Fix T82388: Sculpt mode: Unexpected undo behavior.

Issue exposed by rB4c7b1766a7f1.

Main idea is that non-memfile first undo step should check into previous
memfile and tag the ID it is editing as `future_changed`.

That way, when we go back and undo to the memfile, said IDs are properly
detected as changed and re-read from the memfile.

Otherwise, undo system sees them as unchanged, and just re-use the
current data instead.

Note that currently only Sculpt mode seems affected (probably because it
is storing the mode switch itself as a Sculpt undo step instead of a
memfile one), but similar action might be needed in some other cases
too.

Maniphest Tasks: T82388

Differential Revision: https://developer.blender.org/D9510

1 files changed, 2 insertions, 2 deletions

diff --git a/source/blender/editors/sculpt_paint/paint_hide.c b/source/blender/editors/sculpt_paint/paint_hide.c
index e5d682c27d9..da627c6b7db 100644
--- a/source/blender/editors/sculpt_paint/paint_hide.c
+++ b/source/blender/editors/sculpt_paint/paint_hide.c
@@ -366,10 +366,10 @@ static int hide_show_exec(bContext *C, wmOperator *op)
   /* Start undo. */
   switch (action) {
     case PARTIALVIS_HIDE:
-      SCULPT_undo_push_begin("Hide area");
+      SCULPT_undo_push_begin(ob, "Hide area");
       break;
     case PARTIALVIS_SHOW:
-      SCULPT_undo_push_begin("Show area");
+      SCULPT_undo_push_begin(ob, "Show area");
       break;
   }