Re: [frogs] Enhancement request: Define output-suffix as a configurable context property.

[Ian Hulin <ian@xxxxxxxxxxxx>]

Hi Carl,
That will work, but it's still a work-around.  We'd be avoiding setting it as a context property to keep the architectural thinking clean, while at the same time duplicating the functionality of a property by hand.
What we're in effect doing here is duplicating the behaviour of a property, we're hiding the parser variable and writing a function to write to it. So why not

pvSet =
#(define-music-function (parser layout parser-variable new-value) (variable? string?)
    (set! parser-variable new-value)
    (make-music 'SequentialMusic 'void #t))

then do

\book {
   \pvset output-suffix "gibbon-vole-aardvark"
   {... \score blocks and things ...}
}

But I'm still bothered we may be re-inventing the wheel here.  We've got properties in lily already, and defined ways of setting them (\set, \override and even assigning them in the relevant block).

Could we not add a new define-parser-variable-properties.scm with
(define-public all-pv-properties '())
(define (pv-property-description symbol type? description)
  (if (not (and
        (symbol? symbol)
        (procedure? type?)
        (string? description)))
      (throw 'init-format-error))


  (if (not (equal? #f (object-property symbol 'translation-doc)))
      (ly:error (_ "symbol ~S redefined" symbol)))

  (set-object-property! symbol 'translation-type? type?)
  (set-object-property! symbol 'translation-doc description)
  (set! all-pv-properties (cons symbol all-translation-properties))
  symbol)
 (define-public all-pv-properties
    (map
        (lambda (x)
            (apply pv-property-description x))
            `(
              (output-suffix ,string? "Text to append to the output filename for the current @code{\\book} block")
;;; Maybe add all the other supported parser variables here?

)))

The above should work as I've adapted it unashamedly from define-context-properties.scm

Remaining things to do would be

• add define-parser-variable-properties.scm to build (whimper...)
• get the property access routines to use the new all-pv-properties list

This would be more work,  but give us a cleaner result and it would be less likely to fall foul of a fatwah from new Syntax Standardization project when it gets going.

Opinions?

Cheers,

Ian

Carl Sorensen wrote:

On 9/19/09 7:27 AM, "Ian Hulin" <ian@xxxxxxxxxxxx> wrote:

  

Hi Carl, Neil,

I'm quite happy to re-think the proposal if what I have in mind contravenes
existing design architecture.
Put it down to relative inexperience and the fact I don't get opportunity to
work on lilly as often as I'd like.

Anyhow, here are some of the reasons why I'd like to do something with this
stuff:
* Using parser variables to configure things is evil, because it requires
users to drop into Scheme to set the parser variable. I feel we need to
replace #(define output-suffix "gibbon-vole-aardvark") with something handled
at the lilypond language level.
*  
* At the moment, output-suffix is de facto a property of a \book block.� There
is a design assumption (informal club rule) in lilypond� that we only produce
one back-end output file (.pdf, .png whatever) per \book block.
* However, there is as great big exception to this in the form of midi files,
one of which one is output for every \score block with a \midi present. At the
moment the file name generation code kludges its way around this but it not
very clean, unclear and all this stuff is barely documented.
* So what I'd like to do is to have some way of replacing the Scheme
definition either -
*  \book { 
*  ��� \set output-suffix "gibbon-vole-aardvark"
*  ��� {... \score blocks and things}
* }
* , or 
* \book \with {output-suffix = "gibbon-vole-aardvark"}
* {
* �� {... \score blocks and things}
* }.
    

Could one define a void music function

setOutputSuffix =
#(define-music-function (parser layout new-output-suffix) (string?)
    (define output-suffix new-output-suffix)
    (make-music 'SequentialMusic 'void #t))

then do

\book {
   \setOutputSuffix "gibbon-vole-aardvark"
   {... \score blocks and things ...}
}

I haven't tried it, but I think it may work.

Carl


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