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QPaintEngine Class Reference

The QPaintEngine class provides an abstract definition of how QPainter draws to a given device on a given platform. More...

#include <QPaintEngine>

Public Types

Public Functions


Detailed Description

The QPaintEngine class provides an abstract definition of how QPainter draws to a given device on a given platform.

Qt 4.0 provides several premade implementations of QPaintEngine for the different painter backends we support. We provide one paint engine for each window system and painting framework we support. This includes X11 on Unix/Linux, GDI/GDI+ on Windows and QuickDraw/CoreGraphics on Mac OS X. In addition we provide QPaintEngine implementations for OpenGL (accessible through QGLWidget) and PostScript (accessible through QPSPrinter on X11).

If one wants to use QPainter to draw to a different backend, such as PDF, one must subclass QPaintEngine and reimplement all its virtual functions. The QPaintEngine implementation is then made available by subclassing QPaintDevice and reimplementing the virtual function QPaintDevice::paintEngine().

QPaintEngine is created and owned by the QPaintDevice that created it.

The big advantage of the QPaintEngine approach opposed to the previous QPainter/QPaintDevice::cmd() approach is that it is now possible to adapt to multiple technologies on each platform and take advantage of the to the fullest.

See also QPainter and QPaintDevice::paintEngine().


Member Type Documentation

enum QPaintEngine::DirtyFlag
typedef QPaintEngine::DirtyFlags

The DirtyFlags typedef can store a combination of DirtyFlag values.

enum QPaintEngine::PaintEngineFeature
typedef QPaintEngine::PaintEngineFeatures

This enum is used to describe the features or capabilities that the paint engine has. If a feature is not supported by the engine, QPainter will do a best effort to emulate that feature through other means. The features that are currently emulated are: CoordTransform, PixmapTransform, LinearGradients, PixmapScale, AlphaFill and ClipTransform.

QPaintEngine::CoordTransformThe engine can transform the points in a drawing operation.
QPaintEngine::PenWidthTransformThe engine has support for transforming pen widths.
QPaintEngine::PatternTransformThe engine has support for transforming brush patterns.
QPaintEngine::PixmapTransformThe engine can transform pixmaps, including rotation and shearing.
QPaintEngine::LinearGradientsThe engine can fill with linear gradients
QPaintEngine::PixmapScaleThe engine can scale pixmaps.
QPaintEngine::AlphaFillThe engine can fill and outline with alpha colors
QPaintEngine::PainterPathsThe engine has path support.
QPaintEngine::ClipTransformThe engine is capable of transforming clip regions.
QPaintEngine::PaintOutsidePaintEventThe engine is capable of painting outside of paint events.

The PaintEngineFeatures typedef can store a combination of PaintEngineFeature values.

enum QPaintEngine::PolygonDrawMode

QPaintEngine::OddEvenMode 
QPaintEngine::WindingMode 
QPaintEngine::ConvexMode 
QPaintEngine::PolylineMode 

enum QPaintEngine::Type

QPaintEngine::X11 
QPaintEngine::Windows 
QPaintEngine::Gdiplus(same as Windows)
QPaintEngine::QuickDraw(same as CoreGraphics)
QPaintEngine::MacPrinter 
QPaintEngine::CoreGraphicsMac OS X
QPaintEngine::QWindowSystemQt/Embedded
QPaintEngine::PostScript 
QPaintEngine::OpenGL 
QPaintEngine::PictureQPicture format
QPaintEngine::SVGScalable Vector Graphics XML format
QPaintEngine::UserFirst user type ID
QPaintEngine::MaxUserLast user type ID

Member Function Documentation

QPaintEngine::QPaintEngine ( PaintEngineFeatures caps = 0 )

Creates a paint engine with the featureset specified by caps.

QPaintEngine::~QPaintEngine ()   [virtual]

Destroys the paint engine.

bool QPaintEngine::begin ( QPaintDevice * pdev )   [pure virtual]

Reimplement this function to initialise your paint engine when painting is to start on the paint device pdev. Return true if the initialization was successful; otherwise return false.

See also end() and isActive().

void QPaintEngine::drawEllipse ( const QRectF & rect )   [virtual]

Reimplement this function to draw the largest ellipse that can be contained within rectangle rect.

The default implementation calls drawPolygon().

See also drawPolygon.

void QPaintEngine::drawImage ( const QRectF & rectangle, const QImage & image, const QRectF & sr, Qt::ImageConversionFlags flags = Qt::AutoColor )   [virtual]

Reimplement this function to draw the part of the image specified by the sr rectangle in the given rectangle using the given conversion flags flags, to convert it to a pixmap.

void QPaintEngine::drawLine ( const QLineF & line )   [virtual]

The default implementation splits line into two points and calls the integer version of drawLine().

void QPaintEngine::drawLines ( const QList<QLineF> & lines )   [virtual]

Calls drawLine() for every pair of points in the point array pa.

void QPaintEngine::drawPath ( const QPainterPath & path )   [virtual]

The default implementation ignores the path and does nothing.

void QPaintEngine::drawPixmap ( const QRectF & rectangle, const QPixmap & pixmap, const QRectF & sr, Qt::PixmapDrawingMode mode = Qt::ComposePixmap )   [pure virtual]

Reimplement this function to draw the part of the pixmap specified by the sr rectangle in the given rectangle using the given drawing mode.

void QPaintEngine::drawPoint ( const QPointF & pf )   [virtual]

The default implementation converts pf to an integer point and calls the integer version of drawPoint().

void QPaintEngine::drawPoints ( const QPolygon & p )   [virtual]

Calls drawPoint() to draw every point in the polygon p.

void QPaintEngine::drawPolygon ( const QPolygon & polygon, PolygonDrawMode mode )   [pure virtual]

Reimplement this pure virtual function to draw polygon using the drawing mode mode.

void QPaintEngine::drawRect ( const QRectF & rf )   [virtual]

The default implementation converts rf to an integer rectangle and calls the integer version of drawRect().

void QPaintEngine::drawRects ( const QList<QRectF> & rects )   [virtual]

Draws the rectangles in the list rects.

void QPaintEngine::drawTextItem ( const QPointF & p, const QTextItem & ti )   [virtual]

This function draws the text item ti at position p. The default implementation of this function converts the text to a QPainterPath and paints the resulting path.

void QPaintEngine::drawTiledPixmap ( const QRectF & rect, const QPixmap & pixmap, const QPointF & p, Qt::PixmapDrawingMode mode = Qt::ComposePixmap )   [virtual]

Reimplement this function to draw the pixmap in the given rectangle, starting at the given point. The pixmap will be drawn repeatedly until the rectangle is filled using the given mode.

bool QPaintEngine::end ()   [pure virtual]

Reimplement this function to finish painting on the current paint device. Return true if painting was finished successfully; otherwise return false.

See also begin() and isActive().

bool QPaintEngine::hasFeature ( PaintEngineFeatures feature ) const

Returns true if the paint engine supports the specified feature; otherwise returns false.

bool QPaintEngine::isActive () const

Returns true if the paint engine is actively drawing; otherwise returns false.

See also setActive().

QPaintDevice * QPaintEngine::paintDevice () const

Returns the engine that this engine is painting on if painting is active; otherwise 0;

QPainter * QPaintEngine::painter () const

Returns the paint engine's painter.

QPainter::RenderHints QPaintEngine::renderHints () const

Returns the currently set renderhints.

void QPaintEngine::setActive ( bool state )

Sets the active state of the paint engine to state.

See also isActive().

void QPaintEngine::setPaintDevice ( QPaintDevice * device )

\interalSets the paintdevice that this engine operates on to device

void QPaintEngine::setRenderHint ( QPainter::RenderHint hint, bool on )

Sets the render hint hint on this engine if on is true; otherwise clears the render hint.

QPainter::RenderHints QPaintEngine::supportedRenderHints () const   [virtual]

Returns the set of supported renderhints.

Type QPaintEngine::type () const   [pure virtual]

Reimplement this function to return the paint engine Type.

void QPaintEngine::updateBackground ( Qt::BGMode bgmode, const QBrush & brush )   [pure virtual]

This function is called when the engine needs to be updated with new background settings. bgmode describes the background mode and brush describes the background brush.

void QPaintEngine::updateBrush ( const QBrush & brush, const QPointF & origin )   [pure virtual]

This function is called when the engine needs to be updated with a new brush, specified with brush. origin describes the brush origin.

If the brush is a gradient brush, the gradient points are specified in device coordinates.

void QPaintEngine::updateClipPath ( const QPainterPath & path, Qt::ClipOperation op )   [virtual]

This function is called when the engine needs to be updated with the new clip path. The value of enabled signifies whether or not the clippath should be enabled.

void QPaintEngine::updateClipRegion ( const QRegion & region, Qt::ClipOperation op )   [pure virtual]

void QPaintEngine::updateFont ( const QFont & f )   [pure virtual]

This function is called when the engine needs to be updated with a new font, specified by f

void QPaintEngine::updateMatrix ( const QMatrix & matrix )   [pure virtual]

This function is called when the engine needs to be updated with new transformation settings, specified with matrix.

void QPaintEngine::updatePen ( const QPen & pen )   [pure virtual]

This function is called when the engine needs to be updated with the a new pen, specified by pen.

void QPaintEngine::updateRenderHints ( QPainter::RenderHints hints )   [virtual]

This function is caleed when the engine needs to be updated with the new set of renderhints specified by hints.


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Qt 4.0.0-b1