/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtWidgets module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
** Public license version 3 or any later version approved by the KDE Free
** Qt Foundation. The licenses are as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-2.0.html and
** https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qsizegrip.h"

#ifndef QT_NO_SIZEGRIP

#include "qapplication.h"
#include "qevent.h"
#include "qpainter.h"
#include "qwindow.h"
#include <qpa/qplatformwindow.h>
#include "qstyle.h"
#include "qstyleoption.h"
#include "qlayout.h"
#include "qdebug.h"
#include <QDesktopWidget>

#if 0 // Used to be included in Qt4 for Q_WS_MAC
#include <private/qt_mac_p.h>
#endif

#include <private/qwidget_p.h>
#include <QtWidgets/qabstractscrollarea.h>

QT_BEGIN_NAMESPACE

static QWidget *qt_sizegrip_topLevelWidget(QWidget* w)
{
    while (w && !w->isWindow() && w->windowType() != Qt::SubWindow)
        w = w->parentWidget();
    return w;
}

class QSizeGripPrivate : public QWidgetPrivate
{
    Q_DECLARE_PUBLIC(QSizeGrip)
public:
    QSizeGripPrivate();
    void init();
    QPoint p;
    QRect r;
    int d;
    int dxMax;
    int dyMax;
    Qt::Corner m_corner;
    bool gotMousePress;
    QPointer<QWidget> tlw;
#if 0 // Used to be included in Qt4 for Q_WS_MAC
    void updateMacSizer(bool hide) const;
#endif
    Qt::Corner corner() const;
    inline bool atBottom() const
    {
        return m_corner == Qt::BottomRightCorner || m_corner == Qt::BottomLeftCorner;
    }

    inline bool atLeft() const
    {
        return m_corner == Qt::BottomLeftCorner || m_corner == Qt::TopLeftCorner;
    }

    void updateTopLevelWidget()
    {
        Q_Q(QSizeGrip);
        QWidget *w = qt_sizegrip_topLevelWidget(q);
        if (tlw == w)
            return;
        if (tlw)
            tlw->removeEventFilter(q);
        tlw = w;
        if (tlw)
            tlw->installEventFilter(q);
    }

    // This slot is invoked by QLayout when the size grip is added to
    // a layout or reparented after the tlw is shown. This re-implementation is basically
    // the same as QWidgetPrivate::_q_showIfNotHidden except that it checks
    // for Qt::WindowFullScreen and Qt::WindowMaximized as well.
    void _q_showIfNotHidden()
    {
        Q_Q(QSizeGrip);
        bool showSizeGrip = !(q->isHidden() && q->testAttribute(Qt::WA_WState_ExplicitShowHide));
        updateTopLevelWidget();
        if (tlw && showSizeGrip) {
            Qt::WindowStates sizeGripNotVisibleState = Qt::WindowFullScreen;
#if 1 // Used to be excluded in Qt4 for Q_WS_MAC
            sizeGripNotVisibleState |= Qt::WindowMaximized;
#endif
            // Don't show the size grip if the tlw is maximized or in full screen mode.
            showSizeGrip = !(tlw->windowState() & sizeGripNotVisibleState);
        }
        if (showSizeGrip)
            q->setVisible(true);
    }

    bool m_platformSizeGrip;
};

QSizeGripPrivate::QSizeGripPrivate()
    : dxMax(0)
    , dyMax(0)
    , gotMousePress(false)
    , tlw(0)
    , m_platformSizeGrip(false)
{
}

#if 0 // Used to be included in Qt4 for Q_WS_MAC
void QSizeGripPrivate::updateMacSizer(bool hide) const
{
    Q_Q(const QSizeGrip);
    if (QApplication::closingDown() || !parent)
        return;
    QWidget *topLevelWindow = qt_sizegrip_topLevelWidget(const_cast<QSizeGrip *>(q));
    if(topLevelWindow && topLevelWindow->isWindow())
        QWidgetPrivate::qt_mac_update_sizer(topLevelWindow, hide ? -1 : 1);
}
#endif

Qt::Corner QSizeGripPrivate::corner() const
{
    Q_Q(const QSizeGrip);
    QWidget *tlw = qt_sizegrip_topLevelWidget(const_cast<QSizeGrip *>(q));
    const QPoint sizeGripPos = q->mapTo(tlw, QPoint(0, 0));
    bool isAtBottom = sizeGripPos.y() >= tlw->height() / 2;
    bool isAtLeft = sizeGripPos.x() <= tlw->width() / 2;
    if (isAtLeft)
        return isAtBottom ? Qt::BottomLeftCorner : Qt::TopLeftCorner;
    else
        return isAtBottom ? Qt::BottomRightCorner : Qt::TopRightCorner;
}

/*!
    \class QSizeGrip

    \brief The QSizeGrip class provides a resize handle for resizing top-level windows.

    \ingroup mainwindow-classes
    \ingroup basicwidgets
    \inmodule QtWidgets

    This widget works like the standard Windows resize handle. In the
    X11 version this resize handle generally works differently from
    the one provided by the system if the X11 window manager does not
    support necessary modern post-ICCCM specifications.

    Put this widget anywhere in a widget tree and the user can use it
    to resize the top-level window or any widget with the Qt::SubWindow
    flag set. Generally, this should be in the lower right-hand corner.

    Note that QStatusBar already uses this widget, so if you have a
    status bar (e.g., you are using QMainWindow), then you don't need
    to use this widget explicitly. The same goes for QDialog, for which
    you can just call \l {QDialog::setSizeGripEnabled()}
    {QDialog::setSizeGripEnabled()}.

    On some platforms the size grip automatically hides itself when the
    window is shown full screen or maximised.

    \table 50%
    \row \li \inlineimage fusion-statusbar-sizegrip.png Screenshot of a Fusion style size grip
    \li A size grip widget at the bottom-right corner of a main window, shown in the
    \l{Fusion Style Widget Gallery}{Fusion widget style}.
    \endtable

    The QSizeGrip class inherits QWidget and reimplements the \l
    {QWidget::mousePressEvent()}{mousePressEvent()} and \l
    {QWidget::mouseMoveEvent()}{mouseMoveEvent()} functions to feature
    the resize functionality, and the \l
    {QWidget::paintEvent()}{paintEvent()} function to render the
    size grip widget.

    \sa QStatusBar, QWidget::windowState()
*/


/*!
    Constructs a resize corner as a child widget of  the given \a
    parent.
*/
QSizeGrip::QSizeGrip(QWidget * parent)
    : QWidget(*new QSizeGripPrivate, parent, 0)
{
    Q_D(QSizeGrip);
    d->init();
}


void QSizeGripPrivate::init()
{
    Q_Q(QSizeGrip);
    m_corner = q->isLeftToRight() ? Qt::BottomRightCorner : Qt::BottomLeftCorner;

#if !defined(QT_NO_CURSOR) && !0 /* Used to be included in Qt4 for Q_WS_MAC */
    q->setCursor(m_corner == Qt::TopLeftCorner || m_corner == Qt::BottomRightCorner
                 ? Qt::SizeFDiagCursor : Qt::SizeBDiagCursor);
#endif
    q->setSizePolicy(QSizePolicy(QSizePolicy::Minimum, QSizePolicy::Fixed));
    updateTopLevelWidget();
}


/*!
    Destroys this size grip.
*/
QSizeGrip::~QSizeGrip()
{
}

/*!
  \reimp
*/
QSize QSizeGrip::sizeHint() const
{
    QStyleOption opt(0);
    opt.init(this);
    return (style()->sizeFromContents(QStyle::CT_SizeGrip, &opt, QSize(13, 13), this).
            expandedTo(QApplication::globalStrut()));
}

/*!
    Paints the resize grip.

    Resize grips are usually rendered as small diagonal textured lines
    in the lower-right corner. The paint event is passed in the \a
    event parameter.
*/
void QSizeGrip::paintEvent(QPaintEvent *event)
{
    Q_UNUSED(event);
    Q_D(QSizeGrip);
    QPainter painter(this);
    QStyleOptionSizeGrip opt;
    opt.init(this);
    opt.corner = d->m_corner;
    style()->drawControl(QStyle::CE_SizeGrip, &opt, &painter, this);
}

/*!
    \fn void QSizeGrip::mousePressEvent(QMouseEvent * event)

    Receives the mouse press events for the widget, and primes the
    resize operation. The mouse press event is passed in the \a event
    parameter.
*/

void QSizeGrip::mousePressEvent(QMouseEvent * e)
{
    if (e->button() != Qt::LeftButton) {
        QWidget::mousePressEvent(e);
        return;
    }

    Q_D(QSizeGrip);
    QWidget *tlw = qt_sizegrip_topLevelWidget(this);
    d->p = e->globalPos();
    d->gotMousePress = true;
    d->r = tlw->geometry();

    // Does the platform provide size grip support?
    d->m_platformSizeGrip = false;
    if (tlw->isWindow()
        && tlw->windowHandle()
        && !(tlw->windowFlags() & Qt::X11BypassWindowManagerHint)
        && !tlw->testAttribute(Qt::WA_DontShowOnScreen)
        && !tlw->hasHeightForWidth()) {
        QPlatformWindow *platformWindow = tlw->windowHandle()->handle();
        const QPoint topLevelPos = mapTo(tlw, e->pos());
        d->m_platformSizeGrip = platformWindow && platformWindow->startSystemResize(topLevelPos, d->m_corner);
    }

    if (d->m_platformSizeGrip)
        return;

    // Find available desktop/workspace geometry.
    QRect availableGeometry;
    bool hasVerticalSizeConstraint = true;
    bool hasHorizontalSizeConstraint = true;
    if (tlw->isWindow())
        availableGeometry = QApplication::desktop()->availableGeometry(tlw);
    else {
        const QWidget *tlwParent = tlw->parentWidget();
        // Check if tlw is inside QAbstractScrollArea/QScrollArea.
        // If that's the case tlw->parentWidget() will return the viewport
        // and tlw->parentWidget()->parentWidget() will return the scroll area.
#ifndef QT_NO_SCROLLAREA
        QAbstractScrollArea *scrollArea = qobject_cast<QAbstractScrollArea *>(tlwParent->parentWidget());
        if (scrollArea) {
            hasHorizontalSizeConstraint = scrollArea->horizontalScrollBarPolicy() == Qt::ScrollBarAlwaysOff;
            hasVerticalSizeConstraint = scrollArea->verticalScrollBarPolicy() == Qt::ScrollBarAlwaysOff;
        }
#endif // QT_NO_SCROLLAREA
        availableGeometry = tlwParent->contentsRect();
    }

    // Find frame geometries, title bar height, and decoration sizes.
    const QRect frameGeometry = tlw->frameGeometry();
    const int titleBarHeight = qMax(tlw->geometry().y() - frameGeometry.y(), 0);
    const int bottomDecoration = qMax(frameGeometry.height() - tlw->height() - titleBarHeight, 0);
    const int leftRightDecoration = qMax((frameGeometry.width() - tlw->width()) / 2, 0);

    // Determine dyMax depending on whether the sizegrip is at the bottom
    // of the widget or not.
    if (d->atBottom()) {
        if (hasVerticalSizeConstraint)
            d->dyMax = availableGeometry.bottom() - d->r.bottom() - bottomDecoration;
        else
            d->dyMax = INT_MAX;
    } else {
        if (hasVerticalSizeConstraint)
            d->dyMax = availableGeometry.y() - d->r.y() + titleBarHeight;
        else
            d->dyMax = -INT_MAX;
    }

    // In RTL mode, the size grip is to the left; find dxMax from the desktop/workspace
    // geometry, the size grip geometry and the width of the decoration.
    if (d->atLeft()) {
        if (hasHorizontalSizeConstraint)
            d->dxMax = availableGeometry.x() - d->r.x() + leftRightDecoration;
        else
            d->dxMax = -INT_MAX;
    } else {
        if (hasHorizontalSizeConstraint)
            d->dxMax = availableGeometry.right() - d->r.right() - leftRightDecoration;
        else
            d->dxMax = INT_MAX;
    }
}


/*!
    \fn void QSizeGrip::mouseMoveEvent(QMouseEvent * event)
    Resizes the top-level widget containing this widget. The mouse
    move event is passed in the \a event parameter.
*/
void QSizeGrip::mouseMoveEvent(QMouseEvent * e)
{
    Q_D(QSizeGrip);
    if (e->buttons() != Qt::LeftButton || d->m_platformSizeGrip) {
        QWidget::mouseMoveEvent(e);
        return;
    }

    QWidget* tlw = qt_sizegrip_topLevelWidget(this);
    if (!d->gotMousePress || tlw->testAttribute(Qt::WA_WState_ConfigPending))
        return;

    QPoint np(e->globalPos());

    // Don't extend beyond the available geometry; bound to dyMax and dxMax.
    QSize ns;
    if (d->atBottom())
        ns.rheight() = d->r.height() + qMin(np.y() - d->p.y(), d->dyMax);
    else
        ns.rheight() = d->r.height() - qMax(np.y() - d->p.y(), d->dyMax);

    if (d->atLeft())
        ns.rwidth() = d->r.width() - qMax(np.x() - d->p.x(), d->dxMax);
    else
        ns.rwidth() = d->r.width() + qMin(np.x() - d->p.x(), d->dxMax);

    ns = QLayout::closestAcceptableSize(tlw, ns);

    QPoint p;
    QRect nr(p, ns);
    if (d->atBottom()) {
        if (d->atLeft())
            nr.moveTopRight(d->r.topRight());
        else
            nr.moveTopLeft(d->r.topLeft());
    } else {
        if (d->atLeft())
            nr.moveBottomRight(d->r.bottomRight());
        else
            nr.moveBottomLeft(d->r.bottomLeft());
    }

    tlw->setGeometry(nr);
}

/*!
  \reimp
*/
void QSizeGrip::mouseReleaseEvent(QMouseEvent *mouseEvent)
{
    if (mouseEvent->button() == Qt::LeftButton) {
        Q_D(QSizeGrip);
        d->gotMousePress = false;
        d->p = QPoint();
    } else {
        QWidget::mouseReleaseEvent(mouseEvent);
    }
}

/*!
  \reimp
*/
void QSizeGrip::moveEvent(QMoveEvent * /*moveEvent*/)
{
    Q_D(QSizeGrip);
    // We're inside a resize operation; no update necessary.
    if (!d->p.isNull())
        return;

    d->m_corner = d->corner();
#if !defined(QT_NO_CURSOR) && !0 /* Used to be included in Qt4 for Q_WS_MAC */
    setCursor(d->m_corner == Qt::TopLeftCorner || d->m_corner == Qt::BottomRightCorner
              ? Qt::SizeFDiagCursor : Qt::SizeBDiagCursor);
#endif
}

/*!
  \reimp
*/
void QSizeGrip::showEvent(QShowEvent *showEvent)
{
#if 0 // Used to be included in Qt4 for Q_WS_MAC
    d_func()->updateMacSizer(false);
#endif
    QWidget::showEvent(showEvent);
}

/*!
  \reimp
*/
void QSizeGrip::hideEvent(QHideEvent *hideEvent)
{
#if 0 // Used to be included in Qt4 for Q_WS_MAC
    d_func()->updateMacSizer(true);
#endif
    QWidget::hideEvent(hideEvent);
}

/*!
    \reimp
*/
void QSizeGrip::setVisible(bool visible)
{
    QWidget::setVisible(visible);
}

/*! \reimp */
bool QSizeGrip::eventFilter(QObject *o, QEvent *e)
{
    Q_D(QSizeGrip);
    if ((isHidden() && testAttribute(Qt::WA_WState_ExplicitShowHide))
        || e->type() != QEvent::WindowStateChange
        || o != d->tlw) {
        return QWidget::eventFilter(o, e);
    }
    Qt::WindowStates sizeGripNotVisibleState = Qt::WindowFullScreen;
#if 1 // Used to be excluded in Qt4 for Q_WS_MAC
    sizeGripNotVisibleState |= Qt::WindowMaximized;
#endif
    // Don't show the size grip if the tlw is maximized or in full screen mode.
    setVisible(!(d->tlw->windowState() & sizeGripNotVisibleState));
    setAttribute(Qt::WA_WState_ExplicitShowHide, false);
    return QWidget::eventFilter(o, e);
}

/*!
    \reimp
*/
bool QSizeGrip::event(QEvent *event)
{
    return QWidget::event(event);
}

QT_END_NAMESPACE

#include "moc_qsizegrip.cpp"

#endif //QT_NO_SIZEGRIP