[Lilypond-auto] Issue 2507 in lilypond: Stop the entanglement of context properties and grob property internals

[lilypond]

Status: Accepted
Owner: ----
Labels: Type-Defect

New issue 2507 by address@hidden: Stop the entanglement of context properties  
and grob property internals
http://code.google.com/p/lilypond/issues/detail?id=2507

Currently grob properties are maintained as context properties with pair  
values representing the inner parts of the data structures used for  
implementing \override/\revert.  As a result, something like

\new Staff { \set NoteHead = #'(a) c'4 c' c' c' }

clobbers internal data structures and as a result, crashes LilyPond rather  
hard:

GNU LilyPond 2.15.38
Processing `/tmp/junk.ly'
Parsing...
/tmp/junk.ly:0: warning: no \version statement found, please add

\version "2.15.38"

for future compatibility
Interpreting music...
Compilation segmentation fault (core dumped) at Mon Apr 30 18:26:52

With the inclusion of nested overrides/reverts (not yet working cleanly, cf  
issue 1063) which allow

\override Xxx #'(a b c) = value
\revert Xxx #'(a b c)

as a multi-path-element generalization for

\override Xxx #'a = value
\revert Xxx #'a

it would appear natural to have

\override Xxx #'() = value
\revert Xxx #'()

to be equivalent to

\set Xxx = value
\unset Xxx

and in this manner cease the entanglement of the user interface for context  
properties with the internals of grob properties by making the former a  
special case of the latter.