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)
virtual	~QgsMapLayerRenderer ()
QStringList	errors () const
	Return list of errors (problems) that happened during the rendering. More...
virtual QgsFeedback *	feedback () const
	Access to feedback object of the layer renderer (may be null) More...
QString	layerID () const
	Get 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...

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), is 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:

1. 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.
2. renderer job (still in GUI thread) stores the renderer for later use.
3. renderer job (in worker thread) calls QgsMapLayerRenderer::render()
4. renderer job (again in GUI thread) will check errors() and report them

Note

added in 2.4

Definition at line 45 of file qgsmaplayerrenderer.h.

Constructor & Destructor Documentation

QgsMapLayerRenderer()

QgsMapLayerRenderer::QgsMapLayerRenderer ( const QString &  layerID )

inline

Definition at line 48 of file qgsmaplayerrenderer.h.

~QgsMapLayerRenderer()

virtual QgsMapLayerRenderer::~QgsMapLayerRenderer ( )

inlinevirtual

Definition at line 49 of file qgsmaplayerrenderer.h.

Member Function Documentation

errors()

QStringList QgsMapLayerRenderer::errors ( ) const

inline

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

Definition at line 59 of file qgsmaplayerrenderer.h.

feedback()

virtual QgsFeedback* QgsMapLayerRenderer::feedback ( ) const

inlinevirtual

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

Note

added in QGIS 2.18

Reimplemented in QgsRasterLayerRenderer.

Definition at line 56 of file qgsmaplayerrenderer.h.

layerID()

QString QgsMapLayerRenderer::layerID ( ) const

inline

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

Definition at line 62 of file qgsmaplayerrenderer.h.

render()

virtual bool QgsMapLayerRenderer::render ( )

pure virtual

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

Implemented in QgsVectorLayerRenderer, QgsPluginLayerRenderer, and QgsRasterLayerRenderer.

Member Data Documentation

mErrors

QStringList QgsMapLayerRenderer::mErrors

protected

Definition at line 65 of file qgsmaplayerrenderer.h.

mLayerID

QString QgsMapLayerRenderer::mLayerID

protected

Definition at line 66 of file qgsmaplayerrenderer.h.

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

• /tmp/buildd/qgis-2.18.21+99unstable/src/core/qgsmaplayerrenderer.h