/****************************************************************************
**
** Copyright (C) 2015 The Qt Company Ltd.
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**
** This file is part of the QtWidgets module of the Qt Toolkit.
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** $QT_BEGIN_LICENSE:LGPL21$
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** Alternatively, this file may be used under the terms of the GNU Lesser
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****************************************************************************/

#include "qwindowcontainer_p.h"
#include "qwidget_p.h"
#include <QtGui/qwindow.h>
#include <QDebug>

#include <QMdiSubWindow>
#include <QAbstractScrollArea>

QT_BEGIN_NAMESPACE

class QWindowContainerPrivate : public QWidgetPrivate
{
public:
    Q_DECLARE_PUBLIC(QWindowContainer)

    QWindowContainerPrivate()
        : window(0)
        , oldFocusWindow(0)
        , usesNativeWidgets(false)
    {
    }

    ~QWindowContainerPrivate() { }

    static QWindowContainerPrivate *get(QWidget *w) {
        QWindowContainer *wc = qobject_cast<QWindowContainer *>(w);
        if (wc)
            return wc->d_func();
        return 0;
    }

    void updateGeometry() {
        Q_Q(QWindowContainer);
        if (!q->isWindow() && (q->geometry().bottom() <= 0 || q->geometry().right() <= 0))
            /* Qt (e.g. QSplitter) sometimes prefer to hide a widget by *not* calling
               setVisible(false). This is often done by setting its coordinates to a sufficiently
               negative value so that its clipped outside the parent. Since a QWindow is not clipped
               to widgets in general, it needs to be dealt with as a special case.
            */
            window->setGeometry(q->geometry());
        else if (usesNativeWidgets)
            window->setGeometry(q->rect());
        else
            window->setGeometry(QRect(q->mapTo(q->window(), QPoint()), q->size()));
    }

    void updateUsesNativeWidgets()
    {
        if (usesNativeWidgets || window->parent() == 0)
            return;
        Q_Q(QWindowContainer);
        QWidget *p = q->parentWidget();
        while (p) {
            if (
#ifndef QT_NO_MDIAREA
                qobject_cast<QMdiSubWindow *>(p) != 0 ||
#endif
                qobject_cast<QAbstractScrollArea *>(p) != 0) {
                q->winId();
                usesNativeWidgets = true;
                break;
            }
            p = p->parentWidget();
        }
    }

    void markParentChain() {
        Q_Q(QWindowContainer);
        QWidget *p = q;
        while (p) {
            QWidgetPrivate *d = static_cast<QWidgetPrivate *>(QWidgetPrivate::get(p));
            d->createExtra();
            d->extra->hasWindowContainer = true;
            p = p->parentWidget();
        }
    }

    bool isStillAnOrphan() const {
        return window->parent() == &fakeParent;
    }

    QPointer<QWindow> window;
    QWindow *oldFocusWindow;
    QWindow fakeParent;

    uint usesNativeWidgets : 1;
};



/*!
    \fn QWidget *QWidget::createWindowContainer(QWindow *window, QWidget *parent, Qt::WindowFlags flags);

    Creates a QWidget that makes it possible to embed \a window into
    a QWidget-based application.

    The window container is created as a child of \a parent and with
    window flags \a flags.

    Once the window has been embedded into the container, the
    container will control the window's geometry and
    visibility. Explicit calls to QWindow::setGeometry(),
    QWindow::show() or QWindow::hide() on an embedded window is not
    recommended.

    The container takes over ownership of \a window. The window can
    be removed from the window container with a call to
    QWindow::setParent().

    The window container is attached as a native child window to the
    toplevel window it is a child of. When a window container is used
    as a child of a QAbstractScrollArea or QMdiArea, it will
    create a \l {Native Widgets vs Alien Widgets} {native window} for
    every widget in its parent chain to allow for proper stacking and
    clipping in this use case. Applications with many native child
    windows may suffer from performance issues.

    The window container has a number of known limitations:

    \list

    \li Stacking order; The embedded window will stack on top of the
    widget hierarchy as an opaque box. The stacking order of multiple
    overlapping window container instances is undefined.

    \li Rendering Integration; The window container does not interoperate
    with QGraphicsProxyWidget, QWidget::render() or similar functionality.

    \li Focus Handling; It is possible to let the window container
    instance have any focus policy and it will delegate focus to the
    window via a call to QWindow::requestActivate(). However,
    returning to the normal focus chain from the QWindow instance will
    be up to the QWindow instance implementation itself. For instance,
    when entering a Qt Quick based window with tab focus, it is quite
    likely that further tab presses will only cycle inside the QML
    application. Also, whether QWindow::requestActivate() actually
    gives the window focus, is platform dependent.

    \li Using many window container instances in a QWidget-based
    application can greatly hurt the overall performance of the
    application.

    \endlist
 */

QWidget *QWidget::createWindowContainer(QWindow *window, QWidget *parent, Qt::WindowFlags flags)
{
    return new QWindowContainer(window, parent, flags);
}



/*!
    \internal
 */

QWindowContainer::QWindowContainer(QWindow *embeddedWindow, QWidget *parent, Qt::WindowFlags flags)
    : QWidget(*new QWindowContainerPrivate, parent, flags)
{
    Q_D(QWindowContainer);
    if (!embeddedWindow) {
        qWarning("QWindowContainer: embedded window cannot be null");
        return;
    }

    d->window = embeddedWindow;
    d->window->setParent(&d->fakeParent);
    setAcceptDrops(true);

    connect(QGuiApplication::instance(), SIGNAL(focusWindowChanged(QWindow*)), this, SLOT(focusWindowChanged(QWindow*)));
}

QWindow *QWindowContainer::containedWindow() const
{
    Q_D(const QWindowContainer);
    return d->window;
}

/*!
    \internal
 */

QWindowContainer::~QWindowContainer()
{
    Q_D(QWindowContainer);
    delete d->window;
}



/*!
    \internal
 */

void QWindowContainer::focusWindowChanged(QWindow *focusWindow)
{
    Q_D(QWindowContainer);
    d->oldFocusWindow = focusWindow;
    if (focusWindow == d->window) {
        QWidget *widget = QApplication::focusWidget();
        if (widget)
            widget->clearFocus();
    }
}

/*!
    \internal
 */

bool QWindowContainer::event(QEvent *e)
{
    Q_D(QWindowContainer);
    if (!d->window)
        return QWidget::event(e);

    QEvent::Type type = e->type();
    switch (type) {
    case QEvent::ChildRemoved: {
        QChildEvent *ce = static_cast<QChildEvent *>(e);
        if (ce->child() == d->window)
            d->window = 0;
        break;
    }
    // The only thing we are interested in is making sure our sizes stay
    // in sync, so do a catch-all case.
    case QEvent::Resize:
        d->updateGeometry();
        break;
    case QEvent::Move:
        d->updateGeometry();
        break;
    case QEvent::PolishRequest:
        d->updateGeometry();
        break;
    case QEvent::Show:
        d->updateUsesNativeWidgets();
        if (d->isStillAnOrphan()) {
            d->window->setParent(d->usesNativeWidgets
                                 ? windowHandle()
                                 : window()->windowHandle());
        }
        if (d->window->parent()) {
            d->markParentChain();
            d->window->show();
        }
        break;
    case QEvent::Hide:
        if (d->window->parent())
            d->window->hide();
        break;
    case QEvent::FocusIn:
        if (d->window->parent()) {
            if (d->oldFocusWindow != d->window) {
                d->window->requestActivate();
            } else {
                QWidget *next = nextInFocusChain();
                next->setFocus();
            }
        }
        break;
#ifndef QT_NO_DRAGANDDROP
    case QEvent::Drop:
    case QEvent::DragMove:
    case QEvent::DragLeave:
        QCoreApplication::sendEvent(d->window, e);
        return e->isAccepted();
    case QEvent::DragEnter:
        // Don't reject drag events for the entire widget when one
        // item rejects the drag enter
        QCoreApplication::sendEvent(d->window, e);
        e->accept();
        return true;
#endif
    default:
        break;
    }

    return QWidget::event(e);
}

typedef void (*qwindowcontainer_traverse_callback)(QWidget *parent);
static void qwindowcontainer_traverse(QWidget *parent, qwindowcontainer_traverse_callback callback)
{
    const QObjectList &children = parent->children();
    for (int i=0; i<children.size(); ++i) {
        QWidget *w = qobject_cast<QWidget *>(children.at(i));
        if (w) {
            QWidgetPrivate *wd = static_cast<QWidgetPrivate *>(QWidgetPrivate::get(w));
            if (wd->extra && wd->extra->hasWindowContainer)
                callback(w);
        }
    }
}

void QWindowContainer::toplevelAboutToBeDestroyed(QWidget *parent)
{
    if (QWindowContainerPrivate *d = QWindowContainerPrivate::get(parent)) {
        d->window->setParent(&d->fakeParent);
    }
    qwindowcontainer_traverse(parent, toplevelAboutToBeDestroyed);
}

void QWindowContainer::parentWasChanged(QWidget *parent)
{
    if (QWindowContainerPrivate *d = QWindowContainerPrivate::get(parent)) {
        if (d->window->parent()) {
            d->updateUsesNativeWidgets();
            d->markParentChain();
            QWidget *toplevel = d->usesNativeWidgets ? parent : parent->window();
            if (!toplevel->windowHandle()) {
                QWidgetPrivate *tld = static_cast<QWidgetPrivate *>(QWidgetPrivate::get(toplevel));
                tld->createTLExtra();
                tld->createTLSysExtra();
                Q_ASSERT(toplevel->windowHandle());
            }
            d->window->setParent(toplevel->windowHandle());
            d->updateGeometry();
        }
    }
    qwindowcontainer_traverse(parent, parentWasChanged);
}

void QWindowContainer::parentWasMoved(QWidget *parent)
{
    if (QWindowContainerPrivate *d = QWindowContainerPrivate::get(parent)) {
        if (d->window->parent())
            d->updateGeometry();
    }
    qwindowcontainer_traverse(parent, parentWasMoved);
}

void QWindowContainer::parentWasRaised(QWidget *parent)
{
    if (QWindowContainerPrivate *d = QWindowContainerPrivate::get(parent)) {
        if (d->window->parent())
            d->window->raise();
    }
    qwindowcontainer_traverse(parent, parentWasRaised);
}

void QWindowContainer::parentWasLowered(QWidget *parent)
{
    if (QWindowContainerPrivate *d = QWindowContainerPrivate::get(parent)) {
        if (d->window->parent())
            d->window->lower();
    }
    qwindowcontainer_traverse(parent, parentWasLowered);
}

QT_END_NAMESPACE
