Issue 4348: Part combiner: move direction handling out of iterator

Part combiner: move direction handling out of iterator

[Dan Eble, 2015-04-19 11:40:31]

Call \displayLilyMusic output "NOT A BUG"

[dak, 2015-04-19 11:55:40]

On 2015/04/19 11:40:31, Dan Eble wrote:
> Call \displayLilyMusic output "NOT A BUG"

Why would that be not a bug?

[Dan Eble, 2015-04-19 12:30:08]

On 2015/04/19 11:55:40, dak wrote:
> On 2015/04/19 11:40:31, Dan Eble wrote:
> > Call \displayLilyMusic output "NOT A BUG"
> 
> Why would that be not a bug?

That was my interpretation of Valentin's feedback in
https://code.google.com/p/lilypond/issues/detail?id=4348#c5 .  If you want
something else, please describe it and I will do it.

[Dan Eble, 2015-04-19 17:23:44]

Fix \displayLilyMusic output for \partcombine(Up|Down)

[Keith, 2015-04-19 18:29:18]

Looks good to me.

https://codereview.appspot.com/226430043/diff/20001/input/regression/display-...
File input/regression/display-lily-tests.ly (right):

https://codereview.appspot.com/226430043/diff/20001/input/regression/display-...
input/regression/display-lily-tests.ly:224: \test "NOT A BUG" ##[ \oneVoice #]	%
resetting a bunch of properties
Given that \displayLilyMusic does not reverse-engineer \voiceXxx, it seems it
would take some work to teach it to reverse-engineer \partcombineUp/Down

https://codereview.appspot.com/226430043/diff/40001/lily/part-combine-iterato...
File lily/part-combine-iterator.cc (left):

https://codereview.appspot.com/226430043/diff/40001/lily/part-combine-iterato...
lily/part-combine-iterator.cc:396: SCM lst = get_music ()->get_property
("elements");
Later, it would be good to have PartCombineMusic contain a ContextSpecdMusic for
each of the four output Voices and the Devnull in its 'elements.    Instead of
the loop above, we would step through the list of 'elements and link handles_[]
to the contexts defined by \partcombine.

Then instead of the strings in outlet_names_[] we just use the context-id of
each of the 'elements.   Then we can combine two output Voices into one, such as
CONTEXT_SHARED and CONTEXT_SOLO, by giving the corresponding ContextSpecedMusics
the same context-id.

[Dan Eble, 2015-04-19 18:42:52]

On 2015/04/19 18:29:18, Keith wrote:
> Given that \displayLilyMusic does not reverse-engineer \voiceXxx, it seems it
> would take some work to teach it to reverse-engineer \partcombineUp/Down

In patch set 3, I managed to fake it by continuing to rely on the 'direction
property just for \displayLilyMusic.  I can't see that lasting very long,
though.

[Dan Eble, 2015-04-19 19:04:43]

On 2015/04/19 18:29:18, Keith wrote:
>
https://codereview.appspot.com/226430043/diff/40001/lily/part-combine-iterato...
> lily/part-combine-iterator.cc:396: SCM lst = get_music ()->get_property
> ("elements");
> Later, it would be good to have PartCombineMusic contain a ContextSpecdMusic
for
> each of the four output Voices and the Devnull in its 'elements.    Instead of

I'm hoping to eliminate PartCombineMusic and instead use simultaneous music with
context change commands, though I'm not sure that it is possible.  This sounds
like an excellent plan B.