src/kitemviews/private/kitemlistsmoothscroller.h

   1 /*
   2  * SPDX-FileCopyrightText: 2011 Peter Penz <peter.penz19@gmail.com>
   3  *
   4  * SPDX-License-Identifier: GPL-2.0-or-later
   5  */
   6
   7 #ifndef KITEMLISTSMOOTHSCROLLER_H
   8 #define KITEMLISTSMOOTHSCROLLER_H
   9
  10 #include "dolphin_export.h"
  11
  12 #include <QAbstractAnimation>
  13 #include <QObject>
  14
  15 class QPropertyAnimation;
  16 class QScrollBar;
  17 class QWheelEvent;
  18
  19 /**
  20  * @brief Helper class for KItemListContainer to have a smooth
  21  *        scrolling when adjusting the scrollbars.
  22  */
  23 class DOLPHIN_EXPORT KItemListSmoothScroller : public QObject
  24 {
  25     Q_OBJECT
  26
  27 public:
  28     explicit KItemListSmoothScroller(QScrollBar *scrollBar, QObject *parent = nullptr);
  29     ~KItemListSmoothScroller() override;
  30
  31     void setScrollBar(QScrollBar *scrollBar);
  32     QScrollBar *scrollBar() const;
  33
  34     void setTargetObject(QObject *target);
  35     QObject *targetObject() const;
  36
  37     void setPropertyName(const QByteArray &propertyName);
  38     QByteArray propertyName() const;
  39
  40     /**
  41      * Adjusts the position of the target by \p distance
  42      * pixels. Is invoked in the context of QAbstractScrollArea::scrollContentsBy()
  43      * where the scrollbars already have the new position but the content
  44      * has not been scrolled yet.
  45      */
  46     void scrollContentsBy(qreal distance);
  47
  48     /**
  49      * Does a smooth-scrolling to the position \p position
  50      * on the target and also adjusts the corresponding scrollbar
  51      * to the new position.
  52      */
  53     void scrollTo(qreal position);
  54
  55     /**
  56      * Must be invoked before the scrollbar should get updated to have a new
  57      * maximum. True is returned if the new maximum can be applied. If false
  58      * is returned the maximum has already been reached and the value will
  59      * be reached at the end of the animation.
  60      */
  61     // TODO: This interface is tricky to understand. Try to make this more
  62     // generic/readable if the corresponding code in KItemListContainer got
  63     // stable.
  64     bool requestScrollBarUpdate(int newMaximum);
  65
  66     /**
  67      * Forwards wheel events to the scrollbar, ensuring smooth and proper scrolling
  68      */
  69     void handleWheelEvent(QWheelEvent *event);
  70
  71 Q_SIGNALS:
  72     /**
  73      * Emitted when the scrolling animation has finished
  74      */
  75     void scrollingStopped();
  76
  77 protected:
  78     bool eventFilter(QObject *obj, QEvent *event) override;
  79
  80 private Q_SLOTS:
  81     void slotAnimationStateChanged(QAbstractAnimation::State newState, QAbstractAnimation::State oldState);
  82     /**
  83      * Calculates the duration of the smooth scrolling animation.
  84      * If \p isSmoothScrollingEnabled is true, the duration will be calculated
  85      * using the widget animation duration from the current style. Otherwise,
  86      * the animation will be instantaneous.
  87      */
  88     void updateAnimationDuration(bool isSmoothScrollingEnabled);
  89
  90 private:
  91     bool m_scrollBarPressed;
  92     bool m_smoothScrolling;
  93     QScrollBar *m_scrollBar;
  94     QPropertyAnimation *m_animation;
  95 };
  96
  97 #endif