mahalog

//  IN BOOL fBacklightOn - TRUE to keep the backlight on.
void SetBacklightRequirement(BOOL fBacklightOn)
{
    // The name of the backlight device.
    TCHAR tszBacklightName[] = TEXT("BKL1:");

    static HANDLE s_hBacklightReq = NULL;
   
    if (fBacklightOn)
    {
        if (NULL == s_hBacklightReq)
        {
            // Turn the backlight on by setting the requirement that the backlight device
            // must remain in device state D0 (full power). Replace D0 with D4 (zero power) to
            // turn the backlight off.
            s_hBacklightReq = SetPowerRequirement(tszBacklightName, D0, POWER_NAME, NULL, 0);

            if (!s_hBacklightReq)
                RETAILMSG(1, (L"SetPowerRequirement failed: %X\n", GetLastError()));
        }
    }
    else
    {
        if (s_hBacklightReq)
        {
            if (ERROR_SUCCESS != ReleasePowerRequirement(s_hBacklightReq))
                RETAILMSG(1, (L"ReleasePowerRequirement failed: %X\n", GetLastError()));

            s_hBacklightReq = NULL;
        }
    }
}