Mesh: Move flip faces function to blenkernel

The aim is to replace the `BKE_mesh_faces_flip` functions with
this newer C++ function using the attribute API. But that is must
be called by RNA, so move this to blenkernel to avoid a circular
dependency between the geometry module and RNA.

source/blender/blenkernel/BKE_mesh.hh

@@ -8,10 +8,12 @@
  * \ingroup bke
  */
 
+#include "BLI_index_mask.hh"
+
 #include "BKE_mesh.h"
 
-namespace blender::bke::mesh {
-
+namespace blender::bke {
+namespace mesh {
 /* -------------------------------------------------------------------- */
 /** \name Polygon Data Evaluation
  * \{ */
@@ -270,7 +272,11 @@ inline int edge_other_vert(const int2 &edge, const int vert)
 
 /** \} */
 
-}  // namespace blender::bke::mesh
+}  // namespace mesh
+
+void mesh_flip_faces(Mesh &mesh, const IndexMask &selection);
+
+}  // namespace blender::bke
 
 /* -------------------------------------------------------------------- */
 /** \name Inline Mesh Data Access

source/blender/blenkernel/CMakeLists.txt

@@ -202,6 +202,7 @@ set(SRC
   intern/mesh_debug.cc
   intern/mesh_evaluate.cc
   intern/mesh_fair.cc
+  intern/mesh_flip_faces.cc
   intern/mesh_iterators.cc
   intern/mesh_legacy_convert.cc
   intern/mesh_mapping.cc

source/blender/blenkernel/intern/mesh_flip_faces.cc

@@ -2,8 +2,6 @@
  *
  * SPDX-License-Identifier: GPL-2.0-or-later */
 
-#include "GEO_mesh_flip_faces.hh"
-
 #include "DNA_mesh_types.h"
 
 #include "BLI_task.hh"
@@ -12,9 +10,9 @@
 #include "BKE_attribute_math.hh"
 #include "BKE_mesh.hh"
 
-namespace blender::geometry {
+namespace blender::bke {
 
-void flip_faces(Mesh &mesh, const IndexMask &selection)
+void mesh_flip_faces(Mesh &mesh, const IndexMask &selection)
 {
   if (mesh.faces_num == 0 || selection.is_empty()) {
     return;
@@ -61,4 +59,4 @@ void flip_faces(Mesh &mesh, const IndexMask &selection)
   BKE_mesh_tag_face_winding_changed(&mesh);
 }
 
-}  // namespace blender::geometry
+}  // namespace blender::bke

source/blender/geometry/CMakeLists.txt

@@ -16,7 +16,6 @@ set(SRC
   intern/curve_constraints.cc
   intern/fillet_curves.cc
   intern/mesh_copy_selection.cc
-  intern/mesh_flip_faces.cc
   intern/mesh_merge_by_distance.cc
   intern/mesh_primitive_cuboid.cc
   intern/mesh_split_edges.cc
@@ -37,7 +36,6 @@ set(SRC
   GEO_curve_constraints.hh
   GEO_fillet_curves.hh
   GEO_mesh_copy_selection.hh
-  GEO_mesh_flip_faces.hh
   GEO_mesh_merge_by_distance.hh
   GEO_mesh_primitive_cuboid.hh
   GEO_mesh_split_edges.hh

source/blender/geometry/GEO_mesh_flip_faces.hh

@@ -1,19 +0,0 @@
-/* SPDX-FileCopyrightText: 2023 Blender Foundation
- *
- * SPDX-License-Identifier: GPL-2.0-or-later */
-
-#pragma once
-
-#include "BLI_index_mask.hh"
-
-struct Mesh;
-
-namespace blender::geometry {
-
-/**
- * Reverse the order of the vertices in the selected faces. This effectively changes the
- * direction of the face normal.
- */
-void flip_faces(Mesh &mesh, const IndexMask &selection);
-
-}  // namespace blender::geometry

source/blender/nodes/geometry/nodes/node_geo_flip_faces.cc

@@ -2,14 +2,7 @@
  *
  * SPDX-License-Identifier: GPL-2.0-or-later */
 
-#include "BLI_task.hh"
-
 #include "BKE_mesh.hh"
-#include "BKE_mesh_runtime.h"
-
-#include "BKE_attribute_math.hh"
-
-#include "GEO_mesh_flip_faces.hh"
 
 #include "node_geometry_util.hh"
 
@@ -22,20 +15,6 @@ static void node_declare(NodeDeclarationBuilder &b)
   b.add_output<decl::Geometry>("Mesh").propagate_all();
 }
 
-static void mesh_flip_faces(Mesh &mesh, const Field<bool> &selection_field)
-{
-  if (mesh.faces_num == 0) {
-    return;
-  }
-  const bke::MeshFieldContext field_context{mesh, ATTR_DOMAIN_FACE};
-  fn::FieldEvaluator evaluator{field_context, mesh.faces_num};
-  evaluator.add(selection_field);
-  evaluator.evaluate();
-  const IndexMask selection = evaluator.get_evaluated_as_mask(0);
-
-  geometry::flip_faces(mesh, selection);
-}
-
 static void node_geo_exec(GeoNodeExecParams params)
 {
   GeometrySet geometry_set = params.extract_input<GeometrySet>("Mesh");
@@ -44,7 +23,16 @@ static void node_geo_exec(GeoNodeExecParams params)
 
   geometry_set.modify_geometry_sets([&](GeometrySet &geometry_set) {
     if (Mesh *mesh = geometry_set.get_mesh_for_write()) {
-      mesh_flip_faces(*mesh, selection_field);
+      const bke::MeshFieldContext field_context(*mesh, ATTR_DOMAIN_FACE);
+      fn::FieldEvaluator evaluator(field_context, mesh->faces_num);
+      evaluator.add(selection_field);
+      evaluator.evaluate();
+      const IndexMask selection = evaluator.get_evaluated_as_mask(0);
+      if (selection.is_empty()) {
+        return;
+      }
+
+      bke::mesh_flip_faces(*mesh, selection);
     }
   });