line-wide underline/strikethrough position
Submitted by Behdad Esfahbod
Link to original bug (#371726)
Description
There are a couple of downstream bugs against Pango:
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=207882 (can't find the other)
essentially coming down to having an underline mode (as default?) that chooses a single underline/strikethrough position/thickness per line, instead of per run.
To choose one, you want it to be from the /dominant/ font used in the line. Since we don't have any such concept right now, we can go as far as taking the average over all chars (graphemes?) in the line. That should work pretty good. And to make runs self-contained, this can be implemented by adding new underlin/strikethrough position/thickness attributes, and attach them to runs in PangoLayout.