Added new router

plugins/routers/joint.routers.oneSide.js

@@ -0,0 +1,58 @@
+// Routes the link always to/from a certain side
+//
+// Arguments:
+//   padding ... gap between the element and the first vertex. :: Default 40.
+//   side ... 'left' | 'right' | 'top' | 'bottom' :: Default 'bottom'.
+//
+joint.routers.oneSide = function(vertices, opt, linkView) {
+
+    var side = opt.side || 'bottom';
+    var padding = opt.padding || 40;
+
+    // LinkView contains cached source an target bboxes.
+    // Note that those are Geometry rectangle objects.
+    var sourceBBox = linkView.sourceBBox;
+    var targetBBox = linkView.targetBBox;
+    var sourcePoint = sourceBBox.center();
+    var targetPoint = targetBBox.center();
+
+    var coordinate, coordinateValue, dimension, direction;
+
+    switch (side) {
+        case 'bottom':
+            direction = 1;
+            coordinate = 'y';
+            dimension = 'height';
+            break;
+        case 'top':
+            direction = -1;
+            coordinate = 'y';
+            dimension = 'height';
+            break;
+        case 'left':
+            direction = -1;
+            coordinate = 'x';
+            dimension = 'width';
+            break;
+        case 'right':
+            direction = 1;
+            coordinate = 'x';
+            dimension = 'width';
+            break;
+        default:
+            throw new Error('Router: invalid side');
+    }
+
+    // move the points from the center of the element to outside of it.
+    sourcePoint[coordinate] += direction * (sourceBBox[dimension] / 2 + padding);
+    targetPoint[coordinate] += direction * (targetBBox[dimension] / 2 + padding);
+
+    // make link orthogonal (at least the first and last vertex).
+    if (direction * (sourcePoint[coordinate] - targetPoint[coordinate]) > 0) {
+        targetPoint[coordinate] = sourcePoint[coordinate];
+    } else {
+        sourcePoint[coordinate] = targetPoint[coordinate];
+    }
+
+    return [sourcePoint].concat(vertices, targetPoint);
+};