bug#32345: 12.1.1; wrong preview position for four-byte utf-8 encoded character (xelatex)

[jfbu]

Le 02/08/2018 à 14:13, David Kastrup a écrit :
> jfbu <address@hidden> writes:
>
> > Le 02/08/2018 à 13:34, David Kastrup a écrit :
> > > jfbu <address@hidden> writes:
> > >
> > > > I obtain partial success with
> > > >
> > > > \documentclass{article}
> > > > \usepackage{unicode-math}
> > > > \begin{document}
> > > >
> > > > Test: $𝒞$
> > > >
> > > > \end{document}
> > >
> > > [...]
> > >
> > > > Further the log contains indication something went wrong indeed
> > > >
> > > > l.5 Test: $
> > > >              풞$
> > > > Preview: Tightpage -32891 -32891 32891 32891
> > > > ./testpreview.tex:5: Preview: Snippet 1 ended.(456786+9830x428605).
> > >
> > > Maybe you should bother to mention what you consider "indication
> > > something went wrong indeed".  preview-latex produces error messages on
> > > purpose.  That's the only way to get to the right column.
> > >
> > > The problem here is that the character in the error message appears to
> > > be a different character from what is in the source file, so
> > > preview-latex isn't able to correlate it with the source.
> >
> > So you do understand what I meant then?
>
> No.  I am explaining what the log file content means.  There is nothing
> in your posting suggesting that this was what you were trying to convey
> and I do not consider it likely that a majority of readers of this
> report would have been able to properly see the problem.

The extract from the log file is as in OP's initial post and
the fact that the displayed character is wrong was already
pointed out there, with even the precision that its codepoint #xd49e
was like original character except for missing 1 most significative byte.

> > Have a nice summer
>
> Does that mean that I should refrain from answers on this list in the
> next few months or that you chose to put me into your kill file?  If you
> expect others to read between the lines, those would be the two most
> obvious interpretations of that line.

It meant I intended to refrain from participating to this list which
appears somewhat hostile.  But anyway I am off-line from Internet
for most of the summer so this was easily said by me somewhat too
quickly possibly.

> Just stating what one wants to say tends to make particularly electronic
> communication less troublesome for everybody involved since the usual
> cues in face-to-face communication are not available.
>
> All the best,

The very same document with lualatex in place of xelatex seems
to not experience the same problem, so there might be something
specific to xelatex tokenization of UTF-8 and how it interferes
with the preview-latex hack into $.

I am incompetent for any other remark,

Best,

Jean-François