An application can add and delete items from its menus dynamically by sending MM_INSERTITEM and MM_DELETEITEM messages to the menu window. Any item, including those in submenus, can be deleted by sending a message to the menu window. Messages to insert items in submenus must be sent to the submenu's window (rather than to the window of the top-level menu). You can retrieve the handle of a submenu of the menu bar by sending an MM_QUERYITEM message to the menu-bar and specifying the identifier of the submenu item for the submenu, as shown in the following code fragment:

    /* IDM_MYMENUID is the identifier of the submenu containing the item. */

    MENUITEM mi;
    HWND hwndMenu, hwndSubMenu, hwndPullDown,hwndFrame;

    hwndMenu = WinWindowFromID(hwndFrame, FID_MENU);
    WinSendMsg(hwndMenu,                           /* Handle of menu bar  */
        MM_QUERYITEM,                              /* Message             */
        MPFROM2SHORT(IDM_MYMENUID, TRUE),          /* Submenu identifier  */
        (MPARAM) &mi);                             /* Pointer to MENUITEM */

    hwndPullDown = mi.hwndSubMenu;                 /* Handle to submenu   */

Once the application has the handle of the submenu, it can insert an item by filling in a MENUITEM structure and sending an MM_INSERTITEM message to the submenu. For text-menu items, the application must send a pointer to the text string as well as to the MENUITEM structure, as shown in the following figure.

    PSZ  pszNewItemString;

    mi.iPosition = MIT_END;
    mi.afStyle = MIS_TEXT;
    mi.afAttribute = 0;
    mi.id = IDM_MYMENU_FIRST;
    mi.hwndSubMenu = NULL;
    mi.hItem = 0;

    WinSendMsg(hwndPullDown, MM_INSERTITEM, (MPARAM) &mi,
        (MPARAM) pszNewItemString);

To delete an item, the application sends an MM_DELETEITEM message to the menu bar, specifying the identifier of the item to delete. For example, to clear all the items following IDM_MYMENU_FIRST in a submenu in which the items are numbered sequentially, use the following code:

    USHORT usItemNum;

    /* Clear all the items in MYMENU.                 */
    hwndMenu = WinWindowFromID(hwndFrame, FID_MENU);
    usItemNum = IDM_MYMENU_FIRST;
    while (WinSendMsg(hwndMenu, MM_DELETEITEM,
        MPFROM2SHORT(usItemNum++, TRUE), NULL) != 0);

Adding a complete submenu to the menu bar is a more complicated procedure than that shown in the previous examples. There are two strategies. The recommended technique is to define all possible submenus in your resource-definition file; and then, as your application runs, selectively remove and insert the submenus as needed.

For example, assume that your application has a submenu that you want to be displayed only when a particular application tool is in use. You must first define the submenu as part of the main menu resource in your resource-definition file, so that the system reads in the resource menu template and creates the submenu window along with the rest of the menu. You then can remove the submenu from the menu bar, saving the title of the submenu and the MENUITEM structure that defines the submenu, as shown in the following figure:

    HWND hwndMenu, hwndClient;
    MENUITEM mi;
    CHAR szMenuTitle[MAX_STRINGSIZE];

    /* Remove a submenu so that you can replace it later.           */

    /* Obtain the handle of a menu.                                 */
    hwndMenu = WinWindowFromID(WinQueryWindow(hwndClient, QW_PARENT),
                               FID_MENU);

    /* Obtain information on the item to remove.                    */
    WinSendMsg(hwndMenu, MM_QUERYITEM,
        MPFROM2SHORT(IDM_MENUID, TRUE),  /* TRUE to search submenus */
        (MPARAM)&mi);

    /* Save the text for the submenu item.                          */
    WinSendMsg(hwndMenu, MM_QUERYITEMTEXT,
        MPFROM2SHORT(IDM_FONT, MAX_STRINGSIZE),
        (MPARAM)szMenuTitle);

    /* Remove the item, but retain mi and szMenuTitle.              */
    WinSendMsg(hwndMenu, MM_REMOVEITEM,
        MPFROM2SHORT(IDM_FONT, TRUE), NULL);

It is important to use the MM_REMOVEITEM message, rather than MM_DELETEITEM, to remove the item; deleting the item destroys the submenu window-removing it does not. The submenu should remain intact so that you can insert it later.

To reinsert the submenu, send an MM_INSERTITEM message to the menu bar, passing the MENUITEM structure and menu title that you saved when you removed the item. The following code fragment shows how to insert a submenu that was removed by using the previous code example.

    /* Put the submenu back in and obtain the handle of the menu bar. */
    hwndMenu = WinWindowFromID(
                    WinQueryWindow(hwndClient, QW_PARENT), FID_MENU);

    /* Use the information that you saved when you removed the menu.  */
    WinSendMsg(hwndMenu, MM_INSERTITEM, (MPARAM)&mi,
               (MPARAM)szMenuTitle);

The other technique that you can use to insert a submenu in the menu bar is to build up, in memory, a data structure as a menu template and use that template and WinCreateWindow to create a submenu. The resultant submenu window handle then is placed in the hwndSubMenu field of a MENUITEM structure, and the menu item is sent to the menu bar with an MM_INSERTITEM message.

You also can create an empty submenu window by using WinCreateWindow. Pass NULL for the pCtlData and pPresParams parameters, instead of building the menu template in memory. Then insert a new menu item in the menu bar by using the MM_INSERTITEM message, setting the MIS_SUBMENU style, and putting the window handle of the created menu into the hwndSubMenu field. Then use the MM_INSERTITEM message to insert the items in the new pull-down menu.