[Rd] X11 help please

Duncan Murdoch murdoch at stats.uwo.ca
Tue Jun 19 04:08:21 CEST 2007

Duncan Murdoch wrote:
> The rgl package currently crashes R when running under Xvfb (the 
> "virtual frame buffer" server), at least on MacOSX.  It makes sense that 
> it shouldn't be able to work there (it needs interactivity), but I don't 
> know how to detect the problems before they cause the crash.
> Currently the error happens the first time you try to open an rgl 
> window; when rgl calls XCreateWindow R crashes with the error message
> X Error of failed request:  BadMatch (invalid parameter attributes)
>   Major opcode of failed request:  1 (X_CreateWindow)
>   Serial number of failed request:  28
>   Current serial number in output stream:  29
> I've checked and as far as I can see all the parameters we're sending to 
> XCreateWindow are valid, but I might have missed something:  I don't 
> know much about X11 programming.  (The call is
>   ::Window xwindow = XCreateWindow(
>     xdisplay, RootWindow(xdisplay, DefaultScreen(xdisplay)),
>     0, 0, 256, 256, 0,
>     xvisualinfo->depth,
>     InputOutput,
>     xvisualinfo->visual,
>     valuemask,
>     &attrib
>   );
> but without context that's probably not worth much to others.)
> Are there any experienced X11 programmers out there who can suggest what 
> to do next?

I have now committed some changes to rgl to avoid the crash -- it 
converts the above error into an R error.
I think to actually fix it, I'd need to debug the MacOSX Xvfb code to 
see exactly what it's complaining about.  I don't know where to find 
that source, so this isn't likely to happen soon.

Are there any X11/MacOSX programmers going to the UseR! meeting in 
August?  I'd guess if I could sit down with someone who had experience 
with both of those we could track this down fairly quickly, but I don't 
think I'll be able to do it without that.

Duncan Murdoch

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