@Jack It seems to me that you are not redrawing the chart, so the layout isn't adjusted to the new font size. This part of the code is removed:

// Update layout based on new font and line sizes
chart.isDirtyLegend = true;
chart.redraw(false);

I used this feature. But as thre are lots of categories so I have to manage width of chart dynamic.

When I use https://code.highcharts.com/js/highcharts.js file then the width increase but scroll bar does not shown and can not see complete graph.

When I use https://code.highcharts.com/highcharts.js file width issue resolved and I can see a scroll bar to get all categories but then dynamic font size feature doesn't work.
Below are two versions with issue
http://design.tribondinfosystems.com/vertical.php
http://design.tribondinfosystems.com/vertical2.php

@Derek Moore: It is pure SVG. If you found pieces of HTML in Highcharts, it is because you have added the useHTML option for certain labels. Read more at http://www.highcharts.com/docs/chart-concepts/labels-and-string-formatting#html.

Why can't Highcharts be pure SVG? Instead it is currently a mix of SVG for graph components and HTML for label and text components. The text should scale with with the graph components. Take, for example, the following SVG:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<svg
xmlns:svg="http://www.w3.org/2000/svg&quot;
xmlns="http://www.w3.org/2000/svg&quot;
width="210mm"
height="297mm"
viewBox="0 0 744.09448819 1052.3622047"
id="svg1"
version="1.1">
<g id="layer1">
<text
xml:space="preserve"
style="font-style:normal;font-weight:normal;font-size:40px;line-height:125%;font-family:sans-serif;letter-spacing:0px;word-spacing:0px;fill:#000000;fill-opacity:1;stroke:none;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1"
x="184"
y="131.3622"
id="text1"><tspan
id="tspan1"
x="184"
y="131.3622">This is scalable?</tspan></text>
<ellipse
style="fill:none;fill-opacity:1;stroke:#ff0000;stroke-width:6;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1"
id="path1"
cx="347"
cy="272.36221"
rx="126"
ry="116" />
</g>
</svg>

Here the text will scale with the graph, and there is no need for programmatic access to font scaling.

Looks promising, I'll go and try to implement this.
Thanks!

This idea is extended in http://highcharts.uservoice.com/forums/55896-general/suggestions/3378262-scalable-graph-and-gauge

this idea is basically an extension of http://highcharts.uservoice.com/forums/55896-general/suggestions/2258241-implement-dynamic-font-size