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/*
* ***** BEGIN GPL LICENSE BLOCK *****
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
* ***** END GPL LICENSE BLOCK *****
*/
#include "BLI_dial.h"
#include "BLI_math.h"
#include "MEM_guardedalloc.h"
struct Dial {
/* center of the dial */
float center[2];
/* threshold of the dial. Distance of current position has to be greater
* than the threshold to be used in any calculations */
float threshold_squared;
/* the direction of the first dial position exceeding the threshold. This
* is later used as the basis against which rotation angle is calculated */
float initial_direction[2];
/* cache the last angle to detect rotations bigger than -/+ PI */
float last_angle;
/* number of full rotations */
int rotations;
/* has initial_direction been initialized */
bool initialized;
};
Dial *BLI_dial_initialize(float start_position[2], float threshold)
{
Dial *dial = MEM_callocN(sizeof(Dial), "dial");
copy_v2_v2(dial->center, start_position);
dial->threshold_squared = threshold * threshold;
return dial;
}
float BLI_dial_angle(Dial *dial, float current_position[2])
{
float current_direction[2];
sub_v2_v2v2(current_direction, current_position, dial->center);
/* only update when we have enough precision, by having the mouse adequately away from center */
if (len_squared_v2(current_direction) > dial->threshold_squared) {
float angle;
float cosval, sinval;
normalize_v2(current_direction);
if (!dial->initialized) {
copy_v2_v2(dial->initial_direction, current_direction);
dial->initialized = true;
}
/* calculate mouse angle between initial and final mouse position */
cosval = dot_v2v2(current_direction, dial->initial_direction);
sinval = cross_v2v2(current_direction, dial->initial_direction);
/* clamp to avoid nans in acos */
angle = atan2f(sinval, cosval);
/* change of sign, we passed the 180 degree threshold. This means we need to add a turn.
* to distinguish between transition from 0 to -1 and -PI to +PI, use comparison with PI/2 */
if ((angle * dial->last_angle < 0.0f) &&
(fabsf(dial->last_angle) > (float)M_PI_2))
{
if (dial->last_angle < 0.0f)
dial->rotations--;
else
dial->rotations++;
}
dial->last_angle = angle;
return angle + 2.0f * (float)M_PI * dial->rotations;
}
return dial->last_angle;
}
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