Re: Let's make TextSpanners easier to use!

[Neil Puttock]

2008/10/29 Valentin Villenave <address@hidden>:

> OK, here is a function that works much better.
>
> It works very much like Graham's recent "extra" dynamics: you can
> either have a predefined TextSpanner, either define your spanners
> on-the-fly through a music-function (but in this case you have to
> enter it *before* the starting note).

> %%%%%%%%%%%%%
> #(define (make-text-span txt)
> "Make a TextSpanner that begins with the given STR."
>  (let* ((m (make-music 'TextSpanEvent
>             'span-direction -1))
>         (details (cdr (assoc 'bound-details
>                        (cdr (assoc 'TextSpanner
>                              all-grob-descriptions)))))
>         (left-details (cdr (assoc 'left
>                             details))))
>   (ly:music-set-property! m 'tweaks
>    (acons 'bound-details
>     (acons 'left
>      (acons 'text txt
>       left-details)
>      details)
>     (ly:music-property m 'tweaks)))
>   m))

Looks good. :)

As a minor refinement, you could use assoc-get instead of assoc.

> textSpan=
> #(define-music-function (location parser txt) (string?)
> (make-text-span txt))

Hmm, this isn't as elegant as make-text-span itself; you can't use markup.

It's a bit academic now, but concerning your problem with passing the
text variable in the original example, you need to use a backquote for
the bound-details, together with a comma before txt; this ensures that
the value of txt is substituted in the list, rather than returning the
symbol.

(acons 'bound-details `((left . ((text . ,txt))))

You can see the same syntax in define-grobs.scm for grob callbacks.

Regards,
Neil