Event System: key-press while dragging now activates drag first

When dragging with a large threshold (using a tablet for example),
it's possible to press another key before the drag threshold is reached.

So tweaking then pressing X would show the delete popup instead of
transforming along the X-axis.

Now key presses while dragging cause the drag event to be evaluated
before the key press.

Note that to properly base the mouse-move event on the previous
state the last handled event is now stored in the window.
Without this the inserted mouse-move event may contain invalid values
from the next event (it's modifier state or other `prev_*` values).

Requested by @JulienKaspar.

1 files changed, 5 insertions, 0 deletions

diff --git a/source/blender/windowmanager/WM_types.h b/source/blender/windowmanager/WM_types.h
index 8934f714c21..9edbafafdd3 100644
--- a/source/blender/windowmanager/WM_types.h
+++ b/source/blender/windowmanager/WM_types.h
@@ -610,6 +610,11 @@ typedef enum eWM_EventFlag {
    * See #KMI_REPEAT_IGNORE for details on how key-map handling uses this.
    */
   WM_EVENT_IS_REPEAT = (1 << 1),
+  /**
+   * Mouse-move events may have this flag set to force creating a click-drag event
+   * even when the threshold has not been met.
+   */
+  WM_EVENT_FORCE_DRAG_THRESHOLD = (1 << 2),
 } eWM_EventFlag;
 
 typedef struct wmTabletData {