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/*
* Copyright (c) 2021, kleines Filmröllchen <malu.bertsch@gmail.com>.
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include "Mixer.h"
#include <compare>
namespace AudioServer {
// This is in buffer counts.
// As each buffer is approx 1/40 of a second, this means about 1/4 of a second of fade time.
constexpr int DEFAULT_FADE_TIME = 10;
// A property of an audio system that needs to fade briefly whenever changed.
template<typename T>
class FadingProperty {
public:
FadingProperty(T const value)
: FadingProperty(value, DEFAULT_FADE_TIME)
{
}
FadingProperty(T const value, int const fade_time)
: m_old_value(value)
, m_new_value(move(value))
, m_fade_time(fade_time)
{
}
virtual ~FadingProperty()
{
m_old_value.~T();
m_new_value.~T();
}
FadingProperty<T>& operator=(T const& new_value)
{
// The origin of the fade is wherever we're right now.
m_old_value = static_cast<T>(*this);
m_new_value = new_value;
m_current_fade = 0;
return *this;
}
FadingProperty<T>& operator=(FadingProperty<T> const&) = delete;
operator T() const
{
if (!is_fading())
return m_new_value;
return m_old_value * (1 - m_current_fade) + m_new_value * (m_current_fade);
}
auto operator<=>(FadingProperty<T> const& other) const
{
return static_cast<T>(this) <=> static_cast<T>(other);
}
auto operator<=>(T const& other) const
{
return static_cast<T>(*this) <=> other;
}
void advance_time()
{
m_current_fade += 1.0 / static_cast<double>(m_fade_time);
m_current_fade = clamp(m_current_fade, 0.0, 1.0);
}
bool is_fading() const
{
return m_current_fade < 1;
}
T target() const { return m_new_value; }
private:
T m_old_value {};
T m_new_value {};
double m_current_fade { 0 };
int const m_fade_time;
};
}
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