Right now, it's only possible to request an editing context for either an entire input element or a particular rect of the page. It should be possible to request an editing context for a particular rect within a given input element as well (e.g. get one paragraph of a `<textarea>` instead of the entire thing).
<rdar://problem/65561491>
Created attachment 405757 [details] Patch
Committed r265209: <https://trac.webkit.org/changeset/265209> All reviewed patches have been landed. Closing bug and clearing flags on attachment 405757 [details].