Function getEWMHFrameExtents

src/SFML/Window/Unix/WindowImplX11.cpp:363–414

Get the Frame Extents from EWMH WMs that support it.

// Get the Frame Extents from EWMH WMs that support it.
bool getEWMHFrameExtents(::Display* disp, ::Window win, long& xFrameExtent, long& yFrameExtent)
{
    static const auto supported = isFeatureSupported("_NET_FRAME_EXTENTS");

    if (!supported)
        return false;

    static const auto frameExtents = sf::priv::getAtom("_NET_FRAME_EXTENTS");

    if (frameExtents == None)
        return false;

    bool           gotFrameExtents = false;
    Atom           actualType      = 0;
    int            actualFormat    = 0;
    unsigned long  numItems        = 0;
    unsigned long  numBytesLeft    = 0;
    unsigned char* data            = nullptr;

    const int result = XGetWindowProperty(disp,
                                          win,
                                          frameExtents,
                                          0,
                                          4,
                                          False,
                                          XA_CARDINAL,
                                          &actualType,
                                          &actualFormat,
                                          &numItems,
                                          &numBytesLeft,
                                          &data);

    if ((result == Success) && (actualType == XA_CARDINAL) && (actualFormat == 32) && (numItems == 4) &&
        (numBytesLeft == 0) && (data != nullptr))
    {
        gotFrameExtents = true;

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wcast-align"
        long* extents = reinterpret_cast<long*>(data);
#pragma GCC diagnostic pop

        xFrameExtent = extents[0]; // Left.
        yFrameExtent = extents[2]; // Top.
    }

    // Always free data.
    if (data != nullptr)
        XFree(data);

    return gotFrameExtents;
}

// Check if the current WM is in the list of good WMs that provide
// a correct absolute position for the window when queried.