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I'm trying out pgfplots with gnuplot to generate the data. This works by having pgfplots write some stuff to an external file, run gnuplot on the file, and then use the generated data to plot the graph.

The problem I'm having is that I get different behaviour under xelatex as pdflatex or lualatex. In xelatex, the data file is littered with ^^I whereas in the other two formats these are tabs. It appears that the code ^^I is getting stored as a macro which then gets written out to the file, so possibly there's something funny going on with the ^^I syntax: xelatex is reading it literally. Indeed, when I do \show\pgfplots@TAB (the macro in question) then for pdflatex and lualatex then I get a literal tab whereas for xelatex I get ^^I.

So how do I get a tab in xelatex? And why isn't \gdef\pgfplots@TAB{^^I} working?

(The previous line in the code, by the way, is \catcode`\^^I=12 - I don't know if that has anything to do with it.)

Andrew Stacey
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1 Answers1

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In TeX Live, the formats for pdf(la)tex and lua(la)tex are built loading the tcx translation file cp227.tcx that makes ^^I "printable". This means that a category code 12 ^^I is written out as a real tab character.

On the other hand, xetex ignores tcx translation requests and behaves, in this respect, like Knuth's TeX (but it writes UTF-8, of course).

The same problem arises with \begin{frame}[fragile] with beamer, because the contents of the environment is written to a temporary file, or with \verbatimwrite and similar commands; also the filecontents environment is probably affected.

A solution may be to call xetex with the command line option -8bit, but I don't know if this has other side effects.

egreg
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    Miktex uses cp227.tcx too. And while the --8bit-option is actually not mentioned in the documentation it nevertheless works with xe(la)tex. As far as I can see the chars > ASCII 32 are printable anyway in xetex, so it will affect only (some or all) ASCII 0-32. – Ulrike Fischer Apr 02 '11 at 11:36
  • The -8bit option certainly makes it work. I'll keep an eye out for side effects. Thanks! – Andrew Stacey Apr 02 '11 at 17:41
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    Is there a way to ensure a correct behavior directly in the source code? I could patch pgfplots to do the right thing... – Christian Feuersänger Apr 18 '11 at 20:40
  • @ChristianFeuersänger I just got bitten by this again - I'd even forgotten that I'd asked this question! - at the least, it might be worth mentioning this in the manual at various relevant places (I only looked at the contour gnuplot part so somewhere there would be great). – Andrew Stacey Apr 17 '12 at 09:03
  • @Andrew thanks for the hint. I could do that... but honestly: I fear that such a small hint will be lost in 400 pages of documentation. I would rather have some meaningful error message like "Aargh unsupported use -8bit bla blubb". Perhaps I could write out a file, reread it and check if it contains three chars instead of one ;-) – Christian Feuersänger Apr 17 '12 at 19:07
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    @ChristianFeuersänger How about a "Known limitations" section in the manual? Also you could test for xelatex and print a warning "You're using xelatex. If things don't appear how you expect, try running with the -8bit option." – Andrew Stacey Apr 17 '12 at 19:33
  • @ChristianFeuersänger I've asked a follow-up question http://tex.stackexchange.com/q/52316/86 I suspect the answer is "no", but we can but hope! – Andrew Stacey Apr 17 '12 at 19:53
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    me I do: sed -i -e "s/pdflatex/xelatex/g" -e "s/^^I/\t/g" \jobname.makefile – bioinfornatics Feb 07 '13 at 12:51
  • I enter the same problem when I use mpgraphics package and run it with xelatex engin, which then the *.mp code generated by mpgraphics will display Tab as ^^I. The solution is exactly add -8bit: xelatex -8bit -shell-escape -synctex=1 -src-specials -interaction=nonstopmode $*. – user19832 Jul 13 '16 at 13:00
  • @user19832 Not using tabs is easier, though. ;-) Do you really need -src-specials? – egreg Jul 13 '16 at 13:01
  • @egreg I thought it is essential to make forward searching to work? – user19832 Jul 13 '16 at 13:05
  • @user19832 It's an outdated method; SyncTeX is much better. – egreg Jul 13 '16 at 13:09
  • @egreg Yes, it seems safe to remove the option -src-specials in my xelatex compile command. – user19832 Jul 13 '16 at 13:31