genode/repos/demo/include/util/lazy_value.h
2017-02-28 12:59:29 +01:00

86 lines
1.5 KiB
C++

/*
* \brief Animated value
* \author Norman Feske
* \date 2010-10-29
*/
/*
* Copyright (C) 2010-2017 Genode Labs GmbH
*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU Affero General Public License version 3.
*/
#ifndef _INCLUDE__UTIL__LAZY_VALUE_H_
#define _INCLUDE__UTIL__LAZY_VALUE_H_
template <typename T>
class Lazy_value
{
private:
T _speed;
T _curr;
T _dst;
T _accel;
public:
Lazy_value()
: _speed(0), _curr(0), _dst(0), _accel(1)
{ }
Lazy_value(T value)
: _speed(0), _curr(value), _dst(value), _accel(1)
{ }
void dst(T dst, unsigned steps)
{
_dst = dst;
T delta = (_curr > _dst) ? _curr - _dst : _dst - _curr;
if (steps == 0)
steps = 1;
_accel = (4*delta) / (steps*steps);
_speed = 0;
if (_accel < 1)
_accel = 1;
}
T dst() const { return _dst; }
void assign(T value) { _curr = value; }
void animate()
{
/* destination value reached? */
if (_curr == _dst) {
_speed = 0;
return;
}
/* change value with current speed */
if (_curr > _dst) {
_curr -= _speed;
if (_curr < _dst) _curr = _dst;
} else {
_curr += _speed;
if (_curr > _dst) _curr = _dst;
}
/* adapt speed */
T delta = _curr - _dst;
if (delta < 0) delta = -delta;
if (_speed*_speed < delta*_accel)
_speed += _accel;
else
_speed -= _accel;
if (_speed < 1) _speed = 1;
}
operator T () const { return _curr; }
};
#endif /* _INCLUDE__UTIL__LAZY_VALUE_H_ */