'\" t
.TH QRegion 3qt "18 March 2002" "Trolltech AS" \" -*- nroff -*-
.\" Copyright 1992-2001 Trolltech AS.  All rights reserved.  See the
.\" license file included in the distribution for a complete license
.\" statement.
.\"
.ad l
.nh
.SH NAME
QRegion \- Clip region for a painter
.SH SYNOPSIS
\fC#include <qregion.h>\fR
.PP
.SS "Public Members"
.in +1c
.ti -1c
.BI "enum \fBRegionType\fR { Rectangle, Ellipse }"
.br
.ti -1c
.BI "\fBQRegion\fR ()"
.br
.ti -1c
.BI "\fBQRegion\fR ( int x, int y, int w, int h, RegionType t = Rectangle )"
.br
.ti -1c
.BI "\fBQRegion\fR ( const QRect & r, RegionType t = Rectangle )"
.br
.ti -1c
.BI "\fBQRegion\fR ( const QPointArray & a, bool winding = FALSE )"
.br
.ti -1c
.BI "\fBQRegion\fR ( const QRegion & r )"
.br
.ti -1c
.BI "\fBQRegion\fR ( const QBitmap & bm )"
.br
.ti -1c
.BI "\fB~QRegion\fR ()"
.br
.ti -1c
.BI "QRegion & \fBoperator=\fR ( const QRegion & r )"
.br
.ti -1c
.BI "bool \fBisNull\fR () const"
.br
.ti -1c
.BI "bool \fBisEmpty\fR () const"
.br
.ti -1c
.BI "bool \fBcontains\fR ( const QPoint & p ) const"
.br
.ti -1c
.BI "bool \fBcontains\fR ( const QRect & r ) const"
.br
.ti -1c
.BI "void \fBtranslate\fR ( int dx, int dy )"
.br
.ti -1c
.BI "QRegion \fBunite\fR ( const QRegion & r ) const"
.br
.ti -1c
.BI "QRegion \fBintersect\fR ( const QRegion & r ) const"
.br
.ti -1c
.BI "QRegion \fBsubtract\fR ( const QRegion & r ) const"
.br
.ti -1c
.BI "QRegion \fBeor\fR ( const QRegion & r ) const"
.br
.ti -1c
.BI "QRect \fBboundingRect\fR () const"
.br
.ti -1c
.BI "QMemArray<QRect> \fBrects\fR () const"
.br
.ti -1c
.BI "const QRegion \fBoperator|\fR ( const QRegion & r ) const"
.br
.ti -1c
.BI "const QRegion \fBoperator+\fR ( const QRegion & r ) const"
.br
.ti -1c
.BI "const QRegion \fBoperator&\fR ( const QRegion & r ) const"
.br
.ti -1c
.BI "const QRegion \fBoperator-\fR ( const QRegion & r ) const"
.br
.ti -1c
.BI "const QRegion \fBoperator^\fR ( const QRegion & r ) const"
.br
.ti -1c
.BI "QRegion & \fBoperator|=\fR ( const QRegion & r )"
.br
.ti -1c
.BI "QRegion & \fBoperator+=\fR ( const QRegion & r )"
.br
.ti -1c
.BI "QRegion & \fBoperator&=\fR ( const QRegion & r )"
.br
.ti -1c
.BI "QRegion & \fBoperator-=\fR ( const QRegion & r )"
.br
.ti -1c
.BI "QRegion & \fBoperator^=\fR ( const QRegion & r )"
.br
.ti -1c
.BI "bool \fBoperator==\fR ( const QRegion & r ) const"
.br
.ti -1c
.BI "bool \fBoperator!=\fR ( const QRegion & r ) const"
.br
.ti -1c
.BI "HRGN \fBhandle\fR () const"
.br
.in -1c
.SH RELATED FUNCTION DOCUMENTATION
.in +1c
.ti -1c
.BI "QDataStream & \fBoperator<<\fR ( QDataStream & s, const QRegion & r )"
.br
.ti -1c
.BI "QDataStream & \fBoperator>>\fR ( QDataStream & s, QRegion & r )"
.br
.in -1c
.SH DESCRIPTION
The QRegion class specifies a clip region for a painter.
.PP
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.
.PP
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().
.PP
You can test whether a region isNull(), isEmpty() or if it contains() a QPoint or QRect. The bounding rectangle is given by boundingRect().
.PP
The function rects() gives a decomposition of the region into rectangles.
.PP
Example of using complex regions:
.PP
.nf
.br
    void MyWidget::paintEvent( QPaintEvent * )
.br
    {
.br
    QPainter p;                         // our painter
.br
    QRegion r1( QRect(100,100,200,80),  // r1 = elliptic region
.br
                QRegion::Ellipse );
.br
    QRegion r2( QRect(100,120,90,30) ); // r2 = rectangular region
.br
    QRegion r3 = r1.intersect( r2 );    // r3 = intersection
.br
    p.begin( this );                    // start painting widget
.br
    p.setClipRegion( r3 );              // set clip region
.br
    ...                                 // paint clipped graphics
.br
    p.end();                            // painting done
.br
    }
.br
.fi
.PP
QRegion is an implicitly shared class.
.PP
Due to window system limitations, the width and height of a region is limited to 65535 on Unix/X11.
.PP
See also QPainter::setClipRegion(), QPainter::setClipRect(), Graphics Classes and Image Processing Classes.
.SS "Member Type Documentation"
.SH "QRegion::RegionType"
Determines the shape of the region to be created.
.TP
\fCQRegion::Rectangle\fR - the region covers the entire rectangle.
.TP
\fCQRegion::Ellipse\fR - the region is an ellipse inside the rectangle.
.SH MEMBER FUNCTION DOCUMENTATION
.SH "QRegion::QRegion ()"
Constructs a null region.
.PP
See also isNull().
.SH "QRegion::QRegion ( int x, int y, int w, int h, RegionType t = Rectangle )"
Constructs a rectangular or elliptic region.
.PP
If \fIt\fR is Rectangle, the region is the filled rectangle (\fIx\fR, \fIy\fR, \fIw\fR, \fIh\fR). If \fIt\fR is Ellipse, the region is the filled ellipse with center at (\fIx\fR + \fIw\fR / 2, \fIy\fR + \fIh\fR / 2) and size (\fIw\fR ,\fIh\fR ).
.SH "QRegion::QRegion ( const QRect & r, RegionType t = Rectangle )"
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
.PP
Create a region based on the rectange \fIr\fR with region type \fIt\fR.
.PP
If the rectangle is invalid a null region will be created.
.PP
See also QRegion::RegionType.
.SH "QRegion::QRegion ( const QPointArray & a, bool winding = FALSE )"
Constructs a polygon region from the point array \fIa\fR.
.PP
If \fIwinding\fR is TRUE, the polygon region is filled using the winding algorithm, otherwise the default even-odd fill algorithm is used.
.PP
This constructor may create complex regions that will slow down painting when used.
.SH "QRegion::QRegion ( const QRegion & r )"
Constructs a new region which is equal to \fIr\fR.
.SH "QRegion::QRegion ( const QBitmap & bm )"
Constructs a region from the bitmap \fIbm\fR.
.PP
The resulting region consists of the pixels in \fIbm\fR that are \fCcolor1\fR, as if each pixel was a 1 by 1 rectangle.
.PP
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().
.SH "QRegion::~QRegion ()"
Destroys the region.
.SH "QRect QRegion::boundingRect () const"
Returns the bounding rectangle of this region. An empty region gives a rectangle that is QRect::isNull().
.SH "bool QRegion::contains ( const QPoint & p ) const"
Returns TRUE if the region contains the point \fIp\fR, or FALSE if \fIp\fR is outside the region.
.SH "bool QRegion::contains ( const QRect & r ) const"
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
.PP
Returns TRUE if the region overlaps the rectangle \fIr\fR; or FALSE if \fIr\fR is completely outside the region.
.SH "QRegion QRegion::eor ( const QRegion & r ) const"
Returns a region which is the exclusive or (XOR) of this region and \fIr\fR.
.PP
.ce 1
.B "[Image Omitted]"
.PP
The figure shows the exclusive or of two elliptical regions.
.SH "HRGN QRegion::handle () const"
Returns the region's handle.
.SH "QRegion QRegion::intersect ( const QRegion & r ) const"
Returns a region which is the intersection of this region and \fIr\fR.
.PP
.ce 1
.B "[Image Omitted]"
.PP
The figure shows the intersection of two elliptical regions.
.SH "bool QRegion::isEmpty () const"
Returns TRUE if the region is empty, or FALSE if it is non-empty. An empty region is a region that contains no points.
.PP
Example:
.PP
.nf
.br
    QRegion r1( 10, 10, 20, 20 );
.br
    QRegion r2( 40, 40, 20, 20 );
.br
    QRegion r3;
.br
    r1.isNull();                // FALSE
.br
    r1.isEmpty();               // FALSE
.br
    r3.isNull();                // TRUE
.br
    r3.isEmpty();               // TRUE
.br
    r3 = r1.intersect( r2 );    // r3 = intersection of r1 and r2
.br
    r3.isNull();                // FALSE
.br
    r3.isEmpty();               // TRUE
.br
    r3 = r1.unite( r2 );        // r3 = union of r1 and r2
.br
    r3.isNull();                // FALSE
.br
    r3.isEmpty();               // FALSE
.br
.fi
.PP
See also isNull().
.SH "bool QRegion::isNull () const"
Returns TRUE if the region is a null region, otherwise FALSE.
.PP
A null region is a region that has not been initialized. A null region is always empty.
.PP
See also isEmpty().
.SH "bool QRegion::operator!= ( const QRegion & r ) const"
Returns TRUE if the region is different from \fIr\fR, or FALSE if the regions are equal.
.SH "const QRegion QRegion::operator& ( const QRegion & r ) const"
Applies the intersect() function to this region and \fIr\fR. \fCr1&r2\fR is equivalent to \fCr1.intersect(r2)\fR
.PP
See also intersect().
.SH "QRegion & QRegion::operator&= ( const QRegion & r )"
Applies the intersect() function to this region and \fIr\fR and assigns the result to this region. \fCr1&=r2\fR is equivalent to \fCr1=r1.intersect(r2)\fR
.PP
See also intersect().
.SH "const QRegion QRegion::operator+ ( const QRegion & r ) const"
Applies the unite() function to this region and \fIr\fR. \fCr1+r2\fR is equivalent to \fCr1.unite(r2)\fR
.PP
See also unite() and operator|().
.SH "QRegion & QRegion::operator+= ( const QRegion & r )"
Applies the unite() function to this region and \fIr\fR and assigns the result to this region. \fCr1+=r2\fR is equivalent to \fCr1=r1.unite(r2)\fR
.PP
See also intersect().
.SH "const QRegion QRegion::operator- ( const QRegion & r ) const"
Applies the subtract() function to this region and \fIr\fR. \fCr1-r2\fR is equivalent to \fCr1.subtract(r2)\fR
.PP
See also subtract().
.SH "QRegion & QRegion::operator-= ( const QRegion & r )"
Applies the subtract() function to this region and \fIr\fR and assigns the result to this region. \fCr1-=r2\fR is equivalent to \fCr1=r1.subtract(r2)\fR
.PP
See also subtract().
.SH "QRegion & QRegion::operator= ( const QRegion & r )"
Assigns \fIr\fR to this region and returns a reference to the region.
.SH "bool QRegion::operator== ( const QRegion & r ) const"
Returns TRUE if the region is equal to \fIr\fR, or FALSE if the regions are different.
.SH "const QRegion QRegion::operator^ ( const QRegion & r ) const"
Applies the eor() function to this region and \fIr\fR. \fCr1^r2\fR is equivalent to \fCr1.eor(r2)\fR
.PP
See also eor().
.SH "QRegion & QRegion::operator^= ( const QRegion & r )"
Applies the eor() function to this region and \fIr\fR and assigns the result to this region. \fCr1^=r2\fR is equivalent to \fCr1=r1.eor(r2)\fR
.PP
See also eor().
.SH "const QRegion QRegion::operator| ( const QRegion & r ) const"
Applies the unite() function to this region and \fIr\fR. \fCr1|r2\fR is equivalent to \fCr1.unite(r2)\fR
.PP
See also unite() and operator+().
.SH "QRegion & QRegion::operator|= ( const QRegion & r )"
Applies the unite() function to this region and \fIr\fR and assigns the result to this region. \fCr1|=r2\fR is equivalent to \fCr1=r1.unite(r2)\fR
.PP
See also unite().
.SH "QMemArray<QRect> QRegion::rects () const"
Returns an array of non-overlapping rectangles that make up the region.
.PP
The union of all the rectangles is equal to the original region.
.SH "QRegion QRegion::subtract ( const QRegion & r ) const"
Returns a region which is \fIr\fR subtracted from this region.
.PP
.ce 1
.B "[Image Omitted]"
.PP
The figure shows the result when the ellipse on the right is subtracted from the ellipse on the left. (\fCleft-right\fR )
.SH "void QRegion::translate ( int dx, int dy )"
Translates (moves) the region \fIdx\fR along the X axis and \fIdy\fR along the Y axis.
.SH "QRegion QRegion::unite ( const QRegion & r ) const"
Returns a region which is the union of this region and \fIr\fR.
.PP
.ce 1
.B "[Image Omitted]"
.PP
The figure shows the union of two elliptical regions.
.SH RELATED FUNCTION DOCUMENTATION
.SH "QDataStream & operator<< ( QDataStream & s, const QRegion & r )"
Writes the region \fIr\fR to the stream \fIs\fR and returns a reference to the stream.
.PP
See also Format of the QDataStream operators.
.SH "QDataStream & operator>> ( QDataStream & s, QRegion & r )"
Reads a region from the stream \fIs\fR into \fIr\fR and returns a reference to the stream.
.PP
See also Format of the QDataStream operators.

.SH "SEE ALSO"
.BR http://doc.trolltech.com/qregion.html
.BR http://www.trolltech.com/faq/tech.html
.SH COPYRIGHT
Copyright 1992-2001 Trolltech AS, http://www.trolltech.com.  See the
license file included in the distribution for a complete license
statement.
.SH AUTHOR
Generated automatically from the source code.
.SH BUGS
If you find a bug in Qt, please report it as described in
.BR http://doc.trolltech.com/bughowto.html .
Good bug reports help us to help you. Thank you.
.P
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. 
.P
If you find errors in this manual page, please report them to
.BR qt-bugs@trolltech.com .
Please include the name of the manual page (qregion.3qt) and the Qt
version (3.0.3).