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?) David
