Event-Listener [was Re: repeat partcombine texts]

[Simon Bailey]

On 11 Oct 2013, at 16:17, Simon Bailey wrote:
> i was typesetting a score last week, and there are some a2 sections in the 
> horns that go over multiple systems and pages. is there any way to repeat the 
> current partcombine "text" in brackets at the beginning of a system?
> 
> <<<
> \version "2.17.28"
> 
> partI = \relative c' {c d c d | e f g a | \break g f e f | }
> partII = \relative c' {a b c d | e f g a | g f e d | }
> 
> \partcombine \partI \partII
> >>> 
> 
> or would it be easiest to add a tagged markup to one of the voices manually? 
> [at least easier until the layout of the score changes...]
> 
> mock-up of desired result:
> <<<
> \version "2.17.28"
> 
> partI = \relative c' {c d c d | e f g a | \break g f e f | }
> partII = \relative c' {a b c d | e f g a | g^"(a2)" f e d | }
> 
> \partcombine \partI \partII
> >>> 

I've been spending some time thinking about this issue and it would seem to me 
that I could create an event-listener on unisono-event. 

In this event-listener, initialize a TextSpanner with 
bound-details.left-broken.text = \markup { \parenthesize \aDueText }.
ideally, the TextSpanner should stop when the voices break apart again, but i 
can't find an event for that.

Does that make sense? It should then be fairly simple to extend this to also 
work on Solo I and Solo II.

I've looked at ly/event-listener.ly and using this code, i can see when a 
unisono-event is fired and I assume that i can probably get a TextSpanner to 
start in there with a lot of trial and error. Is there an event fired when the 
unisono state finishes?

And that brings me to the next question: There is a bug in 
ly/event-listener.ly. This construct:

<<<
(format-moment (ly:duration-length (ly:event-property
                                    event
                                    'tempo-unit))))))
>>>

throws the following error:
<<<
ly/event-listener.ly:145:35: In procedure ly:duration-length in expression 
(ly:duration-length (ly:event-property event #)):
ly/event-listener.ly:145:35: Wrong type argument in position 1 (expecting 
Duration): #f
>>>

i have the itchy feeling that this is probably _very_ simple to fix, but i 
wouldn't know where to start looking... 

regards,
sb

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