Inverted polygon renderer: make sure the each symbol category is always rendered in the same order

Author: Hugo Mercier

src/core/symbology-ng/qgsinvertedpolygonrenderer.cpp

@@ -154,18 +154,19 @@ bool QgsInvertedPolygonRenderer::renderFeature( QgsFeature& feature, QgsRenderCo
     return false;
   }
 
-  if ( ! mFeaturesCategoryMap.contains(catId) )
+  if ( ! mSymbolCategories.contains(catId) )
   {
     // the exterior ring must be a square in the destination CRS
     CombinedFeature cFeat;
     cFeat.multiPolygon.append( mExtentPolygon );
     // store the first feature
     cFeat.feature = feature;
-    mFeaturesCategoryMap.insert( catId, cFeat );
+    mSymbolCategories.insert( catId, mSymbolCategories.count() );
+    mFeaturesCategoryMap.append( cFeat );
   }
 
   // update the geometry
-  CombinedFeature& cFeat = mFeaturesCategoryMap[catId];
+  CombinedFeature& cFeat = mFeaturesCategoryMap[ mSymbolCategories[catId] ];
   QgsMultiPolygon multi;
   QgsGeometry* geom = feature.geometry();
   if ( !geom )
@@ -261,11 +262,11 @@ void QgsInvertedPolygonRenderer::stopRender( QgsRenderContext& context )
 
   for ( FeatureCategoryMap::iterator cit = mFeaturesCategoryMap.begin(); cit != mFeaturesCategoryMap.end(); ++cit)
   {
-    QgsFeature feat( cit.value().feature );
+    QgsFeature feat( cit->feature );
     if ( !mPreprocessingEnabled )
     {
       // no preprocessing - the final polygon has already been prepared
-      feat.setGeometry( QgsGeometry::fromMultiPolygon( cit.value().multiPolygon ) );
+      feat.setGeometry( QgsGeometry::fromMultiPolygon( cit->multiPolygon ) );
     }
     else
     {

src/core/symbology-ng/qgsinvertedpolygonrenderer.h

@@ -129,10 +129,13 @@ class CORE_EXPORT QgsInvertedPolygonRenderer : public QgsFeatureRendererV2
     QgsMultiPolygon multiPolygon; //< the final combined geometry
     QgsFeature feature;           //< one feature (for attriute-based rendering)
   };
-  typedef QMap< QByteArray, CombinedFeature > FeatureCategoryMap;
-  /** where features are stored, based on their symbol category */
+  typedef QVector<CombinedFeature> FeatureCategoryMap;
+  /** where features are stored, based on the index of their symbol category @see mSymbolCategories */
   FeatureCategoryMap mFeaturesCategoryMap;
 
+  /** maps a category to an index */
+  QMap<QByteArray, int> mSymbolCategories;
+
   /** the polygon used as exterior ring that covers the current extent */
   QgsPolygon mExtentPolygon;