[Rd] Change in the Tcl/Tk loading in R 2.7.0 (under Unix/Mac OS X)?

[Prof Brian Ripley]

First, this does depend on what build of R you use.  The 'HAVE_AQUA' 
define matters, and is only defined on some Mac OS X builds (e.g. not the 
default one, but the one used for the CRAN binary).

Second, there are several possible versions of Tcl/Tk and X11 on MacOS X, 
and as I suspect one of your R versions was not a CRAN build, I am not 
willing to make assumptions here.  (E.g. I do run a self-compiled 
command-line version of R using ActiveTcl's 8.5.2 code.)

Finally, I see no evidence that this is not specific to Mac OS X, and your 
desired behaviour is still present on other Unix-alikes.

If you want the ability to start Tcl and not Tk on a CRAN build of R for 
Mac OS X, I think you need to negotiate a way to do it as I believe it is 
not intended to be available.  But that's definitely an R-sig-mac topic.

On Sun, 4 May 2008, 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.

That message is only given if (src/library/tcltk/src/tcltk.c in both 2.6.2 
and 2.7.0)

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

so your 2.6.x build appears not to have been defining HAVE_AQUA, which a 
CRAN build would.

> 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 think it is coming from Tk_Init, at

         code = Tk_Init(RTcl_interp);  /* Load Tk into interpreter */
         if (code != TCL_OK)
             error(Tcl_GetStringResult(RTcl_interp));

>> 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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-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595