Re: How to detect SpanBar from inside a make-bar-line definition?

[Thomas Morley]

Am Mi., 13. März 2024 um 23:56 Uhr schrieb Dan Eble
<nine.fierce.ballads@gmail.com>:
>
> On 2024-03-13 17:35, Thomas Morley wrote:
>
> > currently I'm attempting to improve dashed/dotted bar lines wrt to
> > changed staff-space and span bars.
> > We use both definitions for BarLine _and_ SpanBar, but then SpanBar is
> > frequently a little off.
> > It would be nice to have a possibility to detect whether a definition
> > is used for span bars.
>
> What specifically do you want to know?  Do you expect to code something like
>
>      if the grob is a BarLine:
>        adjust ... by ...
>      if the grob is a Divisio:
>        adjust ... by ...
>      if the grob is a SpanBar:
>        adjust ... by ...
>
> If so, it seems that you could add a grob property for that adjustment
> and get it from the grob.
>
> > #(define (make-test-bar-line grob extent)
> >    (let ((grob::make-span-bar? #f))
>
> Another possibility is for the grob's print procedure to pass more
> information down to this function.  That might be more appropriate if
> the information you require is not associated with the grob only, but is
> derived from a number of sources, like the surrounding staves, and would
> be useful for many different glyph print procedures.  Of course,
> ly:bar-line::print would provide values appropriate for bar lines and
> ly:span-bar::print would provide values appropriate for span bars.
>
> These are the opinions off the top of my head and I reserve the right to
> change them.
> --
> Dan
>
Hi Dan,

I don't understand what you propose.

To give a different example, let's look at make-dotted-bar-line (afaik
it's your code).
There you have a `making-span-bar?'-condition, obviously you want a
span bar a little different than bar line.
Though, I noticed a few things:
a) If I implement (pretty-print grob) there, I always get BarLine,
never something else, regardless where I place that.
b) Dotted span bars are not optimal. Compile my example from my
initilal post to get an example.
c) the condition itself may fail, see
/input/regression/non-centered-bar-lines.ly for an example, or try to
set bar-extent to an interval not crossing zero.

Because of b) I tried to patch make-dotted-bar-line, alas I found no
condition to apply the patched functionality to span bars only.

Thus I ask if there is such a condition at all. Or how it could be coded.
Alternatively, I could code a special `make-dotted-span-bar'-procedure
and define the dotted bar line as
(define-bar-line ";" #t #f ";-span")
or the like...

Thanks,
  Harm