BOOL FTYPE ScanDlgProc
(
    HWND        hDlg,                          // window handle
    unsigned    message,                       // type of message
    WPARAM      wParam,                        // additional information
    LPARAM      lParam                         // additional information
)
{
    char        szBuffer[40];

    switch (message)
    {
    case WM_INITDIALOG :

        // ---------------------------------------------------
        // Initialize Scan Time Edit, Maximum accuracy: 40 ms
        // ---------------------------------------------------

        itoa(gwScanTime, szBuffer, 10);
        SendDlgItemMessage(hDlg, IDC_SCAN, EM_REPLACESEL, 0,
                        (LPARAM)((LPSTR)szBuffer));

        return TRUE;

    case WM_COMMAND :

         switch (LOWORD(wParam))
         {
            case IDOK :

                //
                // get scan time
                //

                if (SendDlgItemMessage(hDlg, IDC_SCAN,
                           EM_GETMODIFY, 0, 0))
                {
                    SendDlgItemMessage(hDlg, IDC_SCAN,
                            WM_GETTEXT, 10, (LPARAM)(LPSTR)szBuffer) ;
                    gwScanTime = atoi(szBuffer);
                    SendDlgItemMessage(hDlg, IDC_SCAN,
                              EM_SETMODIFY, FALSE, 0) ;
                }

            case IDCANCEL :
                EndDialog(hDlg, 0);
                return TRUE;

         }
         break;
    }
    return FALSE ;
}


/***************************************************************************
    FUNCTION: MainWndProc(HWND, unsigned, WPARAM, LPARAM)

    PURPOSE:  Processes messages

    MESSAGES:

        WM_CREATE     - create window
        WM_COMMAND    - application menu (About dialog box)
        WM_DESTROY    - destroy window
****************************************************************************/

long FTYPE MainWndProc
(
    HWND        hWnd,                          // window handle
    unsigned    message,                       // type of message
    WPARAM      wParam,                        // additional information
    LPARAM      lParam                         // additional information
)
{
    static  HANDLE  hInstance ;
    HMENU           hMenu;
    HDC             hdc;
    char            szBuffer[120];
    RECT            rect;
    DWORD           dwCurrentTime;
    DWORD           dwErrorTime;
    BOOL            bTimerOverrun;

    switch (message)
    {
        case WM_CREATE:

            //
            // initialize Stop Menu
            //

            hMenu = GetMenu(hWnd);
            EnableMenuItem(hMenu, IDM_STOP, MF_BYCOMMAND | MF_GRAYED);

            hInstance = ((LPCREATESTRUCT) lParam)->hInstance ;

            lpfnConfigDlgProc = MakeProcInstance (ConfigDlgProc, hInstance) ;

            lpfnScanDlgProc = MakeProcInstance (ScanDlgProc, hInstance) ;

            return 0 ;

        case WM_COMMAND:     /* message: from application menu */

            hMenu = GetMenu(hWnd);

            switch (LOWORD(wParam))
            {
                case IDM_SETTING :
                    DialogBox (hInstance, MAKEINTRESOURCE(IDD_SETTING),
                         hWnd, lpfnConfigDlgProc) ;
                    return 0;

                case IDM_SCAN :
                    DialogBox (hInstance, MAKEINTRESOURCE(IDD_SCAN),
                         hWnd, lpfnScanDlgProc) ;
                    return 0;

                case IDM_STOP :

                    //
                    // kill timer and close driver
                    //

                    KillTimer(hWnd, 1);
                    DRV_DeviceClose((LONG far *)&DriverHandle);

                    bRun = FALSE;

                    //
                    // reset menu item status
                    //

                    EnableMenuItem(hMenu, IDM_STOP, MF_BYCOMMAND | MF_GRAYED);
                    EnableMenuItem(hMenu, IDM_START, MF_BYCOMMAND | MF_ENABLED);

                    return 0;

                case IDM_START :

                    //
                    // Open Device
                    //

                    if (gnNumOfSubdevices == 0)
                        ErrCde = DRV_DeviceOpen(
                            DeviceList[gwDevice].dwDeviceNum,
                                (LONG far *)&DriverHandle);
                    else
                        ErrCde = DRV_DeviceOpen(
                            SubDeviceList[gwSubDevice].dwDeviceNum,
                                (LONG far *)&DriverHandle);

                    if (ErrCde != SUCCESS)
                    {
                        strcpy(szErrMsg,"Device open error !");
                        MessageBox(hWnd,(LPCSTR)szErrMsg,"Device Open",MB_OK);
                        return 0;
                    }

                    //
                    // get number of alarm channels
                    //

                    ptDevFeatures.buffer = (LPDEVFEATURES)&DevFeatures;
                    ptDevFeatures.size = sizeof(DEVFEATURES);
                    if ((ErrCde = DRV_DeviceGetFeatures(DriverHandle,
                        (LPT_DeviceGetFeatures)&ptDevFeatures)) != SUCCESS)
                    {
                        DRV_GetErrorMessage(ErrCde,(LPSTR)szErrMsg);
                        MessageBox(hWnd,(LPCSTR)szErrMsg,"Driver Message",MB_OK);
                        DRV_DeviceClose((LONG far *)&DriverHandle);
                        return 0;
                    }

                    // check number of alarm channels
                    if (DevFeatures.usMaxAlarmChl == 0)
                    {
                        MessageBox(hWnd,(LPCSTR)"No Alarm Channel",
                            "Driver Message",MB_OK);
                        DRV_DeviceClose((LONG far *)&DriverHandle);
                        return 0;
                    }

                    //
                    // configures the alarm limits
                    //

                    ptAlarmConfig.chan = gwChannel;
                    ptAlarmConfig.LoLimit = gfLoLimit;
                    ptAlarmConfig.HiLimit = gfHiLimit;

                    if ((ErrCde = DRV_AlarmConfig(DriverHandle,
                         (LPT_AlarmConfig)&ptAlarmConfig)) != 0)
                    {
                        DRV_GetErrorMessage(ErrCde,(LPSTR)szErrMsg);
                        MessageBox(hWnd,(LPCSTR)szErrMsg,"Driver Message",MB_OK);
                        DRV_DeviceClose((LONG far *)&DriverHandle);
                        return 0;
                    }

                    //
                    // enable alarm
                    //

                    ptAlarmEnable.chan = gwChannel;
                    ptAlarmEnable.LatchMode = gwLatchMode;
                    ptAlarmEnable.enabled = 1;

                    if ((ErrCde = DRV_AlarmEnable(DriverHandle,
                         (LPT_AlarmEnable)&ptAlarmEnable)) != 0)
                    {
                        DRV_GetErrorMessage(ErrCde,(LPSTR)szErrMsg);
                        MessageBox(hWnd,(LPCSTR)szErrMsg,"Driver Message",MB_OK);
                        DRV_DeviceClose((LONG far *)&DriverHandle);
                        return 0;
                    }


                    //
                    // enable Stop Menu item and disable the others
                    //

                    EnableMenuItem(hMenu, IDM_STOP, MF_BYCOMMAND | MF_ENABLED);
                    EnableMenuItem(hMenu, IDM_START, MF_BYCOMMAND | MF_GRAYED);

                    //
                    // Set the new timer type and start it up.
                    //

                    if (SetTimer(hWnd, 1, gwScanTime, NULL) == (UINT)NULL)
                    {
                        MessageBox(hWnd, "Couldn't create timer.", "Notice!",
                            MB_OK);
                        DRV_DeviceClose((LONG far *)&DriverHandle);
                        return 0;
                    }

                    bRun = TRUE;

                    gdwStartTime = GetTickCount();
                    gwOverrunCount = 0;

                    return 0;
            }
            return 0;

        case WM_TIMER:

            //
            // Timer set to dispatch a WM_TIMER message has gone off.
            //

            //
            // check if timer is overrun
            //

            dwCurrentTime = GetTickCount();

            gdwElapseTime = gdwElapseTime + (DWORD)gwScanTime;
            dwErrorTime = dwCurrentTime - gdwElapseTime - gdwStartTime;
            if (dwErrorTime > (DWORD)40)        // maximum 40 ms scan time
            {
                gdwElapseTime = dwCurrentTime - gdwStartTime;
                gwOverrunCount ++;
                if (gwOverrunCount >= 10)
                {
                    bTimerOverrun = TRUE;
                    gwOverrunCount = 0;
                }
                else
                    bTimerOverrun = FALSE;
            }
            else
            {
                bTimerOverrun = FALSE;
                gwOverrunCount = 0;
            }

            //
            // check alarm status
            //

            ptAlarmCheck.chan = gwChannel;
            ptAlarmCheck.LoState = (USHORT far *)&gwLoState;
            ptAlarmCheck.HiState = (USHORT far *)&gwHiState;

            if ((ErrCde = DRV_AlarmCheck(DriverHandle,
                       (LPT_AlarmCheck)&ptAlarmCheck)) != 0)
            {
                DRV_GetErrorMessage(ErrCde,(LPSTR)szErrMsg);
                MessageBox(hWnd,(LPCSTR)szErrMsg,"Driver Message",MB_OK);
                KillTimer(hWnd, 1);
                DRV_DeviceClose((LONG far *)&DriverHandle);
                return 0;
            }

            //
            // Display Data
            //

            hdc = GetDC(hWnd);
            GetClientRect(hWnd, &rect);
            InvalidateRect(hWnd, NULL, TRUE);
            UpdateWindow(hWnd);
            if (bTimerOverrun == FALSE)
                sprintf(szBuffer, "Status: High= %d Low=%d",
                    gwHiState, gwLoState);
            else
                sprintf(szBuffer, "Timer Overrun!");

            DrawText(hdc, szBuffer, -1, &rect,
                    DT_SINGLELINE | DT_CENTER | DT_VCENTER);

            ReleaseDC(hWnd, hdc);

            return 0;

        case WM_DESTROY:
            if (bRun == TRUE)
            {
                KillTimer(hWnd, 1);
                DRV_DeviceClose((LONG far *)&DriverHandle);
            }
            PostQuitMessage(0);
            break;

        default:
            return (DefWindowProc(hWnd, message, wParam, lParam));
    }

    return ((LONG)NULL);
}