returns the bounding box
if(!this.bbox){ var shape = this.shape; this.bbox = { x: Math.min(shape.x1, shape.x2), y: Math.min(shape.y1, shape.y2), width: Math.abs(shape.x2 - shape.x1), height: Math.abs(shape.y2 - shape.y1) }; } return this.bbox; // dojox.gfx.Rectangle