Class: QgsGeometryCheck

class qgis.analysis.QgsGeometryCheck(context: QgsGeometryCheckContext, configuration: Dict[str, Any])

Bases: sip.wrapper

Create a new geometry check.


This class implements a geometry check.

Geometry checks run over a set of features and can detect errors like topological or other issues which are reported in the geometry validation panel in QGIS and help a user to create valid geometries.

Implementing a custom geometry check consists of the following parts

A new subclass of QgsGeometryCheck needs to be written and at least the following abstract methods need to be implemented:

  • compatibleGeometryTypes(): A list of geometry types to which this check applies

  • resolutionMethods(): A list of names for (automated) resolution methods that can be used to fix errors of this type

  • description(): A description for the geometry check.

  • id(): A unique id for this check.

  • checkType(): One of QgsGeometryCheck.LayerCheck, QgsGeometryCheck.FeatureCheck,:py:class:QgsGeometryCheck.FeatureNodeCheck

  • collectErrors(): This method will be called to validate geometries. All geometries which should be validated are passed into this method with the parameter ids and should be retrieved from the available featurePools to make use of caching. New errors should be appended to the error list and other message strings to messages. The method needs to return a tuple (errors, messages).

A Geometry check factory manages meta information for checks. There will always be one single geometry check factory created per check type, but it’s possible that multiple QgsGeometryCheck instances are created and used in parallel.

A new subclass of QgsGeometryCheckFactory needs to be written and at least the following abstract methods need to be implemented:

Finally the geometry check factory needs to be registered in QGIS, so the system is aware of the available geometry checks.

# Make sure you always keep a
checkFactory = MyGeometryCheckFactory()


This class is a technology preview and unstable API.

New in version 3.4.

AvailableInValidation = 2
class Change

Bases: sip.wrapper

QgsGeometryCheck.Change(_what: QgsGeometryCheck.ChangeWhat, _type: QgsGeometryCheck.ChangeType, _vidx: QgsVertexId = QgsVertexId()) Create a new Change


ChangeAdded = 0
ChangeChanged = 2
ChangeFeature = 0
ChangeNode = 3
ChangePart = 1
ChangeRemoved = 1
ChangeRing = 2
class ChangeType

Bases: int

class ChangeWhat

Bases: int

class CheckType

Bases: int

FeatureCheck = 1
FeatureNodeCheck = 0
class Flag

Bases: int

class Flags

Bases: sip.wrapper

QgsGeometryCheck.Flags(Union[QgsGeometryCheck.Flags, QgsGeometryCheck.Flag]) QgsGeometryCheck.Flags(QgsGeometryCheck.Flags)


alias of qgis._analysis.QgsGeometryCheck

LayerCheck = 2
class LayerFeatureIds

Bases: sip.wrapper



Returns a list of available resolution methods.

New in version 3.12.

Return type



Returns the check type.

New in version 3.4.

Return type


collectErrors(self, featurePools: object, errors: Iterable[QgsGeometryCheckError], messages: Iterable[str], feedback: QgsFeedback, ids: QgsGeometryCheck.LayerFeatureIds = QgsGeometryCheck.LayerFeatureIds())Tuple[List[QgsGeometryCheckError], List[str]]

The main worker method. Check all features available from featurePools and write errors found to errors. Other status messages can be written to messages. Progress should be reported to feedback. Only features and layers listed in ids should be checked.

New in version 3.4.

  • featurePools (object) –

  • errors (Iterable[QgsGeometryCheckError]) –

  • messages (Iterable[str]) –

  • feedback (QgsFeedback) –

  • ids (QgsGeometryCheck.LayerFeatureIds = QgsGeometryCheck.LayerFeatureIds()) –

Return type

Tuple[List[QgsGeometryCheckError], List[str]]


A list of geometry types for which this check can be performed.

New in version 3.4.

Return type



Returns the context

New in version 3.4.

Return type



Returns a human readable description for this check.

New in version 3.4.

Return type



Flags for this geometry check.

Return type



Returns an id for this check.

New in version 3.4.

Return type


isCompatible(self, layer: QgsVectorLayer)bool

Returns if this geometry check is compatible with layer. By default it checks for the geometry type in ``compatibleGeometryTypes``().

New in version 3.4.


layer (QgsVectorLayer) –

Return type


prepare(self, context: QgsGeometryCheckContext, configuration: Dict[str, Any])

Will be run in the main thread before collectErrors is called (which may be run from a background thread).

New in version 3.10.


Returns a list of descriptions for available resolutions for errors. The index will be passed as method to fixError().

Deprecated since version QGIS: 3.12 use availableResolutionMethods() instead

New in version 3.4.

Return type


staticMetaObject = <PyQt5.QtCore.QMetaObject object>