Re: Issue 1320: Rewriting bar-line::print

[Marc Hohl]

Am 21.03.2012 11:03, schrieb David Kastrup:
> Marc Hohl<address@hidden>  writes:
>
> > Am 21.03.2012 03:20, schrieb David Kastrup:
> > > Marc Hohl<address@hidden>   writes:
> > >
> > > > Is this a feasible approach? What am I currently doing wrong?
> > > > #(define bar-line-stencil-alist
> > > >     '(("|" . thin-stil)
> > > >       ("." . thick-stil)
> > > >       ("" . empty-stil)
> > > >       ))
> > > >             (thin-stil (bar-line::simple-bar-line grob hair extent rounded))
> > > >             (thick-stil (bar-line::simple-bar-line grob fatline extent rounded))
> > > >             (empty-stil (make-filled-box-stencil (cons 0 0) (cons 0 extent)))
> > > >             (stencil (assoc-get glyph bar-line-stencil-alist empty-stil))
> > > >             )
> > > >
> > > >            stencil
> > > >            ))
> > > That does not work.  stencil is set to a symbol, and that symbol is
> > > never converted to a value.  When the function is being executed, the
> > > _symbols_ thin-stil, stick-stil and empty-stil have long lost any
> > > connection with the expressions that they were associated with while the
> > > let-statement was being compiled.
> > >
> > > You could write (local-eval stencil (the-environment)) to let the
> > > lexical environment of the function compilation linger over long enough
> > > to make this work, but you would earn a reward for the unnecessarily
> > > most ugly and unstable code imaginable.
> > >
> > > Instead, try using a case statement.  There is no need to calculate all
> > > stencils and throwing most of them away.
> > That's what I originally did, but my idea was to provide an easy way to
> > add new stencils/bar lines without fiddling with bar-line::print.
> > But if this way is a no-go, I'll use case.
> thin-stil and thick-stil are internals of the function.  The way to make
> this work is as an association list of functions (I don't know the
> problem well enough to know what parameter list they should be getting,
> but they would likely return a stencil, and so it would probably make
> sense to have them get the same parameter list that a stencil callback
> would) and/or finished stencils.  If the variability is likely to be
> restricted to the thickness, you can provide something like
>
> (define ((bar-line::simple-bar-line-maker thickness) grob)
>    [...]
>    (bar-line::simple-bar-line grob thickness extent rounded))
>
> And then put (bar-line::simple-bar-line-maker 1.5) as the function into
> the association list.
Ah, ok, but there are more bar line styles, so this won't solve the problem.

Anyway, I don't get the case statement right - am I too stupid?

Please have a look at the attached file; I don't get a stencil back,
the case statement always uses the else clause.
A (string? glyph) returns #t, so glyph is obviously a string ... ??

Regards,

Marc

barlinetest.ly
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