Re: [PyX-user] Bug(?) in text placement using LaTeX

[André W. <co...@wo...>]

Hi,

I could reproduce it on Debian 11 (not yet released). It seems related 
to the upgrade to TeX Live 2020, which added the l3backend (was not 
present before). This package adds specials by \AtBeginDvi{...}, which 
unboxes the box send to \shipout and re-boxes it. By that the vertical 
alignment, which we set to zero height for the hbox passed to \shipout, 
gets lost at the first box shipped out by PyX.

There is a simple solution in applying this vertical setting at the box 
nested inside, before we also fix the horizontal alignment according to 
the output requirements. This should not introduce any difference for 
regular use, although (as it is TeX/LaTeX) any difference can always be 
utilized (as the l3backend shows). Please try the attached patch. I hope 
it resolves the issue for you. (And we probably should release this soon 
...)


André

PS: The additional special output (warning by PyX) has not yet been 
addressed/silenced. Also, I have not yet checked whether we can continue 
to use the pyx.def output driver as before. There are various open 
questions, which need further investigation ...

Am 22.06.21 um 20:11 schrieb Thomas Bending:
> I've used PyX happily for years, but I've recently noticed what seems to 
> be a bug in text placement when using LaTeX for text processing. Here's 
> my code:
> 
> import pyx
> pyx.text.set(engine = pyx.text.TexEngine)
> c = pyx.canvas.canvas()
> c.text(0, 0, 'A')
> c.text(0, 0, 'B')
> c.writePDFfile('out.pdf')
> 
> This produces the file attached as out_tex.pdf, with the A and B 
> superimposed as I'd expect. However, if I change the engine specified in 
> line 2 to pyx.text.LatexEngine then
> 
>  1. I see the warning /ignoring special 'header=l3backend-dvips.pro
>     <http://l3backend-dvips.pro>'/
>  2. The script produces the file attached as out_latex.pdf, with the A
>     displaced downwards (and hence almost off the page).
> 
> I'm using PyX 0.15, Python 3.9.5, TeX = TeX 3.14159265 (TeX Live 
> 2020/Debian) and LaTeX = pdfTeX 3.14159265-2.6-1.40.21 (TeX Live 
> 2020/Debian), all running under Ubuntu 21.04. I believe that this issue 
> appeared when I upgraded to Ubuntu 21.04, which may also have involved 
> upgrades to some of these packages.
> 
> Can anyone suggest what I can do to prevent this displacement of the 
> text when using the LaTeX engine, please? Is this displacement related 
> to the warning? Any advice welcomed,
> 
> Thomas
> 
> 
> 
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