Graham Percival <[EMAIL PROTECTED]> writes:
> In the current manual, define-music-function is introduced late in the
> scheme chapter. I suspect that this is simply because
> define-music-function is a more recent lilypond construct, and whoever
> added it didn't want to disturb the existing material. Is that
> correct?
You're absolutely right. First, the doc for ly:make-music-function was
introduced, then I added something for define-music-function, preserving
the previous documentation. Reading it again now, it is really strange.
> I'm revising the chapter now (as you can tell from the previous
> half-dozen emails :), and it makes sense to me to _begin_ the chapter
> with define-music-function, and then work through the general theory
> of scheme, lilypond music expressions, etc. In other words, stick the
> define-music-function stuff *before* the current 11.1.1. Are there
> any objections? I really don't think that people need to know what
> #(ly:make-music-function (11.1.3) does before using
> define-music-function, but I still can't claim to fully understand
> #(ly:make-music-function myself, so I might be missing some vital
> info.
ly:make-music-function is the interface with C++ code, and
define-music-function is the public interface. People don't need to know
about ly:make-music-function at all (people who would have to use it
would find it by themselves anyway).
> My current sense is that define-music-function and \displayMusic (and
> perhaps a bit of patience) are the most important parts of 11.1.
> Thoughts?
define-music-function, with a very straight forward use of the #{ #}
syntax, may be introduced first.
%%% Example with one music argument (a note)
custosNote =
#(define-music-function (parser location note)
(ly:music?)
#{
\once \override Voice.NoteHead #'stencil =
#ly:text-interface::print
\once \override Voice.NoteHead #'text =
\markup \musicglyph #"custodes.mensural.u0"
\once \override Voice.Stem #'stencil = ##f
$note
#})
{ c' d' e' f' \custosNote g' }
%%% Example with two music arguments
firstAndSecondTime =
#(define-music-function (parser location first-time second-time)
(ly:music? ly:music?)
#{
\set Score.repeatCommands = #'((volta "1."))
$first-time
\bar ":|"
\set Score.repeatCommands = #'((volta #f) (volta "2."))
$second-time
\set Score.repeatCommands = #'((volta #f))
#})
{ c'2 c'
\firstAndSecondTime { d' d' } { e' e' }
}
%%% Example with a markup argument
tempoMark =
#(define-music-function (parser location tempo-markup)
(markup?)
#{
\once \override Score . RehearsalMark #'self-alignment-X = #-1
\once \override Score . RehearsalMark #'no-spacing-rods = ##t
\once \override Score . RehearsalMark #'padding = #2
\once \override Score . RehearsalMark #'break-align-symbol = #'left-edge
\mark \markup \fontsize #-1 \italic $tempo-markup
#})
{
\tempoMark \markup { Allegro molto. }
c'' c'' c'' c''
\mark "Another mark"
c'' c'' c'' c''
}
In a second step, a more complex example, requiring manipulating music
expressions, could be explained. There, \displayMusic should be used.
I don't have a good example in mind at the moment...
nicolas
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