// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only

#include "qfocusframe.h"
#include "qstyle.h"
#include "qbitmap.h"
#include "qstylepainter.h"
#include "qstyleoption.h"
#include "qdebug.h"
#include <private/qwidget_p.h>

QT_BEGIN_NAMESPACE

class QFocusFramePrivate : public QWidgetPrivate
{
    Q_DECLARE_PUBLIC(QFocusFrame)
    QWidget *widget;
    QWidget *frameParent;
    bool showFrameAboveWidget;
public:
    QFocusFramePrivate() {
        widget = nullptr;
        frameParent = nullptr;
        sendChildEvents = false;
        showFrameAboveWidget = false;
    }
    void updateSize();
    void update();
};

void QFocusFramePrivate::update()
{
    Q_Q(QFocusFrame);
    q->setParent(frameParent);
    updateSize();
    if (q->parentWidget()->rect().intersects(q->geometry())) {
        if (showFrameAboveWidget)
            q->raise();
        else
            q->stackUnder(widget);
        q->show();
    } else {
        q->hide();
    }
}

void QFocusFramePrivate::updateSize()
{
    Q_Q(QFocusFrame);
    if (!widget)
        return;

    QStyleOption opt;
    q->initStyleOption(&opt);
    int vmargin = q->style()->pixelMetric(QStyle::PM_FocusFrameVMargin, &opt, q),
        hmargin = q->style()->pixelMetric(QStyle::PM_FocusFrameHMargin, &opt, q);
    QPoint pos(widget->x(), widget->y());
    if (q->parentWidget() != widget->parentWidget())
        pos = widget->parentWidget()->mapTo(q->parentWidget(), pos);
    QRect geom(pos.x()-hmargin, pos.y()-vmargin,
               widget->width()+(hmargin*2), widget->height()+(vmargin*2));
    if (q->geometry() == geom)
        return;

    q->setGeometry(geom);

    opt.rect = q->rect();
    QStyleHintReturnMask mask;
    if (q->style()->styleHint(QStyle::SH_FocusFrame_Mask, &opt, q, &mask))
        q->setMask(mask.region);
}

/*!
    Initialize \a option with the values from this QFocusFrame. This method is useful
    for subclasses when they need a QStyleOption, but don't want to fill
    in all the information themselves.

    \sa QStyleOption::initFrom()
*/
void QFocusFrame::initStyleOption(QStyleOption *option) const
{
    if (!option)
        return;

    option->initFrom(this);
}

/*!
    \class QFocusFrame
    \brief The QFocusFrame widget provides a focus frame which can be
    outside of a widget's normal paintable area.

    \ingroup basicwidgets
    \inmodule QtWidgets

    Normally an application will not need to create its own
    QFocusFrame as QStyle will handle this detail for
    you. A style writer can optionally use a QFocusFrame to have a
    focus area outside of the widget's paintable geometry. In this way
    space need not be reserved for the widget to have focus but only
    set on a QWidget with QFocusFrame::setWidget. It is, however,
    legal to create your own QFocusFrame on a custom widget and set
    its geometry manually via QWidget::setGeometry however you will
    not get auto-placement when the focused widget changes size or
    placement.
*/

/*!
    Constructs a QFocusFrame.

    The focus frame will not monitor \a parent for updates but rather
    can be placed manually or by using QFocusFrame::setWidget. A
    QFocusFrame sets Qt::WA_NoChildEventsForParent attribute; as a
    result the parent will not receive a QEvent::ChildAdded event,
    this will make it possible to manually set the geometry of the
    QFocusFrame inside of a QSplitter or other child event monitoring
    widget.

    \sa QFocusFrame::setWidget()
*/

QFocusFrame::QFocusFrame(QWidget *parent)
    : QWidget(*new QFocusFramePrivate, parent, { })
{
    setAttribute(Qt::WA_TransparentForMouseEvents);
    setFocusPolicy(Qt::NoFocus);
    setAttribute(Qt::WA_NoChildEventsForParent, true);
    setAttribute(Qt::WA_AcceptDrops, style()->styleHint(QStyle::SH_FocusFrame_AboveWidget, nullptr, this));
}

/*!
    Destructor.
*/

QFocusFrame::~QFocusFrame()
{
}

/*!
  QFocusFrame will track changes to \a widget and resize itself automatically.
  If the monitored widget's parent changes, QFocusFrame will follow the widget
  and place itself around the widget automatically. If the monitored widget is deleted,
  QFocusFrame will set it to zero.

  \sa QFocusFrame::widget()
*/

void
QFocusFrame::setWidget(QWidget *widget)
{
    Q_D(QFocusFrame);

    if (style()->styleHint(QStyle::SH_FocusFrame_AboveWidget, nullptr, this))
        d->showFrameAboveWidget = true;
    else
        d->showFrameAboveWidget = false;

    if (widget == d->widget)
        return;
    if (d->widget) {
        // Remove event filters from the widget hierarchy.
        QWidget *p = d->widget;
        do {
            p->removeEventFilter(this);
            if (!d->showFrameAboveWidget || p == d->frameParent)
                break;
            p = p->parentWidget();
        }while (p);
    }
    if (widget && !widget->isWindow() && widget->parentWidget()->windowType() != Qt::SubWindow) {
        d->widget = widget;
        d->widget->installEventFilter(this);
        QWidget *p = widget->parentWidget();
        QWidget *prev = nullptr;
        if (d->showFrameAboveWidget) {
            // Find the right parent for the focus frame.
            while (p) {
                // Traverse the hirerarchy of the 'widget' for setting event filter.
                // During this if come across toolbar or a top level, use that
                // as the parent for the focus frame. If we find a scroll area
                // use its viewport as the parent.
                bool isScrollArea = false;
                if (p->isWindow() || p->inherits("QToolBar") || (isScrollArea = p->inherits("QAbstractScrollArea"))) {
                    d->frameParent = p;
                    // The previous one in the hierarchy will be the viewport.
                    if (prev && isScrollArea)
                        d->frameParent = prev;
                    break;
                } else {
                    p->installEventFilter(this);
                    prev = p;
                    p = p->parentWidget();
                }
            }
        } else {
            d->frameParent = p;
        }
        d->update();
    } else {
        d->widget = nullptr;
        hide();
    }
}

/*!
  Returns the currently monitored widget for automatically resize and
  update.

   \sa QFocusFrame::setWidget()
*/

QWidget *
QFocusFrame::widget() const
{
    Q_D(const QFocusFrame);
    return d->widget;
}


/*! \reimp */
void
QFocusFrame::paintEvent(QPaintEvent *)
{
    Q_D(QFocusFrame);

    if (!d->widget)
        return;

    QStylePainter p(this);
    QStyleOption option;
    initStyleOption(&option);
    const int vmargin = style()->pixelMetric(QStyle::PM_FocusFrameVMargin, &option, this);
    const int hmargin = style()->pixelMetric(QStyle::PM_FocusFrameHMargin, &option, this);
    QWidgetPrivate *wd = qt_widget_private(d->widget);
    QRect rect = wd->clipRect().adjusted(0, 0, hmargin*2, vmargin*2);
    p.setClipRect(rect);
    p.drawControl(QStyle::CE_FocusFrame, option);
}


/*! \reimp */
bool
QFocusFrame::eventFilter(QObject *o, QEvent *e)
{
    Q_D(QFocusFrame);
    if (o == d->widget) {
        switch(e->type()) {
        case QEvent::Move:
        case QEvent::Resize:
            d->updateSize();
            break;
        case QEvent::Hide:
        case QEvent::StyleChange:
            hide();
            break;
        case QEvent::ParentChange:
            if (d->showFrameAboveWidget) {
                QWidget *w = d->widget;
                setWidget(nullptr);
                setWidget(w);
            } else {
                d->update();
            }
            break;
        case QEvent::Show:
            d->update();
            show();
            break;
        case QEvent::PaletteChange:
            setPalette(d->widget->palette());
            break;
        case QEvent::ZOrderChange:
            if (style()->styleHint(QStyle::SH_FocusFrame_AboveWidget, nullptr, this))
                raise();
            else
                stackUnder(d->widget);
            break;
        case QEvent::Destroy:
            setWidget(nullptr);
            break;
        default:
            break;
        }
    } else if (d->showFrameAboveWidget) {
        // Handle changes in the parent widgets we are monitoring.
        switch(e->type()) {
        case QEvent::Move:
        case QEvent::Resize:
            d->updateSize();
            break;
        case QEvent::ZOrderChange:
            raise();
            break;
        default:
            break;
        }
    }
    return false;
}

/*! \reimp */
bool QFocusFrame::event(QEvent *e)
{
    Q_D(QFocusFrame);

    switch (e->type()) {
    case QEvent::Move:
    case QEvent::Resize:
        if (d->widget) {
            // When we're tracking a widget, we don't allow anyone to move the focus frame around.
            // We do our best with event filters to make it stay on top of the widget, so trying to
            // move the frame somewhere else will be flaky at best. This can e.g happen for general
            // purpose code, like QAbstractScrollView, that bulk-moves all children a certain distance.
            // So we need to call updateSize() when that happens to ensure that the focus frame stays
            // on top of the widget.
            d->updateSize();
        }
        break;
    default:
        return QWidget::event(e);
    }
    return true;
}

QT_END_NAMESPACE

#include "moc_qfocusframe.cpp"