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diff --git a/source/blender/blenlib/BLI_dial.h b/source/blender/blenlib/BLI_dial.h
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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 *****
+ */
+
+#ifndef __BLI_DIAL_H__
+#define __BLI_DIAL_H__
+
+/** \file BLI_dial.h
+ *  \ingroup bli
+ *
+ * \note dials act similar to old rotation based phones and output an angle.
+ * 
+ * They just are initialized with the center of the dial and a threshold value as input.
+ * 
+ * When the distance of the current position of the dial from the center 
+ * exceeds the threshold, this position is used to calculate the initial direction. 
+ * After that, the angle from the initial direction is calculated based on
+ * current and previous directions of the digit, and returned to the user.
+ * 
+ * Usage examples:
+ * \code
+ * float start_position[2] = {0.0f, 0.0f};
+ * float current_position[2];
+ * float threshold = 0.5f;
+ * float angle;
+ * Dial *dial;
+ * 
+ * dial = BLI_dial_initialize(start_position, threshold);
+ *
+ * angle = BLI_dial_angle(dial, curent_position);
+ * 
+ * MEM_freeN(dial);
+ *
+ * \endcode
+ */
+
+typedef struct Dial Dial;
+
+Dial *BLI_dial_initialize(float start_position[2], float threshold);
+
+float BLI_dial_angle(Dial *dial, float current_position[2]);
+
+#endif /* __BLI_DIAL_H__ */