QgsMapLayerRenderer Class Reference

Base class for utility classes that encapsulate information necessary for rendering of map layers. More...

#include <qgsmaplayerrenderer.h>

Inheritance diagram for QgsMapLayerRenderer:

Public Member Functions
	QgsMapLayerRenderer (const QString &layerID, QgsRenderContext *context=nullptr)
	Constructor for QgsMapLayerRenderer, with the associated layerID and render context. More...
virtual	~QgsMapLayerRenderer ()=default
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...
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...

Protected Attributes
QStringList	mErrors
QString	mLayerID

Detailed Description

Base class for utility classes that encapsulate information necessary for rendering of map layers.

The rendering is typically done in a background thread, so it is necessary to keep all structures required for rendering away from the original map layer because it may change any time.

Because the data needs to be copied (to avoid the need for locking), it is highly desirable to use copy-on-write where possible. This way, the overhead of copying (both memory and CPU) will be kept low. Qt containers and various Qt classes use implicit sharing.

The scenario will be:

renderer job (doing preparation in the GUI thread) calls

QgsMapLayer::createMapRenderer() and gets instance of this class. The instance is initialized at that point and should not need additional calls to QgsVectorLayer.

renderer job (still in GUI thread) stores the renderer for later use.

renderer job (in worker thread) calls QgsMapLayerRenderer::render()

renderer job (again in GUI thread) will check errors() and report them

Since

QGIS 2.4

Definition at line 50 of file qgsmaplayerrenderer.h.

Constructor & Destructor Documentation

QgsMapLayerRenderer()

QgsMapLayerRenderer::QgsMapLayerRenderer ( const QString &  layerID, QgsRenderContext *  context = nullptr  )

inline

Constructor for QgsMapLayerRenderer, with the associated layerID and render context.

Definition at line 57 of file qgsmaplayerrenderer.h.

~QgsMapLayerRenderer()

virtual QgsMapLayerRenderer::~QgsMapLayerRenderer ( )

virtualdefault

Member Function Documentation

errors()

QStringList QgsMapLayerRenderer::errors ( ) const

inline

Returns list of errors (problems) that happened during the rendering.

Definition at line 74 of file qgsmaplayerrenderer.h.

feedback()

virtual QgsFeedback* QgsMapLayerRenderer::feedback ( ) const

inlinevirtual

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

Since

QGIS 3.0

Reimplemented in QgsVectorTileLayerRenderer, QgsRasterLayerRenderer, QgsVectorLayerRenderer, QgsMeshLayerRenderer, and QgsAnnotationLayerRenderer.

Definition at line 71 of file qgsmaplayerrenderer.h.

layerId()

QString QgsMapLayerRenderer::layerId ( ) const

inline

Gets access to the ID of the layer rendered by this class.

Definition at line 77 of file qgsmaplayerrenderer.h.

render()

virtual bool QgsMapLayerRenderer::render ( )

pure virtual

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

Implemented in QgsVectorTileLayerRenderer, QgsRasterLayerRenderer, QgsVectorLayerRenderer, QgsMeshLayerRenderer, and QgsAnnotationLayerRenderer.

renderContext()

QgsRenderContext* QgsMapLayerRenderer::renderContext ( )

inline

Returns the render context associated with the renderer.

Since

QGIS 3.10

Definition at line 84 of file qgsmaplayerrenderer.h.

Member Data Documentation

mErrors

QStringList QgsMapLayerRenderer::mErrors

protected

Definition at line 87 of file qgsmaplayerrenderer.h.

mLayerID

QString QgsMapLayerRenderer::mLayerID

protected

Definition at line 88 of file qgsmaplayerrenderer.h.

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

• /build/qgis-3.16.0+99unstable/src/core/qgsmaplayerrenderer.h