[luatex] pdfdecimaldigits < 4

[Hans Hagen]

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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                                           Hans Hagen | PRAGMA ADE
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