Subgroup: other

Class: QgsTracer¶

class qgis.core.QgsTracer¶

Bases: PyQt5.QtCore.QObject

Utility class that construct a planar graph from the input vector layers and provides shortest path search for tracing of existing features.

New in version 2.14: Methods

`blockSignals`
`childEvent`
`children`
`configure`	Allows derived classes to setup the settings just before the tracer is initialized.
`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`	Destroy the existing graph structure if any (de-initialize)
`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`
`sender`
`senderSignalIndex`
`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`

Attributes

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

ErrNoPath = 4¶

ErrNone = 0¶

ErrPoint1 = 2¶

ErrPoint2 = 3¶

ErrTooManyFeatures = 1¶

class PathError¶: Bases: int

childEvent()¶

configure(self)¶: Allows derived classes to setup the settings just before the tracer is initialized. This allows the configuration to be set in a lazy way only when it is really necessary. Default implementation does nothing.

connectNotify()¶

customEvent()¶

destinationCrs(self) → QgsCoordinateReferenceSystem¶: Returns the CRS used for tracing.

See also

setDestinationCrs()

disconnectNotify()¶

extent(self) → QgsRectangle¶: Get extent to which graph’s features will be limited (empty extent means no limit)

findShortestPath(self, p1: QgsPointXY, p2: QgsPointXY) → Tuple[List[QgsPointXY], QgsTracer.PathError]¶

Given two points, find the shortest path and return points on the way. The optional “error” argument may receive error code (PathError enum) if it is not null

Returns:	array of points - trace of linestrings of other features (empty array one error)

hasTopologyProblem(self) → bool¶: Whether there was an error during graph creation due to noding exception, indicating some input data topology problems

New in version 2.16.

init(self) → bool¶: Build the internal data structures. This may take some time depending on how big the input layers are. It is not necessary to call this method explicitly - it will be called by findShortestPath() if necessary.

invalidateGraph(self)¶: Destroy the existing graph structure if any (de-initialize)

isInitialized(self) → bool¶: Whether the internal data structures have been initialized

isPointSnapped(self, pt: QgsPointXY) → bool¶: Find out whether the point is snapped to a vertex or edge (i.e. it can be used for tracing start/stop)

isSignalConnected()¶

layers(self) → object¶: Get layers used for tracing

maxFeatureCount(self) → int¶: Get maximum possible number of features in graph. If the number is exceeded, graph is not created.

offset(self) → float¶: Get offset in map units that should be applied to the traced paths returned from findShortestPath(). Positive offset for right side, negative offset for left side.

New in version 3.0.

offsetParameters(self) → Tuple[int, int, float]¶: Get extra parameters for offset curve algorithm (used when offset is non-zero)

New in version 3.0.

receivers()¶

sender()¶

senderSignalIndex()¶

setDestinationCrs(self, crs: QgsCoordinateReferenceSystem, context: QgsCoordinateTransformContext)¶: Sets the crs and transform context used for tracing.

See also

destinationCrs()

setExtent(self, extent: QgsRectangle)¶: Set extent to which graph’s features will be limited (empty extent means no limit)

setLayers(self, layers: Iterable[QgsVectorLayer])¶: Set layers used for tracing

setMaxFeatureCount(self, count: int)¶: Get maximum possible number of features in graph. If the number is exceeded, graph is not created.

setOffset(self, offset: float)¶: Set offset in map units that should be applied to the traced paths returned from findShortestPath(). Positive offset for right side, negative offset for left side.

New in version 3.0.

setOffsetParameters(self, quadSegments: int, joinStyle: int, miterLimit: float)¶: Set extra parameters for offset curve algorithm (used when offset is non-zero)

New in version 3.0.

timerEvent()¶