I am writing an MFC based application, and I want to disable items on my
main window menu depending on the state of the app. MFC provides a nice
mechanism for doing this for menu items that reside one level down in
the menu tree - the ON_UPDATE_COMMAND_UI support. Unfortunately this
mechanism does not work for items on the main menu. No doubt, Microsoft
would say that disabling main menu items is bad form, but that is
absurd. Does anyone know a simple work around for this problem?
  --Elliot Leonard

Elliot,

The only reason ON_COMMAND_UPDATE_UI handlers don't work for the top-level
menu is that these items are "popup" menus and don't have command ID's. If
you add an immediate command to the top-level menu, then an
ON_UPDATE_COMMAND_UI handler will work just fine. My point is that this is
not a restriction of the top-level menu but of popup menu items in general.
If you cascade a menu off one of your popup menus, you can't control that
item from an ON_UPDATE_COMMAND_UI handler either.

To do what you want to do, try this.

CMenu menu;
menu.LoadMenu(IDR_MAINFRAME); // Substitute your top-level menu resource ID
for the parameter
// In the next line, "index" is the zero-based index to the menu item you
wish to disable
menu.EnableMenuItem(index, MF_GRAYED | MF_BYPOSITION);

You can do this from whatever function changes the application state such
that the menu item is no longer relevant.

--
Dave Smith
MCSE, MCT, MVP

Please post responses, I cannot reply to individual mail

The tricky thing about this problem is not disabling the menubar item
- after all, Enable MenuItem will do that for you - but deciding
whether or not the item need to be disabled in the first place.

Prior to the advent of the ON_COMMAND_UI_UPDATE mechanism, I used to
do this with a recursive menu-walking algorithm that I was
inordinately proud of, but nowadays I've resorted to another
mechanism.

I create a subfunction which is called by the update handler, e.g.

void CMainFrame::OnUpdateConfigurePrintOut (CCmdUI* pCmdUI)
{
   pCmdUI -> Enable (Conf_PrintOut_Available ());

BOOL CMainFrame::Conf_PrintOut_Available ()
{
   if (<some test or other>)
      return TRUE;
   else
      return FALSE ;

The point being that the subfunction can then be called from
elsewhere. For instance, the update handler for the first item in a
popup is called twice - once for the item and once for the popup
itself. So the handler for the first item in a popup can be :

afx_msg void CMainFrame::OnUpdateConfigureCharsDwellinglocn(CCmdUI*
pCmdUI)
{
   // This is the first item in a popup, and gets called once for
   // the popup, then again for the item. In the first case, the
   // m_pSubMenu member variable is none-null. In the first
   // case, we must decide whether or not to enable the popup
   // as a whole.

   if (pCmdUI->m_pSubMenu != NULL)
   {
      // enable popup if ANY subitem is available.

      BOOL bPupEnable = Conf_Chars_Dl_Available () ||
                        Conf_Chars_R_Available ()     ||
                        Conf_Chars_Sc_Available   ()     ||
                        Conf_Chars_Sel_Available  ();

      pCmdUI->m_pMenu->EnableMenuItem (pCmdUI->m_nIndex,
          MF_BYPOSITION |
           (bPupEnable ? MF_ENABLED : (MF_DISABLED | MF_GRAYED)));
   }
   else
   {
      pCmdUI -> Enable (Conf_Chars_Dl_Available ());
   }

But you can see that we can similarly decide whether to enable the top
level menubar item or not, by simply calling all the enable
subfunctions below it :

BOOL  CMainFrame::MenuBar_Configure_Available ()
{
   return (Conf_RO_Available () ||
           Conf_RI_Available () ||
           Conf_EqM_Available () ||
           Conf_EqT_Available  () ||
           Conf_Chars_Dl_Available () ||
           Conf_Chars_R_Available     () ||
           Conf_Chars_Sc_Available       () ||
           Conf_Chars_Se_Available ()  ||
           Conf_PrintOut_Available   ()  ||
           Conf_Ti_Available () );

I simply call these master enable/disable routines anytime something
happens which might result in one of them being disabled.

Bob Moore [MVP]
http://www.mooremvp.freeserve.co.uk
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