Method getPosition

src/SFML/Window/Unix/WindowImplX11.cpp:894–963

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Vector2i WindowImplX11::getPosition() const
{
    using namespace WindowImplX11Impl;

    // Get absolute position of our window relative to root window. This
    // takes into account all information that X11 has, including X11
    // border widths and any decorations. It corresponds to where the
    // window actually is, but not necessarily to where we told it to
    // go using setPosition() and XMoveWindow(). To have the two match
    // as expected, we may have to subtract decorations and borders.
    ::Window child         = 0;
    int      xAbsRelToRoot = 0;
    int      yAbsRelToRoot = 0;

    XTranslateCoordinates(m_display.get(), m_window, DefaultRootWindow(m_display.get()), 0, 0, &xAbsRelToRoot, &yAbsRelToRoot, &child);

    // CASE 1: some rare WMs actually put the window exactly where we tell
    // it to, even with decorations and such, which get shifted back.
    // In these rare cases, we can use the absolute value directly.
    if (isWMAbsolutePositionGood())
        return {xAbsRelToRoot, yAbsRelToRoot};

    // CASE 2: most modern WMs support EWMH and can define _NET_FRAME_EXTENTS
    // with the exact frame size to subtract, so if present, we prefer it and
    // query it first. According to spec, this already includes any borders.
    long xFrameExtent = 0;
    long yFrameExtent = 0;

    if (getEWMHFrameExtents(m_display.get(), m_window, xFrameExtent, yFrameExtent))
    {
        // Get final X/Y coordinates: subtract EWMH frame extents from
        // absolute window position.
        return {(xAbsRelToRoot - static_cast<int>(xFrameExtent)), (yAbsRelToRoot - static_cast<int>(yFrameExtent))};
    }

    // CASE 3: EWMH frame extents were not available, use geometry.
    // We climb back up to the window before the root and use its
    // geometry information to extract X/Y position. This because
    // re-parenting WMs may re-parent the window multiple times, so
    // we'd have to climb up to the furthest ancestor and sum the
    // relative differences and borders anyway; and doing that to
    // subtract those values from the absolute coordinates of the
    // window is equivalent to going up the tree and asking the
    // furthest ancestor what it's relative distance to the root is.
    // So we use that approach because it's simpler.
    // This approach assumes that any window between the root and
    // our window is part of decorations/borders in some way. This
    // seems to hold true for most reasonable WM implementations.
    ::Window ancestor = m_window;
    ::Window root     = DefaultRootWindow(m_display.get());

    while (getParentWindow(m_display.get(), ancestor) != root)
    {
        // Next window up (parent window).
        ancestor = getParentWindow(m_display.get(), ancestor);
    }

    // Get final X/Y coordinates: take the relative position to