Mesh: skip conversion from edit-mesh to mesh in edit-mode

This resolves a performance regression in 2.8x where every edit-mode
update performed an edit-mesh to mesh conversion.

Now the conversion will be lazily initialized if/when it's required.

New BKE_mesh_wrapper_* functions abstract over mesh data access.
Currently only edit-mesh and regular meshes are supported.
In the future sub-surface meshes may be supported too.

1 files changed, 23 insertions, 1 deletions

diff --git a/source/blender/makesdna/DNA_mesh_types.h b/source/blender/makesdna/DNA_mesh_types.h
index dc1a2b5ff1d..029352f3d85 100644
--- a/source/blender/makesdna/DNA_mesh_types.h
+++ b/source/blender/makesdna/DNA_mesh_types.h
@@ -112,7 +112,20 @@ typedef struct Mesh_Runtime {
    * In the future we may leave the mesh-data empty
    * since its not needed if we can use edit-mesh data. */
   char is_original;
-  char _pad[6];
+
+  /** #eMeshWrapperType and others. */
+  char wrapper_type;
+  /**
+   * A type mask from wrapper_type,
+   * in case there are differences in finalizing logic between types.
+   */
+  char wrapper_type_finalize;
+
+  char _pad[4];
+
+  /** Needed in case we need to lazily initialize the mesh. */
+  CustomData_MeshMasks cd_mask_extra;
+
 } Mesh_Runtime;
 
 typedef struct Mesh {
@@ -228,6 +241,15 @@ typedef struct TFace {
 
 /* **************** MESH ********************* */
 
+/** #Mesh_Runtime.wrapper_type */
+typedef enum eMeshWrapperType {
+  /** Use mesh data (#Mesh.mvert,#Mesh.medge, #Mesh.mloop, #Mesh.mpoly). */
+  ME_WRAPPER_TYPE_MDATA = 0,
+  /** Use edit-mesh data (#Mesh.#edit_mesh, #Mesh_Runtime.edit_data). */
+  ME_WRAPPER_TYPE_BMESH = 1,
+  /* ME_WRAPPER_TYPE_SUBD = 2, */ /* TODO */
+} eMeshWrapperType;
+
 /* texflag */
 enum {
   ME_AUTOSPACE = 1,