Fix T69822: Switching sculpt objects breaks undo

This introduces object mode tagging for data which hasn't yet been
written back to the ID data.

Now when selecting other sculpt objects, the original objects data is
flushed back to the ID before writing a memfile undo step.

1 files changed, 5 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_main.h b/source/blender/blenkernel/BKE_main.h
index 1b2e8bcbf42..c48a9cad443 100644
--- a/source/blender/blenkernel/BKE_main.h
+++ b/source/blender/blenkernel/BKE_main.h
@@ -80,6 +80,11 @@ typedef struct Main {
   char recovered;                  /* indicate the main->name (file) is the recovered one */
   /** All current ID's exist in the last memfile undo step. */
   char is_memfile_undo_written;
+  /**
+   * An ID needs it's data to be flushed back.
+   * use "needs_flush_to_id" in edit data to flag data which needs updating.
+   */
+  char is_memfile_undo_flush_needed;
 
   BlendThumbnail *blen_thumb;