File indexing completed on 2024-05-12 05:47:30

 /*
  * SPDX-FileCopyrightText: 2011 Peter Penz <peter.penz19@gmail.com>
  *
  * SPDX-License-Identifier: GPL-2.0-or-later
  */
 
 #include "kitemlistsmoothscroller.h"
 
 #include <QApplication>
 #include <QPropertyAnimation>
 #include <QScrollBar>
 #include <QStyle>
 #include <QWheelEvent>
 
 KItemListSmoothScroller::KItemListSmoothScroller(QScrollBar *scrollBar, QObject *parent)
     : QObject(parent)
     , m_scrollBarPressed(false)
     , m_smoothScrolling(true)
     , m_scrollBar(scrollBar)
     , m_animation(nullptr)
 {
     m_animation = new QPropertyAnimation(this);
     const int animationDuration = m_scrollBar->style()->styleHint(QStyle::SH_Widget_Animation_Duration, nullptr, m_scrollBar);
     const bool animationEnabled = (animationDuration > 0);
     m_animation->setDuration(animationEnabled ? animationDuration : 1);
     connect(m_animation, &QPropertyAnimation::stateChanged, this, &KItemListSmoothScroller::slotAnimationStateChanged);
 
     m_scrollBar->installEventFilter(this);
 }
 
 KItemListSmoothScroller::~KItemListSmoothScroller()
 {
 }
 
 void KItemListSmoothScroller::setScrollBar(QScrollBar *scrollBar)
 {
     m_scrollBar = scrollBar;
 }
 
 QScrollBar *KItemListSmoothScroller::scrollBar() const
 {
     return m_scrollBar;
 }
 
 void KItemListSmoothScroller::setTargetObject(QObject *target)
 {
     m_animation->setTargetObject(target);
 }
 
 QObject *KItemListSmoothScroller::targetObject() const
 {
     return m_animation->targetObject();
 }
 
 void KItemListSmoothScroller::setPropertyName(const QByteArray &propertyName)
 {
     m_animation->setPropertyName(propertyName);
 }
 
 QByteArray KItemListSmoothScroller::propertyName() const
 {
     return m_animation->propertyName();
 }
 
 void KItemListSmoothScroller::scrollContentsBy(qreal distance)
 {
     QObject *target = targetObject();
     if (!target) {
         return;
     }
 
     const QByteArray name = propertyName();
     const qreal currentOffset = target->property(name).toReal();
     if (static_cast<int>(currentOffset) == m_scrollBar->value()) {
         // The current offset is already synchronous to the scrollbar
         return;
     }
 
     const bool animRunning = (m_animation->state() == QAbstractAnimation::Running);
     if (animRunning) {
         // Stopping a running animation means skipping the range from the current offset
         // until the target offset. To prevent skipping of the range the difference
         // is added to the new target offset.
         const qreal oldEndOffset = m_animation->endValue().toReal();
         distance += (currentOffset - oldEndOffset);
     }
 
     const qreal endOffset = currentOffset - distance;
     if (m_smoothScrolling || animRunning) {
         qreal startOffset = currentOffset;
         if (animRunning) {
             // If the animation was running and has been interrupted by assigning a new end-offset
             // one frame must be added to the start-offset to keep the animation smooth. This also
             // assures that animation proceeds even in cases where new end-offset are triggered
             // within a very short timeslots.
             startOffset += (endOffset - currentOffset) * 1000 / (m_animation->duration() * 60);
             if (currentOffset < endOffset) {
                 startOffset = qMin(startOffset, endOffset);
             } else {
                 startOffset = qMax(startOffset, endOffset);
             }
         }
 
         m_animation->stop();
         m_animation->setStartValue(startOffset);
         m_animation->setEndValue(endOffset);
         m_animation->setEasingCurve(animRunning ? QEasingCurve::OutQuad : QEasingCurve::InOutQuad);
         m_animation->start();
         target->setProperty(name, startOffset);
     } else {
         target->setProperty(name, endOffset);
     }
 }
 
 void KItemListSmoothScroller::scrollTo(qreal position)
 {
     int newValue = position;
     newValue = qBound(0, newValue, m_scrollBar->maximum());
 
     if (newValue != m_scrollBar->value()) {
         m_smoothScrolling = true;
         m_scrollBar->setValue(newValue);
     }
 }
 
 bool KItemListSmoothScroller::requestScrollBarUpdate(int newMaximum)
 {
     if (m_animation->state() == QAbstractAnimation::Running) {
         if (newMaximum == m_scrollBar->maximum()) {
             // The value has been changed by the animation, no update
             // of the scrollbars is required as their target state will be
             // reached with the end of the animation.
             return false;
         }
 
         // The maximum has been changed which indicates that the content
         // of the view has been changed. Stop the animation in any case and
         // update the scrollbars immediately.
         m_animation->stop();
     }
     return true;
 }
 
 bool KItemListSmoothScroller::eventFilter(QObject *obj, QEvent *event)
 {
     Q_ASSERT(obj == m_scrollBar);
 
     switch (event->type()) {
     case QEvent::MouseButtonPress:
         m_scrollBarPressed = true;
         m_smoothScrolling = true;
         break;
 
     case QEvent::MouseButtonRelease:
         m_scrollBarPressed = false;
         m_smoothScrolling = false;
         break;
 
     case QEvent::Wheel:
         return false; // we're the ones sending them
 
     default:
         break;
     }
 
     return QObject::eventFilter(obj, event);
 }
 
 void KItemListSmoothScroller::slotAnimationStateChanged(QAbstractAnimation::State newState, QAbstractAnimation::State oldState)
 {
     Q_UNUSED(oldState)
     if (newState == QAbstractAnimation::Stopped && m_smoothScrolling && !m_scrollBarPressed) {
         m_smoothScrolling = false;
     }
     if (newState == QAbstractAnimation::Stopped) {
         Q_EMIT scrollingStopped();
     }
 }
 
 void KItemListSmoothScroller::handleWheelEvent(QWheelEvent *event)
 {
     const bool previous = m_smoothScrolling;
 
     m_smoothScrolling = true;
 
 #if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
     QWheelEvent *copy = event->clone();
     QApplication::sendEvent(m_scrollBar, copy);
     event->setAccepted(copy->isAccepted());
 #else
     QWheelEvent copy = *event;
     QApplication::sendEvent(m_scrollBar, &copy);
     event->setAccepted(copy.isAccepted());
 #endif
 
     m_smoothScrolling = previous;
 }
 
 #include "moc_kitemlistsmoothscroller.cpp"