d3.js - arrows on links in d3js force layout

Question

I'm using the force layout to represent a directed unweighted network. My inspiration comes from the following example: http://bl.ocks.org/mbostock/1153292

I tried to make nodes of different sizes, but I have a little problem. The marker used to draw the arrow on each link points to the center of the circle. If the circle is too big it covers completely the arrow.

How can I handle this?

Answer 1

If you will use a <line> instead of <path>, the following should work for you, I have it working in my current solution. It's based on @?? ?????? 江戸 solution:

In your tick event listener:

linkElements.attr("x1", function(d) { return d.source.x; })
        .attr("y1", function(d) { return d.source.y; })
        .attr("x2", function(d) { 
             return getTargetNodeCircumferencePoint(d)[0];
        })
        .attr("y2", function(d) { 
             return getTargetNodeCircumferencePoint(d)[1];
        });

function getTargetNodeCircumferencePoint(d){

        var t_radius = d.target.nodeWidth/2; // nodeWidth is just a custom attribute I calculate during the creation of the nodes depending on the node width
        var dx = d.target.x - d.source.x;
        var dy = d.target.y - d.source.y;
        var gamma = Math.atan2(dy,dx); // Math.atan2 returns the angle in the correct quadrant as opposed to Math.atan
        var tx = d.target.x - (Math.cos(gamma) * t_radius);
        var ty = d.target.y - (Math.sin(gamma) * t_radius);

        return [tx,ty]; 
}

I am sure this solution can be modified to accomodate <path> elements, however I haven't tried it.