QGIS API Documentation  3.15.0-Master (c0197371fe)
Classes | Public Member Functions | List of all members
QgsRenderedFeatureHandlerInterface Class Referenceabstract

An interface for classes which provider custom handlers for features rendered as part of a map render job. More...

#include <qgsrenderedfeaturehandlerinterface.h>

Classes

struct  RenderedFeatureContext
 

Public Member Functions

virtual ~QgsRenderedFeatureHandlerInterface ()=default
 
virtual void handleRenderedFeature (const QgsFeature &feature, const QgsGeometry &renderedBounds, const QgsRenderedFeatureHandlerInterface::RenderedFeatureContext &context)=0
 Called whenever a feature is rendered during a map render job. More...
 
virtual QSet< QString > usedAttributes (QgsVectorLayer *layer, const QgsRenderContext &context) const
 Returns a list of attributes required by this handler, for the specified layer. More...
 

Detailed Description

An interface for classes which provider custom handlers for features rendered as part of a map render job.

QgsRenderedFeatureHandlerInterface objects are registered in the QgsMapSettings objects used to construct map render jobs. During the rendering operation, the handleRenderedFeature() method will be called once for every rendered feature, allowing the handler to perform some custom task based on the provided information.

They can be used for custom tasks which operate on a set of rendered features, such as creating spatial indexes of the location and rendered symbology bounding box of all features rendered on a map.

Since
QGIS 3.10

Definition at line 46 of file qgsrenderedfeaturehandlerinterface.h.

Constructor & Destructor Documentation

◆ ~QgsRenderedFeatureHandlerInterface()

virtual QgsRenderedFeatureHandlerInterface::~QgsRenderedFeatureHandlerInterface ( )
virtualdefault

Member Function Documentation

◆ handleRenderedFeature()

virtual void QgsRenderedFeatureHandlerInterface::handleRenderedFeature ( const QgsFeature feature,
const QgsGeometry renderedBounds,
const QgsRenderedFeatureHandlerInterface::RenderedFeatureContext context 
)
pure virtual

Called whenever a feature is rendered during a map render job.

The renderedBounds argument specifies the (approximate) bounds of the rendered feature's symbology. E.g. for point geometry features, this will be the bounding box of the marker symbol used to symbolize the point. renderedBounds geometries are specified in painter units (not map units).

Warning
This method may be called from many different threads (for multi-threaded map render operations), and accordingly care must be taken to ensure that handleRenderedFeature() implementations are appropriately thread safe.

The context argument is used to provide additional context relating to the rendering of a feature.

◆ usedAttributes()

virtual QSet<QString> QgsRenderedFeatureHandlerInterface::usedAttributes ( QgsVectorLayer layer,
const QgsRenderContext context 
) const
inlinevirtual

Returns a list of attributes required by this handler, for the specified layer.

Attributes not listed in here may not be requested from the provider at rendering time.

Definition at line 93 of file qgsrenderedfeaturehandlerinterface.h.


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