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What is the scope of the qgsmapcanvas class?
Returns a reference to the expression context scope for the map canvas. This scope is injected into the expression context used for rendering the map, and can be used to apply specific variable overrides for expression evaluation for the map canvas render. New in version 2.12. Emitted when the extents of the map change [signal]
How to set layers in qgsmapcanvas-QGIS?
Sets the list of layers that should be shown in the canvas. If the map canvas has been associated with a map theme via a call to setTheme (), then any calls to setLayers () are ignored. It is necessary to first clear the theme association by calling setTheme () with an empty string before setLayers () calls can be made. New in version 3.0.
Do you have to have theme name in qgsmapcanvas?
The theme name must match a theme present in the associated project’s QgsMapThemeCollection. When the canvas is associated to a map theme, it will automatically follow the layer selection and layer styles from that theme.
What is the Bool for freeze in QGIS?
Freeze/thaw the map canvas. This is used to prevent the canvas from responding to events while layers are being added/removed etc. frozen ( bool = True) – Boolean specifying if the canvas should be frozen (true) or thawed (false). Default is true.
When to create an internal canvas in QGIS?
If no snapping utils instance has been associated previously, an internal will be created for convenience (so map tools do not need to test for existence of the instance). Main canvas in QGIS returns an instance which is always up-to-date with the project’s snapping configuration.
How is the context scope set in QGIS?
Sets an expression context scope for the map canvas. This scope is injected into the expression context used for rendering the map, and can be used to apply specific variable overrides for expression evaluation for the map canvas render. This method will overwrite the existing expression context scope for the canvas.
Can a qgslayertreemapcanvasbridge be used as a layer tree?
Calls to setLayers () or setLayerStyleOverrides () will have no effect, and canvases associated with a QgsLayerTreeMapCanvasBridge will no longer synchronize their state with the layer tree.
When to deprecate decorations as a map canvas item?
TODO: deprecate when decorations are reimplemented as map canvas items – anything related to rendering progress is not visible outside of map canvas – additional drawing shall be done directly within the renderer job or independently as a map canvas item [signal]
What does qgscoordinatereferencesystem ( ) do in CRS 3.0?
New in version 3.0. crs ( QgsCoordinateReferenceSystem = QgsCoordinateReferenceSystem ()) – Freeze/thaw the map canvas. This is used to prevent the canvas from responding to events while layers are being added/removed etc.
How to programatically check for mouse click in pyqgis?
I am completely new to the QGIS API. The best way to make a new tool like the Select Single Feature tool is to inherit from the QgsMapTool class. When your tool is active, which can be set using QgsMapCanvas::setMapTool, any keyboard or click events the canvas gets will be passed onto your custom tool.