windows 7 - C++: check if computer is locked

Question

I'm trying to figure out whether the computer is locked.

I've looked at LockWorkStation function, but the function that I'm hoping to find is IsWorkStationLocked.

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I need to support all windows version >= XP

Answer 1

For windows 7 and abowe WTS API can be used:

bool IsSessionLocked() {
    typedef BOOL (PASCAL * WTSQuerySessionInformation)(HANDLE hServer, DWORD SessionId, WTS_INFO_CLASS WTSInfoClass, LPTSTR* ppBuffer, DWORD* pBytesReturned);
    typedef void (PASCAL * WTSFreeMemory)( PVOID pMemory);

    WTSINFOEXW * pInfo = NULL;
    WTS_INFO_CLASS wtsic = DW_WTSSessionInfoEx;
    bool bRet = false;
    LPTSTR ppBuffer = NULL;
    DWORD dwBytesReturned = 0;
    LONG dwFlags = 0;
    WTSQuerySessionInformation pWTSQuerySessionInformation = NULL;
    WTSFreeMemory pWTSFreeMemory = NULL;

    HMODULE hLib = LoadLibrary( _T("wtsapi32.dll") );
    if (!hLib) {
        return false;
    }
    pWTSQuerySessionInformation = (WTSQuerySessionInformation)GetProcAddress(hLib, "WTSQuerySessionInformationW" );
    if (!pWTSQuerySessionInformation) {
        goto EXIT;
    }

    pWTSFreeMemory = (WTSFreeMemory)GetProcAddress(hLib, "WTSFreeMemory" );
    if (pWTSFreeMemory == NULL) {
        goto EXIT;
    }

    if(pWTSQuerySessionInformation(WTS_CURRENT_SERVER_HANDLE, g_dwSessionID, wtsic, &ppBuffer, &dwBytesReturned)) {
        if(dwBytesReturned > 0) {
            pInfo =  (WTSINFOEXW*)ppBuffer; 
            if (pInfo->Level == 1) {
                dwFlags = pInfo->Data.WTSInfoExLevel1.SessionFlags;
            }
            if (dwFlags == WTS_SESSIONSTATE_LOCK) {
                bRet = true;
            }
        }
        pWTSFreeMemory(ppBuffer);
        ppBuffer = NULL;
    }
EXIT:
    if (hLib != NULL) {
        FreeLibrary(hLib);
    }
    return bRet;
}

Please check following article for supported platforms for WTSINFOEX structure: https://technet.microsoft.com/ru-ru/sysinternals/ee621017