view widgets/WheelCounter.h @ 1330:c1f719094c25 zoom

Ensure getFrameForX returns value on zoom blocksize boundary; take advantage of that (this is essentially reverting to the same behaviour as in the default branch, which we should probably have done all along)
author Chris Cannam
date Fri, 21 Sep 2018 11:50:05 +0100
parents 13f5f84fbfad
children
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/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Sonic Visualiser
    An audio file viewer and annotation editor.
    Centre for Digital Music, Queen Mary, University of London.
    
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License as
    published by the Free Software Foundation; either version 2 of the
    License, or (at your option) any later version.  See the file
    COPYING included with this distribution for more information.
*/

#ifndef SV_WHEEL_COUNTER_H
#define SV_WHEEL_COUNTER_H

#include <QWheelEvent>

/**
 * Manage the little bit of tedious book-keeping associated with
 * translating vertical wheel events into up/down notch counts
 */
class WheelCounter
{
public:
    WheelCounter() : m_pendingWheelAngle(0) { }

    ~WheelCounter() { }

    int count(QWheelEvent *e) {
        
        e->accept();
    
        int delta = e->angleDelta().y();
        if (delta == 0) {
            return 0;
        }

        if (e->phase() == Qt::ScrollBegin ||
            std::abs(delta) >= 120 ||
            (delta > 0 && m_pendingWheelAngle < 0) ||
            (delta < 0 && m_pendingWheelAngle > 0)) {
            m_pendingWheelAngle = delta;
        } else {
            m_pendingWheelAngle += delta;
        }

        if (abs(m_pendingWheelAngle) >= 600) {
            // Sometimes on Linux we're seeing absurdly extreme angles
            // on the first wheel event -- discard those entirely
            m_pendingWheelAngle = 0;
            return 0;
        }

        int count = m_pendingWheelAngle / 120;
        m_pendingWheelAngle -= count * 120;
        return count;
    }

private:
    int m_pendingWheelAngle;
};

#endif