Fix popup submenu in single-window mode

The internal processing code only works for OS windows, since it takes
the mouse position relative to the window and not the viewport. Now we
make sure it's not called in single-window mode.

scene/gui/popup_menu.cpp

@@ -397,10 +397,6 @@ void PopupMenu::_gui_input(const Ref<InputEvent> &p_event) {
 	Ref<InputEventMouseMotion> m = p_event;
 
 	if (m.is_valid()) {
-		if (!item_clickable_area.has_point(m->get_position())) {
-			return;
-		}
-
 		for (List<Rect2>::Element *E = autohide_areas.front(); E; E = E->next()) {
 			if (!Rect2(Point2(), get_size()).has_point(m->get_position()) && E->get().has_point(m->get_position())) {
 				_close_pressed();
@@ -408,6 +404,10 @@ void PopupMenu::_gui_input(const Ref<InputEvent> &p_event) {
 			}
 		}
 
+		if (!item_clickable_area.has_point(m->get_position())) {
+			return;
+		}
+
 		int over = _get_mouse_over(m->get_position());
 		int id = (over < 0 || items[over].separator || items[over].disabled) ? -1 : (items[over].id >= 0 ? items[over].id : over);
 
@@ -747,7 +747,7 @@ void PopupMenu::_notification(int p_what) {
 		} break;
 		case NOTIFICATION_INTERNAL_PROCESS: {
 			//only used when using operating system windows
-			if (get_window_id() != DisplayServer::INVALID_WINDOW_ID && autohide_areas.size()) {
+			if (!is_embedded() && autohide_areas.size()) {
 				Point2 mouse_pos = DisplayServer::get_singleton()->mouse_get_position();
 				mouse_pos -= get_position();
 
@@ -786,7 +786,7 @@ void PopupMenu::_notification(int p_what) {
 
 				set_process_internal(false);
 			} else {
-				if (get_window_id() != DisplayServer::INVALID_WINDOW_ID) {
+				if (!is_embedded()) {
 					set_process_internal(true);
 				}