[skrebbel]

why not? if you control the font and the font size then can't you have harfbuzz tell you how wide each glyph is going to be, and it'll fit precisely? (assuming the browser also uses harfbuzz for this, which it does)

[rjsw]

Because SVG isn't defined to call into harfbuzz.

You don't control the font if the SVG fragment is embedded in HTML.