Is there a public LFC API that will let you measure the dimensions of a line of text?
If you use a plain <text> element, you can't try to read the size in the same call that sets the text, you have to listen for 'onwidth' (because most DOM's defer layout until javascript is idle). I'm pretty sure the kernel has a way to measure text that uses some hackery to do it synchronously. Can we expose that as a public API if it's not already?
