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,QgsGeometryCheck.FeatureNodeCheck

  • link collectErrors() collectErrors(featurePools, errors, messages, feedback, ids)endlink

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:

  • link QgsGeometryCheckFactory.createGeometryCheck() createGeometryCheck(context, configuration)endlink

Needs to return a new subclassed QgsGeometryCheck object that has been written in the previous step.

  • link `id()endlink

A unique id for this geometry check.

  • link QgsGeometryCheckFactory.description() `description()endlink

A description for this geometry check that can be presented to the user for more explanation.

  • link QgsGeometryCheckFactory.isCompatible() QgsGeometryCheckFactory.isCompatible(layer)endlink

Returns a boolean that determines if this check is available for a given layer. This often checks for the geometry type of the layer.

  • link QgsGeometryCheckFactory.flags() flags()endlink

Returns additional flags for a geometry check. If unsure return QgsGeometryCheck.AvailableInValidation.

  • link QgsGeometryCheckFactory.checkType() checkType()endlink

Returns the type of this geometry check.

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 QgsGeometryCheck

LayerCheck = 2
class LayerFeatureIds

Bases: sip.wrapper


checkType(self) → QgsGeometryCheck.CheckType

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]]

compatibleGeometryTypes(self) → object

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


description(self) → str

Returns a human readable description for this check.

New in version 3.4.

Return type


flags(self) → QgsGeometryCheck.Flags

Flags for this geometry check.

Return type


id(self) → str

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.

resolutionMethods(self) → List[str]

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

New in version 3.4.

Return type


staticMetaObject = <PyQt5.QtCore.QMetaObject object>