Copy'n'paste approach for issue #1153.

[jakubjelinek]

I've actually tested only 4.1 backport of this change so far.
The commit also includes one pasto change -
\gre@space@count@additionaltopspacethreshold=2
...
\gre@space@count@additionaltopspacethreshold=0
where the latter IMHO should have been
\gre@space@count@additionaltopspacealtthreshold=0

I've also noticed the Copyright years weren't updated this year, shall that be done before 4.2 is released?

[jakubjelinek]

Thinking about it more, I believe we must be also measuring the maximum height of the alt text for inter-staff spacing, with different baselines for alt text and nabc neumes I bet we also need to measure separately the maximum heights of the alt text vs. maximum height of nabc neumes and use the corresponding baseline for those. Or is that not the case?
As for the copy'n'paste, I think only the \gre@typesetnabcabovelines macro is large enough that it would be perhaps useful to use just one macro with an extra argument instead.

[henryso]

The calculation (not that I understand it completely) that you speak of is \gre@calculate@additionalspaces in gregoriotex-spaces.tex. I think it's being put into \gre@dimen@additionaltopspacealt.

[jakubjelinek]

\gre@dimen@additionaltopspacealt I already replace with \gre@dimen@additionaltopspacenabc
for \GreNabcAboveLines. I've tried Sr. Maria's testcase copied 3 times and the spacing between the top of the nabc neumes and previous line of text is the same when \GreNabcAboveLines and \GreTextAboveLines is used for nabc, so I think with the cleanup change I've just pushed it should DTRT and not be too ugly anymore (but I'm never sure about \relax and % at the end of lines).

[eroux]

This looks ok to me

[henryso]

I'll merge this and review tests some time today.