💿🐜 Antkeeper source code
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196 lines
5.0 KiB
196 lines
5.0 KiB
/*
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* Copyright (C) 2020 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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* Linearly interpolates between two values.
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*
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* @param x Start of the range in which to interpolate.
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* @param y End of the range in which to interpolate.
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* @param a Value used to interpolate between @p x and @p y.
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* @return Interpolated value.
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*/
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template <class T>
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T tween_default_interpolator(const T& x, const T& y, double a);
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/**
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* Container which stores two states along with an interpolator, for quick and easy tweening.
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*
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* @tparam T Value type.
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*/
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template <class T>
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class tween
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{
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public:
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//typedef typename std::remove_pointer<T>::type value_type;
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typedef T value_type;
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typedef typename std::decay<std::function<value_type(const T&, const T&, double)>>::type interpolator_type;
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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 or function object that will be used to interpolate between states 0 and 1.
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*/
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explicit tween(const T& state0, const T& state1, const interpolator_type& interpolator = tween_default_interpolator<T>);
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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 or function object that will be used to interpolate between states 0 and 1.
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*/
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explicit tween(const T& value, const interpolator_type& interpolator = tween_default_interpolator<T>);
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/**
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* Creates a tween.
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*
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* @param interpolator Function or function object that will be used to interpolate between states 0 and 1.
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*/
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explicit tween(const interpolator_type& interpolator = tween_default_interpolator<T>);
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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 state 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 T& operator[](int state) const;
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/// @copydoc tween::operator[](int) const
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T& operator[](int state);
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/**
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* Returns an interpolated state between state 0 and state 1.
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*
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* @param a Interpolation factor. Should be on `[0.0, 1.0]`.
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* @return Interpolated state.
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*/
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value_type interpolate(double a) const;
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/**
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* Sets the function object used to interpolate between states 0 and 1.
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*
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* @param interpolator Interpolator function object.
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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 or function object that is 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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interpolator_type interpolator;
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T state0;
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T state1;
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};
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template <class T>
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inline T tween_default_interpolator(const T& x, const T& y, double a)
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{
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//return x * (1.0 - a) + y * a;
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return y;
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}
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template <>
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inline float tween_default_interpolator<float>(const float& x, const float& y, double a)
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{
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return (y - x) * a + x;
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}
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template <class T>
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tween<T>::tween(const T& value, const interpolator_type& interpolator):
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interpolator(interpolator),
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state0(value),
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state1(value)
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{}
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template <class T>
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tween<T>::tween(const T& state0, const T& state1, const interpolator_type& interpolator):
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interpolator(interpolator),
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state0(state0),
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state1(state1)
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{}
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template <class T>
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tween<T>::tween(const interpolator_type& interpolator):
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interpolator(interpolator)
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{}
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template <class T>
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inline const T& tween<T>::operator[](int state) const
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{
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return (state <= 0) ? state0 : state1;
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}
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template <class T>
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inline T& tween<T>::operator[](int state)
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{
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return (state <= 0) ? state0 : state1;
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}
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template <class T>
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inline typename tween<T>::value_type tween<T>::interpolate(double a) const
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{
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return interpolator(state0, state1, a);
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}
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template <class T>
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inline void tween<T>::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>
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inline const typename tween<T>::interpolator_type& tween<T>::get_interpolator() const
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{
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return interpolator;
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}
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template <class T>
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inline void tween<T>::update()
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{
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state0 = state1;
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}
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template <class T>
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inline void tween<T>::swap()
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{
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std::swap(state0, state1);
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}
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#endif // ANTKEEPER_TWEEN_HPP
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