Handle geometrycollections also in difference results

qgis · Nov 2, 2020 · b9b6171 · b9b6171
1 parent d6247fd
commit b9b6171
Showing 1 changed file with 13 additions and 4 deletions.
diff --git a/src/analysis/processing/qgsoverlayutils.cpp b/src/analysis/processing/qgsoverlayutils.cpp
@@ -54,14 +54,22 @@ bool QgsOverlayUtils::sanitizeIntersectionResult( QgsGeometry &geom, QgsWkbTypes
 
 
 //! Makes sure that what came out from difference of two geometries is good to be used in the output
-static bool sanitizeDifferenceResult( QgsGeometry &geom )
+static bool sanitizeDifferenceResult( QgsGeometry &geom, QgsWkbTypes::GeometryType geometryType )
 {
   if ( geom.isNull() )
   {
     // TODO: not sure if this ever happens - if it does, that means GEOS failed badly - would be good to have a test for such situation
     throw QgsProcessingException( QStringLiteral( "%1\n\n%2" ).arg( QObject::tr( "GEOS geoprocessing error: difference failed." ), geom.lastError() ) );
   }
 
+  //fix geometry collections
+  if ( QgsWkbTypes::flatType( geom.wkbType() ) == QgsWkbTypes::GeometryCollection )
+  {
+    // try to filter out irrelevant parts with different geometry type than what we want
+    geom.convertGeometryCollectionToSubclass( geometryType );
+  }
+
+
   // if geomB covers the whole source geometry, we get an empty geometry collection
   if ( geom.isEmpty() )
     return false;
@@ -76,6 +84,7 @@ static bool sanitizeDifferenceResult( QgsGeometry &geom )
 
 void QgsOverlayUtils::difference( const QgsFeatureSource &sourceA, const QgsFeatureSource &sourceB, QgsFeatureSink &sink, QgsProcessingContext &context, QgsProcessingFeedback *feedback, int &count, int totalCount, QgsOverlayUtils::DifferenceOutput outputAttrs )
 {
+  QgsWkbTypes::GeometryType geometryType = QgsWkbTypes::geometryType( QgsWkbTypes::multiType( sourceA.wkbType() ) );
   QgsFeatureRequest requestB;
   requestB.setNoAttributes();
   if ( outputAttrs != OutputBA )
@@ -147,7 +156,7 @@ void QgsOverlayUtils::difference( const QgsFeatureSource &sourceA, const QgsFeat
         geom = geom.difference( geomB );
       }
 
-      if ( !sanitizeDifferenceResult( geom ) )
+      if ( !sanitizeDifferenceResult( geom, geometryType ) )
         continue;
 
       const QgsAttributes attrsA( featA.attributes() );
@@ -369,7 +378,7 @@ void QgsOverlayUtils::resolveOverlaps( const QgsFeatureSource &source, QgsFeatur
       index.deleteFeature( f );
       geometries.remove( fid1 );
 
-      if ( sanitizeDifferenceResult( g12 ) )
+      if ( sanitizeDifferenceResult( g12, geometryType ) )
       {
         geometries.insert( fid1, g12 );
 
@@ -390,7 +399,7 @@ void QgsOverlayUtils::resolveOverlaps( const QgsFeatureSource &source, QgsFeatur
 
       geometries.remove( fid2 );
 
-      if ( sanitizeDifferenceResult( g21 ) )
+      if ( sanitizeDifferenceResult( g21, geometryType ) )
       {
         geometries.insert( fid2, g21 );