From ade05e5a7ee4c46d2df302622c0c9d35ea3a6743 Mon Sep 17 00:00:00 2001
From: Norman Feske <norman.feske@genode-labs.com>
Date: Fri, 28 Jul 2017 16:27:46 +0200
Subject: [PATCH] gems: utility for calculating bezier curves

---
 repos/gems/include/gems/bezier.h | 71 ++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 repos/gems/include/gems/bezier.h

diff --git a/repos/gems/include/gems/bezier.h b/repos/gems/include/gems/bezier.h
new file mode 100644
index 000000000..edca97614
--- /dev/null
+++ b/repos/gems/include/gems/bezier.h
@@ -0,0 +1,71 @@
+/*
+ * \brief   Utilities for calculating bezier curves
+ * \date    2017-07-28
+ * \author  Norman Feske
+ */
+
+/*
+ * Copyright (C) 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__GEMS__BEZIER_H_
+#define _INCLUDE__GEMS__BEZIER_H_
+
+/**
+ * Calculate quadratic bezier curve
+ *
+ * \param draw_line  functor to be called to draw a line segment
+ * \param levels     number of sub divisions
+ *
+ * The coordinates are specified in clock-wise order with point 1 being
+ * the start and point 3 the end of the curve.
+ */
+template <typename FUNC>
+static inline void bezier(long x1, long y1, long x2, long y2, long x3, long y3,
+                          FUNC const &draw_line, unsigned levels)
+{
+	if (levels-- == 0) {
+		draw_line(x1, y1, x3, y3);
+		return;
+	}
+
+	long const x12  =  (x1 +  x2) / 2,    y12  =  (y1 +  y2) / 2,
+	           x23  =  (x2 +  x3) / 2,    y23  =  (y2 +  y3) / 2,
+	           x123 = (x12 + x23) / 2,    y123 = (y12 + y23) / 2;
+
+	bezier(x1, y1, x12, y12, x123, y123, draw_line, levels);
+	bezier(x123, y123, x23, y23, x3, y3, draw_line, levels);
+}
+
+
+/**
+ * Calculate cubic bezier curve
+ *
+ * The arguments correspond to those of the quadratic version but with point 4
+ * being the end of the curve.
+ */
+template <typename FUNC>
+static inline void bezier(long x1, long y1, long x2, long y2,
+                          long x3, long y3, long x4, long y4,
+                          FUNC const &draw_line, unsigned levels)
+{
+	if (levels-- == 0) {
+		draw_line(x1, y1, x4, y4);
+		return;
+	}
+
+	long const x12   =   (x1 +   x2) / 2,    y12   =   (y1 +   y2) / 2,
+	           x23   =   (x2 +   x3) / 2,    y23   =   (y2 +   y3) / 2,
+	           x34   =   (x3 +   x4) / 2,    y34   =   (y3 +   y4) / 2,
+	           x123  =  (x12 +  x23) / 2,    y123  =  (y12 +  y23) / 2,
+	           x234  =  (x23 +  x34) / 2,    y234  =  (y23 +  y34) / 2,
+	           x1234 = (x123 + x234) / 2,    y1234 = (y123 + y234) / 2;
+
+	bezier(x1, y1, x12, y12, x123, y123, x1234, y1234, draw_line, levels);
+	bezier(x1234, y1234, x234, y234, x34, y34, x4, y4, draw_line, levels);
+}
+
+#endif /* _INCLUDE__GEMS__BEZIER_H_ */