Re: [Rd] X11 help please

From: Duncan Murdoch <murdoch_at_stats.uwo.ca>
Date: Mon, 18 Jun 2007 11:18:24 -0400

On 6/18/2007 9:39 AM, Duncan Murdoch wrote:
> On 6/18/2007 7:56 AM, Hin-Tak Leung wrote:

>> Prof Brian Ripley wrote:
>>> rgl normally works under Xvfb on Linux: we've been using that for the 
>>> testing 'for ever'.
>>> 
>>> However R should not 'crash' on an error in a package, and the X11 device 
>>> has error handlers set up by
>>> 
>>>  	XSetErrorHandler(R_X11Err);
>>>  	XSetIOErrorHandler(R_X11IOErr);
>>> 
>>> I don't see anything comparable in rgl.
>>> 
>>> The error seems to be in the attributes, so I would have a closer look at 
>>> those.  In particular, how are you running Xvfb?: you may need something 
>>> like
>>> 
>>> Xvfb :5 -screen 0 1280x1024x24 &
>>> setenv DISPLAY :5
>>> 
>>> to ensure that you have a reasonable visual and hence colormap.
>>> (On my system the default is 12 bit.)
>> 
>> That's interesting - my first thought of Duncan's problem was unusual
>> colour depth as well, but I thought very few people run their X servers
>> in anything other than 24-bit or true-color mode these days (and any
>> MacOSX hardware should be capable of that anyway); if 12-bit is the
>> Xvfb default it is hightly likely that's the reason.

>
> I don't know the default, but I've been specifying 24 or 32 bit depth
> each time, and rgl is seeing 32 bit depth.
>
>> I have also seen that sort of error messages in CJK related issues,
>> if the X server's font path has some unsual and broken fonts; so it 
>> might be a good idea to disable any non-english locale, etc and try not 
>> to do anything clever in that direction for the time being.

>
> I do get a warning about a missing font when I run Xvfb; Simon Urbanek
> thought it was ignorable, but maybe not:
>
> Could not init font path element /usr/X11R6/lib/X11/fonts/CID/
>
> This happens before R is running, and sometimes again during the run.
>
> I've now implemented XSetErrorHandler(R_X11Err) as Brian suggested, and
> this moves the error elsewhere: R doesn't quit when it hits that error,
> but it dies later because rgl isn't handling its incomplete
> initialization properly. I think that will be relatively easy to track
> down and fix, but I'm still left with two problems I don't know how to
> solve:
>
> 1. Why am I getting this error in the first place? Since things work
> on Linux, this may be a bug in the MacOSX implementation of Xvfb, but
> Google doesn't turn up other reports of that, so it's more likely an rgl
> problem.
>
> 2. XSetErrorHandler() is a global setting. If rgl sets it, then it
> will override the setting that X11() used. Is there a way to retrieve
> the previous setting, so I can set it only temporarily? There doesn't
> appear to be any XGetErrorHandler() function.

This one was easy: the value of the XSetErrorHandler call is the previous handler.

Duncan Murdoch



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