QgsVectorLayerRenderer Class Reference

Implementation of threaded rendering for vector layers. More...

#include <qgsvectorlayerrenderer.h>

Inheritance diagram for QgsVectorLayerRenderer:

Public Member Functions
	QgsVectorLayerRenderer (QgsVectorLayer *layer, QgsRenderContext &context)
	~QgsVectorLayerRenderer () override
QgsFeatureRenderer *	featureRenderer ()
	Returns the feature renderer. More...
QgsFeedback *	feedback () const override
	Access to feedback object of the layer renderer (may be nullptr) More...
bool	forceRasterRender () const override
	Returns true if the renderer must be rendered to a raster paint device (e.g. More...
bool	render () override
	Do the rendering (based on data stored in the class). More...
void	setLayerRenderingTimeHint (int time) override
	Sets approximate render time (in ms) for the layer to render. More...
Public Member Functions inherited from QgsMapLayerRenderer
	QgsMapLayerRenderer (const QString &layerID, QgsRenderContext *context=nullptr)
	Constructor for QgsMapLayerRenderer, with the associated layerID and render context. More...
virtual	~QgsMapLayerRenderer ()
QStringList	errors () const
	Returns list of errors (problems) that happened during the rendering. More...
virtual QgsFeedback *	feedback () const
	Access to feedback object of the layer renderer (may be nullptr) More...
virtual bool	forceRasterRender () const
	Returns true if the renderer must be rendered to a raster paint device (e.g. More...
bool	isReadyToCompose () const
	Returns whether the renderer has already drawn (at least partially) some data. More...
QString	layerId () const
	Gets access to the ID of the layer rendered by this class. More...
virtual bool	render ()=0
	Do the rendering (based on data stored in the class). More...
QgsRenderContext *	renderContext ()
	Returns the render context associated with the renderer. More...
const QgsRenderContext *	renderContext () const
	Returns the render context associated with the renderer. More...
virtual void	setLayerRenderingTimeHint (int time)
	Sets approximate render time (in ms) for the layer to render. More...
QList< QgsRenderedItemDetails * >	takeRenderedItemDetails ()
	Takes the list of rendered item details from the renderer. More...

Additional Inherited Members
Protected Member Functions inherited from QgsMapLayerRenderer
void	appendRenderedItemDetails (QgsRenderedItemDetails *details)
	Appends the details of a rendered item to the renderer. More...
Protected Attributes inherited from QgsMapLayerRenderer
QStringList	mErrors
QString	mLayerID
bool	mReadyToCompose = true
	The flag must be set to false in renderer's constructor if wants to use the smarter map redraws functionality https://github.com/qgis/QGIS-Enhancement-Proposals/issues/181. More...
Static Protected Attributes inherited from QgsMapLayerRenderer
static constexpr int	MAX_TIME_TO_USE_CACHED_PREVIEW_IMAGE = 3000
	Maximum time (in ms) to allow display of a previously cached preview image while rendering layers, before switching to a progressive rendering display. More...

Detailed Description

Implementation of threaded rendering for vector layers.

Note

not available in Python bindings

Since

QGIS 2.4

Definition at line 58 of file qgsvectorlayerrenderer.h.

Constructor & Destructor Documentation

QgsVectorLayerRenderer()

QgsVectorLayerRenderer::QgsVectorLayerRenderer	(	QgsVectorLayer *	layer,
		QgsRenderContext &	context
	)

Definition at line 49 of file qgsvectorlayerrenderer.cpp.

~QgsVectorLayerRenderer()

QgsVectorLayerRenderer::~QgsVectorLayerRenderer ( )

overridedefault

Member Function Documentation

featureRenderer()

QgsFeatureRenderer * QgsVectorLayerRenderer::featureRenderer ( )

inline

Returns the feature renderer.

This may be used for tweaking it before the actual rendering of the layer.

Since

QGIS 3.12

Definition at line 71 of file qgsvectorlayerrenderer.h.

feedback()

QgsFeedback * QgsVectorLayerRenderer::feedback ( ) const

overridevirtual

Access to feedback object of the layer renderer (may be nullptr)

Since

QGIS 3.0

Reimplemented from QgsMapLayerRenderer.

Definition at line 189 of file qgsvectorlayerrenderer.cpp.

forceRasterRender()

bool QgsVectorLayerRenderer::forceRasterRender ( ) const

overridevirtual

Returns true if the renderer must be rendered to a raster paint device (e.g.

QImage).

Some layer settings require layers to be effectively "flattened" while rendering maps, which is achieved by first rendering the layer onto a raster paint device and then compositing the resultant image onto the final map render.

E.g. if a layer contains features with transparency or alternative blending modes, and the effects of these opacity or blending modes should be restricted to only affect other features within the SAME layer, then a flattened raster based render is required.

Subclasses should return true whenever their corresponding layer settings require the layer to always be rendered using a raster paint device.

Since

QGIS 3.18

Reimplemented from QgsMapLayerRenderer.

Definition at line 194 of file qgsvectorlayerrenderer.cpp.

render()

bool QgsVectorLayerRenderer::render ( )

overridevirtual

Do the rendering (based on data stored in the class).

Returns true if the layer was completely rendered successfully (i.e. the render was not canceled early).

Implements QgsMapLayerRenderer.

Definition at line 199 of file qgsvectorlayerrenderer.cpp.

setLayerRenderingTimeHint()

void QgsVectorLayerRenderer::setLayerRenderingTimeHint ( int  time )

overridevirtual

Sets approximate render time (in ms) for the layer to render.

This can be used to specifies a hint at the expected render times for the layer, so that the individual layer renderer subclasses can apply heuristics and determine appropriate update intervals during the render operation.

Note

Not available in Python bindings.

Since

QGIS 3.18

Reimplemented from QgsMapLayerRenderer.

Definition at line 184 of file qgsvectorlayerrenderer.cpp.

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

• /build/qgis-3.28.0+99sid/src/core/vector/qgsvectorlayerrenderer.h
• /build/qgis-3.28.0+99sid/src/core/vector/qgsvectorlayerrenderer.cpp