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QRegion Class Reference
[QtGui module]

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

 #include <QRegion>

Public Types

Public Functions

Related Non-Members


Detailed Description

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.

Additional License Information

For Qt/X11, Qt for Embedded Linux and Windows CE, 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.


Member Type Documentation

enum QRegion::RegionType

Specifies the shape of the region to be created.

ConstantValueDescription
QRegion::Rectangle0the region covers the entire rectangle.
QRegion::Ellipse1the region is an ellipse inside the rectangle.


Member Function Documentation

QRegion::QRegion ()

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

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).

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

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

QRegion::QRegion ( const QRegion & region )

QRegion::QRegion ( const QBitmap & bitmap )

QRegion::~QRegion ()

QRect QRegion::boundingRect () const

bool QRegion::contains ( const QPoint & p ) const

bool QRegion::contains ( const QRect & r ) const

This is an overloaded member function, provided for convenience.

QRegion QRegion::eor ( const QRegion & r ) const

Handle QRegion::handle () const

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.

QRegion QRegion::intersect ( const QRegion & r ) const

QRegion QRegion::intersect ( const QRect & r ) const

This is an overloaded member function, provided for convenience.

QRegion QRegion::intersected ( const QRegion & r ) const

QRegion QRegion::intersected ( const QRect & r ) const

This is an overloaded member function, provided for convenience.

bool QRegion::intersects ( const QRegion & region ) const

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

This function was introduced in Qt 4.2.

bool QRegion::intersects ( const QRect & rect ) const

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.

bool QRegion::isEmpty () const

int QRegion::numRects () const

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

This function was introduced in Qt 4.4.

QVector<QRect> QRegion::rects () const

See also setRects().

void QRegion::setRects ( const QRect * rect, int num )

See also rects().

QRegion QRegion::subtract ( const QRegion & r ) const

QRegion QRegion::subtracted ( const QRegion & r ) const

void QRegion::translate ( int dx, int dy )

void QRegion::translate ( const QPoint & point )

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.

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

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().

QRegion QRegion::translated ( const QPoint & p ) const

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().

QRegion QRegion::unite ( const QRegion & r ) const

QRegion QRegion::unite ( const QRect & r ) const

This is an overloaded member function, provided for convenience.

QRegion QRegion::united ( const QRegion & r ) const

QRegion QRegion::united ( const QRect & r ) const

This is an overloaded member function, provided for convenience.

QRegion QRegion::xored ( const QRegion & r ) const

QRegion::operator QVariant () const

Returns the region as a QVariant

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

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

const QRegion QRegion::operator& ( const QRegion & r ) const

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

See also intersected().

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

This is an overloaded member function, provided for convenience.

This function was introduced in Qt 4.4.

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

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().

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

This is an overloaded member function, provided for convenience.

This function was introduced in Qt 4.4.

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

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

See also united() and operator|().

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

This is an overloaded member function, provided for convenience.

This function was introduced in Qt 4.4.

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

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().

QRegion & QRegion::operator+= ( const QRect & r )

This is an overloaded member function, provided for convenience.

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

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

See also subtracted().

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

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().

QRegion & QRegion::operator= ( const QRegion & )

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

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

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

See also xored().

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

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().

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

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

See also united() and operator+().

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

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().


Related Non-Members

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

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.

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

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.


Copyright © 2008 Trolltech Trademarks
Qt 4.4.0