Re: Issue 34 in lilypond: Grace synchronization

[lilypond]

Comment #20 on issue 34 by address@hidden: Grace synchronization
http://code.google.com/p/lilypond/issues/detail?id=34

I've had another musing.  My proposal of using -inf as normal grace timing  
basically shifts just one problem class to another since some things need  
to happen before graces in other contexts, some after.

So I thought about this: we have a start-of-timestep callback in engravers,  
and event callbacks and end-of-timestep.  Now what we actually want when a  
grace is in a parallel context but not in ours, is to have our  
start-of-timestep callback called before the grace in the other context  
starts its event callbacks, and our end-of-timestep called afterwards.  And  
actually, if there is a preceding event in our own graceless context, its  
end-of-timestep is to be called _afterwards_ as well.

So with a grace, I tend to consider it reasonable to have a  
start-of-timestep for the next event in sequence called before the  
end-of-timestep of the preceding event in the same context is called when a  
grace occurs in a parallel context.  Possibly (but less sure about that)  
even when the grace occurs in one's own context.  The context-moment should  
likely reflect the grace timing, as if one had had a spacer grace in one's  
own voice.

That way typical start-of-timestep actions like creating a new context or  
establishing a new clef or setting context properties or so will happen  
before graces in parallel voices.