Close active menus when moving window to new screen.

src/Fl_win32.cxx

@@ -1267,6 +1267,10 @@ static LRESULT CALLBACK WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lPar
                          lParam_rect->right - lParam_rect->left,
                          lParam_rect->bottom - lParam_rect->top, flags);
             if (ns >= 0) {
+              if (Fl::modal() && Fl::modal()->menu_window()) { // is a menu window active?
+                Fl::e_x_root = 1000000;
+                Fl::modal()->handle(FL_PUSH); // simulate a distant click to close menus
+              }
               scale = Fl::screen_driver()->scale(ns);
               EnumChildWindows(hWnd, child_window_cb, (LPARAM)&scale);
             }

src/Fl_x.cxx

@@ -2216,6 +2216,10 @@ int fl_handle(const XEvent& thisevent)
     if (num == -1) num = olds;
     float s = d->scale(num);
     if (num != olds && !window->menu_window()) {
+      if (Fl::modal() && Fl::modal()->menu_window()) { // is a menu window active?
+        Fl::e_x_root = 1000000;
+        Fl::modal()->handle(FL_PUSH); // simulate a distant click to close menus
+      }
       if (s != d->scale(olds) &&
           !Fl_X11_Window_Driver::data_for_resize_window_between_screens_.busy &&
           window->user_data() != &Fl_X11_Screen_Driver::transient_scale_display) {

src/drivers/Wayland/Fl_Wayland_Window_Driver.cxx

@@ -703,6 +703,13 @@ static void surface_enter(void *data, struct wl_surface *wl_surface,
     (Fl_Wayland_Screen_Driver::output*)wl_output_get_user_data(wl_output);
   if (output == NULL)
     return;
+  // Detect when the parent window of an active menu window enters a screen. If so, we are
+  // moving a window with active menus to a new screen. We want to close all menus.
+  if (Fl::modal() && Fl::modal()->menu_window() &&
+      Fl_Window_Driver::menu_parent() == window->fl_win) {
+    Fl::e_x_root = 1000000;
+    Fl::modal()->handle(FL_PUSH); // simulate a distant click to close menus
+  }
 
   Fl_Wayland_Window_Driver *win_driver = Fl_Wayland_Window_Driver::driver(window->fl_win);
   float pre_scale = Fl::screen_scale(win_driver->screen_num()) * win_driver->wld_scale();