Respect clip region when rendering diagrams

src/core/qgsvectorlayerdiagramprovider.cpp

@@ -173,6 +173,10 @@ void QgsVectorLayerDiagramProvider::registerFeature( QgsFeature &feature, QgsRen
     mFeatures << label;
 }
 
+void QgsVectorLayerDiagramProvider::setClipFeatureGeometry( const QgsGeometry &geometry )
+{
+  mLabelClipFeatureGeom = geometry;
+}
 
 QgsLabelFeature *QgsVectorLayerDiagramProvider::registerDiagram( QgsFeature &feat, QgsRenderContext &context, const QgsGeometry &obstacleGeometry )
 {
@@ -214,23 +218,22 @@ QgsLabelFeature *QgsVectorLayerDiagramProvider::registerDiagram( QgsFeature &fea
     extentGeom.rotate( -mapSettings.rotation(), mapSettings.visibleExtent().center() );
   }
 
-  geos::unique_ptr geomCopy;
-  std::unique_ptr<QgsGeometry> scopedPreparedGeom;
   if ( QgsPalLabeling::geometryRequiresPreparation( geom, context, mSettings.coordinateTransform(), extentGeom ) )
   {
-    scopedPreparedGeom.reset( new QgsGeometry( QgsPalLabeling::prepareGeometry( geom, context, mSettings.coordinateTransform(), extentGeom ) ) );
-    QgsGeometry *preparedGeom = scopedPreparedGeom.get();
-    if ( preparedGeom->isNull() )
-      return nullptr;
-    geomCopy = QgsGeos::asGeos( *preparedGeom );
+    geom = QgsPalLabeling::prepareGeometry( geom, context, mSettings.coordinateTransform(), extentGeom );
   }
-  else
+  if ( geom.isEmpty() )
+    return nullptr;
+
+  const QgsGeometry clipGeometry = mLabelClipFeatureGeom.isNull() ? context.featureClipGeometry() : mLabelClipFeatureGeom;
+  if ( !clipGeometry.isEmpty() )
   {
-    geomCopy = QgsGeos::asGeos( geom );
+    const QgsWkbTypes::GeometryType expectedType = geom.type();
+    geom = geom.intersection( clipGeometry );
+    geom.convertGeometryCollectionToSubclass( expectedType );
   }
-
-  if ( !geomCopy )
-    return nullptr; // invalid geometry
+  if ( geom.isEmpty() )
+    return nullptr;
 
   QgsGeometry preparedObstacleGeom;
   if ( isObstacle && !obstacleGeometry.isNull() && QgsPalLabeling::geometryRequiresPreparation( obstacleGeometry, context, mSettings.coordinateTransform(), extentGeom ) )
@@ -287,7 +290,7 @@ QgsLabelFeature *QgsVectorLayerDiagramProvider::registerDiagram( QgsFeature &fea
     }
   }
 
-  QgsDiagramLabelFeature *lf = new QgsDiagramLabelFeature( feat.id(), std::move( geomCopy ), QSizeF( diagramWidth, diagramHeight ) );
+  QgsDiagramLabelFeature *lf = new QgsDiagramLabelFeature( feat.id(), QgsGeos::asGeos( geom ), QSizeF( diagramWidth, diagramHeight ) );
   lf->setHasFixedPosition( ddPos );
   lf->setFixedPosition( QgsPointXY( ddPosX, ddPosY ) );
   lf->setHasFixedAngle( true );
@@ -342,3 +345,4 @@ QgsLabelFeature *QgsVectorLayerDiagramProvider::registerDiagram( QgsFeature &fea
   lf->setDistLabel( dist );
   return lf;
 }
+

src/core/qgsvectorlayerdiagramprovider.h

@@ -97,6 +97,13 @@ class CORE_EXPORT QgsVectorLayerDiagramProvider : public QgsAbstractLabelProvide
      */
     virtual void registerFeature( QgsFeature &feature, QgsRenderContext &context, const QgsGeometry &obstacleGeometry = QgsGeometry() );
 
+    /**
+     * Sets a \a geometry to use to clip features to when registering them as diagrams.
+     *
+     * \since QGIS 3.16
+     */
+    void setClipFeatureGeometry( const QgsGeometry &geometry );
+
   protected:
     //! initialization method - called from constructors
     void init();
@@ -123,6 +130,8 @@ class CORE_EXPORT QgsVectorLayerDiagramProvider : public QgsAbstractLabelProvide
 
     //! List of generated label features (owned by the provider)
     QList<QgsLabelFeature *> mFeatures;
+
+    QgsGeometry mLabelClipFeatureGeom;
 };
 
 #endif // QGSVECTORLAYERDIAGRAMPROVIDER_H

src/core/qgsvectorlayerrenderer.cpp

@@ -196,6 +196,9 @@ bool QgsVectorLayerRenderer::render()
       context.painter()->setClipPath( path, Qt::IntersectClip );
 
     mLabelClipFeatureGeom = QgsMapClippingUtils::calculateLabelIntersectionGeometry( mClippingRegions, context, mApplyLabelClipGeometries );
+
+    if ( mDiagramProvider )
+      mDiagramProvider->setClipFeatureGeometry( mLabelClipFeatureGeom );
   }
   mRenderer->modifyRequestExtent( requestExtent, context );
 

tests/src/core/testqgsdiagram.cpp

@@ -894,6 +894,63 @@ class TestQgsDiagram : public QObject
       QVERIFY( imageCheck( "textdiagram_datadefined_background" ) );
     }
 
+    void testClipping()
+    {
+      const QString filename = QStringLiteral( TEST_DATA_DIR ) + "/lines.shp";
+      std::unique_ptr< QgsVectorLayer> vl2( new QgsVectorLayer( filename, QStringLiteral( "lines" ), QStringLiteral( "ogr" ) ) );
+
+      QgsStringMap props;
+      props.insert( QStringLiteral( "outline_color" ), QStringLiteral( "#487bb6" ) );
+      props.insert( QStringLiteral( "outline_width" ), QStringLiteral( "1" ) );
+      std::unique_ptr< QgsLineSymbol > symbol( QgsLineSymbol::createSimple( props ) );
+      vl2->setRenderer( new QgsSingleSymbolRenderer( symbol.release() ) );
+
+      QgsDiagramSettings ds;
+      QColor col1 = Qt::red;
+      QColor col2 = Qt::yellow;
+      col1.setAlphaF( 0.5 );
+      col2.setAlphaF( 0.5 );
+      ds.categoryColors = QList<QColor>() << col1;
+      ds.categoryAttributes = QList<QString>() << QStringLiteral( "\"Value\"" );
+      ds.minimumScale = -1;
+      ds.maximumScale = -1;
+      ds.minimumSize = 0;
+      ds.penColor = Qt::green;
+      ds.penWidth = .5;
+      ds.scaleByArea = true;
+      ds.sizeType = QgsUnitTypes::RenderMillimeters;
+      ds.size = QSizeF( 5, 5 );
+      ds.rotationOffset = 0;
+
+      QgsSingleCategoryDiagramRenderer *dr = new QgsSingleCategoryDiagramRenderer();
+      dr->setDiagram( new QgsPieDiagram() );
+      dr->setDiagramSettings( ds );
+      vl2->setDiagramRenderer( dr );
+
+      QgsDiagramLayerSettings dls = QgsDiagramLayerSettings();
+      dls.setPlacement( QgsDiagramLayerSettings::Line );
+      dls.setShowAllDiagrams( true );
+      vl2->setDiagramLayerSettings( dls );
+
+      mMapSettings->setLayers( QList<QgsMapLayer *>() << vl2.get() );
+
+      QgsMapClippingRegion region1( QgsGeometry::fromWkt( "Polygon ((-92 45, -99 36, -94 29, -82 29, -81 45, -92 45))" ) );
+      region1.setFeatureClip( QgsMapClippingRegion::FeatureClippingType::Intersect );
+      mMapSettings->addClippingRegion( region1 );
+
+      QgsMapClippingRegion region2( QgsGeometry::fromWkt( "Polygon ((-85 36, -85 46, -107 47, -108 28, -85 28, -85 36))" ) );
+      region2.setFeatureClip( QgsMapClippingRegion::FeatureClippingType::PainterClip );
+      mMapSettings->addClippingRegion( region2 );
+
+      const bool res = imageCheck( QStringLiteral( "diagram_clipping" ) );
+      mMapSettings->setClippingRegions( QList< QgsMapClippingRegion >() );
+      mMapSettings->setLayers( QList<QgsMapLayer *>() << mPointsLayer );
+
+      QVERIFY( res );
+    }
+
+
+
 };
 
 bool TestQgsDiagram::imageCheck( const QString &testType )