4.2.

See also intersected(), united(), and subtracted().

Returns the region as a QVariant

Returns true if this region is different from the *other* region; otherwise returns false.

Applies the intersected() function to this region and *r*. `r1&r2` is equivalent to `r1.intersected(r2)`.

See also intersected().

This is an overloaded function.

This function was introduced in Qt 4.4.

Applies the intersected() function to this region and *r* and assigns the result to this region. `r1&=r2` is equivalent to `r1` = r1.intersected(r2).

See also intersected().

This is an overloaded function.

This function was introduced in Qt 4.4.

Applies the united() function to this region and *r*. `r1+r2` is equivalent to `r1.united(r2)`.

See also united() and operator|().

This is an overloaded function.

This function was introduced in Qt 4.4.

Applies the united() function to this region and *r* and assigns the result to this region. `r1+=r2` is equivalent to `r1 = r1.united(r2)`.

See also intersected().

Returns a region that is the union of this region with the specified *rect*.

See also united().

Applies the subtracted() function to this region and *r*. `r1-r2` is equivalent to `r1.subtracted(r2)`.

See also subtracted().

Applies the subtracted() function to this region and *r* and assigns the result to this region. `r1-=r2` is equivalent to `r1 = r1.subtracted(r2)`.

See also subtracted().

Assigns *r* to this region and returns a reference to the region.

Returns true if the region is equal to *r*; otherwise returns false.

Applies the xored() function to this region and *r*. `r1^r2` is equivalent to `r1.xored(r2)`.

See also xored().

Applies the xored() function to this region and *r* and assigns the result to this region. `r1^=r2` is equivalent to `r1 = r1.xored(r2)`.

See also xored().

Applies the united() function to this region and *r*. `r1|r2` is equivalent to `r1.united(r2)`.

See also united() and operator+().

Applies the united() function to this region and *r* and assigns the result to this region. `r1|=r2` is equivalent to `r1 = r1.united(r2)`.

See also united().

Writes the region *r* to the stream *s* and returns a reference to the stream.

See also Format of the QDataStream operators.

Reads a region from the stream *s* into *r* and returns a reference to the stream.

See also Format of the QDataStream operators.

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