Re: [Lilypond-auto] Issue 2883 in lilypond: Patch: Make arguments like Context.GrobName accessible as symbol lists

[lilypond]

Updates:
	Cc: address@hidden address@hidden address@hidden  
address@hidden

Comment #14 on issue 2883 by address@hidden: Patch: Make arguments like  
Context.GrobName accessible as symbol lists
http://code.google.com/p/lilypond/issues/detail?id=2883

Ok, getting this patch/branch integrated successfully will require quite a  
bit of heavy lifting, and I am not really able to do all of that myself.

First we need to agree on a solution for the function interfaces that  
currently depend on the distinction string/symbol for recognizing optional  
arguments.

Issue #1 is \tweak.  We currently have two forms of tweak, namely

\tweak #'color #red cis            (tweak of direct grob)
\tweak Accidental #'color #red cis (tweak of particular grob)

The current form of the patch proposes translation into

\tweak color #red cis
\tweak Accidental.color #red cis

It has been pointed out that the latter syntax is confusingly different  
from \override Accidental color = #red (no dot allowed!).

The short form of \tweak is rather prevalent, so we don't want to change  
that.  Alternatives for the second form might be

\on Accidental \tweak color #red cis
\tweakOn Accidental color #red cis
\single \override Accidental color = #red cis

The last line already works but is cumbersome and sufficiently different  
from \tweak that it seems inconvenient.  \on as a separate command has its  
charm for working on tweaks not just generated by the \tweak command, like

\on Accidental \hide cis

as an alternative wording for

\single \hide Accidental cis

Huh.  The grammar of \on does seem a bit strange in usage.  Better  
proposals?

\only Accidental \hide cis

maybe?  Or

\grob Accidental \hide cis

Similarly, the yet again new \footnote interface has no really fabulous way  
to place the grob spec.  The proposal used here has a few advantages (most  
notably never needing \default, not being able to express the invalid  
combination of override-like behavior without grob specification, and  
fitting in a pattern with \hide/\omit), but still does not really have  
people much enthused about it, mostly due to the trialing position of the  
Grob name when using it in override-like manner.

The positive thing is that \footnote now really, really, really is just a  
\once\override or \tweak, so using things like \grob or \single on it is  
feasible, and it works exactly in those circumstances as the other commands  
in that vein do.

Those are the interface design problems.

There is also a lot of documentation work pending, starting with bringing  
the German documentation at least into a state where convert-ly generates  
valid code, or just skip this stage and start from the new English  
version.  Which also needs to be written, or at least retouched.

Then there needs to be an introductory section on LilyPond's relation  
between input syntax and Scheme data structures.  At least the first  
iteration will probably be my lot.  Then one has to look through the whole  
\override/\revert etc section, assuming that we go for the variant without  
#' which seems like something not only I consider desirable.

The documentation work does not to complete before committing, but it will  
still be significant.  And at least the interface changes of \tweak and  
\footnote should be something where we are reasonably sure that it's the  
best we can do.