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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>
namespace sv {
/**
* 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;
};
} // end namespace sv
#endif
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