[Arnavion]

Pixel-correct measurement of fonts / text is a must-have for certain specific applications like subtitle renderers. (I maintain one.)

For a specific example, it's more pleasing to split a long line of text in a way that all the split lines have roughly the same length - "a a a b b b" -> "a a a\nb b b". But CSS only gives you one way to split lines - as much text as possible in all but the last line and whatever's leftover in the last line - "a a a b b\nb". This means a renderer library has to be able to measure the width of text to be able to insert linebreaks itself.