QRegion - Clip region for a painter

       #include <qregion.h>

   Public Members
       enum RegionType { Rectangle, Ellipse }
       QRegion ()
       QRegion ( int x, int y, int w, int h, RegionType =
           Rectangle )
       QRegion ( const QRect &, RegionType = Rectangle )
       QRegion ( const QPointArray &, bool winding=FALSE )
       QRegion ( const QRegion & )
       QRegion ( const QBitmap & )
       ~QRegion ()
       QRegion& operator= ( const QRegion & )
       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 & ) const
       QRegion intersect ( const QRegion & ) const
       QRegion subtract ( const QRegion & ) const
       QRegion eor ( const QRegion & ) const
       QRect boundingRect () const
       QArray<QRect> rects () const
       void setRects ( const QRect *, int )
       QRegion operator| ( const QRegion & ) const
       QRegion operator+ ( const QRegion & ) const
       QRegion operator& ( const QRegion & ) const
       QRegion operator- ( const QRegion & ) const
       QRegion operator^ ( const QRegion & ) const
       QRegion& operator|= ( const QRegion & )
       QRegion& operator+= ( const QRegion & )
       QRegion& operator&= ( const QRegion & )
       QRegion& operator-= ( const QRegion & )
       QRegion& operator^= ( const QRegion & )
       bool operator== ( const QRegion & ) const
       bool operator!= ( const QRegion & r ) const


RELATED FUNCTION DOCUMENTATION

       (Note that these are not member functions.)
       QDataStream & operator>> (QDataStream & s, QRegion & r)
       QDataStream & operator<< (QDataStream & s, const 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.


       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). Use translate() to
       move a region.

       You can test if 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 implicitely shared class.

       Due to window system limitations, the width and height of
       a region is limited to 65535 on Unix/X11.

       See also QPainter::setClipRegion() and
       QPainter::setClipRect().

   Member Type Documentation

QRegion::RegionType

       Determines the shape of the region to be created.

       Rectangle - the region covers the entire rectangle

       Ellipse - the region is an ellipse inside the rectangle


MEMBER FUNCTION DOCUMENTATION


QRegion::QRegion ()

       Constructs a null region.

       See also isNull().


QRegion::QRegion ( const QBitmap & bm )

       Constructs a region from the bitmap bm.

       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 ( 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 r.


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 ellipse with center at (x + w / 2, y + h / 2) and
       size (w ,h ).


QRegion::~QRegion ()

       Destructs 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, or FALSE
       if p is outside the region.


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

       Returns TRUE if the region overlaps the rectangle r, or
       FALSE if r is completely outside the region.


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

       Returns a region which is the exclusive or (XOR) of this
       region and r.

                            [Image Omitted]

       The figure shows the exclusive or of two elliptical
       regions.

       Returns a region which is the intersection of this region
       and r.

                            [Image Omitted]

       The figure shows the intersection of two elliptical
       regions.


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.

       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
       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, or FALSE
       if the regions are equal.


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

       r1&r2 is equivalent to r1.intersect(r2)

       See also intersect().


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

       r1&=r2 is equivalent to r1=r1.intersect(r2)

       See also intersect().

       r1+r2 is equivalent to r1.unite(r2)

       See also unite() and operator|().


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

       r1+=r2 is equivalent to r1=r1.unite(r2)

       See also intersect().


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

       r1-r2 is equivalent to r1.subtract(r2)

       See also subtract().


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

       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, or FALSE if the
       regions are different.


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

       r1^r2 is equivalent to r1.eor(r2)

       See also eor().


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

       r1^=r2 is equivalent to r1=r1.eor(r2)

       See also eor().


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

       r1|r2 is equivalent to r1.unite(r2)

       See also unite() and operator+().


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

       r1|=r2 is equivalent to r1=r1.unite(r2)

       See also unite().


QArray 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.

       Sets the region to be the given set of rectangles. The
       rectangles must be optimal Y-X sorted bands as follows:

       The rectangles must not intersect

       All rectangles with a given top coordinate must have the
              same height.

       No two rectangles may abut horizontally (they should be
              combined into a single wider rectangle in that
              case).

       The rectangles must be sorted ascendingly by Y as the
              major sort key and X as the minor sort key.


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

       Returns a region which is r subtracted from this region.

                            [Image Omitted]

       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.

                            [Image Omitted]

       The figure shows the union of two elliptical regions.


RELATED FUNCTION DOCUMENTATION


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


QDataStream & operator
       Writes the region r to the stream s 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,

       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
       make our job much simpler. Thank you.

       In case of content or formattting problems with 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 (2.3.1).


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