Pop-up menu's in MFC Dialog

When a drop-down menu is displayed, the WM_INITMENUPOPUP message is sent
prior to displaying the menu items. The MFC CFrameWnd::OnInitMenuPopup
function iterates through the menu items and calls the update command UI
handler for the item, if there is one. The appearance of each menu item is
updated to reflect its state (enabled/disabled, checked/unchecked).

The update UI mechanism doesn't work for a dialog box-based application
because CDialog has no OnInitMenuPopup handler and it uses CWnd's default
handler, which does not call update command UI handlers for menu items.

RESOLUTION

Use the following steps to resolve this problem:

Add an ON_WM_INITMENUPOPUP entry to the message map:

BEGIN_MESSAGE_MAP(CTestDlg, CDialog)
 //{{AFX_MSG_MAP(CTestDlg)
 ON_WM_CONTEXTMENU()
 ON_COMMAND(ID_POPUPMENU_PROPERTIES, OnPopupmenuProperties)
 ON_UPDATE_COMMAND_UI(ID_POPUPMENU_PROPERTIES, OnUpdateProperties)
           ........................
           ........................
 //}}AFX_MSG_MAP

 ON_WM_INITMENUPOPUP() // ****** ADD THIS MESSAGE 
END_MESSAGE_MAP()

Add a OnInitMenuPopup member function to your dialog box class and copy the
following code (note that this code is taken largely from
CFrameWnd::OnInitMenuPopup in WinFrm.cpp):

void CTestDlg::OnInitMenuPopup(CMenu *pPopupMenu, UINT nIndex,BOOL bSysMenu)
{
    ASSERT(pPopupMenu != NULL);
    // Check the enabled state of various menu items.

    CCmdUI state;
    state.m_pMenu = pPopupMenu;
    ASSERT(state.m_pOther == NULL);
    ASSERT(state.m_pParentMenu == NULL);

    // Determine if menu is popup in top-level menu and set m_pOther to
    // it if so (m_pParentMenu == NULL indicates that it is secondary popup).
    HMENU hParentMenu;
    if (AfxGetThreadState()->m_hTrackingMenu == pPopupMenu->m_hMenu)
        state.m_pParentMenu = pPopupMenu;    // Parent == child for tracking popup.
    else if ((hParentMenu = ::GetMenu(m_hWnd)) != NULL)
    {
        CWnd* pParent = this;
           // Child windows don't have menus--need to go to the top!
        if (pParent != NULL &&
           (hParentMenu = ::GetMenu(pParent->m_hWnd)) != NULL)
        {
           int nIndexMax = ::GetMenuItemCount(hParentMenu);
           for (int nIndex = 0; nIndex < nIndexMax; nIndex++)
           {
            if (::GetSubMenu(hParentMenu, nIndex) == pPopupMenu->m_hMenu)
            {
                // When popup is found, m_pParentMenu is containing menu.
                state.m_pParentMenu = CMenu::FromHandle(hParentMenu);
                break;
            }
           }
        }
    }
    state.m_nIndexMax = pPopupMenu->GetMenuItemCount();
    for (state.m_nIndex = 0; state.m_nIndex < state.m_nIndexMax;
      state.m_nIndex++)
    {
        state.m_nID = pPopupMenu->GetMenuItemID(state.m_nIndex);
        if (state.m_nID == 0)
           continue; // Menu separator or invalid cmd - ignore it.

        ASSERT(state.m_pOther == NULL);
        ASSERT(state.m_pMenu != NULL);
        if (state.m_nID == (UINT)-1)
        {
           // Possibly a popup menu, route to first item of that popup.
           state.m_pSubMenu = pPopupMenu->GetSubMenu(state.m_nIndex);
           if (state.m_pSubMenu == NULL ||
            (state.m_nID = state.m_pSubMenu->GetMenuItemID(0)) == 0 ||
            state.m_nID == (UINT)-1)
           {
            continue;       // First item of popup can't be routed to.
           }
           state.DoUpdate(this, TRUE);   // Popups are never auto disabled.
        }
        else
        {
           // Normal menu item.
           // Auto enable/disable if frame window has m_bAutoMenuEnable
           // set and command is _not_ a system command.
           state.m_pSubMenu = NULL;
           state.DoUpdate(this, FALSE);
        }

        // Adjust for menu deletions and additions.
        UINT nCount = pPopupMenu->GetMenuItemCount();
        if (nCount < state.m_nIndexMax)
        {
           state.m_nIndex -= (state.m_nIndexMax - nCount);
           while (state.m_nIndex < nCount &&
            pPopupMenu->GetMenuItemID(state.m_nIndex) == state.m_nID)
           {
            state.m_nIndex++;
           }
        }
        state.m_nIndexMax = nCount;
    }
}