> The problem it solves is efficiently calculating the height of some wrapped text on a web page, without actually rendering that text to the page first (very expensive).

But in the end, in a browser, the actual text rendering is still done by the browser?

It's a library that allows to "do stuff" before the browser renders the actual text, but by still having the browser render, eventually, the actual text?

Or is this thing actually doing the final rendering of the text too?