The QgsVectorLayerLabelProvider class implements a label provider for vector layers. More...

#include <qgsvectorlayerlabelprovider.h>

Inheritance diagram for QgsVectorLayerLabelProvider:

[legend]

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

	QgsVectorLayerLabelProvider (const QgsPalLayerSettings &settings, const QString &layerId, const QgsFields &fields, const QgsCoordinateReferenceSystem &crs, QgsAbstractFeatureSource source, bool ownsSource, QgsFeatureRendererV2 renderer=nullptr)
	Construct diagram provider with all the necessary configuration parameters. More...

	~QgsVectorLayerLabelProvider ()

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

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

virtual bool	prepare (const QgsRenderContext &context, QStringList &attributeNames)
	Prepare for registration of features. More...

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

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

virtual	~QgsAbstractLabelProvider ()
	Vritual destructor. More...

Flags	flags () const
	Flags 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...

unsigned int	linePlacementFlags () const
	For layers with linestring geometries - extra placement flags (or-ed combination of QgsPalLayerSettings::LinePlacementFlags) 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 QgsLabelingEngineV2 *engine)
	Associate provider with a labeling engine (should be only called internally from QgsLabelingEngineV2) More...

virtual QList< QgsAbstractLabelProvider * >	subProviders ()
	Return 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...

Static Public Member Functions
static QgsGeometry *	getPointObstacleGeometry (QgsFeature &fet, QgsRenderContext &context, const QgsSymbolV2List &symbols)
	Returns the geometry for a point feature which should be used as an obstacle for labels. More...

Protected Member Functions
void	drawLabelPrivate (pal::LabelPosition *label, QgsRenderContext &context, QgsPalLayerSettings &tmpLyr, QgsPalLabeling::DrawLabelType drawType, double dpiRatio=1.0) const
	Internal label drawing method. More...

void	init ()
	initialization method - called from constructors More...

Protected Attributes
QgsCoordinateReferenceSystem	mCrs
	Layer's CRS. More...

QgsFields	mFields
	Layer's fields. More...

QList< QgsLabelFeature * >	mLabels
	List of generated. More...

QGis::GeometryType	mLayerGeometryType
	Geometry type of layer. More...

bool	mOwnsSource
	Whether layer's feature source is owned. More...

QgsFeatureRendererV2 *	mRenderer

QgsPalLayerSettings	mSettings
	Layer's labeling configuration. More...

QgsAbstractFeatureSource *	mSource
	Layer's feature source. More...

Protected Attributes inherited from QgsAbstractLabelProvider
const QgsLabelingEngineV2 *	mEngine
	Associated labeling engine. More...

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

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

unsigned int	mLinePlacementFlags
	Extra placement flags for linestring geometries. 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...

Friends
class	TestQgsLabelingEngineV2

Additional Inherited Members
Public Types inherited from QgsAbstractLabelProvider
enum	Flag { DrawLabels = 1 << 1, DrawAllLabels = 1 << 2, MergeConnectedLines = 1 << 3, CentroidMustBeInside = 1 << 4, LabelPerFeaturePart = 1 << 6 }

Detailed Description

The QgsVectorLayerLabelProvider class implements a label provider for vector layers.

Parameters for the labeling are taken from the layer's custom properties or from the given settings.

Note: added in QGIS 2.12; this class is not a part of public API yet. See notes in QgsLabelingEngineV2; not available in Python bindings

Definition at line 35 of file qgsvectorlayerlabelprovider.h.

Constructor & Destructor Documentation

◆ QgsVectorLayerLabelProvider() [1/2]

QgsVectorLayerLabelProvider::QgsVectorLayerLabelProvider	(	QgsVectorLayer *	layer,
		const QString &	providerId,
		bool	withFeatureLoop = `true`,
		const QgsPalLayerSettings *	settings = `nullptr`,
		const QString &	layerName = `QString()`
	)

explicit

Convenience constructor to initialize the provider from given vector layer.

Definition at line 52 of file qgsvectorlayerlabelprovider.cpp.

◆ QgsVectorLayerLabelProvider() [2/2]

QgsVectorLayerLabelProvider::QgsVectorLayerLabelProvider	(	const QgsPalLayerSettings &	settings,
		const QString &	layerId,
		const QgsFields &	fields,
		const QgsCoordinateReferenceSystem &	crs,
		QgsAbstractFeatureSource *	source,
		bool	ownsSource,
		QgsFeatureRendererV2 *	renderer = `nullptr`
	)

Construct diagram provider with all the necessary configuration parameters.

Definition at line 76 of file qgsvectorlayerlabelprovider.cpp.

◆ ~QgsVectorLayerLabelProvider()

QgsVectorLayerLabelProvider::~QgsVectorLayerLabelProvider ( )

Definition at line 121 of file qgsvectorlayerlabelprovider.cpp.

Member Function Documentation

◆ drawLabel()

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

overridevirtual

draw this label at the position determined by the labeling engine

Implements QgsAbstractLabelProvider.

Reimplemented in QgsDxfRuleBasedLabelProvider, and QgsDxfLabelProvider.

Definition at line 398 of file qgsvectorlayerlabelprovider.cpp.

◆ drawLabelPrivate()

void QgsVectorLayerLabelProvider::drawLabelPrivate	(	pal::LabelPosition *	label,
		QgsRenderContext &	context,
		QgsPalLayerSettings &	tmpLyr,
		QgsPalLabeling::DrawLabelType	drawType,
		double	dpiRatio = `1.0`
	)		const

protected

Internal label drawing method.

Definition at line 496 of file qgsvectorlayerlabelprovider.cpp.

◆ getPointObstacleGeometry()

QgsGeometry * QgsVectorLayerLabelProvider::getPointObstacleGeometry	(	QgsFeature &	fet,
		QgsRenderContext &	context,
		const QgsSymbolV2List &	symbols
	)

static

Returns the geometry for a point feature which should be used as an obstacle for labels.

This obstacle geometry will respect the dimensions and offsets of the symbol used to render the point, and ensures that labels will not overlap large or offset points.

Parameters

fet	point feature
context	render context
symbols	symbols rendered for point feature

Note: added in QGIS 2.14

Definition at line 323 of file qgsvectorlayerlabelprovider.cpp.

◆ init()

void QgsVectorLayerLabelProvider::init ( )

protected

initialization method - called from constructors

Definition at line 95 of file qgsvectorlayerlabelprovider.cpp.

◆ labelFeatures()

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

overridevirtual

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

Implements QgsAbstractLabelProvider.

Definition at line 258 of file qgsvectorlayerlabelprovider.cpp.

◆ prepare()

bool QgsVectorLayerLabelProvider::prepare	(	const QgsRenderContext &	context,
		QStringList &	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

Reimplemented in QgsRuleBasedLabelProvider.

Definition at line 130 of file qgsvectorlayerlabelprovider.cpp.

◆ registerFeature()

void QgsVectorLayerLabelProvider::registerFeature	(	QgsFeature &	feature,
		QgsRenderContext &	context,
		QgsGeometry *	obstacleGeometry = `nullptr`
	)

virtual

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 (eg, 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.

Reimplemented in QgsRuleBasedLabelProvider.

Definition at line 315 of file qgsvectorlayerlabelprovider.cpp.