[R-pkg-devel] Catching console messages from libGL

[Duncan Murdoch]

I'm working on the initialization code for rgl, especially for the case 
when it is running remotely and the user is connecting using X11.

On some machines, this fails:  I now understand that's because the local 
machine needs to enable "indirect GLX" (IGLX) for it to succeed, and by 
default most current machines have IGLX disabled.  (It can be a security 
risk to enable it.)

Failure looks like this (with the current CRAN version of rgl 0.100.47, 
and the remote system running Ubuntu, my local system running MacOS):

 > library(rgl)
 > open3d()
libGL error: No matching fbConfigs or visuals found
libGL error: failed to load driver: swrast
X Error of failed request:  GLXBadContext
   Major opcode of failed request:  149 (GLX)
   Minor opcode of failed request:  6 (X_GLXIsDirect)
   Serial number of failed request:  42
   Current serial number in output stream:  41

I end up booted right out of R.  I now know how to fix that, and will 
upload an update to CRAN in due course.

On MacOS I can enable IGLX by running

   defaults write org.macosforge.xquartz.X11 enable_iglx -bool true

and restarting XQuartz.  When I do that, I see this (same setup as before):

 > library(rgl)
 > open3d()
libGL error: No matching fbConfigs or visuals found
libGL error: failed to load driver: swrast
glX
   1

Now I want to suppress those two libGL messages, and I'm having trouble 
figuring out how to do it.  If I redirect stderr when I start R, they 
are redirected:  but if I do it after starting R, they aren't:

 > library(rgl)
 > capture.output(open3d(), type = "message")
libGL error: No matching fbConfigs or visuals found
libGL error: failed to load driver: swrast
glX
   1
character(0)

(capture.output with type = "output" gets c("glX", "1"), but leaves the 
libGL messages printing to the console.  sink() behaves similarly.)

So how do I capture stderr (or, off topic here, how do I get libGL to be 
quiet)?

Duncan Murdoch