Class: QgsPointLocator¶

Defines the interface for querying point locations.

This class offers:

query nearest vertices / edges to a point
query vertices / edges in rectangle
query areas covering a point

Works with one layer.

Note

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

The following methods must be implemented: acceptMatch()

Class Hierarchy¶

Base classes¶

QObject

class qgis.core.QgsPointLocator[source]¶

Bases: QObject

__init__(layer: QgsVectorLayer | None, destinationCrs: QgsCoordinateReferenceSystem = QgsCoordinateReferenceSystem(), transformContext: QgsCoordinateTransformContext = QgsCoordinateTransformContext(), extent: QgsRectangle | None = None)

Construct point locator for a layer.

If a valid QgsCoordinateReferenceSystem is passed for destinationCrs then the locator will do the searches on data reprojected to the given CRS. For accurate reprojection it is important to set the correct transformContext if a destinationCrs is specified. This is usually taken from the current QgsProject.transformContext().

If extent is not None, the locator will index only a subset of the layer which falls within that extent.

Parameters:

layer (Optional[QgsVectorLayer])
destinationCrs (QgsCoordinateReferenceSystem = QgsCoordinateReferenceSystem())
transformContext (QgsCoordinateTransformContext = QgsCoordinateTransformContext())
extent (Optional[QgsRectangle] = None)

All = 31¶

Area = 4¶

Centroid = 8¶

Edge = 2¶

Invalid = 0¶

LineEndpoint = 32¶

class Match¶

Bases: object

construct invalid match

QgsPointLocator.Match(t: QgsPointLocator.Type, vl: Optional[QgsVectorLayer], fid: int, dist: float, pt: QgsPointXY, vertexIndex: int = 0, edgePoints: Optional[QgsPointXY] = None)

QgsPointLocator.Match(a0: QgsPointLocator.Match)

distance(self) → float¶

for vertex / edge match units depending on what class returns it (geom.cache: layer units, map canvas snapper: dest crs units)

Return type:: float

edgePoints(self)¶: Only for a valid edge match - obtain endpoints of the edge

featureId(self) → int¶

The id of the feature to which the snapped geometry belongs.

Return type:: int

hasArea(self) → bool¶

Returns True if the Match is an area

Return type:: bool

hasCentroid(self) → bool¶

Returns True if the Match is a centroid

Return type:: bool

hasEdge(self) → bool¶

Returns True if the Match is an edge

Return type:: bool

hasLineEndpoint(self) → bool¶

Returns True if the Match is a line endpoint (start or end vertex).

Added in version 3.20.

Return type:: bool

hasMiddleSegment(self) → bool¶

Returns True if the Match is the middle of a segment

Return type:: bool

hasVertex(self) → bool¶

Returns True if the Match is a vertex

Return type:: bool

interpolatedPoint(self, destinationCrs: QgsCoordinateReferenceSystem = QgsCoordinateReferenceSystem()) → QgsPoint¶

Convenient method to return a point on an edge with linear interpolation of the Z value. The parameter destinationCrs depends of where the instance of this Match is created (geom.cache: layer CRS, map canvas snapper: dest CRS)

Added in version 3.10.

Parameters:: destinationCrs (QgsCoordinateReferenceSystem = QgsCoordinateReferenceSystem())
Return type:: QgsPoint

isValid(self) → bool¶

Return type:: bool

layer(self) → QgsVectorLayer | None¶

The vector layer where the snap occurred. Will be None if the snap happened on an intersection.

Return type:: Optional[QgsVectorLayer]

point(self) → QgsPointXY¶

for vertex / edge match coords depending on what class returns it (geom.cache: layer coords, map canvas snapper: dest coords)

Return type:: QgsPointXY

type(self) → QgsPointLocator.Type¶

Return type:: QgsPointLocator.Type

vertexIndex(self) → int¶

for vertex / edge match (first vertex of the edge)

Return type:: int

class MatchFilter¶

Bases: object

Interface that allows rejection of some matches in intersection queries (e.g. a match can only belong to a particular feature / match must not be a particular point). Implement the interface and pass its instance to QgsPointLocator or QgsSnappingUtils methods.

acceptMatch(self, match: QgsPointLocator.Match) → bool¶

Parameters:: match (QgsPointLocator.Match)
Return type:: bool

MiddleOfSegment = 16¶

class Type¶: Bases: int

class Types¶
class Types(f: QgsPointLocator.Types | QgsPointLocator.Type)
class Types(a0: QgsPointLocator.Types): Bases: object

Vertex = 1¶

cachedGeometryCount(self) → int[source]¶

Returns how many geometries are cached in the index

Return type:: int

destinationCrs(self) → QgsCoordinateReferenceSystem[source]¶

Gets destination CRS - may be an invalid QgsCoordinateReferenceSystem if not doing OTF reprojection

Return type:: QgsCoordinateReferenceSystem

destroyIndex(self)[source]¶

edgesInRect(self, rect: QgsRectangle, filter: QgsPointLocator.MatchFilter | None = None, relaxed: bool = False) → List[QgsPointLocator.Match][source]¶

Find edges within a specified rectangle Optional filter may discard unwanted matches. This method is either blocking or non blocking according to relaxed parameter passed

edgesInRect(self, point: QgsPointXY, tolerance: float, filter: Optional[QgsPointLocator.MatchFilter] = None, relaxed: bool = False) -> List[QgsPointLocator.Match] Override of edgesInRect that construct rectangle from a center point and tolerance This method is either blocking or non blocking according to relaxed parameter passed

Parameters:

rect (QgsRectangle)
filter (Optional[QgsPointLocator.MatchFilter] = None)
relaxed (bool = False)

Return type:

List[QgsPointLocator.Match]

extent(self) → QgsRectangle | None[source]¶

Gets extent of the area point locator covers - if None then it caches the whole layer

Return type:: Optional[QgsRectangle]

hasIndex(self) → bool[source]¶

Indicate whether the data have been already indexed

Return type:: bool

init(self, maxFeaturesToIndex: int = -1, relaxed: bool = False) → bool[source]¶

Prepare the index for queries. Does nothing if the index already exists. If the number of features is greater than the value of maxFeaturesToIndex, creation of index is stopped to make sure we do not run out of memory. If maxFeaturesToIndex is -1, no limits are used.

This method is either blocking or non blocking according to relaxed parameter passed in the constructor. if True, index building will be done in another thread and init() method returns immediately. initFinished() signal will be emitted once the initialization is over.

Returns False if the creation of index is blocking and has been prematurely stopped due to the limit of features, otherwise True