Base class for visual effects which can be applied to QPicture drawings. More...

#include <qgspainteffect.h>

Inheritance diagram for QgsPaintEffect:

[legend]

Public Types
enum	DrawMode { Modifier , Render , ModifyAndRender }
	Drawing modes for effects. More...

Public Member Functions
	QgsPaintEffect ()=default
	Constructor for QgsPaintEffect.

	QgsPaintEffect (const QgsPaintEffect &other)

virtual	~QgsPaintEffect ()

virtual void	begin (QgsRenderContext &context)
	Begins intercepting paint operations to a render context.

virtual QgsPaintEffect *	clone () const =0
	Duplicates an effect by creating a deep copy of the effect.

DrawMode	drawMode () const
	Returns the draw mode for the effect.

bool	enabled () const
	Returns whether the effect is enabled.

virtual void	end (QgsRenderContext &context)
	Ends interception of paint operations to a render context, and draws the result to the render context after being modified by the effect.

virtual QVariantMap	properties () const =0
	Returns the properties describing the paint effect encoded in a string format.

virtual bool	readProperties (const QDomElement &element)
	Restores the effect to the state described by a DOM element.

virtual void	readProperties (const QVariantMap &props)=0
	Reads a string map of an effect's properties and restores the effect to the state described by the properties map.

virtual void	render (QPicture &picture, QgsRenderContext &context)
	Renders a picture using the effect.

virtual bool	saveProperties (QDomDocument &doc, QDomElement &element) const
	Saves the current state of the effect to a DOM element.

void	setDrawMode (DrawMode drawMode)
	Sets the draw mode for the effect.

void	setEnabled (bool enabled)
	Sets whether the effect is enabled.

virtual QString	type () const =0
	Returns the effect type.

Protected Member Functions
virtual QRectF	boundingRect (const QRectF &rect, const QgsRenderContext &context) const
	Returns the bounding rect required for drawing the effect.

virtual void	draw (QgsRenderContext &context)=0
	Handles drawing of the effect's result on to the specified render context.

void	drawSource (QPainter &painter)
	Draws the source QPicture onto the specified painter.

void	fixQPictureDpi (QPainter *painter) const
	Applies a workaround to a QPainter to avoid an issue with incorrect scaling when drawing QPictures.

QPointF	imageOffset (const QgsRenderContext &context) const
	Returns the offset which should be used when drawing the source image on to a destination render context.

const QPicture *	source () const
	Returns the source QPicture.

QImage *	sourceAsImage (QgsRenderContext &context)
	Returns the source QPicture rendered to a new QImage.

Protected Attributes
DrawMode	mDrawMode = ModifyAndRender

bool	mEnabled = true

bool	requiresQPainterDpiFix = true

Friends
class	QgsEffectStack

Detailed Description

Base class for visual effects which can be applied to QPicture drawings.

QgsPaintEffect objects can be used to modify QPicture drawings prior to rendering them with a QPainter operation. There are two methods for drawing using an effect, either drawing a picture directly, or by intercepting drawing operations to a render context.

To directly draw a picture, use the render() method with a source QPicture and destination render context.

Intercepting drawing operations to a render context is achieved by first calling the begin() method, passing a render context. Any drawing operations performed on the render context will not directly affect the context's paint device. When the drawing operations have been completed, call the end() method. This will perform the paint effect on the intercepted drawing operations and render the result to the render context's paint device.

See also: QgsPaintEffectRegistry

Definition at line 51 of file qgspainteffect.h.

Member Enumeration Documentation

◆ DrawMode

enum QgsPaintEffect::DrawMode

Drawing modes for effects.

These modes are used only when effects are drawn as part of an effects stack

See also: QgsEffectStack

Enumerator
Modifier	The result of the effect is not rendered, but is passed on to following effects in the stack.
Render	The result of the effect is rendered on the destination, but does not affect subsequent effects in the stack.
ModifyAndRender	The result of the effect is both rendered and passed on to subsequent effects in the stack.

Definition at line 102 of file qgspainteffect.h.

Constructor & Destructor Documentation

◆ QgsPaintEffect() [1/2]

QgsPaintEffect::QgsPaintEffect ( )

default

Constructor for QgsPaintEffect.

◆ QgsPaintEffect() [2/2]

QgsPaintEffect::QgsPaintEffect ( const QgsPaintEffect & other )

Definition at line 28 of file qgspainteffect.cpp.

◆ ~QgsPaintEffect()

QgsPaintEffect::~QgsPaintEffect ( )

virtual

Definition at line 35 of file qgspainteffect.cpp.

Member Function Documentation

◆ begin()

void QgsPaintEffect::begin ( QgsRenderContext & context )

virtual

Begins intercepting paint operations to a render context.

When the corresponding end() member is called all intercepted paint operations will be drawn to the render context after being modified by the effect.

Parameters

context destination render context

See also: end; render

Definition at line 90 of file qgspainteffect.cpp.

◆ boundingRect()

QRectF QgsPaintEffect::boundingRect	(	const QRectF &	rect,
		const QgsRenderContext &	context
	)		const

protectedvirtual

Returns the bounding rect required for drawing the effect.

This method can be used to expand the bounding rect of a source picture to account for offset or blurring effects.

Parameters

rect	original source bounding rect
context	destination render context

Returns: modified bounding rect

See also: sourceAsImage

Reimplemented in QgsBlurEffect, QgsGlowEffect, QgsShadowEffect, and QgsTransformEffect.

Definition at line 175 of file qgspainteffect.cpp.

◆ clone()

virtual QgsPaintEffect * QgsPaintEffect::clone ( ) const

pure virtual

Duplicates an effect by creating a deep copy of the effect.

Returns: clone of paint effect

Implemented in QgsBlurEffect, QgsColorEffect, QgsEffectStack, QgsOuterGlowEffect, QgsInnerGlowEffect, QgsDrawSourceEffect, QgsDropShadowEffect, QgsInnerShadowEffect, and QgsTransformEffect.

◆ draw()

virtual void QgsPaintEffect::draw ( QgsRenderContext & context )

protectedpure virtual

Handles drawing of the effect's result on to the specified render context.

Derived classes must reimplement this method to apply any transformations to the source QPicture and draw the result using the context's painter.

Parameters

context destination render context

See also: drawSource

Implemented in QgsBlurEffect, QgsColorEffect, QgsEffectStack, QgsGlowEffect, QgsDrawSourceEffect, QgsShadowEffect, and QgsTransformEffect.

◆ drawMode()

DrawMode QgsPaintEffect::drawMode ( ) const

inline

Returns the draw mode for the effect.

This property only has an effect if the paint effect is used in a QgsEffectStack.

Returns: draw mode for effect

See also: setDrawMode

Definition at line 211 of file qgspainteffect.h.

◆ drawSource()

void QgsPaintEffect::drawSource ( QPainter & painter )

protected

Draws the source QPicture onto the specified painter.

Handles scaling of the picture to account for the destination painter's DPI.

Parameters

painter destination painter

See also: source; sourceAsImage

Definition at line 131 of file qgspainteffect.cpp.

◆ enabled()

bool QgsPaintEffect::enabled ( ) const

inline

Returns whether the effect is enabled.

Returns: true if effect is enabled

See also: setEnabled

Definition at line 196 of file qgspainteffect.h.

◆ end()

void QgsPaintEffect::end ( QgsRenderContext & context )

virtual

Ends interception of paint operations to a render context, and draws the result to the render context after being modified by the effect.

Parameters

context destination render context

See also: begin

Definition at line 105 of file qgspainteffect.cpp.

◆ fixQPictureDpi()

void QgsPaintEffect::fixQPictureDpi ( QPainter * painter ) const

protected

Applies a workaround to a QPainter to avoid an issue with incorrect scaling when drawing QPictures.

This may need to be called by derived classes prior to rendering results onto a painter.

Parameters

painter destination painter

Definition at line 181 of file qgspainteffect.cpp.

◆ imageOffset()

QPointF QgsPaintEffect::imageOffset ( const QgsRenderContext & context ) const

protected

Returns the offset which should be used when drawing the source image on to a destination render context.

Parameters

context destination render context

Returns: point offset for image top left corner

See also: sourceAsImage

Definition at line 170 of file qgspainteffect.cpp.

◆ properties()

virtual QVariantMap QgsPaintEffect::properties ( ) const

pure virtual

Returns the properties describing the paint effect encoded in a string format.

Returns: string map of properties, in the form property key, value

See also: readProperties; saveProperties

Implemented in QgsBlurEffect, QgsColorEffect, QgsEffectStack, QgsGlowEffect, QgsDrawSourceEffect, QgsShadowEffect, and QgsTransformEffect.

◆ readProperties() [1/2]

bool QgsPaintEffect::readProperties ( const QDomElement & element )

virtual

Restores the effect to the state described by a DOM element.

Parameters

element DOM element describing an effect's state

Returns: true if read was successful

See also: saveProperties

Reimplemented in QgsEffectStack.

Definition at line 68 of file qgspainteffect.cpp.

◆ readProperties() [2/2]

virtual void QgsPaintEffect::readProperties ( const QVariantMap & props )

pure virtual

Reads a string map of an effect's properties and restores the effect to the state described by the properties map.

Parameters

props effect properties encoded in a string map

See also: properties

Implemented in QgsBlurEffect, QgsColorEffect, QgsEffectStack, QgsGlowEffect, QgsDrawSourceEffect, QgsShadowEffect, and QgsTransformEffect.

◆ render()

void QgsPaintEffect::render	(	QPicture &	picture,
		QgsRenderContext &	context
	)

virtual

Renders a picture using the effect.

Parameters

picture	source QPicture to render
context	destination render context

See also: begin

Definition at line 80 of file qgspainteffect.cpp.

◆ saveProperties()

bool QgsPaintEffect::saveProperties	(	QDomDocument &	doc,
		QDomElement &	element
	)		const

virtual

Saves the current state of the effect to a DOM element.

The default behavior is to save the properties string map returned by properties().

Parameters

doc	destination DOM document
element	destination DOM element

Returns: true if save was successful

See also: readProperties

Reimplemented in QgsEffectStack.

Definition at line 55 of file qgspainteffect.cpp.

◆ setDrawMode()

void QgsPaintEffect::setDrawMode ( const QgsPaintEffect::DrawMode drawMode )

Sets the draw mode for the effect.

This property only has an effect if the paint effect is used in a QgsEffectStack.

Parameters

drawMode draw mode for effect

See also: drawMode

Definition at line 50 of file qgspainteffect.cpp.

◆ setEnabled()

void QgsPaintEffect::setEnabled ( bool enabled )

Sets whether the effect is enabled.

Parameters

enabled set to false to disable the effect

See also: enabled

Definition at line 45 of file qgspainteffect.cpp.

◆ source()

const QPicture * QgsPaintEffect::source ( ) const

inlineprotected

Returns the source QPicture.

The draw() member can utilize this when drawing the effect.

Returns: source QPicture

See also: drawSource; sourceAsImage

Definition at line 252 of file qgspainteffect.h.

◆ sourceAsImage()

QImage * QgsPaintEffect::sourceAsImage ( QgsRenderContext & context )

protected

Returns the source QPicture rendered to a new QImage.

The draw() member can utilize this when drawing the effect. The image will be padded or cropped from the original source QPicture by the results of the boundingRect() method. The result is cached to speed up subsequent calls to sourceAsImage.

Returns: source QPicture rendered to an image

See also: drawSource; source; imageOffset; boundingRect

Definition at line 145 of file qgspainteffect.cpp.

◆ type()

virtual QString QgsPaintEffect::type ( ) const

pure virtual

Returns the effect type.

Returns: unique string representation of the effect type

Implemented in QgsBlurEffect, QgsColorEffect, QgsEffectStack, QgsOuterGlowEffect, QgsInnerGlowEffect, QgsDrawSourceEffect, QgsDropShadowEffect, QgsInnerShadowEffect, and QgsTransformEffect.

Friends And Related Symbol Documentation

◆ QgsEffectStack

friend class QgsEffectStack

friend

Definition at line 307 of file qgspainteffect.h.

Member Data Documentation

◆ mDrawMode

DrawMode QgsPaintEffect::mDrawMode = ModifyAndRender

protected

Definition at line 224 of file qgspainteffect.h.

◆ mEnabled

bool QgsPaintEffect::mEnabled = true

protected

Definition at line 223 of file qgspainteffect.h.

◆ requiresQPainterDpiFix

bool QgsPaintEffect::requiresQPainterDpiFix = true

protected

Definition at line 225 of file qgspainteffect.h.

The documentation for this class was generated from the following files:

/home/fischer/src/qgis-3.38/src/core/effects/qgspainteffect.h
/home/fischer/src/qgis-3.38/src/core/effects/qgspainteffect.cpp

Public Types

Public Member Functions

Protected Member Functions

Protected Attributes

Friends

Detailed Description

Member Enumeration Documentation

◆ DrawMode

Constructor & Destructor Documentation

◆ QgsPaintEffect() [1/2]

◆ QgsPaintEffect() [2/2]

◆ ~QgsPaintEffect()

Member Function Documentation

◆ begin()

◆ boundingRect()

◆ clone()

◆ draw()

◆ drawMode()

◆ drawSource()

◆ enabled()

◆ end()

◆ fixQPictureDpi()

◆ imageOffset()

◆ properties()

◆ readProperties() [1/2]

◆ readProperties() [2/2]

◆ render()

◆ saveProperties()

◆ setDrawMode()

◆ setEnabled()

◆ source()

◆ sourceAsImage()

◆ type()

Friends And Related Symbol Documentation

◆ QgsEffectStack

Member Data Documentation

◆ mDrawMode

◆ mEnabled

◆ requiresQPainterDpiFix