--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/javascript/d3/src/geom/polygon.js	Thu Apr 10 14:20:23 2014 +0200
@@ -0,0 +1,88 @@
+// Note: requires coordinates to be counterclockwise and convex!
+d3.geom.polygon = function(coordinates) {
+
+  coordinates.area = function() {
+    var i = 0,
+        n = coordinates.length,
+        a = coordinates[n - 1][0] * coordinates[0][1],
+        b = coordinates[n - 1][1] * coordinates[0][0];
+    while (++i < n) {
+      a += coordinates[i - 1][0] * coordinates[i][1];
+      b += coordinates[i - 1][1] * coordinates[i][0];
+    }
+    return (b - a) * .5;
+  };
+
+  coordinates.centroid = function(k) {
+    var i = -1,
+        n = coordinates.length - 1,
+        x = 0,
+        y = 0,
+        a,
+        b,
+        c;
+    if (!arguments.length) k = -1 / (6 * coordinates.area());
+    while (++i < n) {
+      a = coordinates[i];
+      b = coordinates[i + 1];
+      c = a[0] * b[1] - b[0] * a[1];
+      x += (a[0] + b[0]) * c;
+      y += (a[1] + b[1]) * c;
+    }
+    return [x * k, y * k];
+  };
+
+  // The Sutherland-Hodgman clipping algorithm.
+  coordinates.clip = function(subject) {
+    var input,
+        i = -1,
+        n = coordinates.length,
+        j,
+        m,
+        a = coordinates[n - 1],
+        b,
+        c,
+        d;
+    while (++i < n) {
+      input = subject.slice();
+      subject.length = 0;
+      b = coordinates[i];
+      c = input[(m = input.length) - 1];
+      j = -1;
+      while (++j < m) {
+        d = input[j];
+        if (d3_geom_polygonInside(d, a, b)) {
+          if (!d3_geom_polygonInside(c, a, b)) {
+            subject.push(d3_geom_polygonIntersect(c, d, a, b));
+          }
+          subject.push(d);
+        } else if (d3_geom_polygonInside(c, a, b)) {
+          subject.push(d3_geom_polygonIntersect(c, d, a, b));
+        }
+        c = d;
+      }
+      a = b;
+    }
+    return subject;
+  };
+
+  return coordinates;
+};
+
+function d3_geom_polygonInside(p, a, b) {
+  return (b[0] - a[0]) * (p[1] - a[1]) < (b[1] - a[1]) * (p[0] - a[0]);
+}
+
+// Intersect two infinite lines cd and ab.
+function d3_geom_polygonIntersect(c, d, a, b) {
+  var x1 = c[0], x2 = d[0], x3 = a[0], x4 = b[0],
+      y1 = c[1], y2 = d[1], y3 = a[1], y4 = b[1],
+      x13 = x1 - x3,
+      x21 = x2 - x1,
+      x43 = x4 - x3,
+      y13 = y1 - y3,
+      y21 = y2 - y1,
+      y43 = y4 - y3,
+      ua = (x43 * y13 - y43 * x13) / (y43 * x21 - x43 * y21);
+  return [x1 + ua * x21, y1 + ua * y21];
+}