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
// Qt-Security score:significant reason:default
 
#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
 
/*!
    \qmltype ScrollBar
    \inherits Control
//!     \nativetype QQuickScrollBar
    \inqmlmodule QtQuick.Controls
    \since 5.7
    \ingroup qtquickcontrols-indicators
    \brief Vertical or horizontal interactive scroll bar.
 
    \image qtquickcontrols-scrollbar.gif
           {Scroll bar handle moving along track}
 
    ScrollBar is an interactive bar that can be used to scroll to a specific
    position. A scroll bar can be either \l vertical or \l horizontal, and can
    be attached to any \l Flickable, such as \l ListView and \l GridView.
    It can also be used with \l ScrollView.
 
    \code
    Flickable {
        // ...
        ScrollBar.vertical: ScrollBar { }
    }
    \endcode
 
    \section1 Attaching ScrollBar to a Flickable
 
    When ScrollBar is attached \l {ScrollBar::vertical}{vertically} or
    \l {ScrollBar::horizontal}{horizontally} to a Flickable, its geometry and
    the following properties are automatically set and updated as appropriate:
 
    \list
    \li \l orientation
    \li \l position
    \li \l {ScrollBar::} {size}
    \li \l active
    \endlist
 
    An attached ScrollBar re-parents itself to the target Flickable. A vertically
    attached ScrollBar resizes itself to the height of the Flickable, and positions
    itself to either side of it based on the \l {Control::mirrored}{layout direction}.
    A horizontally attached ScrollBar resizes itself to the width of the Flickable,
    and positions itself to the bottom. The automatic geometry management can be disabled
    by specifying another parent for the attached ScrollBar. This can be useful, for
    example, if the ScrollBar should be placed outside a clipping Flickable. This is
    demonstrated by the following example:
 
    \code
    Flickable {
        id: flickable
        clip: true
        // ...
        ScrollBar.vertical: ScrollBar {
            parent: flickable.parent
            anchors.top: flickable.top
            anchors.left: flickable.right
            anchors.bottom: flickable.bottom
        }
    }
    \endcode
 
    Notice that ScrollBar does not filter key events of the Flickable it is
    attached to. The following example illustrates how to implement scrolling
    with up and down keys:
 
    \code
    Flickable {
        focus: true
 
        Keys.onUpPressed: scrollBar.decrease()
        Keys.onDownPressed: scrollBar.increase()
 
        ScrollBar.vertical: ScrollBar { id: scrollBar }
    }
    \endcode
 
    \section1 Binding the Active State of Horizontal and Vertical Scroll Bars
 
    Horizontal and vertical scroll bars do not share the \l active state with
    each other by default. In order to keep both bars visible whilst scrolling
    to either direction, establish a two-way binding between the active states
    as presented by the following example:
 
    \snippet qtquickcontrols-scrollbar-active.qml 1
 
    \section1 Non-attached Scroll Bars
 
    It is possible to create an instance of ScrollBar without using the
    attached property API. This is useful when the behavior of the attached
    scroll bar is not sufficient or a \l Flickable is not in use. In the
    following example, horizontal and vertical scroll bars are used to
    scroll over the text without using \l Flickable:
 
    \snippet qtquickcontrols-scrollbar-non-attached.qml 1
 
    \image qtquickcontrols-scrollbar-non-attached.png
           {Scroll bar used standalone without attached property}
 
    When using a non-attached ScrollBar, the following must be done manually:
 
    \list
    \li Layout the scroll bar (with the \l {Item::}{x} and \l {Item::}{y} or
        \l {Item::}{anchors} property, for example).
    \li Set the \l size and \l position properties to determine the size and position
        of the scroll bar in relation to the scrolled item.
    \li Set the \l active property to determine when the scroll bar will be
        visible.
    \endlist
 
    \include varying-delegate-heights-section.qdocinc {file} {1} {ScrollBar}
 
    \sa ScrollIndicator, ScrollView, {Customizing ScrollBar}, {Indicator Controls}
*/
 
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;
    dragPoint = point;
    q->setPressed(true);
    return true;
}
 
bool QQuickScrollBarPrivate::handleMove(const QPointF &point, ulong timestamp)
{
    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);
    setPositionFromDrag(pos, point);
    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);
    setPositionFromDrag(pos, point);
    offset = 0.0;
    dragPoint = {};
    q->setPressed(false);
    return true;
}
 
void QQuickScrollBarPrivate::handleUngrab()
{
    Q_Q(QQuickScrollBar);
    QQuickControlPrivate::handleUngrab();
    offset = 0.0;
    dragPoint = {};
    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);
    d->setSizePolicy(QLayoutPolicy::Preferred, QLayoutPolicy::Fixed);
    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);
}
 
/*!
    \qmlproperty real QtQuick.Controls::ScrollBar::size
 
    This property holds the size of the scroll bar, scaled to \c {0.0 - 1.0}.
 
    \sa {Flickable::visibleArea.heightRatio}{Flickable::visibleArea}
 
    This property is automatically set when the scroll bar is
    \l {Attaching ScrollBar to a Flickable}{attached to a flickable}.
 
    \sa minimumSize, visualSize
*/
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;
 
    const auto oldVisualArea = d->visualArea();
    d->size = size;
    if (d->size + d->position > 1.0) {
        d->setPosition(1.0 - d->size, false);
    }
    // positionAt() depends on the size.
    d->reanchorDragOffset(d->position);
 
    if (isComponentComplete())
        d->resizeContent();
    emit sizeChanged();
    d->visualAreaChange(d->visualArea(), oldVisualArea);
}
 
/*!
    \qmlproperty real QtQuick.Controls::ScrollBar::position
 
    This property holds the position of the scroll bar, scaled to \c {0.0 - 1.0}.
 
    The largest valid scrollbar position is \c {(1.0 - size)}. This gives
    correct behavior for the most used case where moving the scrollbar
    to the end will put the end of the document at the lower end of the
    visible area of the connected Flickable.
 
    \sa {Flickable::visibleArea.yPosition}{Flickable::visibleArea}
 
    This property is automatically set when the scroll bar is
    \l {Attaching ScrollBar to a Flickable}{attached to a flickable}.
 
    \sa visualPosition
*/
qreal QQuickScrollBar::position() const
{
    Q_D(const QQuickScrollBar);
    return d->position;
}
 
void QQuickScrollBar::setPosition(qreal position)
{
    Q_D(QQuickScrollBar);
    d->setPosition(position);
}
 
void QQuickScrollBarPrivate::setPosition(qreal newPosition, bool notifyVisualChange)
{
    // An attached Flickable writes the drag's own position back here unchanged, and those
    // writes must not touch offset - see setPositionFromDrag().
    if (qt_is_finite(newPosition) && !qFuzzyCompare(position, newPosition))
        reanchorDragOffset(newPosition);
    updatePosition(newPosition, notifyVisualChange);
}
 
void QQuickScrollBarPrivate::setPositionFromDrag(qreal newPosition, const QPointF &point)
{
    dragPoint = point;
    // Bypass setPosition(): offset is already accounted for in newPosition, so re-anchoring it
    // would fold the clamping and the snapping applied by the caller back into it.
    updatePosition(newPosition, true /*notifyVisualChange*/);
}
 
void QQuickScrollBarPrivate::updatePosition(qreal newPosition, bool notifyVisualChange)
{
    Q_Q(QQuickScrollBar);
    if (!qt_is_finite(newPosition) || qFuzzyCompare(position, newPosition))
        return;
 
    auto oldVisualArea = visualArea();
    position = newPosition;
    if (q->isComponentComplete())
        resizeContent();
    emit q->positionChanged();
    if (notifyVisualChange)
        visualAreaChange(visualArea(), oldVisualArea);
 
#if QT_CONFIG(accessibility)
    if (QAccessible::isActive() && isAccessible) {
        if (QAccessibleInterface *accessible = QAccessible::queryAccessibleInterface(q)) {
            if (QAccessibleValueInterface *valueInterface = accessible->valueInterface()) {
                QAccessibleValueChangeEvent event(q, valueInterface->currentValue());
                QAccessible::updateAccessibility(&event);
            }
        }
    }
#endif
}
 
void QQuickScrollBarPrivate::reanchorDragOffset(qreal newPosition)
{
    // offset is the distance between the handle and the pointer holding it. Moving the handle,
    // or changing what positionAt() returns, makes that distance stale: measure it again, or
    // the next handleMove() would put the handle back where it was (QTBUG-130890).
    if (pressed)
        offset = positionAt(dragPoint) - newPosition;
}
 
/*!
    \qmlproperty real QtQuick.Controls::ScrollBar::stepSize
 
    This property holds the step size. The default value is \c 0.0.
 
    \sa snapMode, increase(), decrease()
*/
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();
}
 
/*!
    \qmlproperty bool QtQuick.Controls::ScrollBar::active
 
    This property holds whether the scroll bar is active, i.e. when it's \l pressed
    or the attached Flickable is \l {Flickable::moving}{moving}.
 
    It is possible to keep \l {Binding the Active State of Horizontal and Vertical Scroll Bars}
    {both horizontal and vertical bars visible} while scrolling in either direction.
 
    This property is automatically set when the scroll bar is
    \l {Attaching ScrollBar to a Flickable}{attached to a flickable}.
*/
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();
}
 
/*!
    \qmlproperty bool QtQuick.Controls::ScrollBar::pressed
 
    This property holds whether the scroll bar is pressed.
*/
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();
}
 
/*!
    \qmlproperty enumeration QtQuick.Controls::ScrollBar::orientation
 
    This property holds the orientation of the scroll bar.
 
    Possible values:
    \value Qt.Horizontal Horizontal
    \value Qt.Vertical Vertical (default)
 
    This property is automatically set when the scroll bar is
    \l {Attaching ScrollBar to a Flickable}{attached to a flickable}.
 
    \sa horizontal, vertical
*/
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;
 
    if (orientation == Qt::Horizontal)
        d->setSizePolicy(QLayoutPolicy::Preferred, QLayoutPolicy::Fixed);
    else
        d->setSizePolicy(QLayoutPolicy::Fixed, QLayoutPolicy::Preferred);
 
    d->orientation = orientation;
    if (isComponentComplete())
        d->resizeContent();
    emit orientationChanged();
}
 
/*!
    \since QtQuick.Controls 2.2 (Qt 5.9)
    \qmlproperty enumeration QtQuick.Controls::ScrollBar::snapMode
 
    This property holds the snap mode.
 
    Possible values:
    \value ScrollBar.NoSnap The scrollbar does not snap (default).
    \value ScrollBar.SnapAlways The scrollbar snaps while dragged.
    \value ScrollBar.SnapOnRelease The scrollbar does not snap while being dragged, but only after released.
 
    In the following table, the various modes are illustrated with animations.
    The movement and the \l stepSize (\c 0.25) are identical in each animation.
 
    \table
    \header
        \row \li \b Value \li \b Example
        \row \li \c ScrollBar.NoSnap
             \li \image qtquickcontrols-scrollbar-nosnap.gif
                        {Scroll bar without snap mode, sliding freely}
        \row \li \c ScrollBar.SnapAlways
             \li \image qtquickcontrols-scrollbar-snapalways.gif
                        {Scroll bar snapping to items while dragging}
        \row \li \c ScrollBar.SnapOnRelease
             \li \image qtquickcontrols-scrollbar-snaponrelease.gif
                        {Scroll bar snapping to items on release}
    \endtable
 
    \sa stepSize
*/
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();
}
 
/*!
    \since QtQuick.Controls 2.2 (Qt 5.9)
    \qmlproperty bool QtQuick.Controls::ScrollBar::interactive
 
    This property holds whether the scroll bar is interactive. The default value is \c true.
 
    A non-interactive scroll bar is visually and behaviorally similar to \l ScrollIndicator.
    This property is useful for switching between typical mouse- and touch-orientated UIs
    with interactive and non-interactive scroll bars, respectively.
*/
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);
}
 
/*!
    \since QtQuick.Controls 2.2 (Qt 5.9)
    \qmlproperty enumeration QtQuick.Controls::ScrollBar::policy
 
    This property holds the policy of the scroll bar. The default policy is \c ScrollBar.AsNeeded.
 
    Possible values:
    \value ScrollBar.AsNeeded The scroll bar is only shown when the content is too large to fit.
    \value ScrollBar.AlwaysOff The scroll bar is never shown.
    \value ScrollBar.AlwaysOn The scroll bar is always shown.
 
    The following example keeps the vertical scroll bar always visible:
 
    \snippet qtquickcontrols-scrollbar-policy-alwayson.qml 1
 
    Styles may use this property in combination with the \l active property
    in order to implement transient scroll bars. Transient scroll bars are
    hidden shortly after the last interaction event (hover or press). This
    is typically done by animating the opacity of the scroll bar. To override
    this behavior, set the policy to \c ScrollBar.AlwaysOn or
    \c ScrollBar.AlwaysOff, depending on the size of the content compared to
    its view. For example, for a vertical \l ListView:
 
    \snippet qtquickcontrols-scrollbar-policy-alwayson-when-needed.qml 1
*/
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();
}
 
/*!
    \since QtQuick.Controls 2.3 (Qt 5.10)
    \qmlproperty bool QtQuick.Controls::ScrollBar::horizontal
    \readonly
 
    This property holds whether the scroll bar is horizontal.
 
    \sa orientation
*/
bool QQuickScrollBar::isHorizontal() const
{
    Q_D(const QQuickScrollBar);
    return d->orientation == Qt::Horizontal;
}
 
/*!
    \since QtQuick.Controls 2.3 (Qt 5.10)
    \qmlproperty bool QtQuick.Controls::ScrollBar::vertical
    \readonly
 
    This property holds whether the scroll bar is vertical.
 
    \sa orientation
*/
bool QQuickScrollBar::isVertical() const
{
    Q_D(const QQuickScrollBar);
    return d->orientation == Qt::Vertical;
}
 
/*!
    \since QtQuick.Controls 2.4 (Qt 5.11)
    \qmlproperty real QtQuick.Controls::ScrollBar::minimumSize
 
    This property holds the minimum size of the scroll bar, scaled to \c {0.0 - 1.0}.
 
    \sa size, visualSize, visualPosition
*/
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);
}
 
/*!
    \since QtQuick.Controls 2.4 (Qt 5.11)
    \qmlproperty real QtQuick.Controls::ScrollBar::visualSize
    \readonly
 
    This property holds the effective visual size of the scroll bar,
    which may be limited by the \l {minimumSize}{minimum size}.
 
    \sa size, minimumSize
*/
qreal QQuickScrollBar::visualSize() const
{
    Q_D(const QQuickScrollBar);
    return d->visualArea().size;
}
 
/*!
    \since QtQuick.Controls 2.4 (Qt 5.11)
    \qmlproperty real QtQuick.Controls::ScrollBar::visualPosition
    \readonly
 
    This property holds the effective visual position of the scroll bar,
    which may be limited by the \l {minimumSize}{minimum size}.
 
    \sa position, minimumSize
*/
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;
}
 
/*!
    \qmlmethod void QtQuick.Controls::ScrollBar::increase()
 
    Increases the position by \l stepSize or \c 0.1 if stepSize is \c 0.0.
 
    \sa stepSize
*/
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);
}
 
/*!
    \qmlmethod void QtQuick.Controls::ScrollBar::decrease()
 
    Decreases the position by \l stepSize or \c 0.1 if stepSize is \c 0.0.
 
    \sa stepSize
*/
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(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);
 
    if (!flickable)
        return;
 
    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(vertical);
 
    QQuickControlPrivate::hideOldItem(vertical);
    const QQmlProperty visibleProperty(vertical, QStringLiteral("visible"));
    const QQmlProperty parentProperty(vertical, QStringLiteral("parent"));
    QQmlPropertyPrivate::removeBinding(visibleProperty);
    QQmlPropertyPrivate::removeBinding(parentProperty);
 
    if (!flickable)
        return;
 
    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 attached property must be attached to an object deriving from 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);
}
 
/*!
    \qmlattachedproperty ScrollBar QtQuick.Controls::ScrollBar::horizontal
 
    This property attaches a horizontal scroll bar to a \l Flickable.
 
    \code
    Flickable {
        contentWidth: 2000
        ScrollBar.horizontal: ScrollBar { }
    }
    \endcode
 
    \sa {Attaching ScrollBar to a Flickable}
*/
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);
 
        // Call this regardless of whether we have a flickable, because we need to clean up the old
        // horizontal item.
        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();
}
 
/*!
    \qmlattachedproperty ScrollBar QtQuick.Controls::ScrollBar::vertical
 
    This property attaches a vertical scroll bar to a \l Flickable.
 
    \code
    Flickable {
        contentHeight: 2000
        ScrollBar.vertical: ScrollBar { }
    }
    \endcode
 
    \sa {Attaching ScrollBar to a Flickable}
*/
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);
 
        // Call this regardless of whether we have a flickable, because we need to clean up the old
        // vertical item.
        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"