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The QRegion class specifies a clip region for a painter. More...
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
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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 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().
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().
Swaps region other with this region. This operation is very fast and never fails.
This function was introduced in Qt 4.8.
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().
| PyQt 4.10.1 for MacOS | Copyright © Riverbank Computing Ltd and Nokia 2012 | Qt 4.8.4 |