Re: Call for help with bar lines

[Marc Hohl]

Am 26.09.2012 12:34, schrieb address@hidden:
> On 26 sept. 2012, at 12:07, Marc Hohl <address@hidden> wrote:
>
> > Am 26.09.2012 11:47, schrieb address@hidden:
> > > On 26 sept. 2012, at 11:01, Marc Hohl <address@hidden> wrote:
> > >
> > > > Can anyone with more knowledge than me give me a hint what's wrong?
> > > > IIUC correctly, lilypond draws a bar line at the beginning of each line,
> > > > but in most cases, this is an invisible one.
> > > > If you look at the results of input/regression/lyrics-spanbar.ly,
> > > > the whole stuff is shifted that much to the right that lilypond moves
> > > > the rightmost rest to a new line! I can't believe that a bar line with
> > > > zero width can be the cause for this...
> > > >
> > > > Any hints are highly appreciated!
> > > >
> > > > Regards,
> > > >
> > > > Marc
> > > Hey Marc,
> > >
> > > I unfortunately don't have much time to help you out, but I can tell you that 
> > > you are on the right track doing prints to the command line.  I would not, 
> > > however, stash them in lambda functions used as overrides, as this can 
> > > sometimes interfere with pure properties.
> > Thanks for the hint, but I assume that this is not the case here, where I wrap 
> > ly:bar-line::print into
> > a callback ...
> ly:bar-line::print is a registered pure-print-callback (line 2712 of 
> define-grobs.scm), so when you use a custom callback, LilyPond stops finding 
> pure heights of bar lines.  To make sure that pure extents kick in, you'd need 
> to do something like
>
> \override BarLine #'print = #my-print-callback
> \override BarLine #'Y-extent = #(ly:unpure-pure-container 
> ly:grob::stencil-height (lambda (grob s e) (ly:grob::stencil-height grob)))
>
> You can check on the CG subchapter on pure properties for more examples.
I'll have to do that.

On the other hand, it is the x extent that's wrong, and IIUC, this is 
not influenced by any pure/impure decision?

But that's just for the record, because I am pretty sure that Harm found 
the culprit.

Thanks for your help!

Marc

> > > There are a couple classic things I use, most of which are in grob.cc.
> > >
> > > In Grob::pure_relative_y_coordinate, before the last return statement, you can 
> > > put:
> > >
> > > if (name () == "BarLine") print ("RELATIVE COORDINATE for BARLINE at spanned rank 
> > > %d: %4.4f\n", spanned_rank_interval ()[LEFT], out);
> > This can be quite handy, thanks!
> >
> > But back to my original question: can someone please have a quick glimpse at 
> > the regtests?
> > Perhaps he can spot the cuprit very easily ...
> I looked at them and my guess is that the pure extents (and maybe even unpure 
> extents) are being changed, which is why I suggested doing prints to the 
> command line for extents (both X and Y).
>
> Cheers,
> MS