qquickscrollview.cpp

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// Copyright (C) 2020 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 "qquickscrollview_p.h"
#include "qquickpane_p_p.h"
#include "qquickscrollbar_p_p.h"
 
#include <QtQuick/private/qquickflickable_p.h>
 
QT_BEGIN_NAMESPACE
 
 
class QQuickScrollViewPrivate : public QQuickPanePrivate
{
public:
    Q_DECLARE_PUBLIC(QQuickScrollView)
 
    QQmlListProperty<QObject> contentData() override;
    QQmlListProperty<QQuickItem> contentChildren() override;
    QList<QQuickItem *> contentChildItems() const override;
    QQuickItem* getFirstChild() const override;
 
    QQuickItem *getContentItem() override;
 
    enum class ContentItemFlag {
        DoNotSet,
        Set
    };
 
    QQuickFlickable *ensureFlickable(ContentItemFlag contentItemFlag);
    bool setFlickable(QQuickFlickable *flickable, ContentItemFlag contentItemFlag);
 
    void flickableContentWidthChanged();
    void flickableContentHeightChanged();
 
    qreal getContentWidth() const override;
    qreal getContentHeight() const override;
 
    QQuickScrollBar *verticalScrollBar() const;
    QQuickScrollBar *horizontalScrollBar() const;
 
    void setScrollBarsInteractive(bool interactive);
 
    static void contentData_append(QQmlListProperty<QObject> *prop, QObject *obj);
    static qsizetype contentData_count(QQmlListProperty<QObject> *prop);
    static QObject *contentData_at(QQmlListProperty<QObject> *prop, qsizetype index);
    static void contentData_clear(QQmlListProperty<QObject> *prop);
 
    static void contentChildren_append(QQmlListProperty<QQuickItem> *prop, QQuickItem *obj);
    static qsizetype contentChildren_count(QQmlListProperty<QQuickItem> *prop);
    static QQuickItem *contentChildren_at(QQmlListProperty<QQuickItem> *prop, qsizetype index);
    static void contentChildren_clear(QQmlListProperty<QQuickItem> *prop);
 
    void itemImplicitWidthChanged(QQuickItem *item) override;
 
    void updateScrollBarWidth();
    void updateScrollBarHeight();
 
    void disconnectScrollBarSignals(QQuickScrollBarAttachedPrivate *scrollBar);
    bool wasTouched = false;
    QQuickFlickable *flickable = nullptr;
    bool flickableHasExplicitContentWidth = true;
    bool flickableHasExplicitContentHeight = true;
    bool isUpdatingScrollBar = false;
    qreal effectiveScrollBarWidth = 0;
    qreal effectiveScrollBarHeight = 0;
};
 
QList<QQuickItem *> QQuickScrollViewPrivate::contentChildItems() const
{
    if (!flickable)
        return QList<QQuickItem *>();
 
    return flickable->contentItem()->childItems();
}
 
QQuickItem *QQuickScrollViewPrivate::getContentItem()
{
    if (!contentItem)
        executeContentItem();
    // This function is called by QQuickControl::contentItem() to lazily create
    // a contentItem, so we don't need to try to set it again.
    return ensureFlickable(ContentItemFlag::DoNotSet);
}
 
QQuickItem* QQuickScrollViewPrivate::getFirstChild() const
{
    return contentChildItems().value(0);
}
 
QQuickFlickable *QQuickScrollViewPrivate::ensureFlickable(ContentItemFlag contentItemFlag)
{
    Q_Q(QQuickScrollView);
    if (!flickable) {
        flickableHasExplicitContentWidth = false;
        flickableHasExplicitContentHeight = false;
        // Pass ourselves as the Flickable's parent item.
        auto flickable = new QQuickFlickable(q);
        // We almost always want to clip the flickable so that flickable
        // contents doesn't show up outside the scrollview. The only time
        // this is not really needed, is when the scrollview covers the whole
        // window and the scrollbars are transient. But for that corner case, if this
        // optimization is needed, the user can simply create his own flickable
        // child inside the scrollview, and control clipping on it explicit.
        flickable->setClip(true);
        flickable->setPixelAligned(true);
        setFlickable(flickable, contentItemFlag);
    }
    return flickable;
}
 
void QQuickScrollViewPrivate::updateScrollBarWidth()
{
    Q_Q(QQuickScrollView);
    qreal oldEffectiveScrollBarWidth = effectiveScrollBarWidth;
    if (auto *vBar = verticalScrollBar()) {
        if (vBar->policy() == QQuickScrollBar::AlwaysOff || !vBar->isVisible())
            effectiveScrollBarWidth = 0;
        else
            effectiveScrollBarWidth = vBar->width();
    }
    if (effectiveScrollBarWidth != oldEffectiveScrollBarWidth) {
        if (!isUpdatingScrollBar) {
            QScopedValueRollback<bool> rollback(isUpdatingScrollBar, true);
            emit q->effectiveScrollBarWidthChanged();
        }
    }
}
 
void QQuickScrollViewPrivate::updateScrollBarHeight()
{
    Q_Q(QQuickScrollView);
    qreal oldEffectiveScrollBarHeight = effectiveScrollBarHeight;
    if (auto *hBar = horizontalScrollBar()) {
        if (hBar->policy() == QQuickScrollBar::AlwaysOff || !hBar->isVisible())
            effectiveScrollBarHeight = 0;
        else
            effectiveScrollBarHeight = hBar->height();
    }
    if (effectiveScrollBarHeight != oldEffectiveScrollBarHeight) {
        if (!isUpdatingScrollBar) {
            QScopedValueRollback<bool> rollback(isUpdatingScrollBar, true);
            emit q->effectiveScrollBarHeightChanged();
        }
 
    }
}
 
void QQuickScrollViewPrivate::disconnectScrollBarSignals(QQuickScrollBarAttachedPrivate *scrollBar)
{
    if (!scrollBar)
        return;
 
    if (scrollBar->vertical) {
        QObjectPrivate::disconnect(scrollBar->vertical, &QQuickScrollBar::policyChanged, this, &QQuickScrollViewPrivate::updateScrollBarWidth);
        QObjectPrivate::disconnect(scrollBar->vertical, &QQuickScrollBar::visibleChanged, this, &QQuickScrollViewPrivate::updateScrollBarWidth);
    }
    if (scrollBar->horizontal) {
        QObjectPrivate::disconnect(scrollBar->horizontal, &QQuickScrollBar::policyChanged, this, &QQuickScrollViewPrivate::updateScrollBarHeight);
        QObjectPrivate::disconnect(scrollBar->horizontal, &QQuickScrollBar::visibleChanged, this, &QQuickScrollViewPrivate::updateScrollBarHeight);
    }
}
 
bool QQuickScrollViewPrivate::setFlickable(QQuickFlickable *item, ContentItemFlag contentItemFlag)
{
    Q_Q(QQuickScrollView);
    if (item == flickable)
        return false;
 
    QQuickScrollBarAttached *attached = qobject_cast<QQuickScrollBarAttached *>(qmlAttachedPropertiesObject<QQuickScrollBar>(q, false));
 
    if (flickable) {
        flickable->removeEventFilter(q);
 
        if (attached) {
            auto *scrollBar = QQuickScrollBarAttachedPrivate::get(attached);
            scrollBar->setFlickable(nullptr);
            disconnectScrollBarSignals(scrollBar);
        }
 
        QObjectPrivate::disconnect(flickable->contentItem(), &QQuickItem::childrenChanged, this, &QQuickPanePrivate::contentChildrenChange);
        QObjectPrivate::disconnect(flickable, &QQuickFlickable::contentWidthChanged, this, &QQuickScrollViewPrivate::flickableContentWidthChanged);
        QObjectPrivate::disconnect(flickable, &QQuickFlickable::contentHeightChanged, this, &QQuickScrollViewPrivate::flickableContentHeightChanged);
    }
 
    flickable = item;
    if (contentItemFlag == ContentItemFlag::Set)
        q->setContentItem(flickable);
 
    if (flickable) {
        flickable->installEventFilter(q);
        if (hasContentWidth)
            flickable->setContentWidth(contentWidth);
        else
            flickableContentWidthChanged();
        if (hasContentHeight)
            flickable->setContentHeight(contentHeight);
        else
            flickableContentHeightChanged();
 
        if (attached) {
            auto *scrollBar = QQuickScrollBarAttachedPrivate::get(attached);
            scrollBar->setFlickable(flickable);
            if (scrollBar->vertical) {
                QObjectPrivate::connect(scrollBar->vertical, &QQuickScrollBar::policyChanged, this, &QQuickScrollViewPrivate::updateScrollBarWidth);
                QObjectPrivate::connect(scrollBar->vertical, &QQuickScrollBar::visibleChanged, this, &QQuickScrollViewPrivate::updateScrollBarWidth);
            }
            if (scrollBar->horizontal) {
                QObjectPrivate::connect(scrollBar->horizontal, &QQuickScrollBar::policyChanged, this, &QQuickScrollViewPrivate::updateScrollBarHeight);
                QObjectPrivate::connect(scrollBar->horizontal, &QQuickScrollBar::visibleChanged, this, &QQuickScrollViewPrivate::updateScrollBarHeight);
            }
        }
 
        QObjectPrivate::connect(flickable->contentItem(), &QQuickItem::childrenChanged, this, &QQuickPanePrivate::contentChildrenChange);
        QObjectPrivate::connect(flickable, &QQuickFlickable::contentWidthChanged, this, &QQuickScrollViewPrivate::flickableContentWidthChanged);
        QObjectPrivate::connect(flickable, &QQuickFlickable::contentHeightChanged, this, &QQuickScrollViewPrivate::flickableContentHeightChanged);
    }
 
    return true;
}
 
void QQuickScrollViewPrivate::flickableContentWidthChanged()
{
    Q_Q(QQuickScrollView);
    if (!flickable || !componentComplete)
        return;
 
    const qreal cw = flickable->contentWidth();
    if (qFuzzyCompare(cw, implicitContentWidth))
        return;
 
    flickableHasExplicitContentWidth = true;
    implicitContentWidth = cw;
    emit q->implicitContentWidthChanged();
}
 
void QQuickScrollViewPrivate::flickableContentHeightChanged()
{
    Q_Q(QQuickScrollView);
    if (!flickable || !componentComplete)
        return;
 
    const qreal ch = flickable->contentHeight();
    if (qFuzzyCompare(ch, implicitContentHeight))
        return;
 
    flickableHasExplicitContentHeight = true;
    implicitContentHeight = ch;
    emit q->implicitContentHeightChanged();
}
 
qreal QQuickScrollViewPrivate::getContentWidth() const
{
    if (flickable && flickableHasExplicitContentWidth)
        return flickable->contentWidth();
 
    // The scrollview wraps a flickable created by us, and nobody searched for it and
    // modified its contentWidth. In that case, since the application does not control
    // this flickable, we fall back to calculate the content width based on the child
    // items inside it.
    return QQuickPanePrivate::getContentWidth();
}
 
qreal QQuickScrollViewPrivate::getContentHeight() const
{
    if (flickable && flickableHasExplicitContentHeight)
        return flickable->contentHeight();
 
    // The scrollview wraps a flickable created by us, and nobody searched for it and
    // modified its contentHeight. In that case, since the application does not control
    // this flickable, we fall back to calculate the content height based on the child
    // items inside it.
    return QQuickPanePrivate::getContentHeight();
}
 
QQuickScrollBar *QQuickScrollViewPrivate::verticalScrollBar() const
{
    Q_Q(const QQuickScrollView);
    QQuickScrollBarAttached *attached = qobject_cast<QQuickScrollBarAttached *>(qmlAttachedPropertiesObject<QQuickScrollBar>(q, false));
    if (!attached)
        return nullptr;
    return attached->vertical();
}
 
QQuickScrollBar *QQuickScrollViewPrivate::horizontalScrollBar() const
{
    Q_Q(const QQuickScrollView);
    QQuickScrollBarAttached *attached = qobject_cast<QQuickScrollBarAttached *>(qmlAttachedPropertiesObject<QQuickScrollBar>(q, false));
    if (!attached)
        return nullptr;
    return attached->horizontal();
}
 
void QQuickScrollViewPrivate::setScrollBarsInteractive(bool interactive)
{
    QQuickScrollBar *hbar = horizontalScrollBar();
    if (hbar) {
        QQuickScrollBarPrivate *p = QQuickScrollBarPrivate::get(hbar);
        if (!p->explicitInteractive)
            p->setInteractive(interactive);
    }
 
    QQuickScrollBar *vbar = verticalScrollBar();
    if (vbar) {
        QQuickScrollBarPrivate *p = QQuickScrollBarPrivate::get(vbar);
        if (!p->explicitInteractive)
            p->setInteractive(interactive);
    }
}
 
void QQuickScrollViewPrivate::contentData_append(QQmlListProperty<QObject> *prop, QObject *obj)
{
    QQuickScrollViewPrivate *p = static_cast<QQuickScrollViewPrivate *>(prop->data);
    // If we don't yet have a flickable assigned, and this object is a Flickable,
    // make it our contentItem.
    if (!p->flickable && p->setFlickable(qobject_cast<QQuickFlickable *>(obj), ContentItemFlag::Set))
        return;
 
    QQuickFlickable *flickable = p->ensureFlickable(ContentItemFlag::Set);
    Q_ASSERT(flickable);
    // Add the object that was declared as a child of us as a child object of the Flickable.
    QQmlListProperty<QObject> data = flickable->flickableData();
    data.append(&data, obj);
}
 
qsizetype QQuickScrollViewPrivate::contentData_count(QQmlListProperty<QObject> *prop)
{
    QQuickScrollViewPrivate *p = static_cast<QQuickScrollViewPrivate *>(prop->data);
    if (!p->flickable)
        return 0;
 
    QQmlListProperty<QObject> data = p->flickable->flickableData();
    return data.count(&data);
}
 
QObject *QQuickScrollViewPrivate::contentData_at(QQmlListProperty<QObject> *prop, qsizetype index)
{
    QQuickScrollViewPrivate *p = static_cast<QQuickScrollViewPrivate *>(prop->data);
    if (!p->flickable)
        return nullptr;
 
    QQmlListProperty<QObject> data = p->flickable->flickableData();
    return data.at(&data, index);
}
 
void QQuickScrollViewPrivate::contentData_clear(QQmlListProperty<QObject> *prop)
{
    QQuickScrollViewPrivate *p = static_cast<QQuickScrollViewPrivate *>(prop->data);
    if (!p->flickable)
        return;
 
    QQmlListProperty<QObject> data = p->flickable->flickableData();
    return data.clear(&data);
}
 
void QQuickScrollViewPrivate::contentChildren_append(QQmlListProperty<QQuickItem> *prop, QQuickItem *item)
{
    QQuickScrollViewPrivate *p = static_cast<QQuickScrollViewPrivate *>(prop->data);
    if (!p->flickable)
        p->setFlickable(qobject_cast<QQuickFlickable *>(item), ContentItemFlag::Set);
 
    QQuickFlickable *flickable = p->ensureFlickable(ContentItemFlag::Set);
    Q_ASSERT(flickable);
    // Add the item that was declared as a child of us as a child item of the Flickable's contentItem.
    QQmlListProperty<QQuickItem> children = flickable->flickableChildren();
    children.append(&children, item);
}
 
qsizetype QQuickScrollViewPrivate::contentChildren_count(QQmlListProperty<QQuickItem> *prop)
{
    QQuickScrollViewPrivate *p = static_cast<QQuickScrollViewPrivate *>(prop->data);
    if (!p->flickable)
        return 0;
 
    QQmlListProperty<QQuickItem> children = p->flickable->flickableChildren();
    return children.count(&children);
}
 
QQuickItem *QQuickScrollViewPrivate::contentChildren_at(QQmlListProperty<QQuickItem> *prop, qsizetype index)
{
    QQuickScrollViewPrivate *p = static_cast<QQuickScrollViewPrivate *>(prop->data);
    if (!p->flickable)
        return nullptr;
 
    QQmlListProperty<QQuickItem> children = p->flickable->flickableChildren();
    return children.at(&children, index);
}
 
void QQuickScrollViewPrivate::contentChildren_clear(QQmlListProperty<QQuickItem> *prop)
{
    QQuickScrollViewPrivate *p = static_cast<QQuickScrollViewPrivate *>(prop->data);
    if (!p->flickable)
        return;
 
    QQmlListProperty<QQuickItem> children = p->flickable->flickableChildren();
    children.clear(&children);
}
 
void QQuickScrollViewPrivate::itemImplicitWidthChanged(QQuickItem *item)
{
    // a special case for width<->height dependent content (wrapping text) in ScrollView
    if (contentWidth < 0 && !componentComplete)
        return;
 
    QQuickPanePrivate::itemImplicitWidthChanged(item);
}
 
QQuickScrollView::QQuickScrollView(QQuickItem *parent)
    : QQuickPane(*(new QQuickScrollViewPrivate), parent)
{
    Q_D(QQuickScrollView);
    d->contentWidth = -1;
    d->contentHeight = -1;
 
    setFiltersChildMouseEvents(true);
    setWheelEnabled(true);
}
 
QQuickScrollView::~QQuickScrollView()
{
    Q_D(QQuickScrollView);
    QQuickScrollBarAttached *attached = qobject_cast<QQuickScrollBarAttached *>(qmlAttachedPropertiesObject<QQuickScrollBar>(this, false));
    if (attached) {
        auto *scrollBar = QQuickScrollBarAttachedPrivate::get(attached);
        d->disconnectScrollBarSignals(scrollBar);
    }
}
 
qreal QQuickScrollView::effectiveScrollBarWidth()
{
    Q_D(QQuickScrollView);
    return d->effectiveScrollBarWidth;
}
 
qreal QQuickScrollView::effectiveScrollBarHeight()
{
    Q_D(QQuickScrollView);
    return d->effectiveScrollBarHeight;
}
 
QQmlListProperty<QObject> QQuickScrollViewPrivate::contentData()
{
    Q_Q(QQuickScrollView);
    return QQmlListProperty<QObject>(q, this,
                                     QQuickScrollViewPrivate::contentData_append,
                                     QQuickScrollViewPrivate::contentData_count,
                                     QQuickScrollViewPrivate::contentData_at,
                                     QQuickScrollViewPrivate::contentData_clear);
}
 
QQmlListProperty<QQuickItem> QQuickScrollViewPrivate::contentChildren()
{
    Q_Q(QQuickScrollView);
    return QQmlListProperty<QQuickItem>(q, this,
                                        QQuickScrollViewPrivate::contentChildren_append,
                                        QQuickScrollViewPrivate::contentChildren_count,
                                        QQuickScrollViewPrivate::contentChildren_at,
                                        QQuickScrollViewPrivate::contentChildren_clear);
}
 
bool QQuickScrollView::childMouseEventFilter(QQuickItem *item, QEvent *event)
{
    Q_D(QQuickScrollView);
    switch (event->type()) {
    case QEvent::TouchBegin:
        d->wasTouched = true;
        d->setScrollBarsInteractive(false);
        return false;
 
    case QEvent::TouchEnd:
        d->wasTouched = false;
        return false;
 
    case QEvent::MouseButtonPress:
        // NOTE: Flickable does not handle touch events, only synthesized mouse events
        if (static_cast<QMouseEvent *>(event)->source() == Qt::MouseEventNotSynthesized) {
            d->wasTouched = false;
            d->setScrollBarsInteractive(true);
            return false;
        }
        return !d->wasTouched && item == d->flickable;
 
    case QEvent::MouseMove:
    case QEvent::MouseButtonRelease:
        if (static_cast<QMouseEvent *>(event)->source() == Qt::MouseEventNotSynthesized)
            return item == d->flickable;
        break;
 
    case QEvent::HoverEnter:
    case QEvent::HoverMove:
        if (d->wasTouched && (item == d->verticalScrollBar() || item == d->horizontalScrollBar()))
            d->setScrollBarsInteractive(true);
        break;
 
    default:
        break;
    }
 
    return false;
}
 
bool QQuickScrollView::eventFilter(QObject *object, QEvent *event)
{
    Q_D(QQuickScrollView);
    if (event->type() == QEvent::Wheel) {
        d->setScrollBarsInteractive(true);
        if (!d->wheelEnabled) {
            event->ignore();
            return true;
        }
    }
    return QQuickPane::eventFilter(object, event);
}
 
void QQuickScrollView::keyPressEvent(QKeyEvent *event)
{
    Q_D(QQuickScrollView);
    QQuickPane::keyPressEvent(event);
    switch (event->key()) {
    case Qt::Key_Up:
        if (QQuickScrollBar *vbar = d->verticalScrollBar()) {
            vbar->decrease();
            event->accept();
        }
        break;
    case Qt::Key_Down:
        if (QQuickScrollBar *vbar = d->verticalScrollBar()) {
            vbar->increase();
            event->accept();
        }
        break;
    case Qt::Key_Left:
        if (QQuickScrollBar *hbar = d->horizontalScrollBar()) {
            hbar->decrease();
            event->accept();
        }
        break;
    case Qt::Key_Right:
        if (QQuickScrollBar *hbar = d->horizontalScrollBar()) {
            hbar->increase();
            event->accept();
        }
        break;
    default:
        event->ignore();
        break;
    }
}
 
void QQuickScrollView::componentComplete()
{
    Q_D(QQuickScrollView);
    QQuickPane::componentComplete();
    if (!d->contentItem)
        d->ensureFlickable(QQuickScrollViewPrivate::ContentItemFlag::Set);
}
 
void QQuickScrollView::contentItemChange(QQuickItem *newItem, QQuickItem *oldItem)
{
    Q_D(QQuickScrollView);
    if (newItem != d->flickable) {
        // The new flickable was not created by us. In that case, we always
        // assume/require that it has an explicit content size assigned.
        d->flickableHasExplicitContentWidth = true;
        d->flickableHasExplicitContentHeight = true;
        auto newItemAsFlickable = qobject_cast<QQuickFlickable *>(newItem);
        if (newItem && !newItemAsFlickable)
            qmlWarning(this) << "ScrollView only supports Flickable types as its contentItem";
        // This is called by QQuickControlPrivate::setContentItem_helper, so no need to
        // try to set it as the contentItem.
        d->setFlickable(newItemAsFlickable, QQuickScrollViewPrivate::ContentItemFlag::DoNotSet);
        // We do, however, need to set us as its parent item, as setContentItem_helper will only
        // do so if the item doesn't already have a parent. If newItem wasn't declared as our
        // child and was instead imperatively assigned, it may already have a parent item,
        // which we'll need to override.
        if (newItem) {
            newItem->setParentItem(this);
 
            // Make sure that the scroll bars are stacked in front of the flickable,
            // otherwise events won't get through to them.
            QQuickScrollBar *verticalBar = d->verticalScrollBar();
            if (verticalBar)
                verticalBar->stackAfter(newItem);
            QQuickScrollBar *horizontalBar = d->horizontalScrollBar();
            if (horizontalBar)
                horizontalBar->stackAfter(newItem);
        }
    }
    QQuickPane::contentItemChange(newItem, oldItem);
}
 
void QQuickScrollView::contentSizeChange(const QSizeF &newSize, const QSizeF &oldSize)
{
    Q_D(QQuickScrollView);
    QQuickPane::contentSizeChange(newSize, oldSize);
    if (d->flickable) {
        // Only set the content size on the flickable if the flickable doesn't
        // have an explicit assignment from before. Otherwise we can end up overwriting
        // assignments done to those properties by the application. The
        // exception is if the application has assigned a content size
        // directly to the scrollview, which will then win even if the
        // application has assigned something else to the flickable.
        if (d->hasContentWidth || !d->flickableHasExplicitContentWidth) {
            d->flickable->setContentWidth(newSize.width());
            d->updateScrollBarWidth();
        }
        if (d->hasContentHeight || !d->flickableHasExplicitContentHeight) {
            d->flickable->setContentHeight(newSize.height());
            d->updateScrollBarHeight();
        }
    }
}
 
#if QT_CONFIG(accessibility)
QAccessible::Role QQuickScrollView::accessibleRole() const
{
    return QAccessible::Pane;
}
#endif
 
QT_END_NAMESPACE
 
#include "moc_qquickscrollview_p.cpp"