Search of context hierarchy for voice for lyrics is made optional

Search of context hierarchy for voice for lyrics is optional

 - add new context property, searchForVoice, to indicate whether
   the extended search for a voice containing lyric rhythms should
   be conducted

 - test searchForVoice in get_voice_to_lyrics () to decide whether
   to conduct an extended search

 - fixes 1579

[Trevor Daniels, 2011-03-30 14:37:00]

Here's a proposed fix for issue 1579.

I'm not sure if the extended search for a context to
provide lyric rhythms is actually required, especially as
the search sometimes returns inappropriate contexts, but 
in case it is I've simply hidden it behind a new context
property which defaults to #f.  It will then be easy to
either improve the search or remove it entirely later.

[Graham Percival (old account), 2011-03-31 00:36:30]

http://codereview.appspot.com/4323045/diff/1/ly/engraver-init.ly
File ly/engraver-init.ly (left):

http://codereview.appspot.com/4323045/diff/1/ly/engraver-init.ly#oldcode424
ly/engraver-init.ly:424: instrumentName = #'()
I'm missing something from the commit message -- why are you removing these?

[t.daniels_treda.co.uk, 2011-03-31 14:05:38]

> http://codereview.appspot.com/4323045/diff/1/ly/engraver-init.ly#oldcode424
> ly/engraver-init.ly:424: instrumentName = #'()
> I'm missing something from the commit message -- why are you 
> removing
> these?

They were in the context definition twice, so I deleted
one of the duplicates.  Sorry, I should have noted that
in the commit message.

Trevor

[lilypond.patches, 2011-04-01 16:54:14]

Patch listed.

[dak, 2011-04-01 19:55:03]

On 2011/04/01 16:54:14, lilypond.patches wrote:
> Patch listed.

Personally, I think that an association with some respective higher context (aka
inheritance) is such a common type of operation that we should rather try
thinking about how to provide a general mechanism for this kind of thing rather
than a one-shot special mechanism just for lyrics.

[t.daniels_treda.co.uk, 2011-04-02 15:36:33]

From: <dak@gnu.org>

> Personally, I think that an association with some respective 
> higher
> context (aka inheritance) is such a common type of operation that 
> we
> should rather try thinking about how to provide a general 
> mechanism for
> this kind of thing rather than a one-shot special mechanism just 
> for
> lyrics.

David

In this particular case we don't want a search.  The bug
occurs because Lily tries to find a non-existent context
and comes up with an inappropriate one.

Trevor

> http://codereview.appspot.com/4323045/

[Graham Percival (old account), 2011-04-08 03:14:26]

ok, deadline definitely passed.  Please push.

[Trevor Daniels, 2011-04-08 07:32:48]

Pushed
4133b4e0ec939a427a70361ad838c65a84a0dfda