This example shows how to initialize and use the Dynamic Data Facility for displaying an online document. Two functions are defined: the first, SampleObj, creates a window that will display the online information and specifies the second function, SampleWindowProc, as the corresponding window procedure. These two functions are compiled into a DLL and exported, so that IPF can invoke them when it encounters the :ddf and :acviewport tags during execution. The :acviewport tag will specify the DLL name and the SampleObj function; when IPF calls SampleObj, it initializes an application-controlled window with SampleWindowProc as the window procedure and returns the window handle. Later, when IPF encounters the :ddf tag, it will send SampleWindowProc an HM_QUERY_DDF_DATA message. At this point, before calling any of the DDF API, DdfInitialize must first be called to initiate a DDF buffer, after which the other DDF API can be called to display the online information.

#define INCL_WINWINDOWMGR       /* General window management    */
#define INCL_WINMESSAGEMGR      /* Message management           */
#define INCL_WINDIALOGS         /* Dialog boxes                 */
#define INCL_DDF                /* Dynamic Data Facility        */
#define INCL_32
#include <os2.h>
#include <pmhelp.h>

#define COM_HWND 4                /* window word offsets        */
#define PAGE_HWND 8
#define ACVP_HAB  12

USHORT DdfClass = FALSE;

MRESULT EXPENTRY SampleWindowProc(HWND hWnd, ULONG Message,
                                 MPARAM lParam1, MPARAM lParam2);

USHORT APIENTRY SampleObj(PACVP pACVP, PCH Parameter)
{
HWND DdfHwnd;           /* Client window handle                  */
HWND DdfCHwnd;          /* Child window handle                   */
HWND PreviousHwnd;      /* Handle for setting comm window active */

    /* register DDF Base class if not registered already */
    if (!DdfClass)
    {
         if (!WinRegisterClass(
                   pACVP->hAB,        /* Anchor block handle           */
                   "CLASS_Ddf",       /* Application window class name */
                   SampleWindowProc,  /* Address of window procedure   */
                   CS_SYNCPAINT |     /* Window class style            */
                   CS_SIZEREDRAW |
                   CS_MOVENOTIFY,
                   20))               /* Extra storage                 */
        {
            return TRUE;
        }
        DdfClass = TRUE;
    }

    /*  create standard window  */
    if (!(DdfHwnd = WinCreateStdWindow(
                      pACVP->hWndParent, /* ACVP is parent       */
                      0L,                /* No class style       */
                      NULL,              /* Frame control flag   */
                      "CLASS_Ddf",       /* Window class name    */
                      NULL,              /* No title bar         */
                      0L,                /* No special style     */
                      0L,                /* Resource in .EXE     */
                      0,                 /* No window identifier */
                      &DdfCHwnd )))      /* Client window handle */
    {
        return FALSE;
    }

    /* store the frame window handle in ACVP data structure */
    pACVP->hWndACVP = DdfHwnd;

    /* set this window as active communication window */
    PreviousHwnd = (HWND)WinSendMsg(pACVP->hWndParent,
                           HM_SET_OBJCOM_WINDOW,
                           MPFROMHWND(DdfHwnd), NULL);

    /* save returned communication hwnd in reserved word */
    WinSetWindowULong(DdfCHwnd, COM_HWND, (ULONG)PreviousHwnd);

    /* save anchor block handle in reserved word */
    WinSetWindowULong (DdfCHwnd, ACVP_HAB, (ULONG)pACVP->hAB);

    return FALSE;
} /* SampleObj */

MRESULT EXPENTRY SampleWindowProc(HWND hWnd, ULONG Message,
                                 MPARAM lParam1, MPARAM lParam2)
{
    HWND   hwndParent;       /* parent window                        */
    HWND   hwndHelpInstance; /* help instance window                 */
    HDDF   hDdf;             /* DDF handle                           */
    ULONG  DdfID;            /* DDF resource id                      */

    switch (Message)
    {
    case HM_QUERY_DDF_DATA:
        WinSetWindowULong(hWnd, PAGE_HWND, LONGFROMMP(lParam1));
        DdfID = LONGFROMMP(lParam2);
        hwndParent = WinQueryWindow(hWnd, QW_PARENT);
        hwndParent = WinQueryWindow(hwndParent, QW_PARENT);
        hwndHelpInstance = (HWND)WinSendMsg(hwndParent, HM_QUERY,
                                  MPFROMSHORT(HMQW_INSTANCE), NULL);

        /* Allocate 1K Buffer (default)  */
        hDdf = DdfInitialize(
                        hwndHelpInstance, /* Handle of help instance */
                        0L,               /* Default buffer size     */
                        0L                /* Default increment       */
                        );

        if (hDdf == NULLHANDLE)       /* Check return code       */
        {
            return (MRESULT)FALSE;
        }

        return (MRESULT)hDdf;

    default:
        return (WinDefWindowProc(hWnd, Message, lParam1, lParam2));
    }
} /* SampleWindowProc */