Re: Defining event classes

[Nathan Ho]

On Mon, Mar 30, 2015 at 1:44 PM, Nathan Ho <address@hidden> wrote:

Hi list,

What is the most up-to-date way to define my own event classes?

I've looked at frameEngraver as a model but none of the old versions
seem to be working. The most up-to-date one I could find
(https://lists.gnu.org/archive/html/lilypond-user/2013-07/msg00373.html)
gives me numerous "Event class should be a list" errors and the frames
don't show up in the output, while this one
(https://lists.gnu.org/archive/html/lilypond-user/2013-07/msg00554.html)
spits out a few errors and segfaults. I'm using 2.19.17.

Not hugely surprised to see that didn't get a quick answer :)

With some trial and error and fumbling around I came up with the following code. Unlike the frame engraver code, this returns no errors or warnings, but the engraver doesn't seem to notice the BangEvent at all. If I change the listener to listen to music-event, then bang-trigger calls four times (once per note) seemingly ignoring the \bang. What's going on here?

\version "2.19.17"

#(define-event-class 'bang-event 'music-event)

#(define bang-types

   '(

     (BangEvent

      . ((description . "BANG!")

         (types . (bang-event music-event))

         ))

     ))

#(set!

  bang-types

  (map (lambda (x)

         (set-object-property! (car x)

                               'music-description

                               (cdr (assq 'description (cdr x))))

         (let ((lst (cdr x)))

           (set! lst (assoc-set! lst 'name (car x)))

           (set! lst (assq-remove! lst 'description))

           (hashq-set! music-name-to-property-table (car x) lst)

           (cons (car x) lst)))

       bang-types))

#(set! music-descriptions

       (append bang-types music-descriptions))

#(set! music-descriptions

       (sort music-descriptions alist<?))

#(define (bang-trigger engraver event)

   ; use ly:warning as a quick hack to get it to show up in the output log

   (ly:warning "helloooo"))

#(define Bang_engraver

   (make-engraver

     (listeners (bang-event . bang-trigger))))

bang = #(make-music 'BangEvent)

\new Staff \with {

  \consists #Bang_engraver

} {

  c1 c1 \bang c1 c1

} 

Regards,

Nathan