Re: \center-column broken

[Johannes Feulner]

Hi Aron,

the \center-column issue seems to be a problem of the SVG backend. I 
compiled LilyPond from master and use a custom backend based on 
LilyPond's SVG backend. However, the pictures were made with LilyPond's 
standard SVG backend. I've now used the PDF backend,  it is not affected.

Thanks for the "-\tweak parent-alignment-X #CENTER" hint. Works nicely. 
Shouldn't that be the default value?

I had seen the "-" operator before but could not find it in LilyPond's 
docs. Could you please tell me ho it works?

Cheers,

Johannes

Am 14.02.2021 um 16:36 schrieb Aaron Hill:
> On 2021-02-14 7:08 am, Johannes Feulner wrote:
> > Hi there,
> >
> > \center-column is broken. In 2.18 it was still OK. The lines of a
> > \center-column are supposed to be centered under each other. This is
> > at least with 2.23.1 not any longer the case. Please, see attached
> > pictures. The "aaaa" is clearly not centered unter the "|".
> >
> >    \version "2.18.0"
> >
> >    { a'1 a'1
> >       c'' ^\markup
> >      \center-align \box \bold \fontsize #10 \center-column { "|" "aaaa"
> >    "bbb" "|" }
> >    }
>
> For reference, I see the correct behavior with 2.22.0 and 2.23.0, 
> testing with both PDF and cropped PNG output.  (Latest on lilypond.org 
> is 2.23.0-1, so are you compiling something yourself?)
>
> Ultimately, this is a bug with how the glyphs are being rendered, not 
> one related to centering.  Specifically, the wrong font is being 
> rendered compared to the one that determined the physical extent.  If 
> the narrower-looking letters had been intended, \box would have been 
> much tighter around the markup.  This looks like an issue you would 
> get with poor font substitution, so are you able to rule out issues 
> with your PDF viewer and environment?
>
>
> > Another problem is with \center-align. \center-align centers its
> > contents (here the box) over the left edge of the note it is attached
> > to. This does not look very centered at all. It should be centered
> > over the middle of the note's x-extent. This was already wrong in
> > 2.18.
>
> You need to adjust parent-alignment-X as desired:
>
> %%%%
> \version "2.22.0"
>
> { a'1 a'1
>   c'' -\tweak parent-alignment-X #CENTER
>       ^\markup \center-align \box \bold \fontsize #10
>                \center-column { "|" "aaaa" "bbb" "|" } }
> %%%%
>
>
> -- Aaron Hill


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