QGIS API Documentation  3.11.0-Master (461d2edac3)
Public Member Functions | Protected Attributes | List of all members
QgsMapLayerRenderer Class Referenceabstract

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

#include <qgsmaplayerrenderer.h>

Inheritance diagram for QgsMapLayerRenderer:
Inheritance graph
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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 QgsFeedbackfeedback () 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...
 
QgsRenderContextrenderContext ()
 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:

  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
Since
QGIS 2.4

Definition at line 49 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 56 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 73 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 QgsMeshLayerRenderer, QgsVectorLayerRenderer, and QgsRasterLayerRenderer.

Definition at line 70 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 76 of file qgsmaplayerrenderer.h.

◆ render()

virtual bool QgsMapLayerRenderer::render ( )
pure virtual

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

Implemented in QgsMeshLayerRenderer, QgsVectorLayerRenderer, and QgsRasterLayerRenderer.

◆ renderContext()

QgsRenderContext* QgsMapLayerRenderer::renderContext ( )
inline

Returns the render context associated with the renderer.

Since
QGIS 3.10

Definition at line 83 of file qgsmaplayerrenderer.h.

Member Data Documentation

◆ mErrors

QStringList QgsMapLayerRenderer::mErrors
protected

Definition at line 86 of file qgsmaplayerrenderer.h.

◆ mLayerID

QString QgsMapLayerRenderer::mLayerID
protected

Definition at line 87 of file qgsmaplayerrenderer.h.


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