Outliner: avoid creating unnecessary undo steps

The `OUTLINER_OT_item_activate` operator, although it detects when
something changes, always returns `OPERATOR_FINISHED` and thus induces
the creation of undo steps.

So return `OPERATOR_CANCELLED` when nothing changes.

Ref T94080

Reviewed By: Severin

Maniphest Tasks: T94080

Differential Revision: https://developer.blender.org/D13638

1 files changed, 11 insertions, 10 deletions

diff --git a/source/blender/editors/space_outliner/outliner_select.cc b/source/blender/editors/space_outliner/outliner_select.cc
index 3ff8b9e973f..ebb4e529b04 100644
--- a/source/blender/editors/space_outliner/outliner_select.cc
+++ b/source/blender/editors/space_outliner/outliner_select.cc
@@ -1611,8 +1611,7 @@ static int outliner_item_do_activate_from_cursor(bContext *C,
 
   if (!(te = outliner_find_item_at_y(space_outliner, &space_outliner->tree, view_mval[1]))) {
     if (deselect_all) {
-      outliner_flag_set(&space_outliner->tree, TSE_SELECTED, false);
-      changed = true;
+      changed |= outliner_flag_set(&space_outliner->tree, TSE_SELECTED, false);
     }
   }
   /* Don't allow toggle on scene collection */
@@ -1660,17 +1659,19 @@ static int outliner_item_do_activate_from_cursor(bContext *C,
     changed = true;
   }
 
-  if (changed) {
-    if (rebuild_tree) {
-      ED_region_tag_redraw(region);
-    }
-    else {
-      ED_region_tag_redraw_no_rebuild(region);
-    }
+  if (!changed) {
+    return OPERATOR_CANCELLED;
+  }
 
-    ED_outliner_select_sync_from_outliner(C, space_outliner);
+  if (rebuild_tree) {
+    ED_region_tag_redraw(region);
+  }
+  else {
+    ED_region_tag_redraw_no_rebuild(region);
   }
 
+  ED_outliner_select_sync_from_outliner(C, space_outliner);
+
   return OPERATOR_FINISHED;
 }