[Lilypond-auto] Issue 2929 in lilypond: Patch: Allow \tweak to act as a stand-in for \once\override

[lilypond]

Status: New
Owner: ----
Labels: Type-Enhancement Patch-new

New issue 2929 by address@hidden: Patch: Allow \tweak to act as a stand-in for  
\once\override
http://code.google.com/p/lilypond/issues/detail?id=2929

Allow \tweak to act as a stand-in for \once\override

This is actually again a three-commit series, but the changes should
be reviewable together fine as well.  The first commit implements
check-grob-path and is confined entirely to scm/music-functions.scm.

The real commit is in ly/music-functions-init.ly in the definition of
\tweak, bringing its behavior in line with that of tweak-like
commands.  This necessitates a regtest change in
input/regression/lyric-tweak.ly.

The last commit are resulting simplifications elsewhere in
ly/music-functions-init.ly.

Here is the list of commit messages in reverse order:



Let \footnote and \shape rely on \tweak for overrides


Allow \tweak to act as a stand-in for \once\override

Making tweak optionally accept a grob specification instead of music
to tweak makes it compatible with the behavior of functions such as
\footnote and \shape, and actually serves to simplify their
implementation.

One slight complication occurs in lyrics mode, as demonstrated by the
change necessary to input/regression/lyric-tweak.ly: with

    \tweak #'color #red reddish fish,

LilyPond tries an override for a grob named "reddish" and fails.
Tweaks in lyrics mode are highly unusual, have not been supported for
long, and their effect can usually better be accomplished in markup
mode instead.  The fix here is to write

    \tweak #'color #red \markup reddish fish,

since LilyPond does not consider explicit markup a candidate for
conversion into symbols.  The same problem is inherent with other
commands using the same kind of symbol-list-or-music? interface, like
\footnote, \hide, \omit.


Implement function check-grob-path for checking/extending grob path specs

From the function documentation string:

Check a grob path specification @var{path}, a symbol list (or a
single symbol), for validity and possibly complete it.  Returns the
completed specification, or @code{#f} if invalid.  If optional
@var{parser} is given, a syntax error is raised in that case,
optionally using @var{location}.  If an optional keyword argument
@code{#:start @var{start}} is given, the parsing starts at the given
index in the sequence @samp{Context.Grob.property.sub-property...},
with the default of @samp{0} implying the full path.

If there is no valid first element of @var{path} fitting at the given
path location, an optionally given @code{#:default @var{default}} is
used as the respective element instead without checking it for
validity at this position.

The resulting path after possibly prepending @var{default} can be
constrained in length by optional arguments @code{#:min @var{min}} and
@code{#:max @var{max}}, defaulting to @samp{1} and unlimited,
respectively.

http://codereview.appspot.com/6768064