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#include "qglobal.h"
#include "qdesktopwidget.h"
#include "qdesktopwidget_p.h"
#include "qscreen.h"
#include "qwidget_p.h"
#include "qwindow.h"

#include <private/qhighdpiscaling_p.h>
#include <qpa/qplatformscreen.h>

QT_BEGIN_NAMESPACE

QDesktopScreenWidget::QDesktopScreenWidget(QScreen *screen, const QRect &geometry)
    : QWidget(Q_NULLPTR, Qt::Desktop), m_screen(screen)
{
    setVisible(false);
    if (QWindow *winHandle = windowHandle())
        winHandle->setScreen(screen);
    setScreenGeometry(geometry);
}

void QDesktopScreenWidget::setScreenGeometry(const QRect &geometry)
{
    m_geometry = geometry;
    setGeometry(geometry);
}

int QDesktopScreenWidget::screenNumber() const
{
    const QDesktopWidgetPrivate *desktopWidgetP
        = static_cast<const QDesktopWidgetPrivate *>(qt_widget_private(QApplication::desktop()));
    return desktopWidgetP->screens.indexOf(const_cast<QDesktopScreenWidget *>(this));
}

const QRect QDesktopWidget::screenGeometry(const QWidget *widget) const
{
    if (Q_UNLIKELY(!widget)) {
        qWarning("QDesktopWidget::screenGeometry(): Attempt "
                 "to get the screen geometry of a null widget");
        return QRect();
    }
    QRect rect = QWidgetPrivate::screenGeometry(widget);
    if (rect.isNull())
        return screenGeometry(screenNumber(widget));
    else return rect;
}

const QRect QDesktopWidget::availableGeometry(const QWidget *widget) const
{
    if (Q_UNLIKELY(!widget)) {
        qWarning("QDesktopWidget::availableGeometry(): Attempt "
                 "to get the available geometry of a null widget");
        return QRect();
    }
    QRect rect = QWidgetPrivate::screenGeometry(widget);
    if (rect.isNull())
        return availableGeometry(screenNumber(widget));
    else
        return rect;
}

QDesktopScreenWidget *QDesktopWidgetPrivate::widgetForScreen(QScreen *qScreen) const
{
    foreach (QDesktopScreenWidget *widget, screens) {
        if (widget->screen() == qScreen)
            return widget;
    }
    return Q_NULLPTR;
}

void QDesktopWidgetPrivate::_q_updateScreens()
{
    Q_Q(QDesktopWidget);
    const QList<QScreen *> screenList = QGuiApplication::screens();
    const int targetLength = screenList.length();
    bool screenCountChanged = false;

    // Re-build our screens list. This is the easiest way to later compute which signals to emit.
    // Create new screen widgets as necessary. While iterating, keep the old list in place so
    // that widgetForScreen works.
    // Furthermore, we note which screens have changed, and compute the overall virtual geometry.
    QList<QDesktopScreenWidget *> newScreens;
    QList<int> changedScreens;
    QRegion virtualGeometry;

    for (int i = 0; i < targetLength; ++i) {
        QScreen *qScreen = screenList.at(i);
        const QRect screenGeometry = qScreen->geometry();
        QDesktopScreenWidget *screenWidget = widgetForScreen(qScreen);
        if (screenWidget) {
            // an old screen. update geometry and remember the index in the *new* list
            if (screenGeometry != screenWidget->screenGeometry()) {
                screenWidget->setScreenGeometry(screenGeometry);
                changedScreens.push_back(i);
            }
        } else {
            // a new screen, create a widget and connect the signals.
            screenWidget = new QDesktopScreenWidget(qScreen, screenGeometry);
            QObject::connect(qScreen, SIGNAL(geometryChanged(QRect)),
                             q, SLOT(_q_updateScreens()), Qt::QueuedConnection);
            QObject::connect(qScreen, SIGNAL(availableGeometryChanged(QRect)),
                             q, SLOT(_q_availableGeometryChanged()), Qt::QueuedConnection);
            QObject::connect(qScreen, SIGNAL(destroyed()),
                             q, SLOT(_q_updateScreens()), Qt::QueuedConnection);
            screenCountChanged = true;
        }
        // record all the screens and the overall geometry.
        newScreens.push_back(screenWidget);
        virtualGeometry += screenGeometry;
    }

    // Now we apply the accumulated updates.
    screens.swap(newScreens); // now [newScreens] is the old screen list
    Q_ASSERT(screens.size() == targetLength);
    q->setGeometry(virtualGeometry.boundingRect());

    // Delete the QDesktopScreenWidget that are not used any more.
    foreach (QDesktopScreenWidget *screen, newScreens) {
        if (!screens.contains(screen)) {
            delete screen;
            screenCountChanged = true;
        }
    }

    // Finally, emit the signals.
    if (screenCountChanged) {
        // Notice that we trigger screenCountChanged even if a screen was removed and another one added,
        // in which case the total number of screens did not change. This is the only way for applications
        // to notice that a screen was swapped out against another one.
        emit q->screenCountChanged(targetLength);
    }
    foreach (int changedScreen, changedScreens)
        emit q->resized(changedScreen);
}

void QDesktopWidgetPrivate::_q_availableGeometryChanged()
{
    Q_Q(QDesktopWidget);
    if (QScreen *screen = qobject_cast<QScreen *>(q->sender()))
        emit q->workAreaResized(QGuiApplication::screens().indexOf(screen));
}

QDesktopWidget::QDesktopWidget()
    : QWidget(*new QDesktopWidgetPrivate, 0, Qt::Desktop)
{
    Q_D(QDesktopWidget);
    setObjectName(QLatin1String("desktop"));
    d->_q_updateScreens();
    connect(qApp, SIGNAL(screenAdded(QScreen*)), this, SLOT(_q_updateScreens()));
    connect(qApp, SIGNAL(primaryScreenChanged(QScreen*)), this, SIGNAL(primaryScreenChanged()));
}

QDesktopWidget::~QDesktopWidget()
{
}

bool QDesktopWidget::isVirtualDesktop() const
{
    return QGuiApplication::primaryScreen()->virtualSiblings().size() > 1;
}

int QDesktopWidget::primaryScreen() const
{
    return 0;
}

int QDesktopWidget::numScreens() const
{
    return qMax(QGuiApplication::screens().size(), 1);
}

QWidget *QDesktopWidget::screen(int screen)
{
    Q_D(QDesktopWidget);
    if (screen < 0 || screen >= d->screens.length())
        return d->screens.at(0);
    return d->screens.at(screen);
}

const QRect QDesktopWidget::availableGeometry(int screenNo) const
{
    QList<QScreen *> screens = QGuiApplication::screens();
    if (screenNo == -1)
        screenNo = 0;
    if (screenNo < 0 || screenNo >= screens.size())
        return QRect();
    else
        return screens.at(screenNo)->availableGeometry();
}

const QRect QDesktopWidget::screenGeometry(int screenNo) const
{
    QList<QScreen *> screens = QGuiApplication::screens();
    if (screenNo == -1)
        screenNo = 0;
    if (screenNo < 0 || screenNo >= screens.size())
        return QRect();
    else
        return screens.at(screenNo)->geometry();
}

int QDesktopWidget::screenNumber(const QWidget *w) const
{
    if (!w)
        return primaryScreen();

    const QList<QScreen *> allScreens = QGuiApplication::screens();
    QList<QScreen *> screens = allScreens;
    if (screens.isEmpty()) // This should never happen
        return primaryScreen();

    const QWindow *winHandle = w->windowHandle();
    if (!winHandle) {
        if (const QWidget *nativeParent = w->nativeParentWidget())
            winHandle = nativeParent->windowHandle();
    }

    // If there is more than one virtual desktop
    if (screens.count() != screens.constFirst()->virtualSiblings().count()) {
        // Find the root widget, get a QScreen from it and use the
        // virtual siblings for checking the window position.
        if (winHandle) {
            if (const QScreen *winScreen = winHandle->screen())
                screens = winScreen->virtualSiblings();
        }
    }

    // Get the screen number from window position using screen geometry
    // and proper screens.
    QRect frame = w->frameGeometry();
    if (!w->isWindow())
        frame.moveTopLeft(w->mapToGlobal(QPoint(0, 0)));

    QScreen *widgetScreen = Q_NULLPTR;
    int largestArea = 0;
    foreach (QScreen *screen, screens) {
        const QRect deviceIndependentScreenGeometry =
            QHighDpi::fromNativePixels(screen->handle()->geometry(), screen);
        const QRect intersected = deviceIndependentScreenGeometry.intersected(frame);
        int area = intersected.width() * intersected.height();
        if (largestArea < area) {
            widgetScreen = screen;
            largestArea = area;
        }
    }
    return allScreens.indexOf(widgetScreen);
}

int QDesktopWidget::screenNumber(const QPoint &p) const
{
    const QList<QScreen *> screens = QGuiApplication::screens();
    if (!screens.isEmpty()) {
        const QList<QScreen *> primaryScreens = screens.first()->virtualSiblings();
        // Find the screen index on the primary virtual desktop first
        foreach (QScreen *screen, primaryScreens) {
            if (screen->geometry().contains(p))
                return screens.indexOf(screen);
        }
        // If the screen index is not found on primary virtual desktop, find
        // the screen index on all screens except the first which was for
        // sure in the previous loop. Some other screens may repeat. Find
        // only when there is more than one virtual desktop.
        if (screens.count() != primaryScreens.count()) {
            for (int i = 1; i < screens.size(); ++i) {
                if (screens[i]->geometry().contains(p))
                    return i;
            }
        }
    }
    return primaryScreen(); //even better would be closest screen
}

void QDesktopWidget::resizeEvent(QResizeEvent *)
{
}

QT_END_NAMESPACE

#include "moc_qdesktopwidget.cpp"
#include "moc_qdesktopwidget_p.cpp"