From 15b16aaed9fb60bf091b711fdfa5ba75e282c97d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=BCrg=20Lehni?= <juerg@scratchdisk.com>
Date: Sun, 6 Mar 2011 14:45:07 +0000
Subject: [PATCH] Add Line class to basics.

---
 src/basic/Line.js | 50 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100644 src/basic/Line.js

diff --git a/src/basic/Line.js b/src/basic/Line.js
new file mode 100644
index 00000000..f866db3b
--- /dev/null
+++ b/src/basic/Line.js
@@ -0,0 +1,50 @@
+var Line = this.Line = Base.extend({
+	initialize: function(point1, point2, infinite) {
+		// Convention: With 3 parameters, both points are absolute, and infinite
+		// controls wether the line extends beyond the defining points, meaning
+		// intersection outside the line segment are allowed.
+		// With two parameters, the 2nd parameter is a direction, and infinite
+		// is automatially true, since we're describing an infinite line.
+		point1 = Point.read(arguments, 0, 1);
+		point2 = Point.read(arguments, 1, 1);
+		if (arguments.length == 3) {
+			this.point = point1;
+			this.vector = point2.subtract(point1);
+			this.infinite = infinite;
+		} else {
+			this.point = point1;
+			this.vector = point2;
+			this.infinite = true;
+		}
+	},
+
+	intersect: function(line) {
+		var cross = this.vector.cross(line.vector);
+		// Epsilon tolerance
+		if (Math.abs(cross) <= 10e-6)
+			return null;
+		var v = line.point.subtract(this.point)
+			t1 = v.cross(line.vector) / cross,
+			t2 = v.cross(this.vector) / cross;
+		// Check the ranges of t parameters if the line is not allowed to
+		// extend beyond the definition points.
+		return (this.infinite || 0 <= t1 && t1 <= 1)
+				&& (line.infinite || 0 <= t2 && t2 <= 1)
+			? this.point.add(this.vector.multiply(t1)) : null;
+	},
+
+	getSide: function(p) {
+		var v1 = this.vector,
+			v2 = p.subtract(this.point),
+			ccw = v2.cross(v1);
+		if (ccw == 0.0) {
+			ccw = v2.dot(v1);
+			if (ccw > 0.0) {
+				ccw = (v2 - v1).dot(v1);
+				if (ccw < 0.0)
+				    ccw = 0.0;
+			}
+		}
+		return ccw < 0.0 ? -1 : ccw > 0.0 ? 1 : 0;
+	}
+});