Using MRU on submenu

After studying Todd C. Gleason's method for implementing MRU's on a submenu MRU's, I ended up taking a slightly different approach. Namely, a helper function to handle the application's OnUpdateFileMruFile1(CCmdUI* pCmdUI) function.

CRecentFileList::UpdateMenu() seems to work OK if there's another item on the submenu before the MRU. So we insert such an item, update the menu, and then remove the inserted menu.

The update function seems to be called under various circumstances.

• m_pMenu != 0 && m_pSubMenu != 0 -- popup menu opened up but not the submenu
  Don't do anything
• m_pMenu != 0 && m_pSubMenu == 0 -- Opening the submenu
  Fix up then menu
• m_pMenu == 0 && m_pSubMenu == 0 -- We've clicked on menu
  Don't do anything

#ifndef _SUBMENUMRU_H_
#define _SUBMENUMRU_H_

class SubmenuMRU
{
public:
  static void Handle_OnUpdateFileMruFile1(CCmdUI* pCmdUI, CRecentFileList* pRecentFileList);
};

#endif

#include 
#include 

#include "SubmenuMRU.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

void SubmenuMRU::Handle_OnUpdateFileMruFile1(CCmdUI* pCmdUI, CRecentFileList* pRecentFileList)
{
	if (pRecentFileList == NULL) // no MRU files
		pCmdUI->Enable(FALSE);
	else
    {
        if (pCmdUI->m_pMenu && !pCmdUI->m_pSubMenu) // Only do something if we're the submenu
        {
            // Insert a separator so that CRecentFileList::UpdateMenu() will behave
            pCmdUI->m_pMenu->InsertMenu(0, MF_SEPARATOR | MF_BYPOSITION);
            pCmdUI->m_nIndex++;
            pCmdUI->m_nIndexMax++;

            pRecentFileList->UpdateMenu(pCmdUI); // Update the menu

            // Get rid of the separator we just inerted
            pCmdUI->m_pMenu->DeleteMenu(0, MF_BYPOSITION);
            pCmdUI->m_nIndex--;
            pCmdUI->m_nIndexMax--;
        }
    }
}

IDR_MAINFRAME MENU PRELOAD DISCARDABLE 
BEGIN
    POPUP "&File"
    BEGIN
		...
        POPUP "Recent &Files"
        BEGIN
            MENUITEM "Recent File", ID_FILE_MRU_FILE1, GRAYED
        END
        MENUITEM SEPARATOR
        MENUITEM "E&xit", ID_APP_EXIT
    END
	...
END

#include "SubmenuMRU.h"

BEGIN_MESSAGE_MAP(CMenuTestApp, CWinApp)
	...
	ON_UPDATE_COMMAND_UI(ID_FILE_MRU_FILE1, OnUpdateFileMruFile1)
END_MESSAGE_MAP()


void CMenuTestApp::OnUpdateFileMruFile1(CCmdUI* pCmdUI) 
{
    // TODO: Add your command update UI handler code here
    SubmenuMRU::Handle_OnUpdateFileMruFile1(pCmdUI, m_pRecentFileList);
}