# [luatex] pdfdecimaldigits < 4

Hans Hagen pragma at wxs.nl
Tue Jan 19 15:25:11 CET 2016

```On 1/19/2016 1:18 PM, David Carlisle wrote:
>
>
> If pdfdecimal digits is set less than 4 the it appears that you get a
> warning
>
> warning  (pdf backend): forcing decimal digits to 4
>
> The manual could mention in the documentation of pdf.setdecimaldigits
> that if set low then although
> pdf.getdecimaldigits() will return the lower number, the effective value
> will be 4 (if that is what happens?)
>
> This came up as texlive 2015 shared pdftex/luatex format ini files set
>
>
>
> \pdfdecimaldigits=3
>
> in /usr/local/texlive/2015/texmf-dist/tex/generic/config/pdftexconfig.tex
>
> so having translated that to
> \pdfvariable decimaldigits=4
>
> we get a warning in every (plain and latex) document.
>
> So we could change the default to 4 but that would change pdftex as well
> (in the currently suggested setup for texlive 2016 which uses a shared
> setup)
> Or we could separate the setup and use different values for pdftex and
> luatex.
>
> So to help decide could you say why the minimum value of 4 was chosen,
> is there a problem with 3 that we ought to definitely use 4 also in pdftex?
> If not, could luatex allow 3?
>
> Either way could the manual mention that setting the value low gives a
> warning.
>
> (Would it be possible for pdf.setdecimaldigits() to refuse to set the
> lua value to
> a low value, so that pdf.getdecimaldigits() always returns the effective
> value that will be used?)

i'll look at it but when we were looking into some off behaviour for
large values we found that we had to lower the upper bound and that it
also made sense to enlarge the lower bound (the backend truncates
trailing zeros so it's quite efficient) ... because the backend does
lots of transforms 4 digits is already a bit low (context has been using
6 for ages and this setting was introduced in pdftex when we found out
that 3 was now okay ... unless of course you want to have worse output
than possible (tex itself is rather accurate)

Hans

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