Class: QgsMapLayerRenderer

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 them

New in version 2.4: Enums

Methods

errors Returns list of errors (problems) that happened during the rendering
feedback Access to feedback object of the layer renderer (may be None)
layerId Gets access to the ID of the layer rendered by this class
render Do the rendering (based on data stored in the class)

Signals

Attributes

errors(self) → List[str]

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

feedback(self) → QgsFeedback

Access to feedback object of the layer renderer (may be None)

New in version 3.0.

layerId(self) → str

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

render(self) → bool

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