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< (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
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.
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Please include the name of the manual page (qregion.3qt)
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