I didn’t find a way to do it directly without Javascript, but I found a JS quite easy solution, without for loops and without modify the font-size and fits well in all dimensions, that is, the text grows until the limit of the shortest side.
Basically, I use the transform property, calculating the right proportion between the desired size and the current one.
This is the code:
<?xml version="1.0" encoding="UTF-8" ?>
<svg version="1.2" viewBox="0 0 1000 1000" width="1000" height="1000" xmlns="http://www.w3.org/2000/svg" >
<text id="t1" y="50" >MY UGLY TEXT</text>
<script type="application/ecmascript">
var width=500, height=500;
var textNode = document.getElementById("t1");
var bb = textNode.getBBox();
var widthTransform = width / bb.width;
var heightTransform = height / bb.height;
var value = widthTransform < heightTransform ? widthTransform : heightTransform;
textNode.setAttribute("transform", "matrix("+value+", 0, 0, "+value+", 0,0)");
</script>
</svg>In the previous example the text grows until the width == 500, but if I use a box size of width = 500 and height = 30, then the text grows until height == 30.