src/kitemviews/private/kitemlistsmoothscroller.h

   1 /***************************************************************************
   2  *   Copyright (C) 2011 by Peter Penz <peter.penz19@gmail.com>             *
   3  *                                                                         *
   4  *   This program is free software; you can redistribute it and/or modify  *
   5  *   it under the terms of the GNU General Public License as published by  *
   6  *   the Free Software Foundation; either version 2 of the License, or     *
   7  *   (at your option) any later version.                                   *
   8  *                                                                         *
   9  *   This program is distributed in the hope that it will be useful,       *
  10  *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
  11  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
  12  *   GNU General Public License for more details.                          *
  13  *                                                                         *
  14  *   You should have received a copy of the GNU General Public License     *
  15  *   along with this program; if not, write to the                         *
  16  *   Free Software Foundation, Inc.,                                       *
  17  *   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA            *
  18  ***************************************************************************/
  19
  20 #ifndef KITEMLISTSMOOTHSCROLLER_H
  21 #define KITEMLISTSMOOTHSCROLLER_H
  22
  23 #include "dolphin_export.h"
  24
  25 #include <QAbstractAnimation>
  26 #include <QObject>
  27
  28 class QPropertyAnimation;
  29 class QScrollBar;
  30 class QWheelEvent;
  31
  32 /**
  33  * @brief Helper class for KItemListContainer to have a smooth
  34  *        scrolling when adjusting the scrollbars.
  35  */
  36 class DOLPHIN_EXPORT KItemListSmoothScroller : public QObject
  37 {
  38     Q_OBJECT
  39
  40 public:
  41     explicit KItemListSmoothScroller(QScrollBar* scrollBar,
  42                                      QObject* parent = 0);
  43     ~KItemListSmoothScroller() override;
  44
  45     void setScrollBar(QScrollBar* scrollBar);
  46     QScrollBar* scrollBar() const;
  47
  48     void setTargetObject(QObject* target);
  49     QObject* targetObject() const;
  50
  51     void setPropertyName(const QByteArray& propertyName);
  52     QByteArray propertyName() const;
  53
  54     /**
  55      * Adjusts the position of the target by \p distance
  56      * pixels. Is invoked in the context of QAbstractScrollArea::scrollContentsBy()
  57      * where the scrollbars already have the new position but the content
  58      * has not been scrolled yet.
  59      */
  60     void scrollContentsBy(qreal distance);
  61
  62     /**
  63      * Does a smooth-scrolling to the position \p position
  64      * on the target and also adjusts the corresponding scrollbar
  65      * to the new position.
  66      */
  67     void scrollTo(qreal position);
  68
  69     /**
  70      * Must be invoked before the scrollbar should get updated to have a new
  71      * maximum. True is returned if the new maximum can be applied. If false
  72      * is returned the maximum has already been reached and the value will
  73      * be reached at the end of the animation.
  74      */
  75     // TODO: This interface is tricky to understand. Try to make this more
  76     // generic/readable if the corresponding code in KItemListContainer got
  77     // stable.
  78     bool requestScrollBarUpdate(int newMaximum);
  79
  80     /**
  81      * Forwards wheel events to the scrollbar, ensuring smooth and proper scrolling
  82      */
  83     void handleWheelEvent(QWheelEvent* event);
  84
  85 protected:
  86     bool eventFilter(QObject* obj, QEvent* event) override;
  87
  88 private slots:
  89     void slotAnimationStateChanged(QAbstractAnimation::State newState,
  90                                    QAbstractAnimation::State oldState);
  91
  92 private:
  93     bool m_scrollBarPressed;
  94     bool m_smoothScrolling;
  95     QScrollBar* m_scrollBar;
  96     QPropertyAnimation* m_animation;
  97 };
  98
  99 #endif
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