Subgroup: Map

Class: QgsMapCanvasTracer¶

class qgis.gui.QgsMapCanvasTracer¶

Bases: qgis._core.QgsTracer

Extension of QgsTracer that provides extra functionality: - automatic updates of own configuration based on canvas settings - reporting of issues to the user via message bar - determines whether tracing is currently enabled by the user

A simple registry of tracer instances associated to map canvas instances is kept for convenience. (Map tools do not need to create their local tracer instances and map canvas API is not “polluted” by this optional functionality).

New in version 2.14: Methods

`actionEnableSnapping`	Access to action that user may use to toggle snapping on/off.
`actionEnableTracing`	Access to action that user may use to toggle tracing on/off.
`blockSignals`
`childEvent`
`children`
`configure`	Sets configuration from current snapping settings and canvas settings
`connectNotify`
`customEvent`
`deleteLater`
`destinationCrs`	Returns the CRS used for tracing.
`disconnect`
`disconnectNotify`
`dumpObjectInfo`
`dumpObjectTree`
`dynamicPropertyNames`
`event`
`eventFilter`
`extent`	Get extent to which graph’s features will be limited (empty extent means no limit)
`findChild`	findChild(self, Tuple, name: str = ‘’, options: Union[Qt.FindChildOptions, Qt.FindChildOption] = Qt.FindChildrenRecursively) -> QObject
`findChildren`	findChildren(self, Tuple, name: str = ‘’, options: Union[Qt.FindChildOptions, Qt.FindChildOption] = Qt.FindChildrenRecursively) -> List[QObject]
`findShortestPath`	Given two points, find the shortest path and return points on the way.
`hasTopologyProblem`	Whether there was an error during graph creation due to noding exception,
`inherits`
`init`	Build the internal data structures.
`installEventFilter`
`invalidateGraph`
`isInitialized`	Whether the internal data structures have been initialized
`isPointSnapped`	Find out whether the point is snapped to a vertex or edge (i.e.
`isSignalConnected`
`isWidgetType`
`isWindowType`
`killTimer`
`layers`	Get layers used for tracing
`maxFeatureCount`	Get maximum possible number of features in graph.
`metaObject`
`moveToThread`
`objectName`
`offset`	Get offset in map units that should be applied to the traced paths returned from findShortestPath().
`offsetParameters`	Get extra parameters for offset curve algorithm (used when offset is non-zero)
`parent`
`property`
`pyqtConfigure`	Each keyword argument is either the name of a Qt property or a Qt signal.
`receivers`
`removeEventFilter`
`reportError`	Report a path finding error to the user
`sender`
`senderSignalIndex`
`setActionEnableSnapping`	Assign “enable snapping” checkable action to the tracer.
`setActionEnableTracing`	Assign “enable tracing” checkable action to the tracer.
`setDestinationCrs`	Sets the `crs` and transform `context` used for tracing.
`setExtent`	Set extent to which graph’s features will be limited (empty extent means no limit)
`setLayers`	Set layers used for tracing
`setMaxFeatureCount`	Get maximum possible number of features in graph.
`setObjectName`
`setOffset`	Set offset in map units that should be applied to the traced paths returned from findShortestPath().
`setOffsetParameters`	Set extra parameters for offset curve algorithm (used when offset is non-zero)
`setParent`
`setProperty`
`signalsBlocked`
`startTimer`
`thread`
`timerEvent`
`tr`
`tracerForCanvas`	Retrieve instance of this class associated with given canvas (if any).

Attributes

`ErrNoPath`
`ErrNone`
`ErrPoint1`
`ErrPoint2`
`ErrTooManyFeatures`
`destroyed`	destroyed(self, QObject = None) [signal]
`objectNameChanged`	objectNameChanged(self, str) [signal]
`staticMetaObject`

actionEnableSnapping(self) → QAction¶: Access to action that user may use to toggle snapping on/off. May be null if no action was associated.

New in version 3.0.

actionEnableTracing(self) → QAction¶: Access to action that user may use to toggle tracing on/off. May be null if no action was associated

childEvent()¶

configure(self)¶: Sets configuration from current snapping settings and canvas settings

connectNotify()¶

customEvent()¶

disconnectNotify()¶

invalidateGraph()¶

isSignalConnected()¶

receivers()¶

reportError(self, err: QgsTracer.PathError, addingVertex: bool)¶: Report a path finding error to the user

sender()¶

senderSignalIndex()¶

setActionEnableSnapping(self, action: QAction)¶: Assign “enable snapping” checkable action to the tracer. The action is used to determine whether snapping is currently enabled by the user.

New in version 3.0.

setActionEnableTracing(self, action: QAction)¶: Assign “enable tracing” checkable action to the tracer. The action is used to determine whether tracing is currently enabled by the user

timerEvent()¶

tracerForCanvas(canvas: QgsMapCanvas) → QgsMapCanvasTracer¶: Retrieve instance of this class associated with given canvas (if any). The class keeps a simple registry of tracers associated with map canvas instances for easier access to the common tracer by various map tools