The QgsMeshLayerLabelProvider class implements a label provider for mesh layers. More...

#include <qgsmeshlayerlabelprovider.h>

Inheritance diagram for QgsMeshLayerLabelProvider:

Public Member Functions
	QgsMeshLayerLabelProvider (QgsMeshLayer layer, const QString &providerId, const QgsPalLayerSettings settings, const QString &layerName=QString(), bool labelFaces=false)
	Convenience constructor to initialize the provider from given mesh layer.

	~QgsMeshLayerLabelProvider () override

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

bool	labelFaces () const
	Returns `false` if labeling mesh vertices, `true` if labeling mesh faces.

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.

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

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 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	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
QgsCoordinateReferenceSystem	mCrs
	Layer's CRS.

bool	mLabelFaces = false

QList< QgsLabelFeature * >	mLabels
	List of generated.

QgsPalLayerSettings	mSettings
	Layer's labeling configuration.

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.

Friends
class	TestQgsLabelingEngine

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 QgsMeshLayerLabelProvider class implements a label provider for mesh layers.

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

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

Since: QGIS 3.36

Definition at line 40 of file qgsmeshlayerlabelprovider.h.

Constructor & Destructor Documentation

◆ QgsMeshLayerLabelProvider()

QgsMeshLayerLabelProvider::QgsMeshLayerLabelProvider	(	QgsMeshLayer *	layer,
		const QString &	providerId,
		const QgsPalLayerSettings *	settings,
		const QString &	layerName = `QString()`,
		bool	labelFaces = `false`
	)

explicit

Convenience constructor to initialize the provider from given mesh layer.

Definition at line 52 of file qgsmeshlayerlabelprovider.cpp.

◆ ~QgsMeshLayerLabelProvider()

QgsMeshLayerLabelProvider::~QgsMeshLayerLabelProvider ( )

override

Definition at line 99 of file qgsmeshlayerlabelprovider.cpp.

Member Function Documentation

◆ drawLabel()

void QgsMeshLayerLabelProvider::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 148 of file qgsmeshlayerlabelprovider.cpp.

◆ drawLabelPrivate()

void QgsMeshLayerLabelProvider::drawLabelPrivate	(	pal::LabelPosition *	label,
		QgsRenderContext &	context,
		QgsPalLayerSettings &	tmpLyr,
		Qgis::TextComponent	drawType,
		double	dpiRatio = `1.0`
	)		const

protected

Internal label drawing method.

◆ init()

void QgsMeshLayerLabelProvider::init ( )

protected

initialization method - called from constructors

Definition at line 63 of file qgsmeshlayerlabelprovider.cpp.

◆ labelFaces()

bool QgsMeshLayerLabelProvider::labelFaces ( ) const

inline

Returns false if labeling mesh vertices, true if labeling mesh faces.

Definition at line 91 of file qgsmeshlayerlabelprovider.h.

◆ labelFeatures()

QList< QgsLabelFeature * > QgsMeshLayerLabelProvider::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 125 of file qgsmeshlayerlabelprovider.cpp.

◆ prepare()

bool QgsMeshLayerLabelProvider::prepare	(	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 104 of file qgsmeshlayerlabelprovider.cpp.

◆ registerFeature()

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

Definition at line 131 of file qgsmeshlayerlabelprovider.cpp.