Re: Issue 984 in lilypond: Noteheads don't merge when one of the voices contains a second

[lilypond]

Comment #14 on issue 984 by address@hidden: Noteheads don't merge when one of  
the voices contains a second
http://code.google.com/p/lilypond/issues/detail?id=984

It might be harder than you think.  The current code is a total mess that  
for most decisions only consults the properties of the extremal note  
heads.  This only works where all noteheads on a stem are actually  
identical.  Which is the most common case, but definitely the only one.   
The loop over the noteheads will not be correct in several cases where  
there are multiple noteheads, not all of them mergeable.

I am taking so long not because I am just adding a "missing part": that one  
is actually pretty easy.  But because the whole thing needs rewriting.  I  
am not interested in getting a higher number of cases right by accident.   
So that needs some work, some more stuff needs to get pulled into the loop,  
and I need to consult the _corresponding_ noteheads for information about  
merging.  Which means that I have to sort not just the notehead coordinates  
but rather the whole notehead info.

And so forth and so on.  I don't like leaving code where I can just write  
down a number of regtests that will fail under it.