Add experimental global undo speedup.

The feature is hidden behind an experimental option, you'll have to
enable it in the preferences to try it.

This feature is not yet considered fully stable, crashes may happen, as
well as .blend file corruptions (very unlikely, but still possible).

In a nutshell, the ideas behind this code are to:
* Detect unchanged IDs across an undo step.
* Reuse as much as possible existing IDs memory, even when its content
  did change.
* Re-use existing depsgraphs instead of building new ones from scratch.
* Store accumulated recalc flags, to avoid needless re-compute of things
  that did not change, when the ID itself is detected as modified.

See T60695 and D6580 for more technical details.

1 files changed, 4 insertions, 1 deletions

diff --git a/source/blender/blenkernel/BKE_blender_undo.h b/source/blender/blenkernel/BKE_blender_undo.h
index 7392d3947a2..4ecedbbfc1e 100644
--- a/source/blender/blenkernel/BKE_blender_undo.h
+++ b/source/blender/blenkernel/BKE_blender_undo.h
@@ -32,7 +32,10 @@ struct bContext;
 
 struct MemFileUndoData *BKE_memfile_undo_encode(struct Main *bmain,
                                                 struct MemFileUndoData *mfu_prev);
-bool BKE_memfile_undo_decode(struct MemFileUndoData *mfu, struct bContext *C);
+bool BKE_memfile_undo_decode(struct MemFileUndoData *mfu,
+                             const int undo_direction,
+                             const bool use_old_bmain_data,
+                             struct bContext *C);
 void BKE_memfile_undo_free(struct MemFileUndoData *mfu);
 
 #ifdef __cplusplus