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,
  29                                      QObject* parent = nullptr);
  30     ~KItemListSmoothScroller() override;
  31
  32     void setScrollBar(QScrollBar* scrollBar);
  33     QScrollBar* scrollBar() const;
  34
  35     void setTargetObject(QObject* target);
  36     QObject* targetObject() const;
  37
  38     void setPropertyName(const QByteArray& propertyName);
  39     QByteArray propertyName() const;
  40
  41     /**
  42      * Adjusts the position of the target by \p distance
  43      * pixels. Is invoked in the context of QAbstractScrollArea::scrollContentsBy()
  44      * where the scrollbars already have the new position but the content
  45      * has not been scrolled yet.
  46      */
  47     void scrollContentsBy(qreal distance);
  48
  49     /**
  50      * Does a smooth-scrolling to the position \p position
  51      * on the target and also adjusts the corresponding scrollbar
  52      * to the new position.
  53      */
  54     void scrollTo(qreal position);
  55
  56     /**
  57      * Must be invoked before the scrollbar should get updated to have a new
  58      * maximum. True is returned if the new maximum can be applied. If false
  59      * is returned the maximum has already been reached and the value will
  60      * be reached at the end of the animation.
  61      */
  62     // TODO: This interface is tricky to understand. Try to make this more
  63     // generic/readable if the corresponding code in KItemListContainer got
  64     // stable.
  65     bool requestScrollBarUpdate(int newMaximum);
  66
  67     /**
  68      * Forwards wheel events to the scrollbar, ensuring smooth and proper scrolling
  69      */
  70     void handleWheelEvent(QWheelEvent* event);
  71
  72 protected:
  73     bool eventFilter(QObject* obj, QEvent* event) override;
  74
  75 private Q_SLOTS:
  76     void slotAnimationStateChanged(QAbstractAnimation::State newState,
  77                                    QAbstractAnimation::State oldState);
  78
  79 private:
  80     bool m_scrollBarPressed;
  81     bool m_smoothScrolling;
  82     QScrollBar* m_scrollBar;
  83     QPropertyAnimation* m_animation;
  84 };
  85
  86 #endif
  87
  88