Add optimised conversion methods for ogr (multi)polygons to QgsGeometry

Avoids conversion back and forth from wkb to transfer these geometries
from ogr to qgis

src/core/qgsogrutils.cpp

@@ -23,6 +23,9 @@
 #include "qgsmultilinestring.h"
 #include "qgsogrprovider.h"
 #include "qgslinesymbollayer.h"
+#include "qgspolygon.h"
+#include "qgsmultipolygon.h"
+
 #include <QTextCodec>
 #include <QUuid>
 #include <cpl_error.h>
@@ -427,6 +430,38 @@ std::unique_ptr< QgsMultiLineString > ogrGeometryToQgsMultiLineString( OGRGeomet
   return mp;
 }
 
+std::unique_ptr< QgsPolygon > ogrGeometryToQgsPolygon( OGRGeometryH geom )
+{
+  std::unique_ptr< QgsPolygon > polygon = std::make_unique< QgsPolygon >();
+
+  const int count = OGR_G_GetGeometryCount( geom );
+  if ( count >= 1 )
+  {
+    polygon->setExteriorRing( ogrGeometryToQgsLineString( OGR_G_GetGeometryRef( geom, 0 ) ).release() );
+  }
+
+  for ( int i = 1; i < count; ++i )
+  {
+    polygon->addInteriorRing( ogrGeometryToQgsLineString( OGR_G_GetGeometryRef( geom, i ) ).release() );
+  }
+
+  return polygon;
+}
+
+std::unique_ptr< QgsMultiPolygon > ogrGeometryToQgsMultiPolygon( OGRGeometryH geom )
+{
+  std::unique_ptr< QgsMultiPolygon > polygon = std::make_unique< QgsMultiPolygon >();
+
+  const int count = OGR_G_GetGeometryCount( geom );
+  polygon->reserve( count );
+  for ( int i = 0; i < count; ++i )
+  {
+    polygon->addGeometry( ogrGeometryToQgsPolygon( OGR_G_GetGeometryRef( geom, i ) ).release() );
+  }
+
+  return polygon;
+}
+
 QgsWkbTypes::Type QgsOgrUtils::ogrGeometryTypeToQgsWkbType( OGRwkbGeometryType ogrGeomType )
 {
   switch ( ogrGeomType )
@@ -537,19 +572,27 @@ QgsGeometry QgsOgrUtils::ogrGeometryToQgsGeometry( OGRGeometryH geom )
 
     case QgsWkbTypes::LineString:
     {
-      // optimised case for line -- avoid wkb conversion
       return QgsGeometry( ogrGeometryToQgsLineString( geom ) );
     }
 
     case QgsWkbTypes::MultiLineString:
     {
-      // optimised case for line -- avoid wkb conversion
       return QgsGeometry( ogrGeometryToQgsMultiLineString( geom ) );
     }
 
+    case QgsWkbTypes::Polygon:
+    {
+      return QgsGeometry( ogrGeometryToQgsPolygon( geom ) );
+    }
+
+    case QgsWkbTypes::MultiPolygon:
+    {
+      return QgsGeometry( ogrGeometryToQgsMultiPolygon( geom ) );
+    }
+
     default:
       break;
-  };
+  }
 
   // Fallback to inefficient WKB conversions