Add hidden QSettings switch to use a QgsGeometry/GEOS backend for lab…

…el masking If the 'map/maskBackend' QSettings key is set to 'geometry', then QgsGeometryPaintEngine will be used for calculating clip paths for label masking instead of QPainterPath The intention here is that we gain improved flexibility to optimise the creation and logic behind clipping path generation, vs the limited API we get from QPainterPath.
qgis · Jun 3, 2024 · 65fc7b0 · 65fc7b0
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diff --git a/python/PyQt6/core/auto_generated/qgsrendercontext.sip.in b/python/PyQt6/core/auto_generated/qgsrendercontext.sip.in
@@ -955,14 +955,36 @@ rendering using QBrush objects.
 %Docstring
 Add a clip ``path`` to be applied to the ``symbolLayer`` before rendering
 
+.. seealso:: :py:func:`addSymbolLayerClipGeometry`
+
 .. versionadded:: 3.26
 %End
 
     QList<QPainterPath> symbolLayerClipPaths( const QString &symbolLayerId ) const;
 %Docstring
 Returns clip paths to be applied to the ``symbolLayer`` before rendering
 
+.. seealso:: :py:func:`symbolLayerClipGeometries`
+
 .. versionadded:: 3.26
+%End
+
+    void addSymbolLayerClipGeometry( const QString &symbolLayerId, const QgsGeometry &geometry );
+%Docstring
+Add a clip ``geometry`` to be applied to the ``symbolLayer`` before rendering.
+
+.. seealso:: :py:func:`symbolLayerClipGeometries`
+
+.. versionadded:: 3.38
+%End
+
+    QVector<QgsGeometry> symbolLayerClipGeometries( const QString &symbolLayerId ) const;
+%Docstring
+Returns clipping geometries to be applied to the ``symbolLayer`` before rendering
+
+.. seealso:: :py:func:`addSymbolLayerClipGeometry`
+
+.. versionadded:: 3.38
 %End
 
     QgsDoubleRange zRange() const;

diff --git a/python/core/auto_generated/qgsrendercontext.sip.in b/python/core/auto_generated/qgsrendercontext.sip.in
@@ -955,14 +955,36 @@ rendering using QBrush objects.
 %Docstring
 Add a clip ``path`` to be applied to the ``symbolLayer`` before rendering
 
+.. seealso:: :py:func:`addSymbolLayerClipGeometry`
+
 .. versionadded:: 3.26
 %End
 
     QList<QPainterPath> symbolLayerClipPaths( const QString &symbolLayerId ) const;
 %Docstring
 Returns clip paths to be applied to the ``symbolLayer`` before rendering
 
+.. seealso:: :py:func:`symbolLayerClipGeometries`
+
 .. versionadded:: 3.26
+%End
+
+    void addSymbolLayerClipGeometry( const QString &symbolLayerId, const QgsGeometry &geometry );
+%Docstring
+Add a clip ``geometry`` to be applied to the ``symbolLayer`` before rendering.
+
+.. seealso:: :py:func:`symbolLayerClipGeometries`
+
+.. versionadded:: 3.38
+%End
+
+    QVector<QgsGeometry> symbolLayerClipGeometries( const QString &symbolLayerId ) const;
+%Docstring
+Returns clipping geometries to be applied to the ``symbolLayer`` before rendering
+
+.. seealso:: :py:func:`addSymbolLayerClipGeometry`
+
+.. versionadded:: 3.38
 %End
 
     QgsDoubleRange zRange() const;

diff --git a/src/core/maprenderer/qgsmaprendererjob.cpp b/src/core/maprenderer/qgsmaprendererjob.cpp
@@ -42,6 +42,7 @@
 #include "qgsvectorlayerrenderer.h"
 #include "qgsrendereditemresults.h"
 #include "qgsmaskpaintdevice.h"
+#include "qgsgeometrypaintdevice.h"
 #include "qgsrasterrenderer.h"
 #include "qgselevationmap.h"
 #include "qgssettingsentryimpl.h"
@@ -51,6 +52,7 @@
 #include "qgsmeshlayerlabeling.h"
 
 const QgsSettingsEntryBool *QgsMapRendererJob::settingsLogCanvasRefreshEvent = new QgsSettingsEntryBool( QStringLiteral( "logCanvasRefreshEvent" ), QgsSettingsTree::sTreeMap, false );
+const QgsSettingsEntryString *QgsMapRendererJob::settingsMaskBackend = new QgsSettingsEntryString( QStringLiteral( "maskBackend" ), QgsSettingsTree::sTreeMap, QString(), QStringLiteral( "Backend engine to use for selective masking" ) );
 
 ///@cond PRIVATE
 
@@ -683,6 +685,8 @@ std::vector<LayerRenderJob> QgsMapRendererJob::prepareJobs( QPainter *painter, Q
 
 std::vector< LayerRenderJob > QgsMapRendererJob::prepareSecondPassJobs( std::vector< LayerRenderJob > &firstPassJobs, LabelRenderJob &labelJob )
 {
+  const bool useGeometryBackend = settingsMaskBackend->value().compare( QLatin1String( "geometry" ), Qt::CaseInsensitive ) == 0;
+
   std::vector< LayerRenderJob > secondPassJobs;
 
   // We will need to quickly access the associated rendering job of a layer
@@ -812,7 +816,7 @@ std::vector< LayerRenderJob > QgsMapRendererJob::prepareSecondPassJobs( std::vec
     if ( forceVector && !labelHasEffects[ maskId ] )
     {
       // set a painter to get all masking instruction in order to later clip masked symbol layer
-      maskPaintDevice = new QgsMaskPaintDevice( true );
+      maskPaintDevice = useGeometryBackend ? dynamic_cast< QPaintDevice *>( new QgsGeometryPaintDevice( true ) ) : dynamic_cast< QPaintDevice * >( new QgsMaskPaintDevice( true ) );
       maskPainter = new QPainter( maskPaintDevice );
     }
     else
@@ -887,7 +891,7 @@ std::vector< LayerRenderJob > QgsMapRendererJob::prepareSecondPassJobs( std::vec
       if ( forceVector && !maskLayerHasEffects[ job.layerId ] )
       {
         // set a painter to get all masking instruction in order to later clip masked symbol layer
-        maskPaintDevice = new QgsMaskPaintDevice();
+        maskPaintDevice = useGeometryBackend ? dynamic_cast< QPaintDevice *>( new QgsGeometryPaintDevice( true ) ) : dynamic_cast< QPaintDevice * >( new QgsMaskPaintDevice( true ) );
         maskPainter = new QPainter( maskPaintDevice );
       }
       else
@@ -990,10 +994,23 @@ void QgsMapRendererJob::initSecondPassJobs( std::vector< LayerRenderJob > &secon
     for ( const QPair<LayerRenderJob *, int> &p : std::as_const( job.maskJobs ) )
     {
       QPainter *maskPainter = p.first ? p.first->maskPainter.get() : labelJob.maskPainters[p.second].get();
-      QPainterPath path = static_cast<QgsMaskPaintDevice *>( maskPainter->device() )->maskPainterPath();
-      for ( const QString &symbolLayerId : job.context()->disabledSymbolLayersV2() )
+
+      const QSet<QString> layers = job.context()->disabledSymbolLayersV2();
+      if ( QgsMaskPaintDevice *maskDevice = dynamic_cast<QgsMaskPaintDevice *>( maskPainter->device() ) )
+      {
+        QPainterPath path = maskDevice->maskPainterPath();
+        for ( const QString &symbolLayerId : layers )
+        {
+          job.context()->addSymbolLayerClipPath( symbolLayerId, path );
+        }
+      }
+      else if ( QgsGeometryPaintDevice *geometryDevice = dynamic_cast<QgsGeometryPaintDevice *>( maskPainter->device() ) )
       {
-        job.context()->addSymbolLayerClipPath( symbolLayerId, path );
+        const QgsGeometry geometry( geometryDevice->geometry().clone() );
+        for ( const QString &symbolLayerId : layers )
+        {
+          job.context()->addSymbolLayerClipGeometry( symbolLayerId, geometry );
+        }
       }
     }
 

diff --git a/src/core/maprenderer/qgsmaprendererjob.h b/src/core/maprenderer/qgsmaprendererjob.h
@@ -41,6 +41,7 @@ class QgsFeatureFilterProvider;
 class QgsRenderedItemResults;
 class QgsElevationMap;
 class QgsSettingsEntryBool;
+class QgsSettingsEntryString;
 
 #ifndef SIP_RUN
 /// @cond PRIVATE
@@ -481,6 +482,13 @@ class CORE_EXPORT QgsMapRendererJob : public QObject SIP_ABSTRACT
 #ifndef SIP_RUN
     //! Settings entry log canvas refresh event
     static const QgsSettingsEntryBool *settingsLogCanvasRefreshEvent;
+
+    /**
+     * Settings entry for mask painting backend engine.
+     *
+     * \since QGIS 3.38
+     */
+    static const QgsSettingsEntryString *settingsMaskBackend;
 #endif
 
   signals:

diff --git a/src/core/qgsrendercontext.cpp b/src/core/qgsrendercontext.cpp
@@ -83,6 +83,7 @@ QgsRenderContext::QgsRenderContext( const QgsRenderContext &rh )
   , mFrameRate( rh.mFrameRate )
   , mCurrentFrame( rh.mCurrentFrame )
   , mSymbolLayerClipPaths( rh.mSymbolLayerClipPaths )
+  , mSymbolLayerClippingGeometries( rh.mSymbolLayerClippingGeometries )
 #ifdef QGISDEBUG
   , mHasTransformContext( rh.mHasTransformContext )
 #endif
@@ -134,6 +135,7 @@ QgsRenderContext &QgsRenderContext::operator=( const QgsRenderContext &rh )
   mFrameRate = rh.mFrameRate;
   mCurrentFrame = rh.mCurrentFrame;
   mSymbolLayerClipPaths = rh.mSymbolLayerClipPaths;
+  mSymbolLayerClippingGeometries = rh.mSymbolLayerClippingGeometries;
   if ( isTemporal() )
     setTemporalRange( rh.temporalRange() );
 #ifdef QGISDEBUG
@@ -732,6 +734,16 @@ QList<QPainterPath> QgsRenderContext::symbolLayerClipPaths( const QString &symbo
   return mSymbolLayerClipPaths[ symbolLayerId ];
 }
 
+void QgsRenderContext::addSymbolLayerClipGeometry( const QString &symbolLayerId, const QgsGeometry &geometry )
+{
+  mSymbolLayerClippingGeometries[ symbolLayerId ].append( geometry );
+}
+
+QVector<QgsGeometry> QgsRenderContext::symbolLayerClipGeometries( const QString &symbolLayerId ) const
+{
+  return mSymbolLayerClippingGeometries[ symbolLayerId ];
+}
+
 void QgsRenderContext::setDisabledSymbolLayers( const QSet<const QgsSymbolLayer *> &symbolLayers )
 {
   mDisabledSymbolLayers.clear();

diff --git a/src/core/qgsrendercontext.h b/src/core/qgsrendercontext.h
@@ -931,16 +931,36 @@ class CORE_EXPORT QgsRenderContext : public QgsTemporalRangeObject
 
     /**
      * Add a clip \a path to be applied to the \a symbolLayer before rendering
+     * \see addSymbolLayerClipGeometry()
+     *
      * \since QGIS 3.26, arguments changed and public API since 3.30
      */
     void addSymbolLayerClipPath( const QString &symbolLayerId, QPainterPath path );
 
     /**
      * Returns clip paths to be applied to the \a symbolLayer before rendering
+     *
+     *\see symbolLayerClipGeometries()
      * \since QGIS 3.26, arguments changed and public API since 3.30
      */
     QList<QPainterPath> symbolLayerClipPaths( const QString &symbolLayerId ) const;
 
+    /**
+     * Add a clip \a geometry to be applied to the \a symbolLayer before rendering.
+     *
+     * \see symbolLayerClipGeometries()
+     * \since QGIS 3.38
+     */
+    void addSymbolLayerClipGeometry( const QString &symbolLayerId, const QgsGeometry &geometry );
+
+    /**
+     * Returns clipping geometries to be applied to the \a symbolLayer before rendering
+     *
+     * \see addSymbolLayerClipGeometry()
+     * \since QGIS 3.38
+     */
+    QVector<QgsGeometry> symbolLayerClipGeometries( const QString &symbolLayerId ) const;
+
     /**
      * Returns the range of z-values which should be rendered.
      *
@@ -1227,6 +1247,9 @@ class CORE_EXPORT QgsRenderContext : public QgsTemporalRangeObject
     //! clip paths to be applied to the symbol layer before rendering
     QMap< QString, QList<QPainterPath> > mSymbolLayerClipPaths;
 
+    //! Clip geometries to be applied to the symbol layer before rendering
+    QMap< QString, QVector<QgsGeometry> > mSymbolLayerClippingGeometries;
+
 #ifdef QGISDEBUG
     bool mHasTransformContext = false;
 #endif

diff --git a/src/core/symbology/qgssymbollayer.cpp b/src/core/symbology/qgssymbollayer.cpp
@@ -957,21 +957,45 @@ void QgsSymbolLayer::prepareMasks( const QgsSymbolRenderContext &context )
   mClipPath.clear();
 
   const QgsRenderContext &renderContext = context.renderContext();
-  const QList<QPainterPath> clipPaths = renderContext.symbolLayerClipPaths( id() );
-  if ( !clipPaths.isEmpty() )
+
+  const QVector<QgsGeometry> clipGeometries = renderContext.symbolLayerClipGeometries( id() );
+  if ( !clipGeometries.empty() )
   {
-    QPainterPath mergedPaths;
-    mergedPaths.setFillRule( Qt::WindingFill );
-    for ( const QPainterPath &path : clipPaths )
+    QVector< QgsGeometry > fixed;
+    for ( const QgsGeometry &geometry : clipGeometries )
     {
-      mergedPaths.addPath( path );
+      fixed << geometry.makeValid( Qgis::MakeValidMethod::Structure );
     }
 
-    if ( !mergedPaths.isEmpty() )
+    const QgsGeometry mergedGeom = QgsGeometry::unaryUnion( fixed );
+    if ( !mergedGeom.isEmpty() )
+    {
+      const QgsGeometry exterior = QgsGeometry::fromRect(
+                                     QgsRectangle( 0, 0,
+                                         renderContext.outputSize().width(),
+                                         renderContext.outputSize().height() ) );
+      const QgsGeometry maskGeom = exterior.difference( mergedGeom );
+      mClipPath = maskGeom.constGet()->asQPainterPath();
+    }
+  }
+  else
+  {
+    const QList<QPainterPath> clipPaths = renderContext.symbolLayerClipPaths( id() );
+    if ( !clipPaths.isEmpty() )
     {
-      mClipPath.addRect( 0, 0, renderContext.outputSize().width(),
-                         renderContext.outputSize().height() );
-      mClipPath = mClipPath.subtracted( mergedPaths );
+      QPainterPath mergedPaths;
+      mergedPaths.setFillRule( Qt::WindingFill );
+      for ( const QPainterPath &path : clipPaths )
+      {
+        mergedPaths.addPath( path );
+      }
+
+      if ( !mergedPaths.isEmpty() )
+      {
+        mClipPath.addRect( 0, 0, renderContext.outputSize().width(),
+                           renderContext.outputSize().height() );
+        mClipPath = mClipPath.subtracted( mergedPaths );
+      }
     }
   }
 }

diff --git a/tests/src/python/test_selective_masking.py b/tests/src/python/test_selective_masking.py
@@ -16,7 +16,7 @@
 import subprocess
 import tempfile
 
-from qgis.PyQt.QtCore import QRectF, QSize, Qt, QUuid
+from qgis.PyQt.QtCore import QRectF, QSize, Qt, QUuid, QCoreApplication
 from qgis.PyQt.QtGui import QColor, QImage, QPainter
 from qgis.core import (
     Qgis,
@@ -48,7 +48,8 @@
     QgsSymbolLayerUtils,
     QgsUnitTypes,
     QgsWkbTypes,
-    QgsFontUtils
+    QgsFontUtils,
+    QgsSettings
 )
 import unittest
 from qgis.testing import start_app, QgisTestCase
@@ -77,14 +78,9 @@ def renderMapToImageWithTime(mapsettings, parallel=False, cache=None):
     return (job.renderedImage(), job.renderingTime())
 
 
-class TestSelectiveMasking(QgisTestCase):
-
-    @classmethod
-    def control_path_prefix(cls):
-        return "selective_masking"
+class SelectiveMaskingTestBase():
 
     def setUp(self):
-
         self.map_settings = QgsMapSettings()
         crs = QgsCoordinateReferenceSystem('epsg:4326')
         extent = QgsRectangle(-123.0, 22.7, -76.4, 46.9)
@@ -1350,6 +1346,45 @@ def test_layout_export_svg_marker_masking(self):
         self.check_layout_export("layout_export_svg_marker_masking", 0, [self.points_layer, self.lines_layer])
 
 
+class TestSelectiveMaskingQPainterPathBackend(QgisTestCase, SelectiveMaskingTestBase):
+    """
+    Test selective masking with the QPainterPath backend
+    """
+    @classmethod
+    def control_path_prefix(cls):
+        return "selective_masking"
+
+    @classmethod
+    def setUpClass(cls):
+        QgsSettings().setValue('map/maskBackend', 'qpainterpath')
+        QgisTestCase.setUpClass()
+
+    def setUp(self):
+        SelectiveMaskingTestBase.setUp(self)
+
+
+class TestSelectiveMaskingGeometryBackend(QgisTestCase, SelectiveMaskingTestBase):
+    """
+    Test selective masking with the QgsGeometry backend
+    """
+    @classmethod
+    def control_path_prefix(cls):
+        return "selective_masking"
+
+    @classmethod
+    def setUpClass(cls):
+        QgsSettings().setValue('map/maskBackend', 'geometry')
+        QgisTestCase.setUpClass()
+
+    def setUp(self):
+        SelectiveMaskingTestBase.setUp(self)
+
+
 if __name__ == '__main__':
+    QCoreApplication.setOrganizationName("QGIS_Test")
+    QCoreApplication.setOrganizationDomain("SelectiveMaskingTestBase.com")
+    QCoreApplication.setApplicationName("SelectiveMaskingTestBase")
+    QgsSettings().clear()
+
     start_app()
     unittest.main()