getting text width in SVG prior to rendering

Question

I want to put a rectangle around a text in SVG. The height of the text is known to me (the font-size attribute of the text element). But the width is dependent on the actual content. Using getBBox() or getComputedTextLength() should work. But this only works after rendering.

Is there a way to specify that in an other way? For example defining the x and width attributes relative to other values? I didn't find anything like that in the SVG Spec.

Answer 1

Figuring where text ends presumably requires roughly the same underlying code path as the rendering itself implements - going through the width of each character based on the font and style, etc... As I am not aware the SVG standards define a method for directly getting this information without doing the actual full rendering, till such methods emerge or are reported here by others, the approach should be to render invisibly before doing the actual rendering.

You can do that in a hidden layer (z-index, opacity and stuff) or outside the visible viewport, whichever works best in experimentation. You just need to get the browser do the rendering to find out, so you render invisibly for that sake, then use getComputedTextLength()