Fix inverted polygon is distorted when map is rotated

Fixes #26381

src/core/symbology/qgsinvertedpolygonrenderer.cpp

@@ -111,7 +111,6 @@ void QgsInvertedPolygonRenderer::startRender( QgsRenderContext &context, const Q
   // We compute coordinates of the extent which will serve as exterior ring
   // for the final polygon
   // It must be computed in the destination CRS if reprojection is enabled.
-  const QgsMapToPixel &mtp( context.mapToPixel() );
 
   if ( !context.painter() )
   {
@@ -119,15 +118,16 @@ void QgsInvertedPolygonRenderer::startRender( QgsRenderContext &context, const Q
   }
 
   // convert viewport to dest CRS
-  QRect e( context.painter()->viewport() );
   // add some space to hide borders and tend to infinity
-  e.adjust( -e.width() * 5, -e.height() * 5, e.width() * 5, e.height() * 5 );
+  const double buffer = std::max( context.mapExtent().width(), context.mapExtent().height() ) * 0.1;
+  const QRectF outer = context.mapExtent().buffered( buffer ).toRectF();
   QgsPolylineXY exteriorRing;
-  exteriorRing << mtp.toMapCoordinates( e.topLeft() );
-  exteriorRing << mtp.toMapCoordinates( e.topRight() );
-  exteriorRing << mtp.toMapCoordinates( e.bottomRight() );
-  exteriorRing << mtp.toMapCoordinates( e.bottomLeft() );
-  exteriorRing << mtp.toMapCoordinates( e.topLeft() );
+  exteriorRing.reserve( 5 );
+  exteriorRing << outer.topLeft();
+  exteriorRing << outer.topRight();
+  exteriorRing << outer.bottomRight();
+  exteriorRing << outer.bottomLeft();
+  exteriorRing << outer.topLeft();
 
   // copy the rendering context
   mContext = context;
@@ -142,8 +142,7 @@ void QgsInvertedPolygonRenderer::startRender( QgsRenderContext &context, const Q
     // disable projection
     mContext.setCoordinateTransform( QgsCoordinateTransform() );
     // recompute extent so that polygon clipping is correct
-    QRect v( context.painter()->viewport() );
-    mContext.setExtent( QgsRectangle( mtp.toMapCoordinates( v.topLeft() ), mtp.toMapCoordinates( v.bottomRight() ) ) );
+    mContext.setExtent( context.mapExtent() );
     // do we have to recompute the MapToPixel ?
   }
 

tests/src/core/testqgsinvertedpolygonrenderer.cpp

@@ -55,6 +55,7 @@ class TestQgsInvertedPolygon : public QObject
     void preprocess();
     void projectionTest();
     void curvedPolygons();
+    void rotationTest();
 
   private:
     bool mTestHasError =  false ;
@@ -154,7 +155,6 @@ void TestQgsInvertedPolygon::projectionTest()
   mMapSettings.setDestinationCrs( mpPolysLayer->crs() );
 }
 
-// This test relies on GDAL support of curved polygons
 void TestQgsInvertedPolygon::curvedPolygons()
 {
   QString myCurvedPolysFileName = mTestDataDir + "curved_polys.gpkg";
@@ -170,6 +170,16 @@ void TestQgsInvertedPolygon::curvedPolygons()
   mMapSettings.setLayers( QList< QgsMapLayer * >() << mpPolysLayer );
 }
 
+void TestQgsInvertedPolygon::rotationTest()
+{
+  mReport += QLatin1String( "<h2>Inverted polygon renderer, rotation test</h2>\n" );
+  mMapSettings.setRotation( 45 );
+  QVERIFY( setQml( mpPolysLayer, "inverted_polys_single.qml" ) );
+  QVERIFY( imageCheck( "inverted_polys_rotation" ) );
+  mMapSettings.setRotation( 0 );
+}
+
+
 //
 // Private helper functions not called directly by CTest
 //