Subgroup: Map
Class: QgsMapLayerRenderer¶
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class
qgis.core.
QgsMapLayerRenderer
¶ Bases:
sip.wrapper
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 themNew in version 2.4: Methods
errors
Return list of errors (problems) that happened during the rendering feedback
Access to feedback object of the layer renderer (may be null) layerId
Get access to the ID of the layer rendered by this class render
Do the rendering (based on data stored in the class) Attributes
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errors
(self) → List[str]¶ Return list of errors (problems) that happened during the rendering
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feedback
(self) → QgsFeedback¶ Access to feedback object of the layer renderer (may be null)
New in version 3.0.
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layerId
(self) → str¶ Get access to the ID of the layer rendered by this class
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render
(self) → bool¶ Do the rendering (based on data stored in the class)
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