Re: Lyrics break estimation of vertical spacing

[Boris Shingarov]

> Do we really need this to be included in every Interval? I'd have
 > thought that the only data structure that needs to change is
 > Line_details.
 
Right, but how do you get the actual value in there?
It's filled from calling the Y-extent Scheme function, which can be
anything, and in most cases it calls back into C   land, but my
point is that all these APIs are completely generic, you can't
statically tell in which places in code you need the extra interval.
My answer to this is an Interval that can be augmented by another
Interval, but is in all other respects just an Interval.