Re: Add an arbitrary music property

[David Kastrup]

Urs Liska <address@hidden> writes:

> Indeed it does.
> But now that I know how to mark up a whole music expression with a
> custom music-property I see that it may not actually be what I need.
> Is it possible to read out the properties of music expressions in an
> engraver?

No.

> Or do these only respond to grobs? Is *that* what (process-music) is
> for?

Engravers respond to grobs (produced by engravers) and to stream events
(produced by iterators).  process-music does not take an argument.  It's
merely a stage of processing stream events.

Stuff like SequentialMusic expressions never arrive at engravers: they
are processed by the Sequential_iterator which converts the contained
elements into StreamEvent data produced at the proper music time and
broadcast to the right context and its parents.

> What I want to achieve is:
>
>  * Have a music function take a music argument
>  * mark that up with an annotation (that addresses the whole
>    expression, not just a single grob or moment)
>  * in an engraver process the annotation as a whole, for example in
>    order to print the begin and end of the annotated music.
>
> If that isn't possible with the music-property I would probably attach
> grob-properties to the first and last element in the music expression
> and try to figure out the extent of the annotation by that (will
> probably have to do some ID referencing to match the begin/end grobs).

More like attaching stuff to the first and last rhythmic-event.  But you
may be better off attaching applyContext calls of the right nature to
the front and back of the expression.

-- 
David Kastrup