[Rd] [R-SIG-Mac] Starting tcltk without Tk

[Simon Urbanek]

On May 6, 2008, at 3:06 AM, Philippe Grosjean wrote:

> Simon Urbanek wrote:
>> It turns out that the behavior of starting just Tcl was actually a  
>> bug.
>
> Not completely. At least, loading of tcltk was correct when the  
> "bug" was there, but I totally agree that the mechanism used  
> (according to the presence or not of the DISPLAY variable is not the  
> best one). It is not true that there was no intention to allow  
> loading tcltk without Tk. Otherwise, why would you have this  
> (tcltk.c, tcltk_init(), line 643 in the R 2.7.0 source):
>
> warning(_("no DISPLAY variable so Tk is not available"));
>
> This message strongly suggests that starting tcltk without Tk is  
> allowed, and it also suggests the mechanism: by eliminating the  
> DISPLAY environment variable before starting tcltk. It is certainly  
> undocumented, most probably underused, and certainly requires a  
> better way to specify that the user does want to load Tk,... but at  
> least, it worked for me up to now.
>

Philippe, you missed the one important line - please read the whole  
code - there is

#if !defined(Win32) && !defined(HAVE_AQUA)

before that and that is the crucial part.

Cheers,
Simon


>> Apparently the intention was to attempt to start Tk regardless of  
>> the DISPLAY variable, because some TclTk implementation such as  
>> Aqua Tcl/Tk don't require DISPLAY and thus would not be loaded. Due  
>> to a bug (HAVE_AQUA was not included in Rconfig.h before R 2.7.0),  
>> though, this was not the case. I'll leave it to tcltk users/ 
>> maintainers to decide the right way forward. Essentially I see two  
>> options:
>> 1) status quo: tcltk always attempts to load Tk and fails on an error
>> 2) allow some (possibly cross-platform) way of specifying that it  
>> is ok to not load Tk - essentially make failure to load Tk non-fatal.
>
> I vote for the second option.
> Many thanks,
>
> Philippe
>
>> Right now there is no (semantically correct) way to inhibit the  
>> loading of Tk (DISPLAY is a sort of abuse and not a solution).
>> Cheers,
>> Simon
>> (CC to R-devel where this started...)
>> On May 5, 2008, at 9:12 AM, Simon Urbanek wrote:
>>> Philippe,
>>>
>>> I'm not quite sure why you are asking on a Mac list, but the error  
>>> comes from Tcl/Tk. I'd suggest asking on R-devel, the Tcl/Tk used  
>>> in the R binary is the same for R 2.6.x and 2.7.0 so it must be a  
>>> change in tcltk.
>>>
>>> Cheers,
>>> Simon
>>>
>>>
>>> On May 4, 2008, at 7:01 AM, Philippe Grosjean wrote:
>>>
>>>> Hello,
>>>>
>>>> Up to R 2.6.2, I used to start Tcl *without Tk* (I need only Tcl  
>>>> for some part of my work, like a socket server written in Tcl  
>>>> only, for instance) with this code under Mac OS X (particularly  
>>>> on this system, because I don't want to start X11 just to use Tcl  
>>>> code, which is required for Tk!):
>>>>
>>>> > Sys.unsetenv("DISPLAY")
>>>> > library(tcltk)
>>>>
>>>> I got then the message "no DISPLAY variable so Tk is not  
>>>> available", but could work with Tcl without problems.
>>>>
>>>> Now, with R 2.7.0, I got the following and Tcl failed to load:
>>>> Loading Tcl/Tk interface ... Error in fun(...) : no display name  
>>>> and no $DISPLAY environment variable
>>>> Error : .onLoad failed in 'loadNamespace' for 'tcltk'
>>>> Error: package/namespace load failed for 'tcltk'
>>>>
>>>> I try to locate the message "no display name and no $DISPLAY  
>>>> environment variable" in the code but I cannot find it. Could  
>>>> someone help me please?
>>>>
>>>> I understand that starting Tcl without Tk from R is not an  
>>>> intended behaviour, but would it be possible to include an option  
>>>> to do so?
>>>>
>>>> > sessionInfo()
>>>> R version 2.7.0 Patched (2008-04-22 r45460)
>>>> i386-apple-darwin8.10.1
>>>>
>>>> locale:
>>>> en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8
>>>>
>>>> attached base packages:
>>>> [1] stats     graphics  grDevices utils     datasets  methods    
>>>> base
>>>>
>>>> Many thanks,
>>>>
>>>> Philippe Grosjean
>>>> -- 
>>>> ..............................................<°}))><........
>>>> ) ) ) ) )
>>>> ( ( ( ( (    Prof. Philippe Grosjean
>>>> ) ) ) ) )
>>>> ( ( ( ( (    Numerical Ecology of Aquatic Systems
>>>> ) ) ) ) )   Mons-Hainaut University, Belgium
>>>> ( ( ( ( (
>>>> ..............................................................
>>>>
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