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The QRegion class specifies a clip region for a painter. More...
#include <QRegion>
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 reducing flicker.
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
}
QRegion is an implicitly shared class.
Warning: Due to window system limitations, the whole coordinate space for a region is limited to the points between -32767 and 32767 on Windows 95/98/ME. You can circumvent this limitation by using a QPainterPath.
On Embedded Linux, Windows CE and X11 platforms, parts of this class rely on code obtained under the following license:
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.
DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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().
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 member function, provided for convenience.
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().
This is an overloaded member function, provided for convenience.
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.
This is an overloaded member function, provided for convenience.
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.isNull(); // false r1.isEmpty(); // false QRegion r2(40, 40, 20, 20); QRegion r3; r3.isNull(); // true r3.isEmpty(); // true r3 = r1.intersected(r2); // r3: intersection of r1 and r2 r3.isNull(); // false r3.isEmpty(); // true r3 = r1.united(r2); // r3: union of r1 and r2 r3.isNull(); // false r3.isEmpty(); // false
Returns the number of rectangles that will be returned in rects().
This function was introduced in Qt 4.4.
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:
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 member function, provided for convenience.
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 member function, provided for convenience.
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().
This is an overloaded member function, provided for convenience.
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 member function, provided for convenience.
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 member function, provided for convenience.
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 member function, provided for convenience.
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().
This is an overloaded member function, provided for convenience.
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().
This is an overloaded member function, provided for convenience.
Writes the region r to the stream s and returns a reference to the stream.
See also Format of the QDataStream operators.
This is an overloaded member function, provided for convenience.
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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