WM: prevent drag events being continually tested

Click-drag events that weren't handled would continually be tested
for each mouse-motion event.

As well as being redundant, this added the overhead of querying
gizmos twice per motion event.

Now click-drag is only tested once when the drag threshold is reached.

This mitigates T87511, although the single drag test still causes
the snap gizmo to flicker.

1 files changed, 7 insertions, 1 deletions

diff --git a/source/blender/makesdna/DNA_windowmanager_types.h b/source/blender/makesdna/DNA_windowmanager_types.h
index 130b308f224..59091fec4b8 100644
--- a/source/blender/makesdna/DNA_windowmanager_types.h
+++ b/source/blender/makesdna/DNA_windowmanager_types.h
@@ -278,8 +278,14 @@ typedef struct wmWindow {
   char event_queue_check_click;
   /** Enable when #KM_PRESS events are not handled (keyboard/mouse-buttons only). */
   char event_queue_check_drag;
+  /**
+   * Enable when the drag was handled,
+   * to avoid mouse-motion continually triggering drag events which are not handled
+   * but add overhead to gizmo handling (for example), see T87511.
+   */
+  char event_queue_check_drag_handled;
 
-  char _pad0[2];
+  char _pad0[1];
 
   /** Internal, lock pie creation from this event until released. */
   short pie_event_type_lock;