Nicolas Sceaux <nicolas.sce...@gmail.com> writes:
> Le 9 févr. 2010 à 14:42, David Kastrup a écrit :
>
>> I find that syntax tiresome to read. It requires evaluation and thus
>> does not have a close correspondence to print syntax.
>>
>> That's partly because of the way the Scheme engraver example has been
>> written.
>>
>> I'd much prefer it to use backquote syntax, such as
>
> A real improvement would be to add syntax to define scheme engravers,
> something like:
>
> #(define-engraver example-engraver)
>
> #(define-engraver-method example-engraver initialize (trans)
> (display (list "initialize"
> (ly:context-current-moment
> (ly:translator-context trans)) "\n")))
>
> #(define-engraver-listener example-engraver rest-event (engraver event)
> (let* ((x (ly:engraver-make-grob engraver 'TextScript event)))
> (display (list "caught event" event "\ncreate:\n" x "\n"))
> (ly:grob-set-property! x 'text "hi")))
>
> \layout {
> \context {
> \Voice \consists #example-engraver
> }
> }
Actually, what about the following rather minimalistic approach?
#(define-macro (make-engraver . translist)
(define (make-lambdas translist)
`(list
,@(map (lambda (x)
(if (pair? (car x))
`(cons ',(caar x) (lambda ,(cdar x) ,@(cdr x)))
`(cons ',(car x) ,(make-lambdas (cdr x)))))
translist)))
(make-lambdas translist))
\header {
texidoc = "\\consists can take a scheme alist as arguments, which
should be functions, which will be invoked as engraver functions."
}
\version "2.14.0"
\layout {
\context {
\Voice
\consists
#(make-engraver
((initialize trans)
(display (list "initialize"
(ly:context-current-moment
(ly:translator-context trans)) "\n")))
((start-translation-timestep trans)
(display (list "start-trans"
(ly:context-current-moment
(ly:translator-context trans)) "\n")))
(listeners
((rest-event engraver event)
(let*
((x (ly:engraver-make-grob engraver 'TextScript event)))
(display (list "caught event" event "\ncreate:\n" x "\n"))
(ly:grob-set-property! x 'text "hi"))))
(acknowledgers
((note-head-interface engraver grob source-engraver)
(display (list "saw head: " grob " coming from " source-engraver))))
(end-acknowledgers
((beam-interface engraver grob source-engraver)
(display (list "saw end of beam: " grob " coming from "
source-engraver))))
((process-music trans)
(display (list "process-music"
(ly:context-current-moment
(ly:translator-context trans)) "\n")))
((process-acknowledged trans)
(display (list "process-acknowledged"
(ly:context-current-moment
(ly:translator-context trans)) "\n")))
((stop-translation-timestep trans)
(display (list "stop-trans"
(ly:context-current-moment
(ly:translator-context trans)) "\n")))
((finalize trans)
(display (list "finalize"
(ly:context-current-moment
(ly:translator-context trans)) "\n"))))
}}
\relative c' {
c8[ r c]
}
--
David Kastrup
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