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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 Mac OS X and 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 1992-2007 Trolltech ASA, 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 (3.3.8).

Trolltech AS				 2 February 2007			     QRegion(3qt)
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