More sophisticated layouts (from issue #185)

[adrianholovaty]

This pull request brings the agreed-upon changes from #185 (specifically, from this summary comment) into the MNX spec. This introduces more sophisticated methods of mixing and matching notation data within layouts.

The updated docs (as of this pull request) are visible here: https://cdn.githubraw.com/w3c/mnx/issue-185/docs/

The specific changes are:

• Added <voice-layout>, which lives within <staff-layout>. This is a way to say "In this staff, use the notation data from parts X and Y; use upstems for all of part X's notes and use downstems for all of part Y's notes."
• Added <system-layout-change>. This is a way for a system layout to change mid-measure.
• Gave <part-layout> two new attributes, stem and voice. Note that I opted for voice instead of part-voice, to be consistent with the existing staff.
• Added the example document Multiple layouts.
• Added the example document Orchestral layout.
• Added the example document Organ layout.
• Updated the existing example document System layouts to use <voice-layout>.

Special thanks to @clnoel for putting together the example images and markup! Any mistakes are my fault.

For everybody reviewing this, I highly recommend looking at those four example documents to gain some intuition on how this stuff all works and what the benefit is. Speaking personally, I found it hard to understand the new elements/attributes in the long-winded discussion of #185, and seeing specific images made it much clearer.

One final note. The original summary suggested <staff-layout> needs a part-staff attribute, but I didn't see the need to add that in this pull request. Wouldn't this already be handled by the child <part-layout>'s staff attribute? Let me know if I'm missing something.

[ahankinson]

You might consider changing the examples to read "Upper voices" and "Lower voices" instead of "Women" and "Men" since the voice parts are not exclusive to a given gender.

[bhamblok]

The HTML-element <nobr> is a non-standard and deprecated element. https://developer.mozilla.org/en-US/docs/Web/HTML/Element/nobr
We could use <span style="white-space: nowrap;"> instead.

[clnoel]

1. Hmm.. the pre-existing staff attribute on <part-layout> was supposed to be removed as a part of this, in favor of moving it to the <staff-layout> (I forgot to list that in my summary post). In retrospect, however, I prefer having it on the <part-layout>. I think it makes more sense. I'd appreciate other's viewpoints on that, though.
2. I dislike the change from part-voice to voice. I prefer to change staff to part-staff instead. This is a very clear indicator, to me, that we are filtering the part itself, instead of saying, for example, that the <part-layout> is defining a voice id, or is on the second staff down.

Suggested changes:

• Regardless of the decisions for the two points above, the examples should match the definitions and right now they do not. part-voice is used, even though voice is defined in the definitions, and part-staff is used on <staff-layout> even though it is not defined on that element.
• I'm not sure if it was you or me, @adrianholovaty , but I think that in the "Organ Layout" the "organ3StaveSplitOber" layout should use part-staff=2 instead of part-voice="Hauptwerk" and part-staff=3 instead of part-voice="Pedal", since that example was supposed to demonstrate the use of part-staff.

[notator]

I agree with @clnoel on all points.

Also, I think we need to resolve #278 before committing this PR.
How should the label for a staff containing two parts be encoded?

[clnoel]

@notator, while the labels are included in the examples, how we do the labels is not a focus, which is why I did not attempt to recognize the line breaks in the labels of the Orchestral Layout example at all. We can come back later and alter that example once we've hashed it out. I've finally responded to #277, which actually has a potential for greater impact on the new examples, if you want to go examine that. But I don't think that we need to hold up this PR for either unresolved issue. We'll just make a new PR with the changes in it.

[adrianholovaty]

@ahankinson Thanks — that's now fixed in the example ("SA" and "TB").

@clnoel Thanks — I agree part-voice and part-staff are clearer. I've just updated the pull request accordingly, and I've fixed the incorrect bits in the example docs. Could you give it a final readthrough and make sure everything looks good? I believe this is ready to merge but will wait for your OK.

[clnoel]

@adrianholovaty I think you either misunderstood my suggestion for the Organ example, or made a typo.

In the "organ3StaveSplitOber" layout, the following line:
<part-layout part="organ" part-staff="2" stem="down"/>
should instead be
<part-layout part="organ" part-voice="Oberwerk" stem="down"/>

and

<part-layout part="organ" part-voice="Hauptwerk"/>
should instead be:
<part-layout part="organ" part-staff="2"/>

Other than that, I think it looks really good!

--Christina

[adrianholovaty]

@clnoel Thanks for the catch! That's now fixed. I'll go ahead and merge this now.