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b188a4dbc9
Don't just clamp the speed value to a positive number but immediately assign the destination value. This is needed in situations where the number of steps is too low for proper acceleration and deceleration. Issue #3096
89 lines
1.5 KiB
C++
89 lines
1.5 KiB
C++
/*
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* \brief Animated value
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* \author Norman Feske
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* \date 2010-10-29
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*/
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/*
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* Copyright (C) 2010-2017 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU Affero General Public License version 3.
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*/
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#ifndef _INCLUDE__UTIL__LAZY_VALUE_H_
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#define _INCLUDE__UTIL__LAZY_VALUE_H_
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template <typename T>
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class Lazy_value
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{
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private:
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T _speed;
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T _curr;
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T _dst;
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T _accel;
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public:
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Lazy_value()
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: _speed(0), _curr(0), _dst(0), _accel(1)
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{ }
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Lazy_value(T value)
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: _speed(0), _curr(value), _dst(value), _accel(1)
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{ }
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void dst(T dst, unsigned steps)
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{
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_dst = dst;
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T delta = (_curr > _dst) ? _curr - _dst : _dst - _curr;
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if (steps == 0)
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steps = 1;
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_accel = (4*delta) / (steps*steps);
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_speed = 0;
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if (_accel < 1)
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_accel = 1;
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}
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T dst() const { return _dst; }
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void assign(T value) { _curr = value; }
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void animate()
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{
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/* destination value reached? */
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if (_curr == _dst) {
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_speed = 0;
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return;
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}
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/* change value with current speed */
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if (_curr > _dst) {
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_curr -= _speed;
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if (_curr < _dst) _curr = _dst;
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} else {
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_curr += _speed;
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if (_curr > _dst) _curr = _dst;
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}
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/* adapt speed */
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T delta = _curr - _dst;
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if (delta < 0) delta = -delta;
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if (_speed*_speed < delta*_accel)
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_speed += _accel;
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else
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_speed -= _accel;
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if (_speed < 1) {
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_speed = 0;
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_curr = _dst;
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}
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}
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operator T () const { return _curr; }
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};
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#endif /* _INCLUDE__UTIL__LAZY_VALUE_H_ */
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