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/*
* SPDX-FileCopyrightText: 2011 Peter Penz <[email protected]>
*
* 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;
QWheelEvent copy = *event;
QApplication::sendEvent(m_scrollBar, ©);
event->setAccepted(copy.isAccepted());
m_smoothScrolling = previous;
}
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