The QgsVectorLayerDiagramProvider class implements support for diagrams within the labeling engine. More...

#include <qgsvectorlayerdiagramprovider.h>

Inheritance diagram for QgsVectorLayerDiagramProvider:

Public Member Functions
	QgsVectorLayerDiagramProvider (QgsVectorLayer *layer, bool ownFeatureLoop=true)
	Convenience constructor to initialize the provider from given vector layer.

	~QgsVectorLayerDiagramProvider () override
	Clean up.

void	drawLabel (QgsRenderContext &context, pal::LabelPosition *label) const override
	Draw this label at the position determined by the labeling engine.

QList< QgsLabelFeature * >	labelFeatures (QgsRenderContext &context) override
	Returns list of label features (they are owned by the provider and thus deleted on its destruction)

virtual bool	prepare (const QgsRenderContext &context, QSet< QString > &attributeNames)
	Prepare for registration of features.

virtual void	registerFeature (QgsFeature &feature, QgsRenderContext &context, const QgsGeometry &obstacleGeometry=QgsGeometry())
	Register a feature for labeling as one or more QgsLabelFeature objects stored into mFeatures.

void	setClipFeatureGeometry (const QgsGeometry &geometry)
	Sets a geometry to use to clip features to when registering them as diagrams.

Public Member Functions inherited from QgsAbstractLabelProvider
	QgsAbstractLabelProvider (QgsMapLayer *layer, const QString &providerId=QString())
	Construct the provider with default values.

virtual	~QgsAbstractLabelProvider ()=default

virtual void	drawLabelBackground (QgsRenderContext &context, pal::LabelPosition *label) const
	Draw the background for the specified label.

virtual void	drawUnplacedLabel (QgsRenderContext &context, pal::LabelPosition *label) const
	Draw an unplaced label.

Flags	flags () const
	Flags associated with the provider.

QgsMapLayer *	layer () const
	Returns the associated layer, or `nullptr` if no layer is associated with the provider.

QgsExpressionContextScope *	layerExpressionContextScope () const
	Returns the expression context scope created from the layer associated with this provider.

QString	layerId () const
	Returns ID of associated layer, or empty string if no layer is associated with the provider.

double	layerReferenceScale () const
	Returns the symbology reference scale of the layer associated with this provider.

QString	name () const
	Name of the layer (for statistics, debugging etc.) - does not need to be unique.

QgsLabelObstacleSettings::ObstacleType	obstacleType () const
	How the feature geometries will work as obstacles.

Qgis::LabelPlacement	placement () const
	What placement strategy to use for the labels.

double	priority () const
	Default priority of labels (may be overridden by individual labels).

QString	providerId () const
	Returns provider ID - useful in case there is more than one label provider within a layer (e.g.

void	setEngine (const QgsLabelingEngine *engine)
	Associate provider with a labeling engine (should be only called internally from QgsLabelingEngine)

virtual void	startRender (QgsRenderContext &context)
	To be called before rendering of labels begins.

virtual void	stopRender (QgsRenderContext &context)
	To be called after rendering is complete.

virtual QList< QgsAbstractLabelProvider * >	subProviders ()
	Returns list of child providers - useful if the provider needs to put labels into more layers with different configuration.

Qgis::UpsideDownLabelHandling	upsidedownLabels () const
	How to handle labels that would be upside down.

Protected Member Functions
void	init ()
	initialization method - called from constructors

QgsLabelFeature *	registerDiagram (const QgsFeature &feat, QgsRenderContext &context, const QgsGeometry &obstacleGeometry=QgsGeometry())
	helper method to register one diagram feature

Protected Attributes
QgsDiagramRenderer *	mDiagRenderer = nullptr
	Diagram renderer instance (owned by mSettings)

QList< QgsLabelFeature * >	mFeatures
	List of generated label features (owned by the provider)

QgsFields	mFields
	Layer's fields.

QgsGeometry	mLabelClipFeatureGeom

QgsCoordinateReferenceSystem	mLayerCrs
	Layer's CRS.

std::unique_ptr< QgsExpressionContextScope >	mLayerScope

bool	mOwnsSource
	Whether layer's feature source is owned.

QgsDiagramLayerSettings	mSettings
	Diagram layer settings.

QgsAbstractFeatureSource *	mSource = nullptr
	Layer's feature source.

Protected Attributes inherited from QgsAbstractLabelProvider
const QgsLabelingEngine *	mEngine = nullptr
	Associated labeling engine.

Flags	mFlags = DrawLabels
	Flags altering drawing and registration of features.

QgsWeakMapLayerPointer	mLayer
	Weak pointer to source layer.

QString	mLayerId
	Associated layer's ID, if applicable.

QString	mName
	Name of the layer.

QgsLabelObstacleSettings::ObstacleType	mObstacleType = QgsLabelObstacleSettings::ObstacleType::PolygonBoundary
	Type of the obstacle of feature geometries.

Qgis::LabelPlacement	mPlacement = Qgis::LabelPlacement::AroundPoint
	Placement strategy.

double	mPriority = 0.5
	Default priority of labels. 0 = highest priority, 1 = lowest priority.

QString	mProviderId
	Associated provider ID (one layer may have multiple providers, e.g. in rule-based labeling)

Qgis::UpsideDownLabelHandling	mUpsidedownLabels = Qgis::UpsideDownLabelHandling::FlipUpsideDownLabels
	How to handle labels that would be upside down.

Additional Inherited Members
Public Types inherited from QgsAbstractLabelProvider
enum	Flag { DrawLabels = 1 << 1 , MergeConnectedLines = 1 << 3 , CentroidMustBeInside = 1 << 4 }

typedef QFlags< Flag >	Flags

Detailed Description

The QgsVectorLayerDiagramProvider class implements support for diagrams within the labeling engine.

Parameters for the diagrams are taken from the layer settings.

Note: this class is not a part of public API yet. See notes in QgsLabelingEngine; not available in Python bindings

Definition at line 56 of file qgsvectorlayerdiagramprovider.h.

Constructor & Destructor Documentation

◆ QgsVectorLayerDiagramProvider()

QgsVectorLayerDiagramProvider::QgsVectorLayerDiagramProvider	(	QgsVectorLayer *	layer,
		bool	ownFeatureLoop = `true`
	)

explicit

Convenience constructor to initialize the provider from given vector layer.

Definition at line 32 of file qgsvectorlayerdiagramprovider.cpp.

◆ ~QgsVectorLayerDiagramProvider()

QgsVectorLayerDiagramProvider::~QgsVectorLayerDiagramProvider ( )

override

Clean up.

Definition at line 56 of file qgsvectorlayerdiagramprovider.cpp.

Member Function Documentation

◆ drawLabel()

void QgsVectorLayerDiagramProvider::drawLabel	(	QgsRenderContext &	context,
		pal::LabelPosition *	label
	)		const

overridevirtual

Draw this label at the position determined by the labeling engine.

Before any calls to drawLabel(), a provider should be prepared for rendering by a call to startRender() and a corresponding call to stopRender().

Implements QgsAbstractLabelProvider.

Definition at line 109 of file qgsvectorlayerdiagramprovider.cpp.

◆ init()

void QgsVectorLayerDiagramProvider::init ( )

protected

initialization method - called from constructors

Definition at line 48 of file qgsvectorlayerdiagramprovider.cpp.

◆ labelFeatures()

QList< QgsLabelFeature * > QgsVectorLayerDiagramProvider::labelFeatures ( QgsRenderContext & context )

overridevirtual

Returns list of label features (they are owned by the provider and thus deleted on its destruction)

Implements QgsAbstractLabelProvider.

Definition at line 67 of file qgsvectorlayerdiagramprovider.cpp.

◆ prepare()

bool QgsVectorLayerDiagramProvider::prepare	(	const QgsRenderContext &	context,
		QSet< QString > &	attributeNames
	)

virtual

Prepare for registration of features.

Must be called after provider has been added to engine (uses its map settings)

Parameters

context	render context.
attributeNames	list of attribute names to which additional required attributes shall be added

Returns: Whether the preparation was successful - if not, the provider shall not be used

Definition at line 151 of file qgsvectorlayerdiagramprovider.cpp.

◆ registerDiagram()

QgsLabelFeature * QgsVectorLayerDiagramProvider::registerDiagram	(	const QgsFeature &	feat,
		QgsRenderContext &	context,
		const QgsGeometry &	obstacleGeometry = `QgsGeometry()`
	)

protected

helper method to register one diagram feature

Definition at line 188 of file qgsvectorlayerdiagramprovider.cpp.

◆ registerFeature()

void QgsVectorLayerDiagramProvider::registerFeature	(	QgsFeature &	feature,
		QgsRenderContext &	context,
		const QgsGeometry &	obstacleGeometry = `QgsGeometry()`
	)

virtual

Register a feature for labeling as one or more QgsLabelFeature objects stored into mFeatures.

Parameters

feature	feature for diagram
context	render context. The QgsExpressionContext contained within the render context must have already had the feature and fields sets prior to calling this method.
obstacleGeometry	optional obstacle geometry, if a different geometry to the feature's geometry should be used as an obstacle for labels (e.g., if the feature has been rendered with an offset point symbol, the obstacle geometry should represent the bounds of the offset symbol). If not set, the feature's original geometry will be used as an obstacle for labels. Ownership of obstacleGeometry is transferred.

Definition at line 176 of file qgsvectorlayerdiagramprovider.cpp.

◆ setClipFeatureGeometry()

void QgsVectorLayerDiagramProvider::setClipFeatureGeometry ( const QgsGeometry & geometry )

Sets a geometry to use to clip features to when registering them as diagrams.

Since: QGIS 3.16

Definition at line 183 of file qgsvectorlayerdiagramprovider.cpp.

Member Data Documentation

◆ mDiagRenderer

QgsDiagramRenderer* QgsVectorLayerDiagramProvider::mDiagRenderer = nullptr

protected

Diagram renderer instance (owned by mSettings)

Definition at line 112 of file qgsvectorlayerdiagramprovider.h.

◆ mFeatures

QList<QgsLabelFeature *> QgsVectorLayerDiagramProvider::mFeatures

protected

List of generated label features (owned by the provider)

Definition at line 126 of file qgsvectorlayerdiagramprovider.h.

◆ mFields

QgsFields QgsVectorLayerDiagramProvider::mFields

protected

Layer's fields.

Definition at line 117 of file qgsvectorlayerdiagramprovider.h.

◆ mLabelClipFeatureGeom

QgsGeometry QgsVectorLayerDiagramProvider::mLabelClipFeatureGeom

protected

Definition at line 130 of file qgsvectorlayerdiagramprovider.h.

◆ mLayerCrs

QgsCoordinateReferenceSystem QgsVectorLayerDiagramProvider::mLayerCrs

protected

Layer's CRS.

Definition at line 119 of file qgsvectorlayerdiagramprovider.h.

◆ mLayerScope

std::unique_ptr< QgsExpressionContextScope > QgsVectorLayerDiagramProvider::mLayerScope

protected

Definition at line 128 of file qgsvectorlayerdiagramprovider.h.

◆ mOwnsSource

bool QgsVectorLayerDiagramProvider::mOwnsSource

protected

Whether layer's feature source is owned.

Definition at line 123 of file qgsvectorlayerdiagramprovider.h.

◆ mSettings

QgsDiagramLayerSettings QgsVectorLayerDiagramProvider::mSettings

protected

Diagram layer settings.

Definition at line 110 of file qgsvectorlayerdiagramprovider.h.

◆ mSource

QgsAbstractFeatureSource* QgsVectorLayerDiagramProvider::mSource = nullptr

protected

Layer's feature source.

Definition at line 121 of file qgsvectorlayerdiagramprovider.h.

The documentation for this class was generated from the following files:

/build/qgis-3.41.0+git20241225+af5edcb665c+99sid/src/core/vector/qgsvectorlayerdiagramprovider.h
/build/qgis-3.41.0+git20241225+af5edcb665c+99sid/src/core/vector/qgsvectorlayerdiagramprovider.cpp

Public Member Functions

Protected Member Functions

Protected Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ QgsVectorLayerDiagramProvider()

◆ ~QgsVectorLayerDiagramProvider()

Member Function Documentation

◆ drawLabel()

◆ init()

◆ labelFeatures()

◆ prepare()

◆ registerDiagram()

◆ registerFeature()

◆ setClipFeatureGeometry()

Member Data Documentation

◆ mDiagRenderer

◆ mFeatures

◆ mFields

◆ mLabelClipFeatureGeom

◆ mLayerCrs

◆ mLayerScope

◆ mOwnsSource

◆ mSettings

◆ mSource