How can I wrap text labels in a D3 tree visualization for improved readability?

Wrapping Text in D3 Tree

In a D3 tree visualization, sometimes it is desirable to wrap the text labels on the nodes to make the tree more readable. This article demonstrates how to achieve this text wrapping.

The Challenge

Consider the following D3 tree:

Foo is not a long word

Ideally, the text should wrap to:

Foo is
not a
long word

The Solution

To achieve text wrapping, two key modifications are required:

1. Create a Wrap Function:

   Implement a wrap function to add elements to the nodes and control the wrapping width:

   <code class="javascript">function wrap(text, width) {
       text.each(function () {
           var text = d3.select(this),
               words = text.text().split(/\s+/).reverse(),
               word,
               line = [],
               lineNumber = 0,
               lineHeight = 1.1, // ems
               x = text.attr("x"),
               y = text.attr("y"),
               dy = 0, //parseFloat(text.attr("dy")),
               tspan = text.text(null)
                           .append("tspan")
                           .attr("x", x)
                           .attr("y", y)
                           .attr("dy", dy + "em");
           while (word = words.pop()) {
               line.push(word);
               tspan.text(line.join(" "));
               if (tspan.node().getComputedTextLength() > width) {
                   line.pop();
                   tspan.text(line.join(" "));
                   line = [word];
                   tspan = text.append("tspan")
                               .attr("x", x)
                               .attr("y", y)
                               .attr("dy", ++lineNumber * lineHeight + dy + "em")
                               .text(word);
               }
           }
       });
   }</code>

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2. Use the Wrap Function:

   Instead of setting the text on each node, apply the wrap function:

   <code class="javascript">// Add entering nodes in the parent’s old position.
   node.enter().append("text")
       .attr("class", "node")
       .attr("x", function (d) { return d.parent.px; })
       .attr("y", function (d) { return d.parent.py; })
       .text("Foo is not a long word")
       .call(wrap, 30); // wrap the text in <= 30 pixels</code>

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By implementing these modifications, you can successfully wrap the text on the D3 tree nodes.

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