Fix T81589: Correct drag type handling in outliner

Blender crashed when dragging and dropping color into the outliner.
This issue was cause by a missing check for the correct drag type
in `datastack_drop_poll`. The check is added in this commit.
Additionally, a new drag type is introduced for the "data stack"
drag option, that was introduced in commit 1572da858df4, to
differentiate it from the existing WM_DRAG_ID type.

Reviewed By: Severin

Differential Revision: https://developer.blender.org/D9169

1 files changed, 14 insertions, 8 deletions

diff --git a/source/blender/editors/space_outliner/outliner_dragdrop.c b/source/blender/editors/space_outliner/outliner_dragdrop.c
index cbe6887f66e..6c0975498e0 100644
--- a/source/blender/editors/space_outliner/outliner_dragdrop.c
+++ b/source/blender/editors/space_outliner/outliner_dragdrop.c
@@ -847,6 +847,10 @@ static bool datastack_drop_poll(bContext *C,
                                 const wmEvent *event,
                                 const char **r_tooltip)
 {
+  if (drag->type != WM_DRAG_DATASTACK) {
+    return false;
+  }
+
   SpaceOutliner *space_outliner = CTX_wm_space_outliner(C);
   ARegion *region = CTX_wm_region(C);
   bool changed = outliner_flag_set(&space_outliner->tree, TSE_HIGHLIGHTED | TSE_DRAG_ANY, false);
@@ -1363,16 +1367,18 @@ static int outliner_item_drag_drop_invoke(bContext *C,
     WM_operator_properties_free(&op_ptr);
   }
 
-  wmDrag *drag = WM_event_start_drag(C, data.icon, WM_DRAG_ID, NULL, 0.0, WM_DRAG_NOP);
+  const bool use_datastack_drag = ELEM(tselem->type,
+                                       TSE_MODIFIER,
+                                       TSE_MODIFIER_BASE,
+                                       TSE_CONSTRAINT,
+                                       TSE_CONSTRAINT_BASE,
+                                       TSE_GPENCIL_EFFECT,
+                                       TSE_GPENCIL_EFFECT_BASE);
 
-  if (ELEM(tselem->type,
-           TSE_MODIFIER,
-           TSE_MODIFIER_BASE,
-           TSE_CONSTRAINT,
-           TSE_CONSTRAINT_BASE,
-           TSE_GPENCIL_EFFECT,
-           TSE_GPENCIL_EFFECT_BASE)) {
+  const int wm_drag_type = use_datastack_drag ? WM_DRAG_DATASTACK : WM_DRAG_ID;
+  wmDrag *drag = WM_event_start_drag(C, data.icon, wm_drag_type, NULL, 0.0, WM_DRAG_NOP);
 
+  if (use_datastack_drag) {
     TreeElement *te_bone = NULL;
     bPoseChannel *pchan = outliner_find_parent_bone(te, &te_bone);
     datastack_drop_data_init(drag, (Object *)tselem->id, pchan, te, tselem, te->directdata);