fix(SelectiveMasking): Call parent method to install masks

Fixes qgis#57564
Parent method startFeatureRenderer needs to be called so masks could
be installed.

src/core/symbology/qgslinesymbollayer.cpp

@@ -1536,8 +1536,10 @@ bool QgsTemplatedLineSymbolLayerBase::canCauseArtifactsBetweenAdjacentTiles() co
          || ( mPlacements & Qgis::MarkerLinePlacement::SegmentCenter );
 }
 
-void QgsTemplatedLineSymbolLayerBase::startFeatureRender( const QgsFeature &, QgsRenderContext & )
+void QgsTemplatedLineSymbolLayerBase::startFeatureRender( const QgsFeature &, QgsRenderContext &context )
 {
+  installMasks( context, true );
+
   mRenderingFeature = true;
   mHasRenderedFirstPart = false;
 }
@@ -4100,4 +4102,3 @@ Qgis::RenderUnit QgsFilledLineSymbolLayer::outputUnit() const
   }
   return Qgis::RenderUnit::Unknown;
 }
-

tests/src/python/test_selective_masking.py

@@ -26,13 +26,16 @@
     QgsLayoutItemMap,
     QgsLayoutItemPage,
     QgsLayoutSize,
+    QgsLineSymbol,
     QgsMapRendererCache,
     QgsMapRendererCustomPainterJob,
     QgsMapRendererParallelJob,
     QgsMapRendererSequentialJob,
     QgsMapSettings,
+    QgsMarkerLineSymbolLayer,
     QgsMarkerSymbol,
     QgsMaskMarkerSymbolLayer,
+    QgsNullSymbolRenderer,
     QgsOuterGlowEffect,
     QgsPalLayerSettings,
     QgsPathResolver,
@@ -1349,6 +1352,30 @@ def test_layout_export_svg_marker_masking(self):
         # no rasters
         self.check_layout_export("layout_export_svg_marker_masking", 0, [self.points_layer, self.lines_layer])
 
+    def test_markerline_masked(self):
+        """
+        Test a layout export where a QgsMarkerLineSymbolLayer is masked
+        """
+
+        sl = QgsMarkerLineSymbolLayer(True, 7)
+        circle_symbol = QgsMarkerSymbol.createSimple({'size': '3'})
+        sl.setSubSymbol(circle_symbol)
+
+        self.lines_layer.setRenderer(QgsSingleSymbolRenderer(QgsLineSymbol([sl])))
+        self.polys_layer.setRenderer(QgsNullSymbolRenderer())
+
+        label_settings = self.polys_layer.labeling().settings()
+        fmt = label_settings.format()
+        # enable a mask
+        fmt.mask().setEnabled(True)
+        fmt.mask().setSize(4.0)
+        # and mask other symbol layers underneath
+        fmt.mask().setMaskedSymbolLayers([QgsSymbolLayerReference(self.lines_layer.id(), sl.id())])
+        label_settings.setFormat(fmt)
+        self.polys_layer.labeling().setSettings(label_settings)
+
+        self.check_layout_export("layout_export_markerline_masked", 0, [self.polys_layer, self.lines_layer])
+
 
 if __name__ == '__main__':
     start_app()