1 files changed, 38 insertions, 3 deletions

diff --git a/scene/main/viewport.cpp b/scene/main/viewport.cpp
index 8c67dcc8a1..d512f1809c 100644
--- a/scene/main/viewport.cpp
+++ b/scene/main/viewport.cpp
@@ -821,7 +821,14 @@ void Viewport::_notification(int p_what) {
 			}
 
 		} break;
-		case NOTIFICATION_WM_MOUSE_EXIT:
+		case NOTIFICATION_WM_MOUSE_EXIT: {
+			_drop_physics_mouseover();
+
+			// Unlike on loss of focus (NOTIFICATION_WM_WINDOW_FOCUS_OUT), do not
+			// drop the gui mouseover here, as a scrollbar may be dragged while the
+			// mouse is outside the window (without the window having lost focus).
+			// See bug #39634
+		} break;
 		case NOTIFICATION_WM_WINDOW_FOCUS_OUT: {
 			_drop_physics_mouseover();
 
@@ -1809,6 +1816,8 @@ void Viewport::_gui_input_event(Ref<InputEvent> p_event) {
 	if (mb.is_valid()) {
 		gui.key_event_accepted = false;
 
+		Control *over = nullptr;
+
 		Point2 mpos = mb->get_position();
 		if (mb->is_pressed()) {
 			Size2 pos = mpos;
@@ -1961,6 +1970,31 @@ void Viewport::_gui_input_event(Ref<InputEvent> p_event) {
 				gui.drag_data=Variant(); //always clear
 			}*/
 
+			// In case the mouse was released after for example dragging a scrollbar,
+			// check whether the current control is different from the stored one. If
+			// it is different, rather than wait for it to be updated the next time the
+			// mouse is moved, notify the control so that it can e.g. drop the highlight.
+			// This code is duplicated from the mm.is_valid()-case further below.
+			if (gui.mouse_focus) {
+				over = gui.mouse_focus;
+			} else {
+				over = _gui_find_control(mpos);
+			}
+
+			if (gui.mouse_focus_mask == 0 && over != gui.mouse_over) {
+				if (gui.mouse_over) {
+					_gui_call_notification(gui.mouse_over, Control::NOTIFICATION_MOUSE_EXIT);
+				}
+
+				_gui_cancel_tooltip();
+
+				if (over) {
+					_gui_call_notification(over, Control::NOTIFICATION_MOUSE_ENTER);
+				}
+			}
+
+			gui.mouse_over = over;
+
 			set_input_as_handled();
 		}
 	}
@@ -2021,10 +2055,11 @@ void Viewport::_gui_input_event(Ref<InputEvent> p_event) {
 			}
 		}
 
+		// These sections of code are reused in the mb.is_valid() case further up
+		// for the purpose of notifying controls about potential changes in focus
+		// when the mousebutton is released.
 		if (gui.mouse_focus) {
 			over = gui.mouse_focus;
-			//recompute focus_inv_xform again here
-
 		} else {
 			over = _gui_find_control(mpos);
 		}