[ESS] ESS installation with cygwin needs unsetting DISPLAY

[Rodney Sparapani]

Nitin Jain wrote:
> Dear all,
> 
> I am facing a problem in ESS installation when using with cygwin. Here are the steps that I followed:
> 
> - unzipped .tgz ess file 
> - added the ess path in init.el
> (load "/cygdrive/C/cygwin/usr/share/xemacs/xemacs-packages/lisp/ess-5.3.5/lisp/ess-site")
> - Modiffied  /usr/share/xemacs/xemacs-packages/lisp/ess-5.3.5/lisp/essd-r-args.el file to comment the tooltip lines:
> (eval-when-compile
>     (require 'tooltip)); for tooltip-show
> 
> 
> When I start cygwin and type, 
> xemacs a.R -f R &
> it asks me for the starting R directory to which I press enter and then I get the message "Process R is not running"
> 
> However, when I open another xterm and do: "unset DISPLAY", the above command works fine (though several times, it hangs and then i have to restart cygwin).
> 
> The difference in the two xemacs sessions is that 1st one (with default DISPLAY set to 127.0.0.1:0.0), xemacs opens with grey background (much like default unix xemacs) whereas after unsetting DISPLAY, I get xemacs with white background (much like native xemacs on windows).
> 
> Is this a bug or am I missing something?
> 
> Thanks.
> 
> Best,
> Nitin
> 

This behavior is most likely a side-effect of ESS.  ESS can be run under 
2 different "flavors" on Windows.  1. vanilla, native Windows or 2. 
tutti-frutti: Unix-like Cygwin.  1. should work best if you are working 
with R/S-plus or SAS locally, i.e. Windows native versions of those 
packages.  2. will work best if you are running these packages remotely, 
i.e. ESS-elsewhere.  At the time that this was designed, native Windows 
xemacs and Unix-like Cygwin xemacs were separate installs so you could 
have both.  But, it seems that recently, Cygwin has managed to include 
both flavors in one install.  In the future, this will make supporting 
ESS on Windows easier (assuming GNU emacs is similarly contrived by 
Cygwin).  And, I'm guessing, that it looks for the DISPLAY environment 
variable to decide your favorite flavor.  YMMV

Rodney