Sculpt: Implement undo of Apply Base during sculpt session

The idea is to push both base mesh geometry and PBVH coordinates
so it is possible to undo everything without loosing data which was
not flushed from sculpt session to base mesh.

It is possible do memory optimization to avoid push custom data
layers which are not touched by operator, but before doing that
better to ensure this is a correct and working approach.

Differential Revision: https://developer.blender.org/D7381

1 files changed, 1 insertions, 0 deletions

diff --git a/source/blender/editors/sculpt_paint/sculpt_intern.h b/source/blender/editors/sculpt_paint/sculpt_intern.h
index e2fd54596e7..b379c1ab8af 100644
--- a/source/blender/editors/sculpt_paint/sculpt_intern.h
+++ b/source/blender/editors/sculpt_paint/sculpt_intern.h
@@ -478,6 +478,7 @@ typedef struct SculptUndoNode {
    * the object when undoing the operation
    *
    * Modified geometry is stored after the modification and is used to redo the modification. */
+  bool geometry_clear_pbvh;
   SculptUndoNodeGeometry geometry_original;
   SculptUndoNodeGeometry geometry_modified;