|Subject:||Why are book blocks objects but not contexts in Lilypond?|
|Date:||Sun, 27 Sep 2009 22:16:26 +0100|
|User-agent:||Thunderbird 188.8.131.52 (X11/20090817)|
I'm looking at this in terms of design inconsistencies rather than documentation issues.
I've been looking around at the code and documentation regarding contexts and noted these statements:
LM 3.3.2 says
"Note that there is no(My bolding)
LM 3.1.1 says
EveryThere are a couple of parser variables relevant to \book output-count and output-prefix (only output-prefix is still used as of 2.13.4). I reckon output-prefix and possibly then the filename part of the output filespec would be valid properties for \book. I also think Book would be a valid context for these to live in.
However, at the moment contexts are designed to be part of the process of translating music source code into final format of some sort (e.g. .png, .pdf), and are associated with engravers and suchlike. The Book context would be concerned with whereabouts that output was headed.
I had been thinking of adding all the parser variables as properties, but have since had a look at the original list Marl Polesky generated and have come to the conclusion parser variables seem to be a very mixed bag: for things which are supposed to be user-settable this seems to be because maybe the developer couldn't think of a place that fitted for them: afterGraceFraction should have been an optional parameter to the afterGrace function, and output-count and output-prefix should have had some way of being attached to the \book in the lilypond language; showFirstLength and showLastLength are associated with the skipTypeSetting property which LR 3.4.2 lists as a score property so show*Length should be in define-context-properties.scm where skipTypesetting is defined. The rest of the parser variables look like they are genuine internal things for use in Scheme code.
So, if \book is really the top of the tree, and a lilypond file is either:
I would like lilypond to have a Book context sitting above Score in the context hierarchy.
How could I add Book as a valid context?
I already understand how to add new properties to the lists in define-context-properties.scm.
I haven't yet found out how \set, \unset, \override or \revert code decides which of the property lists like all-music-properties, all-translation-properties or all-backend-properties to search for a valid property definition.
Thanks in advance for any help, tips, pointers or comments.
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