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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 RENDER_TIMER_H
#define RENDER_TIMER_H
#include <chrono>
namespace sv {
class RenderTimer
{
public:
enum Type {
/// A normal rendering operation with normal responsiveness demands
FastRender,
/// An operation that the user might accept being slower
SlowRender,
/// An operation that should always complete, i.e. as if there
/// were no RenderTimer in use, but without having to change
/// client code structurally
NoTimeout
};
/**
* Create a new RenderTimer and start timing. Make one of these
* before rendering, and then call outOfTime() regularly during
* rendering. If outOfTime() returns true, abandon rendering! and
* schedule the rest for after some user responsiveness has
* happened.
*/
RenderTimer(Type t) :
m_start(std::chrono::steady_clock::now()),
m_haveLimits(true),
m_minFraction(0.15),
m_almostFraction(0.65),
m_softLimit(0.1),
m_hardLimit(0.2),
m_softLimitOverridden(false) {
if (t == NoTimeout) {
m_haveLimits = false;
} else if (t == SlowRender) {
m_softLimit = 0.2;
m_hardLimit = 0.4;
}
}
/**
* Return true if we have run out of time and should suspend
* rendering and handle user events instead. Call this regularly
* during rendering work: fractionComplete should be an estimate
* of how much of the work has been done as of this call, as a
* number between 0.0 (none of it) and 1.0 (all of it).
*/
bool outOfTime(double fractionComplete) {
if (!m_haveLimits || fractionComplete < m_minFraction) {
return false;
}
auto t = std::chrono::steady_clock::now();
double elapsed = std::chrono::duration<double>(t - m_start).count();
if (elapsed > m_hardLimit) {
return true;
} else if (!m_softLimitOverridden && elapsed > m_softLimit) {
if (fractionComplete > m_almostFraction) {
// If we're "almost done" by the time we reach the
// soft limit, ignore it (though always respect the
// hard limit, above). Otherwise respect the soft
// limit and report out of time now.
m_softLimitOverridden = true;
} else {
return true;
}
}
return false;
}
double secondsPerItem(int itemsRendered) const {
if (itemsRendered == 0) return 0.0;
auto t = std::chrono::steady_clock::now();
double elapsed = std::chrono::duration<double>(t - m_start).count();
return elapsed / itemsRendered;
}
private:
std::chrono::time_point<std::chrono::steady_clock> m_start;
bool m_haveLimits;
double m_minFraction; // proportion, 0.0 -> 1.0
double m_almostFraction; // proportion, 0.0 -> 1.0
double m_softLimit; // seconds
double m_hardLimit; // seconds
bool m_softLimitOverridden;
};
} // end namespace sv
#endif
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