/*
* Copyright (C) 2021 Christopher J. Howard
*
* This file is part of Antkeeper source code.
*
* Antkeeper source code 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 3 of the License, or
* (at your option) any later version.
*
* Antkeeper source code is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Antkeeper source code. If not, see .
*/
#ifndef ANTKEEPER_TWEEN_HPP
#define ANTKEEPER_TWEEN_HPP
#include
#include
#include
/**
* Container which stores two states along with an interpolator, for quick and easy tweening.
*
* @tparam T Value type.
* @tparam S Scalar type.
*/
template
class tween
{
public:
static_assert(std::is_scalar::value);
typedef T value_type;
typedef S scalar_type;
typedef typename std::decay>::type interpolator_type;
private:
/// Throws an error if no interpolator is set.
static value_type interpolator_error(const value_type&, const value_type&, scalar_type);
public:
/**
* Creates a tween.
*
* @param state0 Initial value of state 0.
* @param state1 Initial value of state 1.
* @param interpolator Function used to interpolate between states 0 and 1.
*/
tween(const value_type& state0, const value_type& state1, interpolator_type interpolator = tween::interpolator_error);
/**
* Creates a tween.
*
* @param value Initial value of states 0 and 1.
* @param interpolator Function used to interpolate between states 0 and 1.
*/
explicit tween(const value_type& value, interpolator_type interpolator = tween::interpolator_error);
/**
* Creates a tween.
*/
tween();
/**
* Returns a reference to the specified tween state.
*
* @param i Index of a tween state. Should be either `0` or `1`.
* @return Reference to the specified tween state.
*/
const value_type& operator[](int i) const;
/// @copydoc tween::operator[](int) const
value_type& operator[](int i);
/// @copydoc tween::interpolate(scalar_type) const
value_type operator[](scalar_type a) const;
/**
* Returns an interpolated state between state 0 and state 1. If no interpolator is set, state 1 will be returned.
*
* @param a Interpolation factor on `[0.0, 1.0]`.
* @return Interpolated state, or state 1 if no interpolator is set.
*/
value_type interpolate(scalar_type a) const;
/**
* Sets the function used to interpolate between states 0 and 1.
*
* @param interpolator Interpolator function.
*/
void set_interpolator(const interpolator_type& interpolator);
/**
* Returns the function used to interpolate between states 0 and 1.
*/
const interpolator_type& get_interpolator() const;
/**
* Sets state 0 = state 1.
*/
void update();
/**
* Swaps state 0 and state 1.
*/
void swap();
private:
value_type states[2];
interpolator_type interpolator;
};
template
typename tween::value_type tween::interpolator_error(const value_type&, const value_type&, scalar_type)
{
throw std::runtime_error("tween interpolator not set");
}
template
tween::tween(const value_type& value, interpolator_type interpolator):
states{value, value},
interpolator(interpolator)
{}
template
tween::tween(const value_type& state0, const value_type& state1, interpolator_type interpolator):
states{state0, state1},
interpolator(interpolator)
{}
template
tween::tween():
interpolator(nullptr)
{}
template
inline const typename tween::value_type& tween::operator[](int i) const
{
return states[i];
}
template
inline typename tween::value_type& tween::operator[](int i)
{
return states[i];
}
template
inline typename tween::value_type tween::operator[](scalar_type a) const
{
return interpolate(a);
}
template
inline typename tween::value_type tween::interpolate(scalar_type a) const
{
return interpolator(states[0], states[1], a);
}
template
inline void tween::set_interpolator(const interpolator_type& interpolator)
{
this->interpolator = interpolator;
}
template
inline const typename tween::interpolator_type& tween::get_interpolator() const
{
return interpolator;
}
template
inline void tween::update()
{
states[0] = states[1];
}
template
inline void tween::swap()
{
std::swap(states[0], states[1]);
}
#endif // ANTKEEPER_TWEEN_HPP