Label provider for rule based labeling. More...

#include <qgsrulebasedlabeling.h>

Inheritance diagram for QgsRuleBasedLabelProvider:

[legend]

Public Member Functions
	QgsRuleBasedLabelProvider (const QgsRuleBasedLabeling &rules, QgsVectorLayer *layer, bool withFeatureLoop=true)

virtual QgsVectorLayerLabelProvider *	createProvider (QgsVectorLayer layer, const QString &providerId, bool withFeatureLoop, const QgsPalLayerSettings settings)
	create a label provider

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

QList< QgsLabelFeature * >	registerFeature (const QgsFeature &feature, QgsRenderContext &context, const QgsGeometry &obstacleGeometry=QgsGeometry(), const QgsSymbol *symbol=nullptr) override
	Register a feature for labeling as one or more QgsLabelFeature objects stored into mLabels.

QList< QgsAbstractLabelProvider * >	subProviders () override
	Returns subproviders.

Public Member Functions inherited from QgsVectorLayerLabelProvider
	QgsVectorLayerLabelProvider (Qgis::GeometryType geometryType, const QgsFields &fields, const QgsCoordinateReferenceSystem &crs, const QString &providerId, const QgsPalLayerSettings settings, QgsMapLayer layer, const QString &layerName=QString())
	Constructor to initialize the provider from any map layer (e.g. vector tile layer)

	QgsVectorLayerLabelProvider (QgsVectorLayer layer, const QString &providerId, bool withFeatureLoop, const QgsPalLayerSettings settings, const QString &layerName=QString())
	Convenience constructor to initialize the provider from given vector layer.

	~QgsVectorLayerLabelProvider () override

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

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

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

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

void	setFields (const QgsFields &fields)
	Sets fields of this label provider.

const QgsPalLayerSettings &	settings () const
	Returns the layer's settings.

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

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

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

virtual	~QgsAbstractLabelProvider ()=default

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)

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

Protected Attributes
std::unique_ptr< QgsRuleBasedLabeling >	mRules
	owned copy

QgsRuleBasedLabeling::RuleToProviderMap	mSubProviders
	label providers are owned by labeling engine

Protected Attributes inherited from QgsVectorLayerLabelProvider
QgsCoordinateReferenceSystem	mCrs
	Layer's CRS.

QgsFields	mFields
	Layer's fields.

QList< QgsLabelFeature * >	mLabels
	List of generated.

Qgis::GeometryType	mLayerGeometryType
	Geometry type of layer.

QgsFeatureRenderer *	mRenderer = nullptr

QgsPalLayerSettings	mSettings
	Layer's labeling configuration.

std::unique_ptr< QgsAbstractFeatureSource >	mSource
	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.

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

Static Public Member Functions inherited from QgsVectorLayerLabelProvider
static QgsGeometry	getPointObstacleGeometry (QgsFeature &fet, QgsRenderContext &context, const QgsSymbolList &symbols)
	Returns the geometry for a point feature which should be used as an obstacle for labels.

Protected Member Functions inherited from QgsVectorLayerLabelProvider
void	drawLabelPrivate (pal::LabelPosition *label, QgsRenderContext &context, QgsPalLayerSettings &tmpLyr, Qgis::TextComponent drawType, double dpiRatio=1.0) const
	Internal label drawing method.

void	init ()
	initialization method - called from constructors

Detailed Description

Label provider for rule based labeling.

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

Definition at line 407 of file qgsrulebasedlabeling.h.

Constructor & Destructor Documentation

◆ QgsRuleBasedLabelProvider()

QgsRuleBasedLabelProvider::QgsRuleBasedLabelProvider	(	const QgsRuleBasedLabeling &	rules,
		QgsVectorLayer *	layer,
		bool	withFeatureLoop = `true`
	)

Definition at line 20 of file qgsrulebasedlabeling.cpp.

Member Function Documentation

◆ createProvider()

QgsVectorLayerLabelProvider * QgsRuleBasedLabelProvider::createProvider	(	QgsVectorLayer *	layer,
		const QString &	providerId,
		bool	withFeatureLoop,
		const QgsPalLayerSettings *	settings
	)

virtual

create a label provider

Reimplemented in QgsRuleBasedLabelSinkProvider.

Definition at line 27 of file qgsrulebasedlabeling.cpp.

◆ prepare()

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

overridevirtual

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

Reimplemented from QgsVectorLayerLabelProvider.

Definition at line 32 of file qgsrulebasedlabeling.cpp.

◆ registerFeature()

QList< QgsLabelFeature * > QgsRuleBasedLabelProvider::registerFeature	(	const QgsFeature &	feature,
		QgsRenderContext &	context,
		const QgsGeometry &	obstacleGeometry = `QgsGeometry()`,
		const QgsSymbol *	symbol = `nullptr`
	)

overridevirtual

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

Parameters

feature	feature to label
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.
symbol	feature symbol to label (ownership is not transferred - the symbol must exist until after labeling is complete)

Returns: a list of the newly generated label features. Ownership of these label features is not transferred (it has already been assigned to the label provider).

Reimplemented from QgsVectorLayerLabelProvider.

Definition at line 42 of file qgsrulebasedlabeling.cpp.

◆ subProviders()

QList< QgsAbstractLabelProvider * > QgsRuleBasedLabelProvider::subProviders ( )

overridevirtual

Returns subproviders.

Reimplemented from QgsAbstractLabelProvider.

Definition at line 48 of file qgsrulebasedlabeling.cpp.

Member Data Documentation

◆ mRules

std::unique_ptr<QgsRuleBasedLabeling> QgsRuleBasedLabelProvider::mRules

protected

owned copy

Definition at line 426 of file qgsrulebasedlabeling.h.

◆ mSubProviders

QgsRuleBasedLabeling::RuleToProviderMap QgsRuleBasedLabelProvider::mSubProviders

protected

label providers are owned by labeling engine

Definition at line 428 of file qgsrulebasedlabeling.h.

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

/build/qgis-3.41.0+git20241110+fda2aa46e9a+99sid/src/core/labeling/qgsrulebasedlabeling.h
/build/qgis-3.41.0+git20241110+fda2aa46e9a+99sid/src/core/labeling/qgsrulebasedlabeling.cpp

Public Member Functions

Protected Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ QgsRuleBasedLabelProvider()

Member Function Documentation

◆ createProvider()

◆ prepare()

◆ registerFeature()

◆ subProviders()

Member Data Documentation

◆ mRules

◆ mSubProviders