(xmenu_show ) [USE_X_TOOLKIT]: Implement a Motif behavior for the menubar. Now,

if you move the pointer on another menubar item while displaying the contents
of a selected menubar item, the current pulldown menu is closed and the new
one corresponding to the new pointed item is displayed.
Clean up code.
Handle the MotionNotify events in the XEvent loop.

src/xmenu.c

@@ -859,9 +859,10 @@ xmenu_show (f, val, x, y, menubarp, vw)
      int menubarp;
      widget_value *vw;
 {
-  int menu_id, id = (int)f;
+  int menu_id, item_length;
   Lisp_Object selection;
   Widget menu;
+  XlwMenuWidget menuw = (XlwMenuWidget) f->display.x->menubar_widget;
 
   /*
    * Define and allocate a foreign event queue to hold events
@@ -915,6 +916,14 @@ xmenu_show (f, val, x, y, menubarp, vw)
     pop_up_menu (mw, &dummy);
   }
 
+  if (menubarp)
+    {
+      item_length = (x + string_width (menuw, vw->name) 
+		     + (2 * (menuw->menu.horizontal_spacing 
+			     + menuw->menu.shadow_thickness))
+		     - 4);
+    }
+
   /* Enters XEvent loop */
   while (1)
     {
@@ -929,6 +938,38 @@ xmenu_show (f, val, x, y, menubarp, vw)
       else
 	if (event.type == Expose)
 	  process_expose_from_menu (event);
+      else 
+	if (event.type == MotionNotify 
+	        && menubarp
+	        && ((event.xmotion.y_root 
+		      >= (f->display.x->widget->core.y 
+			       + f->display.x->widget->core.border_width))
+		    && (event.xmotion.y_root
+			< (f->display.x->widget->core.y
+			   + f->display.x->widget->core.border_width
+			   + f->display.x->menubar_widget->core.height)))
+	    && (event.xmotion.x_root >= item_length
+		|| event.xmotion.x_root < (x - 4)))
+	  {
+	    BLOCK_INPUT;
+	    XtUngrabPointer ((Widget)
+			     ((XlwMenuWidget)
+			      ((CompositeWidget)menu)->composite.children[0]),
+			     event.xbutton.time);
+	    lw_destroy_all_widgets (menu_id); 
+	    UNBLOCK_INPUT;
+
+	    event.type = ButtonPress;
+	        event.xbutton.time = CurrentTime;
+	        event.xbutton.button = Button1;
+	    event.xbutton.window = XtWindow (f->display.x->menubar_widget);
+	    event.xbutton.x = (event.xbutton.x_root 
+			       - (f->display.x->widget->core.x
+				  + f->display.x->widget->core.border_width));
+	    XPutBackEvent (XDISPLAY &event);
+	    break;
+	  }
+
       XtDispatchEvent (&event);
       feq_tmp = (XMEventQue *) malloc (sizeof (XMEventQue));