[Rcpp-devel] grDevices issue with RInside

hi dirk,

i'm having an issue with grDevices, but the issue only seems to appear 
when i using my library with RInside on windows.

one of the packages we use (ggjoy) calls the grDevices::pdf() function, 
which tries to load the enc/WinAnsi.enc file from grDevices package. 
however, as can be seen here

https://jona.thon.love/rinside.png

it doesn't look relative to the R_HOME, but to `C:\`.

fossicking through the grDevices source code, i find this:

https://github.com/wch/r-source/blob/b7e8221be0266371b5b12e3549cf052c1eed10bc/src/library/grDevices/src/devPS.c#L507

suggesting that the value of this R_Home variable is an empty string

however, the R_HOME environmental variable is set appropriately, and 
calling any number of the `R.home()`, `Sys.getenv('R_HOME')` return the 
expected value. further, this particular installation is used by tens of 
thousand of users, and produces plots fine ... this is the only 
exception we've found so far.

you don't have any intuitions as to what may be the problem here, and 
how we could work around it?

with thanks

jonathon