4 files changed, 49 insertions, 8 deletions

diff --git a/source/blender/windowmanager/WM_types.h b/source/blender/windowmanager/WM_types.h
index 2f431bcd208..e9f12287d29 100644
--- a/source/blender/windowmanager/WM_types.h
+++ b/source/blender/windowmanager/WM_types.h
@@ -510,6 +510,10 @@ typedef struct wmGesture {
   struct wmGesture *next, *prev;
   /** #wmEvent.type */
   int event_type;
+  /** #wmEvent.modifier */
+  uint8_t event_modifier;
+  /** #wmEvent.keymodifier */
+  short event_keymodifier;
   /** Gesture type define. */
   int type;
   /** bounds of region to draw gesture within. */
@@ -628,6 +632,11 @@ typedef struct wmEvent {
   double prev_click_time;
   /** The location when the key is pressed (used to enforce drag thresholds). */
   int prev_click_xy[2];
+  /** The `modifier` at the point of the click action. */
+  uint8_t prev_click_modifier;
+  /** The `keymodifier` at the point of the click action. */
+  short prev_click_keymodifier;
+
   /**
    * The previous value of #wmEvent.xy,
    * Unlike other previous state variables, this is set on any mouse motion.
diff --git a/source/blender/windowmanager/intern/wm_event_system.c b/source/blender/windowmanager/intern/wm_event_system.c
index 326b8c167b8..6753978eece 100644
--- a/source/blender/windowmanager/intern/wm_event_system.c
+++ b/source/blender/windowmanager/intern/wm_event_system.c
@@ -3161,21 +3161,27 @@ static int wm_handlers_do(bContext *C, wmEvent *event, ListBase *handlers)
         if (WM_event_drag_test(event, event->prev_click_xy)) {
           win->event_queue_check_drag_handled = true;
 
-          int xy[2] = {UNPACK2(event->xy)};
-          short val = event->val;
-          short type = event->type;
+          const int prev_xy[2] = {UNPACK2(event->xy)};
+          const short prev_val = event->val;
+          const short prev_type = event->type;
+          const uint8_t prev_modifier = event->modifier;
+          const short prev_keymodifier = event->keymodifier;
 
           copy_v2_v2_int(event->xy, event->prev_click_xy);
           event->val = KM_CLICK_DRAG;
           event->type = event->prev_type;
+          event->modifier = event->prev_click_modifier;
+          event->keymodifier = event->prev_click_keymodifier;
 
           CLOG_INFO(WM_LOG_HANDLERS, 1, "handling PRESS_DRAG");
 
           action |= wm_handlers_do_intern(C, win, event, handlers);
 
-          event->val = val;
-          event->type = type;
-          copy_v2_v2_int(event->xy, xy);
+          event->keymodifier = prev_keymodifier;
+          event->modifier = prev_modifier;
+          event->val = prev_val;
+          event->type = prev_type;
+          copy_v2_v2_int(event->xy, prev_xy);
 
           win->event_queue_check_click = false;
           if (!wm_action_not_handled(action)) {
@@ -3205,7 +3211,16 @@ static int wm_handlers_do(bContext *C, wmEvent *event, ListBase *handlers)
         }
       }
       else if (event->val == KM_RELEASE) {
-        win->event_queue_check_drag = false;
+        if (win->event_queue_check_drag) {
+          if ((event->prev_type != event->type) &&
+              (ISKEYMODIFIER(event->type) || (event->type == event->prev_click_keymodifier))) {
+            /* Support releasing modifier keys without canceling the drag event, see T89989.
+             * NOTE: this logic is replicated for tweak gestures. */
+          }
+          else {
+            win->event_queue_check_drag = false;
+          }
+        }
       }
 
       if (event->prev_type == event->type) {
@@ -4692,6 +4707,8 @@ static void wm_event_prev_click_set(wmEvent *event, wmEvent *event_state)
   event->prev_click_time = event_state->prev_click_time = PIL_check_seconds_timer();
   event->prev_click_xy[0] = event_state->prev_click_xy[0] = event_state->xy[0];
   event->prev_click_xy[1] = event_state->prev_click_xy[1] = event_state->xy[1];
+  event->prev_click_modifier = event_state->prev_click_modifier = event_state->modifier;
+  event->prev_click_keymodifier = event_state->prev_click_keymodifier = event_state->keymodifier;
 }
 
 static wmEvent *wm_event_add_mousemove(wmWindow *win, const wmEvent *event)
diff --git a/source/blender/windowmanager/intern/wm_gesture.c b/source/blender/windowmanager/intern/wm_gesture.c
index 581c5f8a198..86ada4aaf2a 100644
--- a/source/blender/windowmanager/intern/wm_gesture.c
+++ b/source/blender/windowmanager/intern/wm_gesture.c
@@ -42,6 +42,8 @@ wmGesture *WM_gesture_new(wmWindow *window, const ARegion *region, const wmEvent
 
   gesture->type = type;
   gesture->event_type = event->type;
+  gesture->event_modifier = event->modifier;
+  gesture->event_keymodifier = event->keymodifier;
   gesture->winrct = region->winrct;
   gesture->user_data.use_free = true; /* Free if userdata is set. */
   gesture->modal_state = GESTURE_MODAL_NOP;
diff --git a/source/blender/windowmanager/intern/wm_gesture_ops.c b/source/blender/windowmanager/intern/wm_gesture_ops.c
index 2a27a8df411..d7e62d549d0 100644
--- a/source/blender/windowmanager/intern/wm_gesture_ops.c
+++ b/source/blender/windowmanager/intern/wm_gesture_ops.c
@@ -507,6 +507,8 @@ static void gesture_tweak_modal(bContext *C, const wmEvent *event)
           tevent.type = EVT_TWEAK_M;
         }
         tevent.val = val;
+        tevent.modifier = gesture->event_modifier;
+        tevent.keymodifier = gesture->event_keymodifier;
         tevent.is_repeat = false;
         /* mouse coords! */
 
@@ -533,7 +535,18 @@ static void gesture_tweak_modal(bContext *C, const wmEvent *event)
       }
       break;
     default:
-      if (!ISTIMER(event->type) && event->type != EVENT_NONE) {
+      if (ISTIMER(event->type)) {
+        /* Ignore timers. */
+      }
+      else if (event->type == EVENT_NONE) {
+        /* Ignore none events. */
+      }
+      else if ((event->val == KM_RELEASE) &&
+               (ISKEYMODIFIER(event->type) || (event->type == event->prev_click_keymodifier))) {
+        /* Support releasing modifier keys without canceling the drag event, see T89989.
+         * NOTE: this logic is replicated for drag events. */
+      }
+      else {
         gesture_end = true;
       }
       break;