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