When a geometry generator symbol layer is used as part of a

SUBSYMBOL, the $geometry part of the expression must refer to the shape which is being rendered by the parent symbol, and not the original feature's geometry
qgis · Oct 23, 2021 · 0838fd9 · 0838fd9
1 parent c7102e8
commit 0838fd9
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Showing 3 changed files with 47 additions and 3 deletions.
diff --git a/src/core/symbology/qgsgeometrygeneratorsymbollayer.cpp b/src/core/symbology/qgsgeometrygeneratorsymbollayer.cpp
@@ -333,10 +333,12 @@ void QgsGeometryGeneratorSymbolLayer::render( QgsSymbolRenderContext &context, Q
   QgsExpressionContext &expressionContext = context.renderContext().expressionContext();
   QgsFeature f = expressionContext.feature();
 
-  if ( !context.feature() && points )
+  if ( ( !context.feature() || context.renderContext().flags() & Qgis::RenderContextFlag::RenderingSubSymbol ) && points )
   {
     // oh dear, we don't have a feature to work from... but that's ok, we are probably being rendered as a plain old symbol!
-    // in this case we need to build up a feature which represents the points being rendered
+    // in this case we need to build up a feature which represents the points being rendered.
+    // note that we also do this same logic when we are rendering a subsymbol. In that case the $geometry part of the
+    // expression should refer to the shape of the subsymbol being rendered, NOT the feature's original geometry
     QgsGeometry drawGeometry;
 
     // step 1 - convert points and rings to geometry

diff --git a/tests/src/python/test_qgsgeometrygeneratorsymbollayer.py b/tests/src/python/test_qgsgeometrygeneratorsymbollayer.py
@@ -44,7 +44,8 @@
     QgsRenderContext,
     QgsRenderChecker,
     QgsCoordinateReferenceSystem,
-    QgsCoordinateTransform
+    QgsCoordinateTransform,
+    QgsArrowSymbolLayer
 )
 
 from qgis.testing import start_app, unittest
@@ -327,6 +328,47 @@ def test_no_feature_coordinate_transform(self):
 
         self.assertTrue(self.imageCheck('geometrygenerator_nofeature', 'geometrygenerator_nofeature', image))
 
+    def test_subsymbol(self):
+        """
+        Test rendering a generator in a subsymbol of another symbol
+        """
+        sym = QgsLineSymbol()
+        arrow = QgsArrowSymbolLayer()
+        arrow.setIsRepeated(False)
+        arrow.setArrowStartWidth(10)
+        arrow.setArrowWidth(5)
+        arrow.setHeadLength(20)
+        arrow.setHeadThickness(10)
+
+        sym.changeSymbolLayer(0, arrow)
+
+        self.lines_layer.renderer().setSymbol(sym)
+
+        # here "$geometry" must refer to the created ARROW shape, NOT the original feature line geometry!
+        generator_layer = QgsGeometryGeneratorSymbolLayer.create(
+            {'geometryModifier': 'buffer($geometry, 3)'})
+        generator_layer.setSymbolType(QgsSymbol.Fill)
+        generator_layer.setUnits(QgsUnitTypes.RenderMillimeters)
+        self.assertIsNotNone(generator_layer.subSymbol())
+
+        generator_layer.subSymbol().symbolLayer(0).setColor(QColor(255, 255, 255))
+        generator_layer.subSymbol().symbolLayer(0).setStrokeColor(QColor(0, 0, 0))
+        generator_layer.subSymbol().symbolLayer(0).setStrokeWidth(2)
+
+        sub_symbol = QgsFillSymbol()
+        sub_symbol.changeSymbolLayer(0, generator_layer)
+        arrow.setSubSymbol(sub_symbol)
+
+        rendered_layers = [self.lines_layer]
+        self.mapsettings.setLayers(rendered_layers)
+
+        renderchecker = QgsMultiRenderChecker()
+        renderchecker.setMapSettings(self.mapsettings)
+        renderchecker.setControlName('expected_geometrygenerator_subsymbol')
+        res = renderchecker.runTest('geometrygenerator_subsymbol')
+        self.report += renderchecker.report()
+        self.assertTrue(res)
+
     def imageCheck(self, name, reference_image, image):
         self.report += "<h2>Render {}</h2>\n".format(name)
         temp_dir = QDir.tempPath() + '/'

diff --git a/...s/expected_geometrygenerator_subsymbol/expected_geometrygenerator_subsymbol.png b/...s/expected_geometrygenerator_subsymbol/expected_geometrygenerator_subsymbol.png