Fix T44740: Tweak events stuck (ignored release)

Tweak event was being added to the end of the event queue (out of order),
meaning any mouse releases already in the queue wouldn't be used to exit the gesture.
Gestures could get stuck (mostly when the system wasn't able to handle events fast enough).

Now tweak events are now added in order.

3 files changed, 26 insertions, 5 deletions

diff --git a/source/blender/windowmanager/WM_api.h b/source/blender/windowmanager/WM_api.h
index 2131d5aae4a..5491769fac2 100644
--- a/source/blender/windowmanager/WM_api.h
+++ b/source/blender/windowmanager/WM_api.h
@@ -182,8 +182,15 @@ void        WM_report_banner_show(const struct bContext *C);
 void        WM_report(const struct bContext *C, ReportType type, const char *message);
 void        WM_reportf(const struct bContext *C, ReportType type, const char *format, ...) ATTR_PRINTF_FORMAT(3, 4);
 
-void		wm_event_add(struct wmWindow *win, const struct wmEvent *event_to_add);
-void		wm_event_init_from_window(struct wmWindow *win, struct wmEvent *event);
+void wm_event_add_ex(
+        struct wmWindow *win, const struct wmEvent *event_to_add,
+        const struct wmEvent *event_to_add_after)
+        ATTR_NONNULL(1, 2);
+void wm_event_add(
+        struct wmWindow *win, const struct wmEvent *event_to_add)
+        ATTR_NONNULL(1, 2);
+
+void wm_event_init_from_window(struct wmWindow *win, struct wmEvent *event);
 
 
 			/* at maximum, every timestep seconds it triggers event_type events */
diff --git a/source/blender/windowmanager/intern/wm_event_system.c b/source/blender/windowmanager/intern/wm_event_system.c
index 516e9907b7e..06449f5d45e 100644
--- a/source/blender/windowmanager/intern/wm_event_system.c
+++ b/source/blender/windowmanager/intern/wm_event_system.c
@@ -97,7 +97,7 @@ static int wm_operator_call_internal(bContext *C, wmOperatorType *ot, PointerRNA
 
 /* ************ event management ************** */
 
-void wm_event_add(wmWindow *win, const wmEvent *event_to_add)
+void wm_event_add_ex(wmWindow *win, const wmEvent *event_to_add, const wmEvent *event_to_add_after)
 {
 	wmEvent *event = MEM_mallocN(sizeof(wmEvent), "wmEvent");
 	
@@ -105,7 +105,18 @@ void wm_event_add(wmWindow *win, const wmEvent *event_to_add)
 
 	update_tablet_data(win, event);
 
-	BLI_addtail(&win->queue, event);
+	if (event_to_add_after == NULL) {
+		BLI_addtail(&win->queue, event);
+	}
+	else {
+		/* note, strictly speaking this breaks const-correctness, however we're only changing 'next' member */
+		BLI_insertlinkafter(&win->queue, (void *)event_to_add_after, event);
+	}
+}
+
+void wm_event_add(wmWindow *win, const wmEvent *event_to_add)
+{
+	wm_event_add_ex(win, event_to_add, NULL);
 }
 
 void wm_event_free(wmEvent *event)
diff --git a/source/blender/windowmanager/intern/wm_operators.c b/source/blender/windowmanager/intern/wm_operators.c
index 6820493132b..1ab1ac8a28d 100644
--- a/source/blender/windowmanager/intern/wm_operators.c
+++ b/source/blender/windowmanager/intern/wm_operators.c
@@ -3467,7 +3467,10 @@ static void tweak_gesture_modal(bContext *C, const wmEvent *event)
 					tevent.type = EVT_TWEAK_M;
 				tevent.val = val;
 				/* mouse coords! */
-				wm_event_add(window, &tevent);
+
+				/* important we add immediately after this event, so future mouse releases
+				 * (which may be in the queue already), are handled in order, see T44740 */
+				wm_event_add_ex(window, &tevent, event);
 				
 				WM_gesture_end(C, gesture); /* frees gesture itself, and unregisters from window */
 			}