anim.h

class Animator : public Timer
{
public:
	enum class State
	{
		Started,
		Running,
		Finished
	};
	Animator(int updateinterval = 40) : m_update_interval(updateinterval)
	{
		CurveFunc = [](double x){ return x; }; // by default, just a linear mapping
	}
	using animfunc = std::function<void(State, double)>;
	// CurveFunc is given a value between 0.0-1.0 and must return a value between 0.0-1.0
	std::function<double(double)> CurveFunc;
	void timerCallback() override
	{
		double elapsed = Time::getMillisecondCounterHiRes()-m_starttime;
		double normpos = 1.0 / m_dur * elapsed;
		if (m_cb)
		{
			if (normpos >= 1.0)
			{
				m_cb(State::Finished, CurveFunc(1.0));
				stopTimer();
			}
			else 
				m_cb(State::Running, CurveFunc(normpos));
		}
	}
	void start(double duration,animfunc f)
	{
		m_cb = f;
		m_dur = jlimit(0.1, 600.0, duration)*1000.0;
		m_starttime = Time::getMillisecondCounterHiRes();
		if (m_cb)
			m_cb(State::Started, CurveFunc(0.0));
		startTimer(m_update_interval);
	}
	void stop()
	{
		stopTimer();
		if (m_cb)
			m_cb(State::Finished, CurveFunc(1.0));
	}
private:
	animfunc m_cb;
	double m_starttime = 0.0;
	double m_dur = 0.1;
	int m_update_interval = 40;
};