Class: QgsAbstractMapToolHandler¶

An abstract base class for map tool handlers, implementing application level UI logic.

QgsAbstractMapToolHandler subclasses 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(QgsMapTool):
   ...

class MyMapToolHandler(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, QgsVectorLayer) and layer.isEditable()

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

my_handler = MyMapToolHandler(my_tool, my_action)
iface.registerMapToolHandler(my_handler)

Added in version 3.16.

Note

This is an abstract class, with methods which must be implemented by a subclass.

The following methods must be implemented: isCompatibleWithLayer()

Abstract Methods

isCompatibleWithLayer

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

Methods

`action`	Returns the action associated with toggling the tool.
`mapTool`	Returns the tool associated with this handler.

Virtual Methods

In PyQGIS, only methods marked as virtual can be safely overridden in a Python subclass of QgsAbstractMapToolHandler. See the FAQ for more details.

setLayerForTool

Sets the layer to use for the tool.

class qgis.gui.QgsAbstractMapToolHandler[source]¶

Bases: object

__init__(tool: QgsMapTool | None, action: QAction | None)

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.

Warning

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

Parameters:

tool (Optional[QgsMapTool])
action (Optional[QAction])

__init__(a0: QgsAbstractMapToolHandler)

Parameters:: a0 (QgsAbstractMapToolHandler)

class Context¶

Bases: object

Context of a QgsAbstractMapToolHandler call.

Added in version 3.16.

dummy: bool¶: Placeholder only

action(self) → QAction | None[source]¶

Returns the action associated with toggling the tool.

Return type:: Optional[QAction]

abstract isCompatibleWithLayer(self, layer: QgsMapLayer | None, context: QgsAbstractMapToolHandler.Context) → bool[source]¶

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

Additional information is available through the context argument.

Parameters:

layer (Optional[QgsMapLayer])
context (QgsAbstractMapToolHandler.Context)

Return type:

bool

mapTool(self) → QgsMapTool | None[source]¶

Returns the tool associated with this handler.

Return type:: Optional[QgsMapTool]

virtual setLayerForTool(self, layer: QgsMapLayer | None)[source]¶

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.

Parameters:: layer (Optional[QgsMapLayer])