[font-metrics-api] Which line box? #334
Description
https://drafts.css-houdini.org/font-metrics-api/#fontmetrics-definition mentions several times "the line box". Which line box is that? What happens if the input text contains a preserved (e.g. with white-space: pre) newline? If the input element contains <br>, or a block, or an atomic (e.g. image) inline?
I think this draft is missing, for each of ach of measureElement and measureText, a detailed algorithm for how to turn their respective arguments into a single line of text. (Only text, with no line break.) Maybe it should raise in some cases?