From: Reid Thompson <Reid.Thompson@...>
Date: 2012-03-22T02:50:29+09:00
Subject: Re: Ruby+Tcl/Tk+Cygwin

On Thu, 2012-03-22 at 00:51 +0900, Matt Maycock wrote:
> Hello List!
> 
> 
> /usr/lib/ruby/1.8/tk.rb:1127:in `initialize': tcltklib: fail to
> Tk_Init(). no display name and no $DISPLAY environment variable
> (RuntimeError)
>         from /usr/lib/ruby/1.8/tk.rb:1127:in `new'
>         from /usr/lib/ruby/1.8/tk.rb:1127
snip
> Is this a problem on the ruby side?  With ActiveTcl?  Should I use
> XWindows somehow with cygwin since it's asking for Display?

The active state tcl/tk is windows based.
The cygwin tcl/tk is X-windows based.
It looks like the cygwin tcl/tk got invoked.
Try starting the cygwin X server, and invoke your script from the xterm
that starts up with it