The QgsAbstractLabelProvider class is an interface class. More...

#include <qgslabelingengine.h>

Inheritance diagram for QgsAbstractLabelProvider:

[legend]

Public Types
enum	Flag { DrawLabels = 1 << 1, DrawAllLabels = 1 << 2, MergeConnectedLines = 1 << 3, CentroidMustBeInside = 1 << 4, LabelPerFeaturePart = 1 << 6 }

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

virtual	~QgsAbstractLabelProvider ()=default

virtual void	drawLabel (QgsRenderContext &context, pal::LabelPosition *label) const =0
	draw this label at the position determined by the labeling engine More...

Flags	flags () const
	Flags associated with the provider. More...

virtual QList< QgsLabelFeature * >	labelFeatures (QgsRenderContext &context)=0
	Returns list of label features (they are owned by the provider and thus deleted on its destruction) More...

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

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

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

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

QgsPalLayerSettings::Placement	placement () const
	What placement strategy to use for the labels. More...

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

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

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

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

QgsPalLayerSettings::UpsideDownLabels	upsidedownLabels () const
	How to handle labels that would be upside down. More...

Protected Attributes
const QgsLabelingEngine *	mEngine = nullptr
	Associated labeling engine. More...

Flags	mFlags
	Flags altering drawing and registration of features. More...

QgsWeakMapLayerPointer	mLayer
	Weak pointer to source layer. More...

QString	mLayerId
	Associated layer's ID, if applicable. More...

QString	mName
	Name of the layer. More...

QgsPalLayerSettings::ObstacleType	mObstacleType
	Type of the obstacle of feature geometries. More...

QgsPalLayerSettings::Placement	mPlacement
	Placement strategy. More...

double	mPriority
	Default priority of labels. More...

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

QgsPalLayerSettings::UpsideDownLabels	mUpsidedownLabels
	How to handle labels that would be upside down. More...

Detailed Description

The QgsAbstractLabelProvider class is an interface class.

Implementations return list of labels and their associated geometries - these are used by QgsLabelingEngine to compute the final layout of labels.

Implementations also take care of drawing the returned final label positions.

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

Since: QGIS 2.12

Definition at line 43 of file qgslabelingengine.h.

Member Enumeration Documentation

◆ Flag

enum QgsAbstractLabelProvider::Flag

Enumerator
DrawLabels	Whether the labels should be rendered.
DrawAllLabels	Whether all features will be labelled even though overlaps occur.
MergeConnectedLines	Whether adjacent lines (with the same label text) should be merged.
CentroidMustBeInside	Whether location of centroid must be inside of polygons.
LabelPerFeaturePart	Whether to label each part of multi-part features separately.

Definition at line 55 of file qgslabelingengine.h.

Constructor & Destructor Documentation

◆ QgsAbstractLabelProvider()

QgsAbstractLabelProvider::QgsAbstractLabelProvider	(	QgsMapLayer *	layer,
		const QString &	providerId = `QString()`
	)

Construct the provider with default values.

Definition at line 389 of file qgslabelingengine.cpp.

◆ ~QgsAbstractLabelProvider()

virtual QgsAbstractLabelProvider::~QgsAbstractLabelProvider ( )

virtualdefault

Member Function Documentation

◆ drawLabel()

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

pure virtual

draw this label at the position determined by the labeling engine

Implemented in QgsDxfRuleBasedLabelProvider, QgsVectorLayerDiagramProvider, QgsVectorLayerLabelProvider, and QgsDxfLabelProvider.

◆ flags()

Flags QgsAbstractLabelProvider::flags ( ) const

inline

Flags associated with the provider.

Definition at line 91 of file qgslabelingengine.h.

◆ labelFeatures()

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

pure virtual

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

Implemented in QgsVectorLayerDiagramProvider, and QgsVectorLayerLabelProvider.

◆ layer()

QgsMapLayer* QgsAbstractLabelProvider::layer ( ) const

inline

Returns the associated layer, or nullptr if no layer is associated with the provider.

Definition at line 81 of file qgslabelingengine.h.

◆ layerId()

QString QgsAbstractLabelProvider::layerId ( ) const

inline

Returns ID of associated layer, or empty string if no layer is associated with the provider.

Definition at line 78 of file qgslabelingengine.h.

◆ name()

QString QgsAbstractLabelProvider::name ( ) const

inline

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

Definition at line 75 of file qgslabelingengine.h.

◆ obstacleType()

QgsPalLayerSettings::ObstacleType QgsAbstractLabelProvider::obstacleType ( ) const

inline

How the feature geometries will work as obstacles.

Definition at line 100 of file qgslabelingengine.h.

◆ placement()

QgsPalLayerSettings::Placement QgsAbstractLabelProvider::placement ( ) const

inline

What placement strategy to use for the labels.

Definition at line 94 of file qgslabelingengine.h.

◆ priority()

double QgsAbstractLabelProvider::priority ( ) const

inline

Default priority of labels (may be overridden by individual labels)

Definition at line 97 of file qgslabelingengine.h.

◆ providerId()

QString QgsAbstractLabelProvider::providerId ( ) const

inline

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

in case of rule-based labeling - provider ID = rule's key). May be empty string if layer ID is sufficient for identification of provider's configuration.

Definition at line 88 of file qgslabelingengine.h.

◆ setEngine()

void QgsAbstractLabelProvider::setEngine ( const QgsLabelingEngine * engine )

inline

Associate provider with a labeling engine (should be only called internally from QgsLabelingEngine)

Definition at line 53 of file qgslabelingengine.h.

◆ subProviders()

virtual QList<QgsAbstractLabelProvider *> QgsAbstractLabelProvider::subProviders ( )

inlinevirtual

Returns list of child providers - useful if the provider needs to put labels into more layers with different configuration.

Reimplemented in QgsRuleBasedLabelProvider.

Definition at line 72 of file qgslabelingengine.h.

◆ upsidedownLabels()

QgsPalLayerSettings::UpsideDownLabels QgsAbstractLabelProvider::upsidedownLabels ( ) const

inline

How to handle labels that would be upside down.

Definition at line 103 of file qgslabelingengine.h.

Member Data Documentation

◆ mEngine

const QgsLabelingEngine* QgsAbstractLabelProvider::mEngine = nullptr

protected

Associated labeling engine.

Definition at line 107 of file qgslabelingengine.h.

◆ mFlags

Flags QgsAbstractLabelProvider::mFlags

protected

Flags altering drawing and registration of features.

Definition at line 118 of file qgslabelingengine.h.

◆ mLayer

QgsWeakMapLayerPointer QgsAbstractLabelProvider::mLayer

protected

Weak pointer to source layer.

Definition at line 114 of file qgslabelingengine.h.

◆ mLayerId

QString QgsAbstractLabelProvider::mLayerId

protected

Associated layer's ID, if applicable.

Definition at line 112 of file qgslabelingengine.h.

◆ mName

QString QgsAbstractLabelProvider::mName

protected

Name of the layer.

Definition at line 110 of file qgslabelingengine.h.

◆ mObstacleType

QgsPalLayerSettings::ObstacleType QgsAbstractLabelProvider::mObstacleType

protected

Type of the obstacle of feature geometries.

Definition at line 124 of file qgslabelingengine.h.

◆ mPlacement

QgsPalLayerSettings::Placement QgsAbstractLabelProvider::mPlacement

protected

Placement strategy.

Definition at line 120 of file qgslabelingengine.h.

◆ mPriority

double QgsAbstractLabelProvider::mPriority

protected

Default priority of labels.

Definition at line 122 of file qgslabelingengine.h.

◆ mProviderId

QString QgsAbstractLabelProvider::mProviderId

protected

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

Definition at line 116 of file qgslabelingengine.h.

◆ mUpsidedownLabels

QgsPalLayerSettings::UpsideDownLabels QgsAbstractLabelProvider::mUpsidedownLabels

protected

How to handle labels that would be upside down.

Definition at line 126 of file qgslabelingengine.h.

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

/tmp/buildd/qgis-3.8.0+99unstable/src/core/qgslabelingengine.h
/tmp/buildd/qgis-3.8.0+99unstable/src/core/qgslabelingengine.cpp

Public Types

Public Member Functions

Protected Attributes

Detailed Description

Member Enumeration Documentation

◆ Flag

Constructor & Destructor Documentation

◆ QgsAbstractLabelProvider()

◆ ~QgsAbstractLabelProvider()

Member Function Documentation

◆ drawLabel()

◆ flags()

◆ labelFeatures()

◆ layer()

◆ layerId()

◆ name()

◆ obstacleType()

◆ placement()

◆ priority()

◆ providerId()

◆ setEngine()

◆ subProviders()

◆ upsidedownLabels()

Member Data Documentation

◆ mEngine

◆ mFlags

◆ mLayer

◆ mLayerId

◆ mName

◆ mObstacleType

◆ mPlacement

◆ mPriority

◆ mProviderId

◆ mUpsidedownLabels