src/kitemviews/private/kitemlistsmoothscroller.cpp

   1 /*
   2  * SPDX-FileCopyrightText: 2011 Peter Penz <peter.penz19@gmail.com>
   3  *
   4  * SPDX-License-Identifier: GPL-2.0-or-later
   5  */
   6
   7 #include "kitemlistsmoothscroller.h"
   8
   9 #include <KConfigGroup>
  10 #include <KSharedConfig>
  11
  12 #include <QApplication>
  13 #include <QDBusConnection>
  14 #include <QPropertyAnimation>
  15 #include <QScrollBar>
  16 #include <QStyle>
  17 #include <QWheelEvent>
  18
  19 KItemListSmoothScroller::KItemListSmoothScroller(QScrollBar *scrollBar, QObject *parent)
  20     : QObject(parent)
  21     , m_scrollBarPressed(false)
  22     , m_smoothScrolling(true)
  23     , m_scrollBar(scrollBar)
  24     , m_animation(nullptr)
  25 {
  26     m_animation = new QPropertyAnimation(this);
  27
  28     KSharedConfig::Ptr globalConfig = KSharedConfig::openConfig(QStringLiteral("kdeglobals"), KConfig::IncludeGlobals);
  29     KConfigGroup configGroup(globalConfig, QStringLiteral("KDE"));
  30     updateAnimationDuration(configGroup.readEntry("SmoothScroll", true));
  31
  32     QDBusConnection::sessionBus().connect(QStringLiteral(""),
  33                                           QStringLiteral("/SmoothScroll"),
  34                                           QStringLiteral("org.kde.SmoothScroll"),
  35                                           QStringLiteral("notifyChange"),
  36                                           this,
  37                                           SLOT(updateAnimationDuration(bool)));
  38     connect(m_animation, &QPropertyAnimation::stateChanged, this, &KItemListSmoothScroller::slotAnimationStateChanged);
  39
  40     m_scrollBar->installEventFilter(this);
  41 }
  42
  43 KItemListSmoothScroller::~KItemListSmoothScroller()
  44 {
  45 }
  46
  47 void KItemListSmoothScroller::setScrollBar(QScrollBar *scrollBar)
  48 {
  49     m_scrollBar = scrollBar;
  50 }
  51
  52 QScrollBar *KItemListSmoothScroller::scrollBar() const
  53 {
  54     return m_scrollBar;
  55 }
  56
  57 void KItemListSmoothScroller::setTargetObject(QObject *target)
  58 {
  59     m_animation->setTargetObject(target);
  60 }
  61
  62 QObject *KItemListSmoothScroller::targetObject() const
  63 {
  64     return m_animation->targetObject();
  65 }
  66
  67 void KItemListSmoothScroller::setPropertyName(const QByteArray &propertyName)
  68 {
  69     m_animation->setPropertyName(propertyName);
  70 }
  71
  72 QByteArray KItemListSmoothScroller::propertyName() const
  73 {
  74     return m_animation->propertyName();
  75 }
  76
  77 void KItemListSmoothScroller::scrollContentsBy(qreal distance)
  78 {
  79     QObject *target = targetObject();
  80     if (!target) {
  81         return;
  82     }
  83
  84     const QByteArray name = propertyName();
  85     const qreal currentOffset = target->property(name).toReal();
  86     if (static_cast<int>(currentOffset) == m_scrollBar->value()) {
  87         // The current offset is already synchronous to the scrollbar
  88         return;
  89     }
  90
  91     const bool animRunning = (m_animation->state() == QAbstractAnimation::Running);
  92     if (animRunning) {
  93         // Stopping a running animation means skipping the range from the current offset
  94         // until the target offset. To prevent skipping of the range the difference
  95         // is added to the new target offset.
  96         const qreal oldEndOffset = m_animation->endValue().toReal();
  97         distance += (currentOffset - oldEndOffset);
  98     }
  99
 100     const qreal endOffset = currentOffset - distance;
 101     if (m_smoothScrolling || animRunning) {
 102         qreal startOffset = currentOffset;
 103         if (animRunning) {
 104             // If the animation was running and has been interrupted by assigning a new end-offset
 105             // one frame must be added to the start-offset to keep the animation smooth. This also
 106             // assures that animation proceeds even in cases where new end-offset are triggered
 107             // within a very short timeslots.
 108             startOffset += (endOffset - currentOffset) * 1000 / (m_animation->duration() * 60);
 109             if (currentOffset < endOffset) {
 110                 startOffset = qMin(startOffset, endOffset);
 111             } else {
 112                 startOffset = qMax(startOffset, endOffset);
 113             }
 114         }
 115
 116         m_animation->stop();
 117         m_animation->setStartValue(startOffset);
 118         m_animation->setEndValue(endOffset);
 119         m_animation->setEasingCurve(animRunning ? QEasingCurve::OutQuad : QEasingCurve::InOutQuad);
 120         m_animation->start();
 121         target->setProperty(name, startOffset);
 122     } else {
 123         target->setProperty(name, endOffset);
 124     }
 125 }
 126
 127 void KItemListSmoothScroller::scrollTo(qreal position)
 128 {
 129     int newValue = position;
 130     newValue = qBound(0, newValue, m_scrollBar->maximum());
 131
 132     if (newValue != m_scrollBar->value()) {
 133         m_smoothScrolling = true;
 134         m_scrollBar->setValue(newValue);
 135     }
 136 }
 137
 138 bool KItemListSmoothScroller::requestScrollBarUpdate(int newMaximum)
 139 {
 140     if (m_animation->state() == QAbstractAnimation::Running) {
 141         if (newMaximum == m_scrollBar->maximum()) {
 142             // The value has been changed by the animation, no update
 143             // of the scrollbars is required as their target state will be
 144             // reached with the end of the animation.
 145             return false;
 146         }
 147
 148         // The maximum has been changed which indicates that the content
 149         // of the view has been changed. Stop the animation in any case and
 150         // update the scrollbars immediately.
 151         m_animation->stop();
 152     }
 153     return true;
 154 }
 155
 156 bool KItemListSmoothScroller::eventFilter(QObject *obj, QEvent *event)
 157 {
 158     Q_ASSERT(obj == m_scrollBar);
 159
 160     switch (event->type()) {
 161     case QEvent::MouseButtonPress:
 162         m_scrollBarPressed = true;
 163         m_smoothScrolling = true;
 164         break;
 165
 166     case QEvent::MouseButtonRelease:
 167         m_scrollBarPressed = false;
 168         m_smoothScrolling = false;
 169         break;
 170
 171     case QEvent::Wheel:
 172         return false; // we're the ones sending them
 173
 174     default:
 175         break;
 176     }
 177
 178     return QObject::eventFilter(obj, event);
 179 }
 180
 181 void KItemListSmoothScroller::slotAnimationStateChanged(QAbstractAnimation::State newState, QAbstractAnimation::State oldState)
 182 {
 183     Q_UNUSED(oldState)
 184     if (newState == QAbstractAnimation::Stopped && m_smoothScrolling && !m_scrollBarPressed) {
 185         m_smoothScrolling = false;
 186     }
 187     if (newState == QAbstractAnimation::Stopped) {
 188         Q_EMIT scrollingStopped();
 189     }
 190 }
 191
 192 void KItemListSmoothScroller::updateAnimationDuration(bool isSmoothScrollingEnabled)
 193 {
 194     if (isSmoothScrollingEnabled) {
 195         // Breeze sets SH_Widget_Animation_Duration from the KDE global animation speed setting
 196         const int animationDuration = m_scrollBar->style()->styleHint(QStyle::SH_Widget_Animation_Duration, nullptr, m_scrollBar);
 197         const bool animationEnabled = (animationDuration > 0);
 198         m_animation->setDuration(animationEnabled ? animationDuration : 1);
 199     } else {
 200         m_animation->setDuration(1);
 201     }
 202 }
 203
 204 void KItemListSmoothScroller::handleWheelEvent(QWheelEvent *event)
 205 {
 206     const bool previous = m_smoothScrolling;
 207
 208     m_smoothScrolling = true;
 209
 210     QWheelEvent *copy = event->clone();
 211     QApplication::sendEvent(m_scrollBar, copy);
 212     event->setAccepted(copy->isAccepted());
 213
 214     m_smoothScrolling = previous;
 215 }
 216
 217 #include "moc_kitemlistsmoothscroller.cpp"