How to drag nodes with children in d3 circle packing? - d3.js

Question

I have been trying to drag in d3 packed nodes using this code as a basis https://codepen.io/MrHen/pen/GZQOPW. Unfortunately I can't find a method to use so that when a node with children is dragged around it's (visible) children move with the parent. I use this function to drag circles around:
var drag = d3.behavior.drag()
.on("drag", function(d, i) {
d.x += d3.event.dx;
d.y += d3.event.dy;
draw();
})
I the example above for instance I want to be able to drag the nodes on layer 1 (light blue) and when I do this their children change their position so they stay (visually) in the borders of their parents.
Thank you!

Answer 1

First remove the pointer-events: none on the root and middle nodes. Then set yourself up a little recursion to walk a node's descendants and update their position:
function recurOnChildren(d) {
d.x += d3.event.dx;
d.y += d3.event.dy;
if (!d.children) return;
d.children.forEach(c => {
recurOnChildren(c);
});
}
And call from your drag handler:
var drag = d3.behavior.drag()
.on("drag", function(d, i) {
recurOnChildren(d);
draw();
})
Running code:
var margin = 20,
diameter = 960;
var color = d3.scale.linear()
.domain([-1, 5])
.range(["hsl(152,80%,80%)", "hsl(228,30%,40%)"])
.interpolate(d3.interpolateHcl);
var pack = d3.layout.pack()
.padding(2)
.size([diameter - margin, diameter - margin])
.value(function(d) {
return d.size;
})
var svg = d3.select("body").append("svg")
.attr("width", diameter)
.attr("height", diameter)
.append("g")
.attr("transform", "translate(" + diameter / 2 + "," + diameter / 2 + ")");
d3.json("https://gist.githubusercontent.com/mbostock/7607535/raw/695f8ed6298c06a946406c707200a1f6b21875d8/flare.json", function(error, root) {
if (error) throw error;
var focus = root,
nodes = pack.nodes(root),
view;
function recurOnChildren(d) {
d.x += d3.event.dx;
d.y += d3.event.dy;
if (!d.children) return;
d.children.forEach(c => {
recurOnChildren(c);
});
}
var drag = d3.behavior.drag()
.on("drag", function(d, i) {
recurOnChildren(d);
draw();
})
var circle = svg.selectAll("circle")
.data(nodes)
.enter().append("circle")
.attr("class", function(d) {
return d.parent ? d.children ? "node node--middle" : "node node--leaf" : "node node--root";
})
.style("fill", function(d) {
return d.children ? color(d.depth) : null;
});
var text = svg.selectAll("text")
.data(nodes)
.enter().append("text")
.attr("class", "label")
.style("fill-opacity", function(d) {
return d.parent === root ? 1 : 0;
})
.style("display", function(d) {
return d.parent === root ? "inline" : "none";
})
.text(function(d) {
return d.name;
});
var node = svg.selectAll("circle,text");
svg.selectAll(".node").call(drag);
d3.select("body")
.style("background", color(-1))
draw();
function draw() {
var k = diameter / (root.r * 2 + margin);
node.attr("transform", function(d) {
return "translate(" + (d.x - root.x) * k + "," + (d.y - root.y) * k + ")";
});
circle.attr("r", function(d) {
return d.r * k;
});
}
});
.node {
cursor: pointer;
}
.node:hover {
stroke: #000;
stroke-width: 1.5px;
}
.node--leaf {
fill: white;
}
.label {
font: 11px "Helvetica Neue", Helvetica, Arial, sans-serif;
text-anchor: middle;
text-shadow: 0 1px 0 #fff, 1px 0 0 #fff, -1px 0 0 #fff, 0 -1px 0 #fff;
}
.label {
pointer-events: none;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.17/d3.min.js"></script>