in bits/opcache-instance-id.php [688:709]
function click(d) {
if (!d.children) return;
kx = (d.y ? w - 40 : w) / (1 - d.y);
ky = h / d.dx;
x.domain([d.y, 1]).range([d.y ? 40 : 0, w]);
y.domain([d.x, d.x + d.dx]);
var t = g.transition()
.duration(d3.event.altKey ? 7500 : 750)
.attr("transform", function(d) { return "translate(" + x(d.y) + "," + y(d.x) + ")"; });
t.select("rect")
.attr("width", d.dy * kx)
.attr("height", function(d) { return d.dx * ky; });
t.select("text")
.attr("transform", transform)
.style("opacity", function(d) { return d.dx * ky > 12 ? 1 : 0; });
d3.event.stopPropagation();
}