QRegion(3qt) QRegion(3qt)
NAME
QRegion - Clip region for a painter
SYNOPSIS
#include <qregion.h>
Public Members
enum RegionType { Rectangle, Ellipse }
QRegion ()
QRegion ( int x, int y, int w, int h, RegionType t = Rectangle )
QRegion ( const QRect & r, RegionType t = Rectangle )
QRegion ( const QPointArray & a, bool winding = FALSE )
QRegion ( const QRegion & r )
QRegion ( const QBitmap & bm )
~QRegion ()
QRegion & operator= ( const QRegion & r )
bool isNull () const
bool isEmpty () const
bool contains ( const QPoint & p ) const
bool contains ( const QRect & r ) const
void translate ( int dx, int dy )
QRegion unite ( const QRegion & r ) const
QRegion intersect ( const QRegion & r ) const
QRegion subtract ( const QRegion & r ) const
QRegion eor ( const QRegion & r ) const
QRect boundingRect () const
QMemArray<QRect> rects () const
const QRegion operator| ( const QRegion & r ) const
const QRegion operator+ ( const QRegion & r ) const
const QRegion operator& ( const QRegion & r ) const
const QRegion operator- ( const QRegion & r ) const
const QRegion operator^ ( const QRegion & r ) const
QRegion & operator|= ( const QRegion & r )
QRegion & operator+= ( const QRegion & r )
QRegion & operator&= ( const QRegion & r )
QRegion & operator-= ( const QRegion & r )
QRegion & operator^= ( const QRegion & r )
bool operator== ( const QRegion & r ) const
bool operator!= ( const QRegion & r ) const
HRGN handle () const
RELATED FUNCTION DOCUMENTATION
QDataStream & operator<< ( QDataStream & s, const QRegion & r )
QDataStream & operator>> ( QDataStream & s, QRegion & r )
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() 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 unite(), intersect(), subtract() or eor() (exclusive or). You can move a region using translate().
You can test whether a region isNull(), isEmpty() or if it contains() a QPoint or QRect. The bounding rectangle is given by boundingRect().
The function rects() gives a decomposition of the region into rectangles.
Example of using complex regions:
void MyWidget::paintEvent( QPaintEvent * )
{
QPainter p; // our painter
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.intersect( r2 ); // r3 = intersection
p.begin( this ); // start painting widget
p.setClipRegion( r3 ); // set clip region
... // paint clipped graphics
p.end(); // painting done
}
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.
See also QPainter::setClipRegion(), QPainter::setClipRect(), Graphics Classes, and Image Processing Classes.
Member Type Documentation
QRegion::RegionType
Specifies the shape of the region to be created.
QRegion::Rectangle - the region covers the entire rectangle.
QRegion::Ellipse - the region is an ellipse inside the rectangle.
MEMBER FUNCTION DOCUMENTATION
QRegion::QRegion ()
Constructs a null region.
See also isNull().
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 )
This is an overloaded member function, provided for convenience. It behaves essentially like the above 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.
QRegion::QRegion ( const QPointArray & a, bool winding = FALSE )
Constructs a polygon region from the point array a.
If winding is TRUE, the polygon region is filled using the winding algorithm, otherwise the default even-odd fill algorithm is used.
This constructor may create complex regions that will slow down painting when used.
QRegion::QRegion ( const QRegion & r )
Constructs a new region which is equal to region r.
QRegion::QRegion ( const QBitmap & bm )
Constructs a region from the bitmap bm.
The resulting region consists of the pixels in bitmap bm that are 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().
QRegion::~QRegion ()
Destroys the region.
QRect QRegion::boundingRect () const
Returns the bounding rectangle of this region. An empty region gives a rectangle that is QRect::isNull().
bool QRegion::contains ( const QPoint & p ) const
Returns TRUE if the region contains the point p; otherwise returns FALSE.
bool QRegion::contains ( const QRect & r ) const
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns TRUE if the region overlaps the rectangle r; otherwise returns FALSE.
QRegion QRegion::eor ( const QRegion & r ) const
Returns a region which is the exclusive or (XOR) of this region and r.
<center>
[Image Omitted]
</center>
The figure shows the exclusive or of two elliptical regions.
HRGN QRegion::handle () const
Returns the region's handle.
QRegion QRegion::intersect ( const QRegion & r ) const
Returns a region which is the intersection of this region and r.
<center>
[Image Omitted]
</center>
The figure shows the intersection of two elliptical regions.
bool QRegion::isEmpty () const
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 );
QRegion r2( 40, 40, 20, 20 );
QRegion r3;
r1.isNull(); // FALSE
r1.isEmpty(); // FALSE
r3.isNull(); // TRUE
r3.isEmpty(); // TRUE
r3 = r1.intersect( r2 ); // r3 = intersection of r1 and r2
r3.isNull(); // FALSE
r3.isEmpty(); // TRUE
r3 = r1.unite( r2 ); // r3 = union of r1 and r2
r3.isNull(); // FALSE
r3.isEmpty(); // FALSE
See also isNull().
bool QRegion::isNull () const
Returns TRUE if the region is a null region; otherwise returns FALSE.
A null region is a region that has not been initialized. A null region is always empty.
See also isEmpty().
bool QRegion::operator!= ( const QRegion & r ) const
Returns TRUE if the region is different from r; otherwise returns FALSE.
const QRegion QRegion::operator& ( const QRegion & r ) const
Applies the intersect() function to this region and r. r1&r2 is equivalent to r1.intersect(r2)
See also intersect().
QRegion &; QRegion::operator&= ( const QRegion & r )
Applies the intersect() function to this region and r and assigns the result to this region. r1&=r2 is equivalent to r1=r1.intersect(r2)
See also intersect().
const QRegion QRegion::operator+ ( const QRegion & r ) const
Applies the unite() function to this region and r. r1+r2 is equivalent to r1.unite(r2)
See also unite() and operator|().
QRegion &; QRegion::operator+= ( const QRegion & r )
Applies the unite() function to this region and r and assigns the result to this region. r1+=r2 is equivalent to r1=r1.unite(r2)
See also intersect().
const QRegion QRegion::operator- ( const QRegion & r ) const
Applies the subtract() function to this region and r. r1-r2 is equivalent to r1.subtract(r2)
See also subtract().
QRegion &; QRegion::operator-= ( const QRegion & r )
Applies the subtract() function to this region and r and assigns the result to this region. r1-=r2 is equivalent to r1=r1.subtract(r2)
See also subtract().
QRegion &; QRegion::operator= ( const QRegion & r )
Assigns r to this region and returns a reference to the region.
bool QRegion::operator== ( const QRegion & r ) const
Returns TRUE if the region is equal to r; otherwise returns FALSE.
const QRegion QRegion::operator^ ( const QRegion & r ) const
Applies the eor() function to this region and r. r1^r2 is equivalent to r1.eor(r2)
See also eor().
QRegion &; QRegion::operator^= ( const QRegion & r )
Applies the eor() function to this region and r and assigns the result to this region. r1^=r2 is equivalent to r1=r1.eor(r2)
See also eor().
const QRegion QRegion::operator| ( const QRegion & r ) const
Applies the unite() function to this region and r. r1|r2 is equivalent to r1.unite(r2)
See also unite() and operator+().
QRegion &; QRegion::operator|= ( const QRegion & r )
Applies the unite() function to this region and r and assigns the result to this region. r1|=r2 is equivalent to r1=r1.unite(r2)
See also unite().
QMemArray<;QRect> QRegion::rects () const
Returns an array of non-overlapping rectangles that make up the region.
The union of all the rectangles is equal to the original region.
QRegion QRegion::subtract ( const QRegion & r ) const
Returns a region which is r subtracted from this region.
<center>
[Image Omitted]
</center>
The figure shows the result when the ellipse on the right is subtracted from the ellipse on the left. (left-right )
void QRegion::translate ( int dx, int dy )
Translates (moves) the region dx along the X axis and dy along the Y axis.
QRegion QRegion::unite ( const QRegion & r ) const
Returns a region which is the union of this region and r.
<center>
[Image Omitted]
</center>
The figure shows the union of two elliptical regions.
RELATED FUNCTION DOCUMENTATION
QDataStream &; operator<< ( QDataStream & s, const QRegion & r )
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 )
Reads a region from the stream s into r and returns a reference to the stream.
See also Format of the QDataStream operators.
SEE ALSO
http://doc.trolltech.com/qregion.html http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2001 Trolltech AS, http://www.trolltech.com. See the license file included in the distribution for a complete license
statement.
AUTHOR
Generated automatically from the source code.
BUGS
If you find a bug in Qt, please report it as described in http://doc.trolltech.com/bughowto.html. Good bug reports help us to help you.
Thank you.
The definitive Qt documentation is provided in HTML format; it is located at $QTDIR/doc/html and can be read using Qt Assistant or with a
web browser. This man page is provided as a convenience for those users who prefer man pages, although this format is not officially
supported by Trolltech.
If you find errors in this manual page, please report them to qt-bugs@trolltech.com. Please include the name of the manual page
(qregion.3qt) and the Qt version (3.1.1).
Trolltech AS 9 December 2002 QRegion(3qt)