Class: QgsAbstractMapToolHandler

class qgis.gui.QgsAbstractMapToolHandler(tool: QgsMapTool, action: QAction)

Bases: sip.wrapper

Constructor for a map tool handler for the specified tool.

The action argument must be set to the action associated with switching to the tool.

The ownership of neither tool nor action is transferred, and the caller is responsible for ensuring that these objects exist for the lifetime of the handler.


The handler will be responsible for creating the appropriate connections between the action and the tool. These should NOT be manually connected elsewhere!


An abstract base class for map tool handlers which automatically handle all the necessary logic for toggling the map tool and enabling/disabling the associated action when the QGIS application is in a state permissible for the tool.

Creating these handlers avoids a lot of complex setup code and manual connections which are otherwise necessary to ensure that a map tool is correctly activated and deactivated when the state of the QGIS application changes (e.g. when the active layer is changed, when edit modes are toggled, when other map tools are switched to, etc).

  • ### Example

class MyMapTool(:py:class:`.QgsMapTool`):

class MyMapToolHandler(:py:class:`.QgsAbstractMapToolHandler`):

   def __init__(self, tool, action):
       super().__init__(tool, action)

   def isCompatibleWithLayer(self, layer, context):
       # this tool can only be activated when an editable vector layer is selected
       return isinstance(layer, :py:class:`.QgsVectorLayer`) and layer.isEditable()

my_tool = MyMapTool()
my_action = QAction('My Map Tool')

my_handler = MyMapToolHandler(my_tool, my_action)

New in version 3.16.

class Context

Bases: sip.wrapper


action(self) → QAction

Returns the action associated with toggling the tool.

Return type


isCompatibleWithLayer(self, layer: QgsMapLayer, context: QgsAbstractMapToolHandler.Context) → bool

Returns True if the associated map tool is compatible with the specified layer.

Additional information is available through the context argument.

Return type



Returns the tool associated with this handler.

Return type


setLayerForTool(self, layer: QgsMapLayer)

Sets the layer to use for the tool.

Called whenever a new layer should be associated with the tool, e.g. as a result of the user selecting a different active layer.

The default implementation does nothing.


layer (QgsMapLayer) –