qgsgeometry: Add polygon to polyhedralsurface conversion in coerceToType

This allows to edit a vector layer of polyhedral surface to add new
polygon features.

src/core/geometry/qgsgeometry.cpp

@@ -45,6 +45,7 @@ email                : morb at ozemail dot com dot au
 #include "qgslinestring.h"
 #include "qgscircle.h"
 #include "qgscurve.h"
+#include "qgspolyhedralsurface.h"
 
 struct QgsGeometryPrivate
 {
@@ -1772,6 +1773,22 @@ QVector<QgsGeometry> QgsGeometry::coerceToType( const Qgis::WkbType type, double
     newGeom = QgsGeometry( std::move( mp ) );
   }
 
+  //(Multi)Polygon to PolyhedralSurface
+  if ( QgsWkbTypes::flatType( type ) == Qgis::WkbType::PolyhedralSurface &&
+       QgsWkbTypes::flatType( QgsWkbTypes::singleType( newGeom.wkbType() ) ) == Qgis::WkbType::Polygon )
+  {
+    std::unique_ptr< QgsPolyhedralSurface > polySurface = std::make_unique< QgsPolyhedralSurface >();
+    const QgsGeometry source = newGeom;
+    for ( auto part = source.const_parts_begin(); part != source.const_parts_end(); ++part )
+    {
+      if ( const QgsPolygon *polygon = qgsgeometry_cast< const QgsPolygon * >( *part ) )
+      {
+        polySurface->addPatch( polygon->clone() );
+      }
+    }
+    newGeom = QgsGeometry( std::move( polySurface ) );
+  }
+
   // Single -> multi
   if ( QgsWkbTypes::isMultiType( type ) && ! newGeom.isMultipart( ) )
   {

tests/src/python/test_qgsgeometry.py

@@ -6903,6 +6903,14 @@ def coerce_to_wkt(wkt, type, defaultZ=None, defaultM=None):
                                        QgsWkbTypes.Type.MultiCurve),
                          ['MultiCurve (LineString (0 0, 1 1))'])
 
+        # Polygon to PolyhedralSurface
+        self.assertEqual(coerce_to_wkt('Polygon ((1 1, 1 2, 2 2, 5 5, 1 1))',
+                                       QgsWkbTypes.Type.PolyhedralSurface),
+                         ['PolyhedralSurface (((1 1, 1 2, 2 2, 5 5, 1 1)))'])
+        self.assertEqual(coerce_to_wkt('Polygon Z((1 1 2, 1 2 2, 2 2 3, 5 5 3, 1 1 2))',
+                                       QgsWkbTypes.Type.PolyhedralSurfaceZ),
+                         ['PolyhedralSurfaceZ (((1 1 2, 1 2 2, 2 2 3, 5 5 3, 1 1 2)))'])
+
     def testTriangularWaves(self):
         """Test triangular waves"""
         self.assertEqual(QgsGeometry.fromWkt('Point (1 1)').triangularWaves(1, 2).asWkt(3), 'Point (1 1)')