qquickscrollbar.cpp

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// Copyright (C) 2017 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 "qquickscrollbar_p.h"
#include "qquickscrollbar_p_p.h"
#include "qquickscrollview_p.h"
 
#include <QtQml/qqmlinfo.h>
#include <QtQuick/private/qquickflickable_p.h>
#if QT_CONFIG(accessibility)
#include <QtQuick/private/qquickaccessibleattached_p.h>
#endif
 
QT_BEGIN_NAMESPACE
 
 
static const QQuickItemPrivate::ChangeTypes QsbChangeTypes = QQuickItemPrivate::Geometry | QQuickItemPrivate::Destroyed;
static const QQuickItemPrivate::ChangeTypes QsbHorizontalChangeTypes = QsbChangeTypes | QQuickItemPrivate::ImplicitHeight;
static const QQuickItemPrivate::ChangeTypes QsbVerticalChangeTypes = QsbChangeTypes | QQuickItemPrivate::ImplicitWidth;
 
QQuickScrollBarPrivate::VisualArea QQuickScrollBarPrivate::visualArea() const
{
    qreal visualPos = position;
 
    if (minimumSize > size && size != 1.0)
        visualPos = position / (1.0 - size) * (1.0 - minimumSize);
 
    qreal maximumSize = qMax<qreal>(0.0, 1.0 - visualPos);
    qreal visualSize =  qMax<qreal>(minimumSize,
                                    qMin<qreal>(qMax(size, minimumSize) + qMin<qreal>(0, visualPos),
                                                maximumSize));
 
    visualPos = qMax<qreal>(0,qMin<qreal>(visualPos,qMax<qreal>(0, 1.0 - visualSize)));
 
    return VisualArea(visualPos, visualSize);
}
 
qreal QQuickScrollBarPrivate::logicalPosition(qreal position) const
{
    if (minimumSize > size && minimumSize != 1.0)
        return position * (1.0 - size) / (1.0 - minimumSize);
    return position;
}
 
qreal QQuickScrollBarPrivate::snapPosition(qreal position) const
{
    const qreal effectiveStep = stepSize * (1.0 - size);
    if (qFuzzyIsNull(effectiveStep))
        return position;
 
    return qRound(position / effectiveStep) * effectiveStep;
}
 
qreal QQuickScrollBarPrivate::positionAt(const QPointF &point) const
{
    Q_Q(const QQuickScrollBar);
    if (orientation == Qt::Horizontal)
        return logicalPosition(point.x() - q->leftPadding()) / q->availableWidth();
    else
        return logicalPosition(point.y() - q->topPadding()) / q->availableHeight();
}
 
void QQuickScrollBarPrivate::setInteractive(bool enabled)
{
    Q_Q(QQuickScrollBar);
    if (interactive == enabled)
        return;
 
    interactive = enabled;
    if (interactive) {
        q->setAcceptedMouseButtons(Qt::LeftButton);
#if QT_CONFIG(quicktemplates2_multitouch)
        q->setAcceptTouchEvents(true);
#endif
#if QT_CONFIG(cursor)
        q->setCursor(Qt::ArrowCursor);
#endif
    } else {
        q->setAcceptedMouseButtons(Qt::NoButton);
#if QT_CONFIG(quicktemplates2_multitouch)
        q->setAcceptTouchEvents(false);
#endif
#if QT_CONFIG(cursor)
        q->unsetCursor();
#endif
        q->ungrabMouse();
    }
    emit q->interactiveChanged();
}
 
void QQuickScrollBarPrivate::updateActive()
{
    Q_Q(QQuickScrollBar);
#if QT_CONFIG(quicktemplates2_hover)
    bool hover = hovered;
#else
    bool hover = false;
#endif
    q->setActive(moving || (interactive && (pressed || hover)));
}
 
void QQuickScrollBarPrivate::resizeContent()
{
    Q_Q(QQuickScrollBar);
    if (!contentItem)
        return;
 
    // - negative overshoot (pos < 0): clamp the pos to 0, and deduct the overshoot from the size
    // - positive overshoot (pos + size > 1): clamp the size to 1-pos
    const VisualArea visual = visualArea();
 
    if (orientation == Qt::Horizontal) {
        contentItem->setPosition(QPointF(q->leftPadding() + visual.position * q->availableWidth(), q->topPadding()));
        contentItem->setSize(QSizeF(q->availableWidth() * visual.size, q->availableHeight()));
    } else {
        contentItem->setPosition(QPointF(q->leftPadding(), q->topPadding() + visual.position * q->availableHeight()));
        contentItem->setSize(QSizeF(q->availableWidth(), q->availableHeight() * visual.size));
    }
}
 
void QQuickScrollBarPrivate::itemImplicitWidthChanged(QQuickItem *item)
{
    Q_Q(QQuickScrollBar);
    QQuickControlPrivate::itemImplicitWidthChanged(item);
    QQuickIndicatorButton *indicatorButton = q->decreaseVisual();
    if (!indicatorButton || item != indicatorButton->indicator()) {
        indicatorButton = q->increaseVisual();
        if (!indicatorButton || item != indicatorButton->indicator())
            return;
    }
    if (indicatorButton)
        emit indicatorButton->implicitIndicatorWidthChanged();
}
 
void QQuickScrollBarPrivate::itemImplicitHeightChanged(QQuickItem *item)
{
    Q_Q(QQuickScrollBar);
    QQuickControlPrivate::itemImplicitHeightChanged(item);
    QQuickIndicatorButton *indicatorButton = q->decreaseVisual();
    if (!indicatorButton || item != indicatorButton->indicator()) {
        indicatorButton = q->increaseVisual();
        if (!indicatorButton || item != indicatorButton->indicator())
            return;
    }
    if (indicatorButton)
        emit indicatorButton->implicitIndicatorHeightChanged();
}
 
bool QQuickScrollBarPrivate::handlePress(const QPointF &point, ulong timestamp)
{
    Q_Q(QQuickScrollBar);
    QQuickControlPrivate::handlePress(point, timestamp);
    if (QQuickIndicatorButton *indicatorButton = q->decreaseVisual()) {
        QQuickItem *decreaseArrow = indicatorButton->indicator();
        if (decreaseArrow && decreaseArrow->contains(q->mapToItem(decreaseArrow, point + QPointF(0.5, 0.5)))) {
            indicatorButton->setPressed(true);
            q->decrease();
            return true;
        }
    }
 
    if (QQuickIndicatorButton *increaseObject = q->increaseVisual()) {
        QQuickItem *increaseArrow = increaseObject->indicator();
        if (increaseArrow && increaseArrow->contains(q->mapToItem(increaseArrow, point + QPointF(0.5, 0.5)))) {
            increaseObject->setPressed(true);
            q->increase();
            return true;
        }
    }
 
    offset = positionAt(point) - position;
    qreal sz = qMax(size, logicalPosition(minimumSize));
    if (offset < 0 || offset > sz)
        offset = sz / 2;
    q->setPressed(true);
    return true;
}
 
bool QQuickScrollBarPrivate::handleMove(const QPointF &point, ulong timestamp)
{
    Q_Q(QQuickScrollBar);
    QQuickControlPrivate::handleMove(point, timestamp);
 
    /*
     * handleMove() will be called as soon as you hold the mouse button down *anywhere* on the
     * ScrollBar, including the increase/decrease button indicator areas. So without the following
     * early return, it would move the scrollbar handle to one of its extremeties. That would
     * ruin the behavior we would like when clicking e.g. the "increase button": To step the
     * scrollbar gently.
     */
    if (!pressed)
        return true;
 
    qreal pos = qMax<qreal>(0.0, qMin<qreal>(positionAt(point) - offset, 1.0 - size));
    if (snapMode == QQuickScrollBar::SnapAlways)
        pos = snapPosition(pos);
    q->setPosition(pos);
    return true;
}
 
bool QQuickScrollBarPrivate::handleRelease(const QPointF &point, ulong timestamp)
{
    Q_Q(QQuickScrollBar);
    QQuickControlPrivate::handleRelease(point, timestamp);
 
    if (orientation == Qt::Vertical) {
        if (point.y() < q->topPadding() || point.y() >= (q->height() - q->bottomPadding()))
            return true;
    } else /* orientation == Qt::Horizontal */{
        if (point.x() < q->leftPadding() || point.x() >= (q->width() - q->rightPadding()))
            return true;
    }
 
    qreal pos = qMax<qreal>(0.0, qMin<qreal>(positionAt(point) - offset, 1.0 - size));
    if (snapMode != QQuickScrollBar::NoSnap)
        pos = snapPosition(pos);
    q->setPosition(pos);
    offset = 0.0;
    q->setPressed(false);
    return true;
}
 
void QQuickScrollBarPrivate::handleUngrab()
{
    Q_Q(QQuickScrollBar);
    QQuickControlPrivate::handleUngrab();
    offset = 0.0;
    q->setPressed(false);
}
 
void QQuickScrollBarPrivate::visualAreaChange(const VisualArea &newVisualArea, const VisualArea &oldVisualArea)
{
    Q_Q(QQuickScrollBar);
    if (!qFuzzyCompare(newVisualArea.size, oldVisualArea.size))
        emit q->visualSizeChanged();
    if (!qFuzzyCompare(newVisualArea.position, oldVisualArea.position))
        emit q->visualPositionChanged();
}
 
void QQuickScrollBarPrivate::updateHover(const QPointF &pos, std::optional<bool> newHoverState)
{
    Q_Q(QQuickScrollBar);
    auto updateHoverOnButton = [&](QQuickIndicatorButton *sbButton) {
        if (sbButton) {
            bool hovered = newHoverState.value_or(false);
            if (!newHoverState.has_value()) {
                if (QQuickItem *indicator = sbButton->indicator())
                    hovered = indicator->contains(q->mapToItem(indicator, pos));
            }
            sbButton->setHovered(hovered);
        }
    };
    updateHoverOnButton(q->decreaseVisual());
    updateHoverOnButton(q->increaseVisual());
}
 
QQuickScrollBar::QQuickScrollBar(QQuickItem *parent)
    : QQuickControl(*(new QQuickScrollBarPrivate), parent)
{
    Q_D(QQuickScrollBar);
    d->decreaseVisual = new QQuickIndicatorButton(this);
    d->increaseVisual = new QQuickIndicatorButton(this);
    setKeepMouseGrab(true);
    setAcceptedMouseButtons(Qt::LeftButton);
#if QT_CONFIG(quicktemplates2_multitouch)
    setAcceptTouchEvents(true);
#endif
#if QT_CONFIG(cursor)
    setCursor(Qt::ArrowCursor);
#endif
}
 
QQuickScrollBarAttached *QQuickScrollBar::qmlAttachedProperties(QObject *object)
{
    return new QQuickScrollBarAttached(object);
}
 
qreal QQuickScrollBar::size() const
{
    Q_D(const QQuickScrollBar);
    return d->size;
}
 
void QQuickScrollBar::setSize(qreal size)
{
    Q_D(QQuickScrollBar);
    if (!qt_is_finite(size))
        return;
    size = qBound(0.0, size, 1.0);
    if (qFuzzyCompare(d->size, size))
        return;
    d->size = size;
 
    auto oldVisualArea = d->visualArea();
    d->size = qBound(0.0, size, 1.0);
    if (d->size + d->position > 1.0) {
        setPosition(1.0 - d->size);
        oldVisualArea = d->visualArea();
    }
 
    if (isComponentComplete())
        d->resizeContent();
    emit sizeChanged();
    d->visualAreaChange(d->visualArea(), oldVisualArea);
}
 
qreal QQuickScrollBar::position() const
{
    Q_D(const QQuickScrollBar);
    return d->position;
}
 
void QQuickScrollBar::setPosition(qreal position)
{
    Q_D(QQuickScrollBar);
    if (!qt_is_finite(position) || qFuzzyCompare(d->position, position))
        return;
 
    auto oldVisualArea = d->visualArea();
    d->position = position;
    if (isComponentComplete())
        d->resizeContent();
    emit positionChanged();
    d->visualAreaChange(d->visualArea(), oldVisualArea);
}
 
qreal QQuickScrollBar::stepSize() const
{
    Q_D(const QQuickScrollBar);
    return d->stepSize;
}
 
void QQuickScrollBar::setStepSize(qreal step)
{
    Q_D(QQuickScrollBar);
    if (!qt_is_finite(step) || qFuzzyCompare(d->stepSize, step))
        return;
 
    d->stepSize = step;
    emit stepSizeChanged();
}
 
bool QQuickScrollBar::isActive() const
{
    Q_D(const QQuickScrollBar);
    return d->active;
}
 
void QQuickScrollBar::setActive(bool active)
{
    Q_D(QQuickScrollBar);
    if (d->active == active)
        return;
 
    d->active = active;
    emit activeChanged();
}
 
bool QQuickScrollBar::isPressed() const
{
    Q_D(const QQuickScrollBar);
    return d->pressed;
}
 
void QQuickScrollBar::setPressed(bool pressed)
{
    Q_D(QQuickScrollBar);
    if (!pressed) {
        if (QQuickIndicatorButton *button = decreaseVisual())
            button->setPressed(false);
        if (QQuickIndicatorButton *button = increaseVisual())
            button->setPressed(false);
    }
    if (d->pressed == pressed)
        return;
 
    d->pressed = pressed;
    setAccessibleProperty("pressed", pressed);
    d->updateActive();
    emit pressedChanged();
}
 
Qt::Orientation QQuickScrollBar::orientation() const
{
    Q_D(const QQuickScrollBar);
    return d->orientation;
}
 
void QQuickScrollBar::setOrientation(Qt::Orientation orientation)
{
    Q_D(QQuickScrollBar);
    if (d->orientation == orientation)
        return;
 
    d->orientation = orientation;
    if (isComponentComplete())
        d->resizeContent();
    emit orientationChanged();
}
 
QQuickScrollBar::SnapMode QQuickScrollBar::snapMode() const
{
    Q_D(const QQuickScrollBar);
    return d->snapMode;
}
 
void QQuickScrollBar::setSnapMode(SnapMode mode)
{
    Q_D(QQuickScrollBar);
    if (d->snapMode == mode)
        return;
 
    d->snapMode = mode;
    emit snapModeChanged();
}
 
bool QQuickScrollBar::isInteractive() const
{
    Q_D(const QQuickScrollBar);
    return d->interactive;
}
 
void QQuickScrollBar::setInteractive(bool interactive)
{
    Q_D(QQuickScrollBar);
    d->explicitInteractive = true;
    d->setInteractive(interactive);
}
 
void QQuickScrollBar::resetInteractive()
{
    Q_D(QQuickScrollBar);
    d->explicitInteractive = false;
    d->setInteractive(true);
}
 
QQuickScrollBar::Policy QQuickScrollBar::policy() const
{
    Q_D(const QQuickScrollBar);
    return d->policy;
}
 
void QQuickScrollBar::setPolicy(Policy policy)
{
    Q_D(QQuickScrollBar);
    if (d->policy == policy)
        return;
 
    d->policy = policy;
    emit policyChanged();
}
 
bool QQuickScrollBar::isHorizontal() const
{
    Q_D(const QQuickScrollBar);
    return d->orientation == Qt::Horizontal;
}
 
bool QQuickScrollBar::isVertical() const
{
    Q_D(const QQuickScrollBar);
    return d->orientation == Qt::Vertical;
}
 
qreal QQuickScrollBar::minimumSize() const
{
    Q_D(const QQuickScrollBar);
    return d->minimumSize;
}
 
void QQuickScrollBar::setMinimumSize(qreal minimumSize)
{
    Q_D(QQuickScrollBar);
    if (!qt_is_finite(minimumSize) || qFuzzyCompare(d->minimumSize, minimumSize))
        return;
 
    auto oldVisualArea = d->visualArea();
    d->minimumSize = qBound(0.0, minimumSize, 1.0);
    if (isComponentComplete())
        d->resizeContent();
    emit minimumSizeChanged();
    d->visualAreaChange(d->visualArea(), oldVisualArea);
}
 
qreal QQuickScrollBar::visualSize() const
{
    Q_D(const QQuickScrollBar);
    return d->visualArea().size;
}
 
qreal QQuickScrollBar::visualPosition() const
{
    Q_D(const QQuickScrollBar);
    return d->visualArea().position;
}
 
QQuickIndicatorButton *QQuickScrollBar::decreaseVisual()
{
    Q_D(QQuickScrollBar);
    return d->decreaseVisual;
}
 
QQuickIndicatorButton *QQuickScrollBar::increaseVisual()
{
    Q_D(QQuickScrollBar);
    return d->increaseVisual;
}
 
void QQuickScrollBar::increase()
{
    Q_D(QQuickScrollBar);
    qreal step = qFuzzyIsNull(d->stepSize) ? 0.1 : d->stepSize;
    bool wasActive = d->active;
    setActive(true);
    setPosition(qMin<qreal>(1.0 - d->size, d->position + step));
    setActive(wasActive);
}
 
void QQuickScrollBar::decrease()
{
    Q_D(QQuickScrollBar);
    qreal step = qFuzzyIsNull(d->stepSize) ? 0.1 : d->stepSize;
    bool wasActive = d->active;
    setActive(true);
    setPosition(qMax<qreal>(0.0, d->position - step));
    setActive(wasActive);
}
 
void QQuickScrollBar::mousePressEvent(QMouseEvent *event)
{
    Q_D(QQuickScrollBar);
    QQuickControl::mousePressEvent(event);
    d->handleMove(event->position(), event->timestamp());
}
 
#if QT_CONFIG(quicktemplates2_hover)
void QQuickScrollBar::hoverChange()
{
    Q_D(QQuickScrollBar);
    d->updateActive();
}
 
void QQuickScrollBar::hoverEnterEvent(QHoverEvent *event)
{
    Q_D(QQuickScrollBar);
    QQuickControl::hoverEnterEvent(event);
    d->updateHover(event->position());
    event->ignore();
}
 
void QQuickScrollBar::hoverMoveEvent(QHoverEvent *event)
{
    Q_D(QQuickScrollBar);
    QQuickControl::hoverMoveEvent(event);
    d->updateHover(event->position());
    event->ignore();
}
 
void QQuickScrollBar::hoverLeaveEvent(QHoverEvent *event)
{
    Q_D(QQuickScrollBar);
    QQuickControl::hoverLeaveEvent(event);
 
    d->updateHover(QPoint(), false);    //position is not needed when we force it to unhover
    event->ignore();
}
#endif
 
void QQuickScrollBar::classBegin()
{
    Q_D(QQuickScrollBar);
    QQuickControl::classBegin();
 
    QQmlContext *context = qmlContext(this);
    if (context) {
        QQmlEngine::setContextForObject(d->decreaseVisual, context);
        QQmlEngine::setContextForObject(d->increaseVisual, context);
    }
}
 
void QQuickScrollBar::componentComplete()
{
    Q_D(QQuickScrollBar);
    QQuickIndicatorButtonPrivate::get(d->decreaseVisual)->executeIndicator(true);
    QQuickIndicatorButtonPrivate::get(d->increaseVisual)->executeIndicator(true);
 
    QQuickControl::componentComplete();
}
 
#if QT_CONFIG(accessibility)
void QQuickScrollBar::accessibilityActiveChanged(bool active)
{
    QQuickControl::accessibilityActiveChanged(active);
 
    Q_D(QQuickScrollBar);
    if (active) {
        setAccessibleProperty("pressed", d->pressed);
 
        if (QQuickAccessibleAttached *accessibleAttached = QQuickControlPrivate::accessibleAttached(this)) {
            connect(accessibleAttached, &QQuickAccessibleAttached::increaseAction, this, &QQuickScrollBar::increase);
            connect(accessibleAttached, &QQuickAccessibleAttached::decreaseAction, this, &QQuickScrollBar::decrease);
        }
    } else {
        if (QQuickAccessibleAttached *accessibleAttached = QQuickControlPrivate::accessibleAttached(this)) {
            disconnect(accessibleAttached, &QQuickAccessibleAttached::increaseAction, this, &QQuickScrollBar::increase);
            disconnect(accessibleAttached, &QQuickAccessibleAttached::decreaseAction, this, &QQuickScrollBar::decrease);
        }
    }
}
 
QAccessible::Role QQuickScrollBar::accessibleRole() const
{
    return QAccessible::ScrollBar;
}
#endif
 
void QQuickScrollBarAttachedPrivate::setFlickable(QQuickFlickable *item)
{
    if (flickable) {
        // NOTE: Use removeItemChangeListener(Geometry) instead of updateOrRemoveGeometryChangeListener(Size).
        // The latter doesn't remove the listener but only resets its types. Thus, it leaves behind a dangling
        // pointer on destruction.
        QQuickItemPrivate::get(flickable)->removeItemChangeListener(this, QQuickItemPrivate::Geometry);
        QQuickItemPrivate::get(flickable)->removeItemChangeListener(this, QQuickItemPrivate::Destroyed);
        if (horizontal)
            cleanupHorizontal();
        if (vertical)
            cleanupVertical();
    }
 
    flickable = item;
 
    if (item) {
        // Don't know how to combine these calls into one, and as long as they're separate calls,
        // the remove* calls above need to be separate too, otherwise they will have no effect.
        QQuickItemPrivate::get(item)->updateOrAddGeometryChangeListener(this, QQuickGeometryChange::Size);
        QQuickItemPrivate::get(item)->updateOrAddItemChangeListener(this, QQuickItemPrivate::Destroyed);
        if (horizontal)
            initHorizontal();
        if (vertical)
            initVertical();
    }
}
 
void QQuickScrollBarAttachedPrivate::initHorizontal()
{
    Q_ASSERT(flickable && horizontal);
 
    connect(flickable, &QQuickFlickable::movingHorizontallyChanged, this, &QQuickScrollBarAttachedPrivate::activateHorizontal);
 
    // TODO: export QQuickFlickableVisibleArea
    QObject *area = flickable->property("visibleArea").value<QObject *>();
    QObject::connect(area, SIGNAL(widthRatioChanged(qreal)), horizontal, SLOT(setSize(qreal)));
    QObject::connect(area, SIGNAL(xPositionChanged(qreal)), horizontal, SLOT(setPosition(qreal)));
 
    // ensure that the ScrollBar is stacked above the Flickable in a ScrollView
    QQuickItem *parent = horizontal->parentItem();
    if (parent && parent == flickable->parentItem())
        horizontal->stackAfter(flickable);
 
    // If a scroll bar was previously hidden (due to e.g. setting a new contentItem
    // on a ScrollView), we need to make sure that we un-hide it.
    if (auto control = qobject_cast<QQuickControl*>(q_func()->parent())) {
        const auto visibility = horizontal->policy() != QQuickScrollBar::AlwaysOff
            ? QQuickControlPrivate::UnhideVisibility::Show : QQuickControlPrivate::UnhideVisibility::Hide;
        QQuickControlPrivate::unhideOldItem(control, horizontal, visibility);
    }
 
    layoutHorizontal();
    horizontal->setSize(area->property("widthRatio").toReal());
    horizontal->setPosition(area->property("xPosition").toReal());
}
 
void QQuickScrollBarAttachedPrivate::initVertical()
{
    Q_ASSERT(flickable && vertical);
 
    connect(flickable, &QQuickFlickable::movingVerticallyChanged, this, &QQuickScrollBarAttachedPrivate::activateVertical);
 
    // TODO: export QQuickFlickableVisibleArea
    QObject *area = flickable->property("visibleArea").value<QObject *>();
    QObject::connect(area, SIGNAL(heightRatioChanged(qreal)), vertical, SLOT(setSize(qreal)));
    QObject::connect(area, SIGNAL(yPositionChanged(qreal)), vertical, SLOT(setPosition(qreal)));
 
    // ensure that the ScrollBar is stacked above the Flickable in a ScrollView
    QQuickItem *parent = vertical->parentItem();
    if (parent && parent == flickable->parentItem())
        vertical->stackAfter(flickable);
 
    if (auto control = qobject_cast<QQuickControl*>(q_func()->parent())) {
        const auto visibility = vertical->policy() != QQuickScrollBar::AlwaysOff
            ? QQuickControlPrivate::UnhideVisibility::Show : QQuickControlPrivate::UnhideVisibility::Hide;
        QQuickControlPrivate::unhideOldItem(control, vertical, visibility);
    }
 
    layoutVertical();
    vertical->setSize(area->property("heightRatio").toReal());
    vertical->setPosition(area->property("yPosition").toReal());
}
 
void QQuickScrollBarAttachedPrivate::cleanupHorizontal()
{
    Q_ASSERT(flickable && horizontal);
 
    QQuickControlPrivate::hideOldItem(horizontal);
    // ScrollBar.qml has a binding to visible and ScrollView.qml has a binding to parent.
    // If we just set visible to false and parent to null, these bindings will overwrite
    // them upon component completion as part of the binding evaluation.
    // That's why we remove the binding completely.
    const QQmlProperty visibleProperty(horizontal, QStringLiteral("visible"));
    const QQmlProperty parentProperty(horizontal, QStringLiteral("parent"));
    QQmlPropertyPrivate::removeBinding(visibleProperty);
    QQmlPropertyPrivate::removeBinding(parentProperty);
 
    disconnect(flickable, &QQuickFlickable::movingHorizontallyChanged, this, &QQuickScrollBarAttachedPrivate::activateHorizontal);
 
    // TODO: export QQuickFlickableVisibleArea
    QObject *area = flickable->property("visibleArea").value<QObject *>();
    QObject::disconnect(area, SIGNAL(widthRatioChanged(qreal)), horizontal, SLOT(setSize(qreal)));
    QObject::disconnect(area, SIGNAL(xPositionChanged(qreal)), horizontal, SLOT(setPosition(qreal)));
}
 
void QQuickScrollBarAttachedPrivate::cleanupVertical()
{
    Q_ASSERT(flickable && vertical);
 
    QQuickControlPrivate::hideOldItem(vertical);
    const QQmlProperty visibleProperty(vertical, QStringLiteral("visible"));
    const QQmlProperty parentProperty(vertical, QStringLiteral("parent"));
    QQmlPropertyPrivate::removeBinding(visibleProperty);
    QQmlPropertyPrivate::removeBinding(parentProperty);
 
    disconnect(flickable, &QQuickFlickable::movingVerticallyChanged, this, &QQuickScrollBarAttachedPrivate::activateVertical);
 
    // TODO: export QQuickFlickableVisibleArea
    QObject *area = flickable->property("visibleArea").value<QObject *>();
    QObject::disconnect(area, SIGNAL(heightRatioChanged(qreal)), vertical, SLOT(setSize(qreal)));
    QObject::disconnect(area, SIGNAL(yPositionChanged(qreal)), vertical, SLOT(setPosition(qreal)));
}
 
void QQuickScrollBarAttachedPrivate::activateHorizontal()
{
    QQuickScrollBarPrivate *p = QQuickScrollBarPrivate::get(horizontal);
    p->moving = flickable->isMovingHorizontally();
    p->updateActive();
}
 
void QQuickScrollBarAttachedPrivate::activateVertical()
{
    QQuickScrollBarPrivate *p = QQuickScrollBarPrivate::get(vertical);
    p->moving = flickable->isMovingVertically();
    p->updateActive();
}
 
// TODO: QQuickFlickable::maxXYExtent()
class QQuickFriendlyFlickable : public QQuickFlickable
{
    friend class QQuickScrollBarAttachedPrivate;
};
 
void QQuickScrollBarAttachedPrivate::scrollHorizontal()
{
    if (!flickable)
        return;
 
    QQuickFriendlyFlickable *f = reinterpret_cast<QQuickFriendlyFlickable *>(flickable);
 
    const qreal viewwidth = f->width();
    const qreal maxxextent = -f->maxXExtent() + f->minXExtent();
    const qreal cx = horizontal->position() * (maxxextent + viewwidth) - f->minXExtent();
 
    if (!qIsNaN(cx) && !qFuzzyCompare(cx, flickable->contentX()))
        flickable->setContentX(cx);
}
 
void QQuickScrollBarAttachedPrivate::scrollVertical()
{
    if (!flickable)
        return;
 
    QQuickFriendlyFlickable *f = reinterpret_cast<QQuickFriendlyFlickable *>(flickable);
 
    const qreal viewheight = f->height();
    const qreal maxyextent = -f->maxYExtent() + f->minYExtent();
    const qreal cy = vertical->position() * (maxyextent + viewheight) - f->minYExtent();
 
    if (!qIsNaN(cy) && !qFuzzyCompare(cy, flickable->contentY()))
        flickable->setContentY(cy);
}
 
void QQuickScrollBarAttachedPrivate::mirrorVertical()
{
    layoutVertical(true);
}
 
void QQuickScrollBarAttachedPrivate::layoutHorizontal(bool move)
{
    Q_ASSERT(horizontal && flickable);
    if (horizontal->parentItem() != flickable)
        return;
    horizontal->setWidth(flickable->width());
    if (move)
        horizontal->setY(flickable->height() - horizontal->height());
}
 
void QQuickScrollBarAttachedPrivate::layoutVertical(bool move)
{
    Q_ASSERT(vertical && flickable);
    if (vertical->parentItem() != flickable)
        return;
    vertical->setHeight(flickable->height());
    if (move)
        vertical->setX(vertical->isMirrored() ? 0 : flickable->width() - vertical->width());
}
 
void QQuickScrollBarAttachedPrivate::itemGeometryChanged(QQuickItem *item, const QQuickGeometryChange change, const QRectF &diff)
{
    Q_UNUSED(item);
    Q_UNUSED(change);
    if (horizontal && horizontal->height() > 0) {
#ifdef QT_QUICK_NEW_GEOMETRY_CHANGED_HANDLING // TODO: correct/rename diff to oldGeometry
        bool move = qFuzzyIsNull(horizontal->y()) || qFuzzyCompare(horizontal->y(), diff.height() - horizontal->height());
#else
        bool move = qFuzzyIsNull(horizontal->y()) || qFuzzyCompare(horizontal->y(), item->height() - diff.height() - horizontal->height());
#endif
        if (flickable)
            layoutHorizontal(move);
    }
    if (vertical && vertical->width() > 0) {
#ifdef QT_QUICK_NEW_GEOMETRY_CHANGED_HANDLING // TODO: correct/rename diff to oldGeometry
        bool move = qFuzzyIsNull(vertical->x()) || qFuzzyCompare(vertical->x(), diff.width() - vertical->width());
#else
        bool move = qFuzzyIsNull(vertical->x()) || qFuzzyCompare(vertical->x(), item->width() - diff.width() - vertical->width());
#endif
        if (flickable)
            layoutVertical(move);
    }
}
 
void QQuickScrollBarAttachedPrivate::itemImplicitWidthChanged(QQuickItem *item)
{
    if (item == vertical && flickable)
        layoutVertical(true);
}
 
void QQuickScrollBarAttachedPrivate::itemImplicitHeightChanged(QQuickItem *item)
{
    if (item == horizontal && flickable)
        layoutHorizontal(true);
}
 
void QQuickScrollBarAttachedPrivate::itemDestroyed(QQuickItem *item)
{
    if (item == flickable)
        flickable = nullptr;
    if (item == horizontal)
        horizontal = nullptr;
    if (item == vertical)
        vertical = nullptr;
}
 
QQuickScrollBarAttached::QQuickScrollBarAttached(QObject *parent)
    : QObject(*(new QQuickScrollBarAttachedPrivate), parent)
{
    Q_D(QQuickScrollBarAttached);
    d->setFlickable(qobject_cast<QQuickFlickable *>(parent));
 
    if (parent && !d->flickable && !qobject_cast<QQuickScrollView *>(parent))
        qmlWarning(parent) << "ScrollBar must be attached to a Flickable or ScrollView";
}
 
QQuickScrollBarAttached::~QQuickScrollBarAttached()
{
    Q_D(QQuickScrollBarAttached);
    if (d->horizontal) {
        QQuickItemPrivate::get(d->horizontal)->removeItemChangeListener(d, QsbHorizontalChangeTypes);
        d->horizontal = nullptr;
    }
    if (d->vertical) {
        QQuickItemPrivate::get(d->vertical)->removeItemChangeListener(d, QsbVerticalChangeTypes);
        d->vertical = nullptr;
    }
    d->setFlickable(nullptr);
}
 
QQuickScrollBar *QQuickScrollBarAttached::horizontal() const
{
    Q_D(const QQuickScrollBarAttached);
    return d->horizontal;
}
 
void QQuickScrollBarAttached::setHorizontal(QQuickScrollBar *horizontal)
{
    Q_D(QQuickScrollBarAttached);
    if (d->horizontal == horizontal)
        return;
 
    if (d->horizontal) {
        QQuickItemPrivate::get(d->horizontal)->removeItemChangeListener(d, QsbHorizontalChangeTypes);
        QObjectPrivate::disconnect(d->horizontal, &QQuickScrollBar::positionChanged, d, &QQuickScrollBarAttachedPrivate::scrollHorizontal);
 
        if (d->flickable)
            d->cleanupHorizontal();
    }
 
    d->horizontal = horizontal;
 
    if (horizontal) {
        if (!horizontal->parentItem())
            horizontal->setParentItem(qobject_cast<QQuickItem *>(parent()));
        horizontal->setOrientation(Qt::Horizontal);
 
        QQuickItemPrivate::get(horizontal)->addItemChangeListener(d, QsbHorizontalChangeTypes);
        QObjectPrivate::connect(horizontal, &QQuickScrollBar::positionChanged, d, &QQuickScrollBarAttachedPrivate::scrollHorizontal);
 
        if (d->flickable)
            d->initHorizontal();
    }
    emit horizontalChanged();
}
 
QQuickScrollBar *QQuickScrollBarAttached::vertical() const
{
    Q_D(const QQuickScrollBarAttached);
    return d->vertical;
}
 
void QQuickScrollBarAttached::setVertical(QQuickScrollBar *vertical)
{
    Q_D(QQuickScrollBarAttached);
    if (d->vertical == vertical)
        return;
 
    if (d->vertical) {
        QQuickItemPrivate::get(d->vertical)->removeItemChangeListener(d, QsbVerticalChangeTypes);
        QObjectPrivate::disconnect(d->vertical, &QQuickScrollBar::mirroredChanged, d, &QQuickScrollBarAttachedPrivate::mirrorVertical);
        QObjectPrivate::disconnect(d->vertical, &QQuickScrollBar::positionChanged, d, &QQuickScrollBarAttachedPrivate::scrollVertical);
 
        if (d->flickable)
            d->cleanupVertical();
    }
 
    d->vertical = vertical;
 
    if (vertical) {
        if (!vertical->parentItem())
            vertical->setParentItem(qobject_cast<QQuickItem *>(parent()));
        vertical->setOrientation(Qt::Vertical);
 
        QQuickItemPrivate::get(vertical)->addItemChangeListener(d, QsbVerticalChangeTypes);
        QObjectPrivate::connect(vertical, &QQuickScrollBar::mirroredChanged, d, &QQuickScrollBarAttachedPrivate::mirrorVertical);
        QObjectPrivate::connect(vertical, &QQuickScrollBar::positionChanged, d, &QQuickScrollBarAttachedPrivate::scrollVertical);
 
        if (d->flickable)
            d->initVertical();
    }
    emit verticalChanged();
}
 
QT_END_NAMESPACE
 
#include "moc_qquickscrollbar_p.cpp"