animated_value.hpp

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#ifndef EAGINE_ANIMATED_VALUE_HPP
#define EAGINE_ANIMATED_VALUE_HPP
 
#include "math/functions.hpp"
#include "valid_if/positive.hpp"
#include <type_traits>
 
namespace eagine {
//------------------------------------------------------------------------------
template <typename T, typename F, typename S = float>
class animated_value {
public:
    animated_value() = default;
 
    animated_value(const T& initial)
      : _curr{initial}
      , _next{initial} {}
 
    auto set(T value, valid_if_positive<F> duration, S slope) -> auto& {
        _curr = _next;
        _next = value;
        _duration = extract(duration);
        _phase = F(0);
        _slope = slope;
        return *this;
    }
 
    auto set(T value, valid_if_positive<F> duration) -> auto& {
        return set(value, duration, 2);
    }
 
    auto get() const -> T {
        return math::blend(
          _next,
          _curr,
          math::sigmoid01(math::clamp(_phase / _duration, 0, 1), _slope));
    }
 
    auto update(F deltaT) -> auto& {
        _phase += deltaT;
        return *this;
    }
 
    auto is_done() const noexcept -> bool {
        return _phase >= _duration;
    }
 
private:
    T _curr{0};
    T _next{0};
    F _duration{1};
    F _phase{_duration};
    S _slope{2};
};
//------------------------------------------------------------------------------
} // namespace eagine
 
#endif