Implements a derived label provider for use with QgsLabelSink. More...

#include <qgslabelsink.h>

Inheritance diagram for QgsLabelSinkProvider:

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Public Member Functions
	QgsLabelSinkProvider (QgsVectorLayer layer, const QString &providerId, QgsLabelSink sink, const QgsPalLayerSettings *settings)
	Creates a rule based label sink provider which will draw/register labels in sink.

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

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

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)

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

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

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)

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.

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

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.

Detailed Description

Implements a derived label provider for use with QgsLabelSink.

Note: not available in Python bindings

Since: QGIS 3.14

Definition at line 74 of file qgslabelsink.h.

Constructor & Destructor Documentation

◆ QgsLabelSinkProvider()

QgsLabelSinkProvider::QgsLabelSinkProvider	(	QgsVectorLayer *	layer,
		const QString &	providerId,
		QgsLabelSink *	sink,
		const QgsPalLayerSettings *	settings
	)

explicit

Creates a rule based label sink provider which will draw/register labels in sink.

Definition at line 23 of file qgslabelsink.cpp.

Member Function Documentation

◆ drawLabel()

void QgsLabelSinkProvider::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 29 of file qgslabelsink.cpp.

◆ drawUnplacedLabel()

void QgsLabelSinkProvider::drawUnplacedLabel	(	QgsRenderContext &	context,
		pal::LabelPosition *	label
	)		const

overridevirtual

Draw an unplaced label.

These correspond to features which were registered for labeling, but which could not be labeled (e.g. due to conflicting labels).

The default behavior is to draw nothing for these labels.

Note: This method is only used if the Qgis::Qgis::LabelingFlag::DrawUnplacedLabels flag is set on the labeling engine.

Since: QGIS 3.10

Reimplemented from QgsAbstractLabelProvider.

Definition at line 35 of file qgslabelsink.cpp.

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

/build/qgis-3.41.0+git20241122+3440c17df1d+99sid/src/core/labeling/qgslabelsink.h
/build/qgis-3.41.0+git20241122+3440c17df1d+99sid/src/core/labeling/qgslabelsink.cpp