Subgroup: other
Class: QgsTracer¶
-
class
qgis.core.
QgsTracer
¶ Bases:
PyQt5.QtCore.QObject
Constructor for QgsTracer.
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
childEvent
configure
Allows derived classes to setup the settings just before the tracer is initialized. connectNotify
customEvent
destinationCrs
Returns the CRS used for tracing. disconnectNotify
extent
Get extent to which graph’s features will be limited (empty extent means no limit) 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, indicating some input data topology problems init
Build the internal data structures. 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. isSignalConnected
layers
Get layers used for tracing maxFeatureCount
Get maximum possible number of features in graph. 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) receivers
sender
senderSignalIndex
setDestinationCrs
Sets the crs
and transformcontext
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. 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) timerEvent
Signals
Attributes
ErrNoPath
ErrNone
ErrPoint1
ErrPoint2
ErrTooManyFeatures
-
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
-
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 transformcontext
used for tracing.See also
-
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
()¶
-