Undo System: avoid redundant decoding on undo

In most cases the undo system was loading undo steps twice.

This was needed since some undo systems (sculpt, paint, text)
require stepping out of the current undo step.

Use a flag to limit this to the undo systems that need it.

This improves performance for other undo systems.
This gives around 1.96x speedup in edit-mesh for high-poly objects.

Reviewed by: mont29

Ref D11893

1 files changed, 1 insertions, 1 deletions

diff --git a/source/blender/editors/space_image/image_undo.c b/source/blender/editors/space_image/image_undo.c
index 082f66b57af..cc6effd0f71 100644
--- a/source/blender/editors/space_image/image_undo.c
+++ b/source/blender/editors/space_image/image_undo.c
@@ -1006,7 +1006,7 @@ void ED_image_undosys_type(UndoType *ut)
    * specific case, see `image_undosys_step_encode` code. We cannot specify
    * `UNDOTYPE_FLAG_NEED_CONTEXT_FOR_ENCODE` though, as it can be called with a NULL context by
    * current code. */
-  ut->flags = 0;
+  ut->flags = UNDOTYPE_FLAG_DECODE_ACTIVE_STEP;
 
   ut->step_size = sizeof(ImageUndoStep);
 }