Post by GL
Where can I find useful information about LuaTeX, in order to get the
\pdfelapsedtime (pdfTeX primitive... is there an equivalent on LuaTeX?)
\pdfsavepos (same remark)
The LuaTeX reference manual can be found here:
Read in particular about \pdfvariable, \pdffeedback, and \pdfextension.
In general, a pdfTeX primitive \pdfBLAH is expressed in LuaTeX as
Alas, your specific questions represent special cases. I believe
\pdfelapsedtime does not have a direct LuaTeX analogue, but you can
implement it with Lua code; and \savepos does the job of \pdfsavepos.
The luatex85 package implements a number of pdfTeX primitives in terms
of their LuaTeX equivalents, which you may find convenient.