How to apply d3.js svg clipping after zooming

Question

I am trying to use an svg-clippath with d3.js and the zoom behaviour. The following code creates a rectangle, which will then be clipped by a rectangualar clipping region. <

Answer 1

I had the same problem and spent the last couple of hours trying to figure out a solution. Apparently, the clip-path operates on the object prior to transformation. So I tried to reverse-transform the clip object when performing the zoom transformation, and this worked !

It is something in the spirit of:

var clip_orig_x = 100, clip_orig_y = 100;
function zoomed() {
    var t = d3.event.translate;
    var s = d3.event.scale;

    // standard zoom transformation:
    container.attr("transform", "translate(" + t +")scale(" + s + ")"); 

    // the trick: reverse transform the clip object!
    clip.attr("transform", "scale(" + 1/s + ")")
        .attr("x", clip_orig_x - t[0]) 
        .attr("y", clip_orig_y - t[1]);
}

where clip is the rectangle in the clipPath. Because of interactions between zooming and translation, you need to set "x" and "y" explicitly instead of using transform.

I am sure experienced d3 programmers out there will come up with a better solution, but this works !