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QPaintEngine Class Reference
[QtGui module]

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

Types

Methods


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 and CoreGraphics on Mac OS X. In addition we provide QPaintEngine implementations for OpenGL (accessible through QGLWidget) and PostScript (accessible through QPSPrinter on X11). Additionally there is a raster-based paint engine that is a fallback for when an engine does not support a certain capability.

If one wants to use QPainter to draw to a different backend, 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 Qt 3's QPainter/QPaintDevice.cmd() approach is that it is now possible to adapt to multiple technologies on each platform and take advantage of each to the fullest.


Type Documentation

QPaintEngine.DirtyFlag

Constant Value Description
QPaintEngine.DirtyPen 0x0001 The pen is dirty and needs to be updated.
QPaintEngine.DirtyBrush 0x0002 The brush is dirty and needs to be updated.
QPaintEngine.DirtyBrushOrigin 0x0004 The brush origin is dirty and needs to updated.
QPaintEngine.DirtyFont 0x0008 The font is dirty and needs to be updated.
QPaintEngine.DirtyBackground 0x0010 The background is dirty and needs to be updated.
QPaintEngine.DirtyBackgroundMode 0x0020 The background mode is dirty and needs to be updated.
QPaintEngine.DirtyTransform 0x0040 The transform is dirty and needs to be updated.
QPaintEngine.DirtyClipRegion 0x0080 The clip region is dirty and needs to be updated.
QPaintEngine.DirtyClipPath 0x0100 The clip path is dirty and needs to be updated.
QPaintEngine.DirtyHints 0x0200 The render hints is dirty and needs to be updated.
QPaintEngine.DirtyCompositionMode 0x0400 The composition mode is dirty and needs to be updated.
QPaintEngine.DirtyClipEnabled 0x0800 Whether clipping is enabled or not is dirty and needs to be updated.
QPaintEngine.DirtyOpacity 0x1000 The constant opacity has changed and needs to be updated as part of the state change in QPaintEngine.updateState().
QPaintEngine.AllDirty 0xffff Convenience enum used internally.

These types are used by QPainter to trigger lazy updates of the various states in the QPaintEngine using QPaintEngine.updateState().

A paint engine must update every dirty state.

The DirtyFlags type is a typedef for QFlags<DirtyFlag>. It stores an OR combination of DirtyFlag values.

QPaintEngine.PaintEngineFeature

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 and pass on an alpha blended QImage to the engine with the emulated results. Some features cannot be emulated: AlphaBlend and PorterDuff.

Constant Value Description
QPaintEngine.AlphaBlend 0x00000080 The engine can alpha blend primitives.
QPaintEngine.Antialiasing 0x00000400 The engine can use antialising to improve the appearance of rendered primitives.
QPaintEngine.BlendModes 0x00008000 The engine supports blending modes.
QPaintEngine.BrushStroke 0x00000800 The engine supports drawing strokes that contain brushes as fills, not just solid colors (e.g. a dashed gradient line of width 2).
QPaintEngine.ConicalGradientFill 0x00000040 The engine supports conical gradient fills.
QPaintEngine.ConstantOpacity 0x00001000 The engine supports the feature provided by QPainter.setOpacity().
QPaintEngine.LinearGradientFill 0x00000010 The engine supports linear gradient fills.
QPaintEngine.MaskedBrush 0x00002000 The engine is capable of rendering brushes that has a texture with an alpha channel or a mask.
QPaintEngine.ObjectBoundingModeGradients 0x00010000 The engine has native support for gradients with coordinate mode QGradient.ObjectBoundingMode. Otherwise, if QPaintEngine.PatternTransform is supported, object bounding mode gradients are converted to gradients with coordinate mode QGradient.LogicalMode and a brush transform for the coordinate mapping.
QPaintEngine.PainterPaths 0x00000200 The engine has path support.
QPaintEngine.PaintOutsidePaintEvent 0x20000000 The engine is capable of painting outside of paint events.
QPaintEngine.PatternBrush 0x00000008 The engine is capable of rendering brushes with the brush patterns specified in Qt.BrushStyle.
QPaintEngine.PatternTransform 0x00000002 The engine has support for transforming brush patterns.
QPaintEngine.PerspectiveTransform 0x00004000 The engine has support for performing perspective transformations on primitives.
QPaintEngine.PixmapTransform 0x00000004 The engine can transform pixmaps, including rotation and shearing.
QPaintEngine.PorterDuff 0x00000100 The engine supports Porter-Duff operations
QPaintEngine.PrimitiveTransform 0x00000001 The engine has support for transforming drawing primitives.
QPaintEngine.RadialGradientFill 0x00000020 The engine supports radial gradient fills.
QPaintEngine.RasterOpModes 0x00020000 The engine supports bitwise raster operations.
QPaintEngine.AllFeatures 0xffffffff All of the above features. This enum value is usually used as a bit mask.

The PaintEngineFeatures type is a typedef for QFlags<PaintEngineFeature>. It stores an OR combination of PaintEngineFeature values.

QPaintEngine.PolygonDrawMode

Constant Value Description
QPaintEngine.OddEvenMode 0 The polygon should be drawn using OddEven fill rule.
QPaintEngine.WindingMode 1 The polygon should be drawn using Winding fill rule.
QPaintEngine.ConvexMode 2 The polygon is a convex polygon and can be drawn using specialized algorithms where available.
QPaintEngine.PolylineMode 3 Only the outline of the polygon should be drawn.

QPaintEngine.Type

Constant Value Description
QPaintEngine.X11 0  
QPaintEngine.Windows 1  
QPaintEngine.MacPrinter 4  
QPaintEngine.CoreGraphics 3 Mac OS X's Quartz2D (CoreGraphics)
QPaintEngine.QuickDraw 2 Mac OS X's QuickDraw
QPaintEngine.QWindowSystem 5 Qt for Embedded Linux
QPaintEngine.PostScript 6  
QPaintEngine.OpenGL 7  
QPaintEngine.Picture 8 QPicture format
QPaintEngine.SVG 9 Scalable Vector Graphics XML format
QPaintEngine.Raster 10  
QPaintEngine.Direct3D 11 Windows only, Direct3D based engine
QPaintEngine.Pdf 12 Portable Document Format
QPaintEngine.OpenVG 13  
QPaintEngine.User 50 First user type ID
QPaintEngine.MaxUser 100 Last user type ID
QPaintEngine.OpenGL2 14  
QPaintEngine.PaintBuffer 15  
QPaintEngine.Blitter 16  

Method Documentation

QPaintEngine.__init__ (self, PaintEngineFeatures features = 0)

Creates a paint engine with the featureset specified by caps.

bool QPaintEngine.begin (self, QPaintDevice pdev)

This method is abstract and should be reimplemented in any sub-class.

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().

QPaintEngine.drawEllipse (self, QRectF r)

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

The default implementation calls drawPolygon().

QPaintEngine.drawEllipse (self, QRect r)

The default implementation of this function calls the floating point version of this function

QPaintEngine.drawImage (self, QRectF r, QImage pm, QRectF sr, Qt.ImageConversionFlags flags = Qt.AutoColor)

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.

QPaintEngine.drawLines (self, QLine lines)

The default implementation splits the list of lines in lines into lineCount separate calls to drawPath() or drawPolygon() depending on the feature set of the paint engine.

QPaintEngine.drawLines (self, QLineF lines)

This is an overloaded function.

The default implementation converts the first lineCount lines in lines to a QLineF and calls the floating point version of this function.

QPaintEngine.drawPath (self, QPainterPath path)

The default implementation ignores the path and does nothing.

QPaintEngine.drawPixmap (self, QRectF r, QPixmap pm, QRectF sr)

This method is abstract and should be reimplemented in any sub-class.

Reimplement this function to draw the part of the pm specified by the sr rectangle in the given r.

QPaintEngine.drawPoints (self, QPointF points)

Draws the first pointCount points in the buffer points

QPaintEngine.drawPoints (self, QPoint points)

Draws the first pointCount points in the buffer points

The default implementation converts the first pointCount QPoints in points to QPointFs and calls the floating point version of drawPoints.

QPaintEngine.drawPolygon (self, QPointF points, PolygonDrawMode mode)

Reimplement this virtual function to draw the polygon defined by the pointCount first points in points, using mode mode.

Note: At least one of the drawPolygon() functions must be reimplemented.

QPaintEngine.drawPolygon (self, QPoint points, PolygonDrawMode mode)

This is an overloaded function.

Reimplement this virtual function to draw the polygon defined by the pointCount first points in points, using mode mode.

Note: At least one of the drawPolygon() functions must be reimplemented.

QPaintEngine.drawRects (self, QRect rects)

Draws the first rectCount rectangles in the buffer rects. The default implementation of this function calls drawPath() or drawPolygon() depending on the feature set of the paint engine.

QPaintEngine.drawRects (self, QRectF rects)

This is an overloaded function.

The default implementation converts the first rectCount rectangles in the buffer rects to a QRectF and calls the floating point version of this function.

QPaintEngine.drawTextItem (self, QPointF p, QTextItem textItem)

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

QPaintEngine.drawTiledPixmap (self, QRectF r, QPixmap pixmap, QPointF s)

Reimplement this function to draw the pixmap in the given rect, starting at the given p. The pixmap will be drawn repeatedly until the rect is filled.

bool QPaintEngine.end (self)

This method is abstract and should be reimplemented in any sub-class.

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 (self, PaintEngineFeatures feature)

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

bool QPaintEngine.isActive (self)

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

See also setActive().

QPaintDevice QPaintEngine.paintDevice (self)

Returns the device that this engine is painting on, if painting is active; otherwise returns 0.

QPainter QPaintEngine.painter (self)

Returns the paint engine's painter.

QPaintEngine.setActive (self, bool newState)

Sets the active state of the paint engine to state.

See also isActive().

QPaintEngine.setPaintDevice (self, QPaintDevice device)

Type QPaintEngine.type (self)

This method is abstract and should be reimplemented in any sub-class.

Reimplement this function to return the paint engine Type.

QPaintEngine.updateState (self, QPaintEngineState state)

This method is abstract and should be reimplemented in any sub-class.

Reimplement this function to update the state of a paint engine.

When implemented, this function is responsible for checking the paint engine's current state and update the properties that are changed. Use the QPaintEngineState.state() function to find out which properties that must be updated, then use the corresponding get function to retrieve the current values for the given properties.

See also QPaintEngineState.


PyQt 4.12 for X11Copyright © Riverbank Computing Ltd and The Qt Company 2015Qt 4.8.7