platforms/xcb/qxcbscreen.cpp

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#include "qxcbscreen.h"
#include "qxcbwindow.h"
#include "qxcbcursor.h"
#include "qxcbimage.h"
#include "qnamespace.h"
#include "qxcbxsettings.h"

#include <stdio.h>

#include <QDebug>
#include <QtAlgorithms>

#include <qpa/qwindowsysteminterface.h>
#include <private/qmath_p.h>
#include <QtGui/private/qhighdpiscaling_p.h>

QT_BEGIN_NAMESPACE

QXcbVirtualDesktop::QXcbVirtualDesktop(QXcbConnection *connection, xcb_screen_t *screen, int number)
    : QXcbObject(connection)
    , m_screen(screen)
    , m_number(number)
{
    const QByteArray cmAtomName =  "_NET_WM_CM_S" + QByteArray::number(m_number);
    m_net_wm_cm_atom = connection->internAtom(cmAtomName.constData());
    m_compositingActive = connection->getSelectionOwner(m_net_wm_cm_atom);

    m_workArea = getWorkArea();

    readXResources();

    auto rootAttribs = Q_XCB_REPLY_UNCHECKED(xcb_get_window_attributes, xcb_connection(),
                                             screen->root);
    const quint32 existingEventMask = !rootAttribs ? 0 : rootAttribs->your_event_mask;

    const quint32 mask = XCB_CW_EVENT_MASK;
    const quint32 values[] = {
        // XCB_CW_EVENT_MASK
        XCB_EVENT_MASK_ENTER_WINDOW
        | XCB_EVENT_MASK_LEAVE_WINDOW
        | XCB_EVENT_MASK_PROPERTY_CHANGE
        | XCB_EVENT_MASK_STRUCTURE_NOTIFY // for the "MANAGER" atom (system tray notification).
        | existingEventMask // don't overwrite the event mask on the root window
    };

    xcb_change_window_attributes(xcb_connection(), screen->root, mask, values);

    auto reply = Q_XCB_REPLY_UNCHECKED(xcb_get_property, xcb_connection(),
                                       false, screen->root,
                                       atom(QXcbAtom::_NET_SUPPORTING_WM_CHECK),
                                       XCB_ATOM_WINDOW, 0, 1024);
    if (reply && reply->format == 32 && reply->type == XCB_ATOM_WINDOW) {
        xcb_window_t windowManager = *((xcb_window_t *)xcb_get_property_value(reply.get()));

        if (windowManager != XCB_WINDOW_NONE)
            m_windowManagerName = QXcbWindow::windowTitle(connection, windowManager);
    }

    xcb_depth_iterator_t depth_iterator =
        xcb_screen_allowed_depths_iterator(screen);

    while (depth_iterator.rem) {
        xcb_depth_t *depth = depth_iterator.data;
        xcb_visualtype_iterator_t visualtype_iterator =
            xcb_depth_visuals_iterator(depth);

        while (visualtype_iterator.rem) {
            xcb_visualtype_t *visualtype = visualtype_iterator.data;
            m_visuals.insert(visualtype->visual_id, *visualtype);
            m_visualDepths.insert(visualtype->visual_id, depth->depth);
            xcb_visualtype_next(&visualtype_iterator);
        }

        xcb_depth_next(&depth_iterator);
    }

    auto dpiChangedCallback = [](QXcbVirtualDesktop *desktop, const QByteArray &, const QVariant &property, void *) {
        bool ok;
        int dpiTimes1k = property.toInt(&ok);
        if (!ok)
            return;
        int dpi = dpiTimes1k / 1024;
        if (desktop->m_forcedDpi == dpi)
            return;
        desktop->m_forcedDpi = dpi;
        for (QXcbScreen *screen : desktop->connection()->screens())
            QWindowSystemInterface::handleScreenLogicalDotsPerInchChange(screen->QPlatformScreen::screen(), dpi, dpi);
    };
    xSettings()->registerCallbackForProperty("Xft/DPI", dpiChangedCallback, nullptr);
}

QXcbVirtualDesktop::~QXcbVirtualDesktop()
{
    delete m_xSettings;

    for (auto cmap : qAsConst(m_visualColormaps))
        xcb_free_colormap(xcb_connection(), cmap);
}

QDpi QXcbVirtualDesktop::dpi() const
{
    const QSize virtualSize = size();
    const QSize virtualSizeMillimeters = physicalSize();

    return QDpi(Q_MM_PER_INCH * virtualSize.width() / virtualSizeMillimeters.width(),
                Q_MM_PER_INCH * virtualSize.height() / virtualSizeMillimeters.height());
}

QXcbScreen *QXcbVirtualDesktop::screenAt(const QPoint &pos) const
{
    const auto screens = connection()->screens();
    for (QXcbScreen *screen : screens) {
        if (screen->virtualDesktop() == this && screen->geometry().contains(pos))
            return screen;
    }
    return nullptr;
}

void QXcbVirtualDesktop::addScreen(QPlatformScreen *s)
{
    ((QXcbScreen *) s)->isPrimary() ? m_screens.prepend(s) : m_screens.append(s);
}

void QXcbVirtualDesktop::setPrimaryScreen(QPlatformScreen *s)
{
    const int idx = m_screens.indexOf(s);
    Q_ASSERT(idx > -1);
    m_screens.swapItemsAt(0, idx);
}

QXcbXSettings *QXcbVirtualDesktop::xSettings() const
{
    if (!m_xSettings) {
        QXcbVirtualDesktop *self = const_cast<QXcbVirtualDesktop *>(this);
        self->m_xSettings = new QXcbXSettings(self);
    }
    return m_xSettings;
}

bool QXcbVirtualDesktop::compositingActive() const
{
    if (connection()->hasXFixes())
        return m_compositingActive;
    else
        return connection()->getSelectionOwner(m_net_wm_cm_atom);
}

void QXcbVirtualDesktop::handleXFixesSelectionNotify(xcb_xfixes_selection_notify_event_t *notify_event)
{
    if (notify_event->selection == m_net_wm_cm_atom)
        m_compositingActive = notify_event->owner;
}

void QXcbVirtualDesktop::subscribeToXFixesSelectionNotify()
{
    if (connection()->hasXFixes()) {
        const uint32_t mask = XCB_XFIXES_SELECTION_EVENT_MASK_SET_SELECTION_OWNER |
                              XCB_XFIXES_SELECTION_EVENT_MASK_SELECTION_WINDOW_DESTROY |
                              XCB_XFIXES_SELECTION_EVENT_MASK_SELECTION_CLIENT_CLOSE;
        xcb_xfixes_select_selection_input_checked(xcb_connection(), connection()->getQtSelectionOwner(), m_net_wm_cm_atom, mask);
    }
}

/*!
    \brief handle the XCB screen change event and update properties

    On a mobile device, the ideal use case is that the accelerometer would
    drive the orientation. This could be achieved by using QSensors to read the
    accelerometer and adjusting the rotation in QML, or by reading the
    orientation from the QScreen object and doing the same, or in many other
    ways. However, on X we have the XRandR extension, which makes it possible
    to have the whole screen rotated, so that individual apps DO NOT have to
    rotate themselves. Apps could optionally use the
    QScreen::primaryOrientation property to optimize layout though.
    Furthermore, there is no support in X for accelerometer events anyway. So
    it makes more sense on a Linux system running X to just run a daemon which
    monitors the accelerometer and runs xrandr automatically to do the rotation,
    then apps do not have to be aware of it (but probably the window manager
    would resize them accordingly). updateGeometry() is written with this
    design in mind. Therefore the physical geometry, available geometry,
    virtual geometry, orientation and primaryOrientation should all change at
    the same time.  On a system which cannot rotate the whole screen, it would
    be correct for only the orientation (not the primary orientation) to
    change.
*/
void QXcbVirtualDesktop::handleScreenChange(xcb_randr_screen_change_notify_event_t *change_event)
{
    // No need to do anything when screen rotation did not change - if any
    // xcb output geometry has changed, we will get RRCrtcChangeNotify and
    // RROutputChangeNotify events next
    if (change_event->rotation == m_rotation)
        return;

    m_rotation = change_event->rotation;
    switch (m_rotation) {
    case XCB_RANDR_ROTATION_ROTATE_0: // xrandr --rotate normal
        m_screen->width_in_pixels = change_event->width;
        m_screen->height_in_pixels = change_event->height;
        m_screen->width_in_millimeters = change_event->mwidth;
        m_screen->height_in_millimeters = change_event->mheight;
        break;
    case XCB_RANDR_ROTATION_ROTATE_90: // xrandr --rotate left
        m_screen->width_in_pixels = change_event->height;
        m_screen->height_in_pixels = change_event->width;
        m_screen->width_in_millimeters = change_event->mheight;
        m_screen->height_in_millimeters = change_event->mwidth;
        break;
    case XCB_RANDR_ROTATION_ROTATE_180: // xrandr --rotate inverted
        m_screen->width_in_pixels = change_event->width;
        m_screen->height_in_pixels = change_event->height;
        m_screen->width_in_millimeters = change_event->mwidth;
        m_screen->height_in_millimeters = change_event->mheight;
        break;
    case XCB_RANDR_ROTATION_ROTATE_270: // xrandr --rotate right
        m_screen->width_in_pixels = change_event->height;
        m_screen->height_in_pixels = change_event->width;
        m_screen->width_in_millimeters = change_event->mheight;
        m_screen->height_in_millimeters = change_event->mwidth;
        break;
    // We don't need to do anything with these, since QScreen doesn't store reflection state,
    // and Qt-based applications probably don't need to care about it anyway.
    case XCB_RANDR_ROTATION_REFLECT_X: break;
    case XCB_RANDR_ROTATION_REFLECT_Y: break;
    }

    for (QPlatformScreen *platformScreen: qAsConst(m_screens)) {
        QDpi ldpi = platformScreen->logicalDpi();
        QWindowSystemInterface::handleScreenLogicalDotsPerInchChange(platformScreen->screen(), ldpi.first, ldpi.second);
    }
}

/*! \internal

    Using _NET_WORKAREA to calculate the available desktop geometry on multi-head systems (systems
    with more than one monitor) is unreliable. Different WMs have different interpretations of what
    _NET_WORKAREA means with multiple attached monitors. This gets worse when monitors have
    different dimensions and/or screens are not virtually aligned. In Qt we want the available
    geometry per monitor (QScreen), not desktop (represented by _NET_WORKAREA). WM specification
    does not have an atom for this. Thus, QScreen is limted by the lack of support from the
    underlying system.

    One option could be that Qt does WM's job of calculating this by subtracting geometries of
    _NET_WM_STRUT_PARTIAL and windows where _NET_WM_WINDOW_TYPE(ATOM) = _NET_WM_WINDOW_TYPE_DOCK.
    But this won't work on Gnome 3 shell as it seems that on this desktop environment the tool panel
    is painted directly on the root window. Maybe there is some Gnome/GTK API that could be used
    to get height of the panel, but I did not find one. Maybe other WMs have their own tricks, so
    the reliability of this approach is questionable.
 */
QRect QXcbVirtualDesktop::getWorkArea() const
{
    QRect r;
    auto workArea = Q_XCB_REPLY_UNCHECKED(xcb_get_property, xcb_connection(), false, screen()->root,
                                          atom(QXcbAtom::_NET_WORKAREA),
                                          XCB_ATOM_CARDINAL, 0, 1024);
    if (workArea && workArea->type == XCB_ATOM_CARDINAL && workArea->format == 32 && workArea->value_len >= 4) {
        // If workArea->value_len > 4, the remaining ones seem to be for WM's virtual desktops
        // (don't mess with QXcbVirtualDesktop which represents an X screen).
        // But QScreen doesn't know about that concept.  In reality there could be a
        // "docked" panel (with _NET_WM_STRUT_PARTIAL atom set) on just one desktop.
        // But for now just assume the first 4 values give us the geometry of the
        // "work area", AKA "available geometry"
        uint32_t *geom = (uint32_t*)xcb_get_property_value(workArea.get());
        r = QRect(geom[0], geom[1], geom[2], geom[3]);
    } else {
        r = QRect(QPoint(), size());
    }
    return r;
}

void QXcbVirtualDesktop::updateWorkArea()
{
    QRect workArea = getWorkArea();
    if (m_workArea != workArea) {
        m_workArea = workArea;
        for (QPlatformScreen *screen : qAsConst(m_screens))
            ((QXcbScreen *)screen)->updateAvailableGeometry();
    }
}

static inline QSizeF sizeInMillimeters(const QSize &size, const QDpi &dpi)
{
    return QSizeF(Q_MM_PER_INCH * size.width() / dpi.first,
                  Q_MM_PER_INCH * size.height() / dpi.second);
}

bool QXcbVirtualDesktop::xResource(const QByteArray &identifier,
                                   const QByteArray &expectedIdentifier,
                                   QByteArray& stringValue)
{
    if (identifier.startsWith(expectedIdentifier)) {
        stringValue = identifier.mid(expectedIdentifier.size());
        return true;
    }
    return false;
}

static bool parseXftInt(const QByteArray& stringValue, int *value)
{
    Q_ASSERT(value);
    bool ok;
    *value = stringValue.toInt(&ok);
    return ok;
}

static bool parseXftDpi(const QByteArray& stringValue, int *value)
{
    Q_ASSERT(value);
    bool ok = parseXftInt(stringValue, value);
    // Support GNOME 3 bug that wrote DPI with fraction:
    if (!ok)
        *value = qRound(stringValue.toDouble(&ok));
    return ok;
}

static QFontEngine::HintStyle parseXftHintStyle(const QByteArray& stringValue)
{
    if (stringValue == "hintfull")
        return QFontEngine::HintFull;
    else if (stringValue == "hintnone")
        return QFontEngine::HintNone;
    else if (stringValue == "hintmedium")
        return QFontEngine::HintMedium;
    else if (stringValue == "hintslight")
        return QFontEngine::HintLight;

    return QFontEngine::HintStyle(-1);
}

static QFontEngine::SubpixelAntialiasingType parseXftRgba(const QByteArray& stringValue)
{
    if (stringValue == "none")
        return QFontEngine::Subpixel_None;
    else if (stringValue == "rgb")
        return QFontEngine::Subpixel_RGB;
    else if (stringValue == "bgr")
        return QFontEngine::Subpixel_BGR;
    else if (stringValue == "vrgb")
        return QFontEngine::Subpixel_VRGB;
    else if (stringValue == "vbgr")
        return QFontEngine::Subpixel_VBGR;

    return QFontEngine::SubpixelAntialiasingType(-1);
}

void QXcbVirtualDesktop::readXResources()
{
    int offset = 0;
    QByteArray resources;
    while (true) {
        auto reply = Q_XCB_REPLY_UNCHECKED(xcb_get_property, xcb_connection(),
                                           false, screen()->root,
                                           XCB_ATOM_RESOURCE_MANAGER,
                                           XCB_ATOM_STRING, offset/4, 8192);
        bool more = false;
        if (reply && reply->format == 8 && reply->type == XCB_ATOM_STRING) {
            resources += QByteArray((const char *)xcb_get_property_value(reply.get()), xcb_get_property_value_length(reply.get()));
            offset += xcb_get_property_value_length(reply.get());
            more = reply->bytes_after != 0;
        }

        if (!more)
            break;
    }

    QList<QByteArray> split = resources.split('\n');
    for (int i = 0; i < split.size(); ++i) {
        const QByteArray &r = split.at(i);
        int value;
        QByteArray stringValue;
        if (xResource(r, "Xft.dpi:\t", stringValue)) {
            if (parseXftDpi(stringValue, &value))
                m_forcedDpi = value;
        } else if (xResource(r, "Xft.hintstyle:\t", stringValue)) {
            m_hintStyle = parseXftHintStyle(stringValue);
        } else if (xResource(r, "Xft.antialias:\t", stringValue)) {
            if (parseXftInt(stringValue, &value))
                m_antialiasingEnabled = value;
        } else if (xResource(r, "Xft.rgba:\t", stringValue)) {
            m_subpixelType = parseXftRgba(stringValue);
        }
    }
}

QSurfaceFormat QXcbVirtualDesktop::surfaceFormatFor(const QSurfaceFormat &format) const
{
    const xcb_visualid_t xcb_visualid = connection()->hasDefaultVisualId() ? connection()->defaultVisualId()
                                                                           : screen()->root_visual;
    const xcb_visualtype_t *xcb_visualtype = visualForId(xcb_visualid);

    const int redSize = qPopulationCount(xcb_visualtype->red_mask);
    const int greenSize = qPopulationCount(xcb_visualtype->green_mask);
    const int blueSize = qPopulationCount(xcb_visualtype->blue_mask);

    QSurfaceFormat result = format;

    if (result.redBufferSize() < 0)
        result.setRedBufferSize(redSize);

    if (result.greenBufferSize() < 0)
        result.setGreenBufferSize(greenSize);

    if (result.blueBufferSize() < 0)
        result.setBlueBufferSize(blueSize);

    return result;
}

const xcb_visualtype_t *QXcbVirtualDesktop::visualForFormat(const QSurfaceFormat &format) const
{
    const xcb_visualtype_t *candidate = nullptr;

    for (const xcb_visualtype_t &xcb_visualtype : m_visuals) {

        const int redSize = qPopulationCount(xcb_visualtype.red_mask);
        const int greenSize = qPopulationCount(xcb_visualtype.green_mask);
        const int blueSize = qPopulationCount(xcb_visualtype.blue_mask);
        const int alphaSize = depthOfVisual(xcb_visualtype.visual_id) - redSize - greenSize - blueSize;

        if (format.redBufferSize() != -1 && redSize != format.redBufferSize())
            continue;

        if (format.greenBufferSize() != -1 && greenSize != format.greenBufferSize())
            continue;

        if (format.blueBufferSize() != -1 && blueSize != format.blueBufferSize())
            continue;

        if (format.alphaBufferSize() != -1 && alphaSize != format.alphaBufferSize())
            continue;

        // Try to find a RGB visual rather than e.g. BGR or GBR
        if (qCountTrailingZeroBits(xcb_visualtype.blue_mask) == 0)
            return &xcb_visualtype;

        // In case we do not find anything we like, just remember the first one
        // and hope for the best:
        if (!candidate)
            candidate = &xcb_visualtype;
    }

    return candidate;
}

const xcb_visualtype_t *QXcbVirtualDesktop::visualForId(xcb_visualid_t visualid) const
{
    QMap<xcb_visualid_t, xcb_visualtype_t>::const_iterator it = m_visuals.find(visualid);
    if (it == m_visuals.constEnd())
        return nullptr;
    return &*it;
}

quint8 QXcbVirtualDesktop::depthOfVisual(xcb_visualid_t visualid) const
{
    QMap<xcb_visualid_t, quint8>::const_iterator it = m_visualDepths.find(visualid);
    if (it == m_visualDepths.constEnd())
        return 0;
    return *it;
}

xcb_colormap_t QXcbVirtualDesktop::colormapForVisual(xcb_visualid_t visualid) const
{
    auto it = m_visualColormaps.constFind(visualid);
    if (it != m_visualColormaps.constEnd())
        return *it;

    auto cmap = xcb_generate_id(xcb_connection());
    xcb_create_colormap(xcb_connection(),
                        XCB_COLORMAP_ALLOC_NONE,
                        cmap,
                        screen()->root,
                        visualid);
    m_visualColormaps.insert(visualid, cmap);
    return cmap;
}

QXcbScreen::QXcbScreen(QXcbConnection *connection, QXcbVirtualDesktop *virtualDesktop,
                       xcb_randr_output_t outputId, xcb_randr_get_output_info_reply_t *output,
                       const xcb_xinerama_screen_info_t *xineramaScreenInfo, int xineramaScreenIdx)
    : QXcbObject(connection)
    , m_virtualDesktop(virtualDesktop)
    , m_output(outputId)
    , m_crtc(output ? output->crtc : XCB_NONE)
    , m_outputName(getOutputName(output))
    , m_outputSizeMillimeters(output ? QSize(output->mm_width, output->mm_height) : QSize())
{
    if (connection->hasXRandr()) {
        xcb_randr_select_input(xcb_connection(), screen()->root, true);
        auto crtc = Q_XCB_REPLY_UNCHECKED(xcb_randr_get_crtc_info, xcb_connection(),
                                          m_crtc, output ? output->timestamp : 0);
        if (crtc) {
            updateGeometry(QRect(crtc->x, crtc->y, crtc->width, crtc->height), crtc->rotation);
            updateRefreshRate(crtc->mode);
        }
    } else if (xineramaScreenInfo) {
        m_geometry = QRect(xineramaScreenInfo->x_org, xineramaScreenInfo->y_org,
                           xineramaScreenInfo->width, xineramaScreenInfo->height);
        m_availableGeometry = m_geometry & m_virtualDesktop->workArea();
        m_sizeMillimeters = sizeInMillimeters(m_geometry.size(), m_virtualDesktop->dpi());
        if (xineramaScreenIdx > -1)
            m_outputName += QLatin1Char('-') + QString::number(xineramaScreenIdx);
    }

    if (m_geometry.isEmpty())
        m_geometry = QRect(QPoint(), virtualDesktop->size());

    if (m_availableGeometry.isEmpty())
        m_availableGeometry = m_geometry & m_virtualDesktop->workArea();

    if (m_sizeMillimeters.isEmpty())
        m_sizeMillimeters = virtualDesktop->physicalSize();

    m_cursor = new QXcbCursor(connection, this);

    if (connection->hasXRandr()) { // Parse EDID
        QByteArray edid = getEdid();
        if (m_edid.parse(edid)) {
            qCDebug(lcQpaScreen, "EDID data for output \"%s\": identifier '%s', manufacturer '%s',"
                                 "model '%s', serial '%s', physical size: %.2fx%.2f",
                    name().toLatin1().constData(),
                    m_edid.identifier.toLatin1().constData(),
                    m_edid.manufacturer.toLatin1().constData(),
                    m_edid.model.toLatin1().constData(),
                    m_edid.serialNumber.toLatin1().constData(),
                    m_edid.physicalSize.width(), m_edid.physicalSize.height());
        } else {
            // This property is defined by the xrandr spec. Parsing failure indicates a valid error,
            // but keep this as debug, for details see 4f515815efc318ddc909a0399b71b8a684962f38.
            qCDebug(lcQpaScreen) << "Failed to parse EDID data for output" << name() <<
                                    "edid data: " << edid;
        }
    }
}

QXcbScreen::~QXcbScreen()
{
    delete m_cursor;
}

QString QXcbScreen::getOutputName(xcb_randr_get_output_info_reply_t *outputInfo)
{
    QString name;
    if (outputInfo) {
        name = QString::fromUtf8((const char*)xcb_randr_get_output_info_name(outputInfo),
                                 xcb_randr_get_output_info_name_length(outputInfo));
    } else {
        QByteArray displayName = connection()->displayName();
        int dotPos = displayName.lastIndexOf('.');
        if (dotPos != -1)
            displayName.truncate(dotPos);
        name = QString::fromLocal8Bit(displayName) + QLatin1Char('.')
                + QString::number(m_virtualDesktop->number());
    }
    return name;
}

QString QXcbScreen::manufacturer() const
{
    return m_edid.manufacturer;
}

QString QXcbScreen::model() const
{
    return m_edid.model;
}

QString QXcbScreen::serialNumber() const
{
    return m_edid.serialNumber;
}

QWindow *QXcbScreen::topLevelAt(const QPoint &p) const
{
    xcb_window_t root = screen()->root;

    int x = p.x();
    int y = p.y();

    xcb_window_t parent = root;
    xcb_window_t child = root;

    do {
        auto translate_reply = Q_XCB_REPLY_UNCHECKED(xcb_translate_coordinates, xcb_connection(), parent, child, x, y);
        if (!translate_reply) {
            return nullptr;
        }

        parent = child;
        child = translate_reply->child;
        x = translate_reply->dst_x;
        y = translate_reply->dst_y;

        if (!child || child == root)
            return nullptr;

        QPlatformWindow *platformWindow = connection()->platformWindowFromId(child);
        if (platformWindow)
            return platformWindow->window();
    } while (parent != child);

    return nullptr;
}

void QXcbScreen::windowShown(QXcbWindow *window)
{
    // Freedesktop.org Startup Notification
    if (!connection()->startupId().isEmpty() && window->window()->isTopLevel()) {
        sendStartupMessage(QByteArrayLiteral("remove: ID=") + connection()->startupId());
        connection()->clearStartupId();
    }
}

QSurfaceFormat QXcbScreen::surfaceFormatFor(const QSurfaceFormat &format) const
{
    return m_virtualDesktop->surfaceFormatFor(format);
}

const xcb_visualtype_t *QXcbScreen::visualForId(xcb_visualid_t visualid) const
{
    return m_virtualDesktop->visualForId(visualid);
}

void QXcbScreen::sendStartupMessage(const QByteArray &message) const
{
    xcb_window_t rootWindow = root();

    xcb_client_message_event_t ev;
    ev.response_type = XCB_CLIENT_MESSAGE;
    ev.format = 8;
    ev.type = connection()->atom(QXcbAtom::_NET_STARTUP_INFO_BEGIN);
    ev.sequence = 0;
    ev.window = rootWindow;
    int sent = 0;
    int length = message.length() + 1; // include NUL byte
    const char *data = message.constData();
    do {
        if (sent == 20)
            ev.type = connection()->atom(QXcbAtom::_NET_STARTUP_INFO);

        const int start = sent;
        const int numBytes = qMin(length - start, 20);
        memcpy(ev.data.data8, data + start, numBytes);
        xcb_send_event(connection()->xcb_connection(), false, rootWindow, XCB_EVENT_MASK_PROPERTY_CHANGE, (const char *) &ev);

        sent += numBytes;
    } while (sent < length);
}

QRect QXcbScreen::availableGeometry() const
{
    static bool enforceNetWorkarea = !qEnvironmentVariableIsEmpty("QT_RELY_ON_NET_WORKAREA_ATOM");
    bool isMultiHeadSystem = virtualSiblings().length() > 1;
    bool useScreenGeometry = isMultiHeadSystem && !enforceNetWorkarea;
    return useScreenGeometry ? m_geometry : m_availableGeometry;
}

QImage::Format QXcbScreen::format() const
{
    QImage::Format format;
    bool needsRgbSwap;
    qt_xcb_imageFormatForVisual(connection(), screen()->root_depth, visualForId(screen()->root_visual), &format, &needsRgbSwap);
    // We are ignoring needsRgbSwap here and just assumes the backing-store will handle it.
    if (format != QImage::Format_Invalid)
        return format;
    return QImage::Format_RGB32;
}

int QXcbScreen::forcedDpi() const
{
    const int forcedDpi = m_virtualDesktop->forcedDpi();
    if (forcedDpi > 0)
        return forcedDpi;
    return 0;
}

QDpi QXcbScreen::logicalDpi() const
{
    const int forcedDpi = this->forcedDpi();
    if (forcedDpi > 0)
        return QDpi(forcedDpi, forcedDpi);

    // Fall back to physical virtual desktop DPI, but prevent
    // using DPI values lower than 96. This ensuers that connecting
    // to e.g. a TV works somewhat predictabilly.
    QDpi virtualDesktopPhysicalDPi = m_virtualDesktop->dpi();
    return QDpi(std::max(virtualDesktopPhysicalDPi.first, 96.0),
                std::max(virtualDesktopPhysicalDPi.second, 96.0));
}

QPlatformCursor *QXcbScreen::cursor() const
{
    return m_cursor;
}

void QXcbScreen::setOutput(xcb_randr_output_t outputId,
                           xcb_randr_get_output_info_reply_t *outputInfo)
{
    m_output = outputId;
    m_crtc = outputInfo ? outputInfo->crtc : XCB_NONE;
    m_mode = XCB_NONE;
    m_outputName = getOutputName(outputInfo);
    // TODO: Send an event to the QScreen instance that the screen changed its name
}

int QXcbScreen::virtualDesktopNumberStatic(const QScreen *screen)
{
    if (screen && screen->handle())
        return static_cast<const QXcbScreen *>(screen->handle())->screenNumber();

    return 0;
}

void QXcbScreen::updateGeometry(xcb_timestamp_t timestamp)
{
    if (!connection()->hasXRandr())
        return;

    auto crtc = Q_XCB_REPLY_UNCHECKED(xcb_randr_get_crtc_info, xcb_connection(),
                                      m_crtc, timestamp);
    if (crtc)
        updateGeometry(QRect(crtc->x, crtc->y, crtc->width, crtc->height), crtc->rotation);
}

void QXcbScreen::updateGeometry(const QRect &geometry, uint8_t rotation)
{
    const Qt::ScreenOrientation oldOrientation = m_orientation;

    switch (rotation) {
    case XCB_RANDR_ROTATION_ROTATE_0: // xrandr --rotate normal
        m_orientation = Qt::LandscapeOrientation;
        m_sizeMillimeters = m_outputSizeMillimeters;
        break;
    case XCB_RANDR_ROTATION_ROTATE_90: // xrandr --rotate left
        m_orientation = Qt::PortraitOrientation;
        m_sizeMillimeters = m_outputSizeMillimeters.transposed();
        break;
    case XCB_RANDR_ROTATION_ROTATE_180: // xrandr --rotate inverted
        m_orientation = Qt::InvertedLandscapeOrientation;
        m_sizeMillimeters = m_outputSizeMillimeters;
        break;
    case XCB_RANDR_ROTATION_ROTATE_270: // xrandr --rotate right
        m_orientation = Qt::InvertedPortraitOrientation;
        m_sizeMillimeters = m_outputSizeMillimeters.transposed();
        break;
    }

    // It can be that physical size is unknown while virtual size
    // is known (probably back-calculated from DPI and resolution),
    // e.g. on VNC or with some hardware.
    if (m_sizeMillimeters.isEmpty())
        m_sizeMillimeters = sizeInMillimeters(geometry.size(), m_virtualDesktop->dpi());

    m_geometry = geometry;
    m_availableGeometry = geometry & m_virtualDesktop->workArea();
    QWindowSystemInterface::handleScreenGeometryChange(QPlatformScreen::screen(), m_geometry, m_availableGeometry);
    if (m_orientation != oldOrientation)
        QWindowSystemInterface::handleScreenOrientationChange(QPlatformScreen::screen(), m_orientation);
}

void QXcbScreen::updateAvailableGeometry()
{
    QRect availableGeometry = m_geometry & m_virtualDesktop->workArea();
    if (m_availableGeometry != availableGeometry) {
        m_availableGeometry = availableGeometry;
        QWindowSystemInterface::handleScreenGeometryChange(QPlatformScreen::screen(), m_geometry, m_availableGeometry);
    }
}

void QXcbScreen::updateRefreshRate(xcb_randr_mode_t mode)
{
    if (!connection()->hasXRandr())
        return;

    if (m_mode == mode)
        return;

    // we can safely use get_screen_resources_current here, because in order to
    // get here, we must have called get_screen_resources before
    auto resources = Q_XCB_REPLY_UNCHECKED(xcb_randr_get_screen_resources_current,
                                           xcb_connection(), screen()->root);
    if (resources) {
        xcb_randr_mode_info_iterator_t modesIter =
            xcb_randr_get_screen_resources_current_modes_iterator(resources.get());
        for (; modesIter.rem; xcb_randr_mode_info_next(&modesIter)) {
            xcb_randr_mode_info_t *modeInfo = modesIter.data;
            if (modeInfo->id == mode) {
                const uint32_t dotCount = modeInfo->htotal * modeInfo->vtotal;
                m_refreshRate = (dotCount != 0) ? modeInfo->dot_clock / qreal(dotCount) : 0;
                m_mode = mode;
                break;
            }
        }

        QWindowSystemInterface::handleScreenRefreshRateChange(QPlatformScreen::screen(), m_refreshRate);
    }
}

static inline bool translate(xcb_connection_t *connection, xcb_window_t child, xcb_window_t parent,
                             int *x, int *y)
{
    auto translate_reply = Q_XCB_REPLY_UNCHECKED(xcb_translate_coordinates,
                                                 connection, child, parent, *x, *y);
    if (!translate_reply)
        return false;
    *x = translate_reply->dst_x;
    *y = translate_reply->dst_y;
    return true;
}

QPixmap QXcbScreen::grabWindow(WId window, int xIn, int yIn, int width, int height) const
{
    if (width == 0 || height == 0)
        return QPixmap();

    int x = xIn;
    int y = yIn;
    QXcbScreen *screen = const_cast<QXcbScreen *>(this);
    xcb_window_t root = screen->root();

    auto rootReply = Q_XCB_REPLY_UNCHECKED(xcb_get_geometry, xcb_connection(), root);
    if (!rootReply)
        return QPixmap();

    const quint8 rootDepth = rootReply->depth;

    QSize windowSize;
    quint8 effectiveDepth = 0;
    if (window) {
        auto windowReply = Q_XCB_REPLY_UNCHECKED(xcb_get_geometry, xcb_connection(), window);
        if (!windowReply)
            return QPixmap();
        windowSize = QSize(windowReply->width, windowReply->height);
        effectiveDepth = windowReply->depth;
        if (effectiveDepth == rootDepth) {
            // if the depth of the specified window and the root window are the
            // same, grab pixels from the root window (so that we get the any
            // overlapping windows and window manager frames)

            // map x and y to the root window
            if (!translate(xcb_connection(), window, root, &x, &y))
                return QPixmap();

            window = root;
        }
    } else {
        window = root;
        effectiveDepth = rootDepth;
        windowSize = m_geometry.size();
        x += m_geometry.x();
        y += m_geometry.y();
    }

    if (width < 0)
        width = windowSize.width() - xIn;
    if (height < 0)
        height = windowSize.height() - yIn;

    auto attributes_reply = Q_XCB_REPLY_UNCHECKED(xcb_get_window_attributes, xcb_connection(), window);

    if (!attributes_reply)
        return QPixmap();

    const xcb_visualtype_t *visual = screen->visualForId(attributes_reply->visual);

    xcb_pixmap_t pixmap = xcb_generate_id(xcb_connection());
    xcb_create_pixmap(xcb_connection(), effectiveDepth, pixmap, window, width, height);

    uint32_t gc_value_mask = XCB_GC_SUBWINDOW_MODE;
    uint32_t gc_value_list[] = { XCB_SUBWINDOW_MODE_INCLUDE_INFERIORS };

    xcb_gcontext_t gc = xcb_generate_id(xcb_connection());
    xcb_create_gc(xcb_connection(), gc, pixmap, gc_value_mask, gc_value_list);

    xcb_copy_area(xcb_connection(), window, pixmap, gc, x, y, 0, 0, width, height);

    QPixmap result = qt_xcb_pixmapFromXPixmap(connection(), pixmap, width, height, effectiveDepth, visual);
    xcb_free_gc(xcb_connection(), gc);
    xcb_free_pixmap(xcb_connection(), pixmap);

    return result;
}

QXcbXSettings *QXcbScreen::xSettings() const
{
    return m_virtualDesktop->xSettings();
}

QByteArray QXcbScreen::getOutputProperty(xcb_atom_t atom) const
{
    QByteArray result;

    auto reply = Q_XCB_REPLY(xcb_randr_get_output_property, xcb_connection(),
                             m_output, atom, XCB_ATOM_ANY, 0, 100, false, false);
    if (reply && reply->type == XCB_ATOM_INTEGER && reply->format == 8) {
        quint8 *data = new quint8[reply->num_items];
        memcpy(data, xcb_randr_get_output_property_data(reply.get()), reply->num_items);
        result = QByteArray(reinterpret_cast<const char *>(data), reply->num_items);
        delete[] data;
    }

    return result;
}

QByteArray QXcbScreen::getEdid() const
{
    QByteArray result;
    if (!connection()->hasXRandr())
        return result;

    // Try a bunch of atoms
    result = getOutputProperty(atom(QXcbAtom::EDID));
    if (result.isEmpty())
        result = getOutputProperty(atom(QXcbAtom::EDID_DATA));
    if (result.isEmpty())
        result = getOutputProperty(atom(QXcbAtom::XFree86_DDC_EDID1_RAWDATA));

    return result;
}

static inline void formatRect(QDebug &debug, const QRect r)
{
    debug << r.width() << 'x' << r.height()
        << Qt::forcesign << r.x() << r.y() << Qt::noforcesign;
}

static inline void formatSizeF(QDebug &debug, const QSizeF s)
{
    debug << s.width() << 'x' << s.height() << "mm";
}

QDebug operator<<(QDebug debug, const QXcbScreen *screen)
{
    const QDebugStateSaver saver(debug);
    debug.nospace();
    debug << "QXcbScreen(" << (const void *)screen;
    if (screen) {
        debug << Qt::fixed << qSetRealNumberPrecision(1);
        debug << ", name=" << screen->name();
        debug << ", geometry=";
        formatRect(debug, screen->geometry());
        debug << ", availableGeometry=";
        formatRect(debug, screen->availableGeometry());
        debug << ", devicePixelRatio=" << screen->devicePixelRatio();
        debug << ", logicalDpi=" << screen->logicalDpi();
        debug << ", physicalSize=";
        formatSizeF(debug, screen->physicalSize());
        // TODO 5.6 if (debug.verbosity() > 2) {
        debug << ", screenNumber=" << screen->screenNumber();
        const QSize virtualSize = screen->virtualDesktop()->size();
        debug << ", virtualSize=" << virtualSize.width() << 'x' << virtualSize.height() << " (";
        formatSizeF(debug, virtualSize);
        debug << "), orientation=" << screen->orientation();
        debug << ", depth=" << screen->depth();
        debug << ", refreshRate=" << screen->refreshRate();
        debug << ", root=" << Qt::hex << screen->root();
        debug << ", windowManagerName=" << screen->windowManagerName();
    }
    debug << ')';
    return debug;
}

QT_END_NAMESPACE