Inter process communication using Tk/send hangs on suspended processes

[Greg McFarlane]

The only things I can think of are to fork separate processes to do
each send and kill them if they do not respond quickly.  The other way
was for each program to create a unique property on the X root window
that could be queried.  But trawling through the Tk man pages and
sources, I did not find a Tk interface to this feature of X.

On 15 Feb, Rob W. W. Hooft wrote:
> I have a group of python programs. Whenever any new program is started,
> it will try to establish connections to each of the other ones
> using Tk/send (it is asking each for their background color, and will
> choose a new one for itself). This is done using "root=setup.setup()",
> the setup module is appended to this message.
> 
> The problem occurs when any pre-existing program has been suspended:
> in such a case the Tk/send does not return. I also can not seem to set
> a timeout on the communications (my attempts are in commented
> code). Are there any better suggestions?
> 
> Regards,
> 
> Rob Hooft.
> --------------------------------------------------------------------
> #
> __version__ = '$Id: setup.py,v 1.9 1999/08/04 09:16:21 hooft Exp $'
> #
> # GUI Startup
> #
> # (C) Rob W.W. Hooft, Nonius BV, 1997--1999
> #
> import os,signal
> import Tkinter,Pmw
> 
> TclError=Tkinter.TclError
> 
> bgcolors=["grey85","#DFF","#DDF","#FDF","#FDD","#FFD","#DFD"]
> 
> #def timeouthandler(sig,frame):
> #    print "WARNING: no response from other Tk application."
> #    raise TclError
> 
> def usedcolors(root):
>     used=[]
>     names=list(root.winfo_interps())
>     names.sort()
>     names.reverse()
>     for name in names:
>         try:
>             #signal.signal(signal.SIGALRM,timeouthandler)
>             #signal.alarm(3)
>             root.send(name, 'winfo name .')
>             #signal.alarm(0)
>             #signal.signal(signal.SIGALRM,signal.SIG_DFL)
>         except TclError:
>             # Inoperative window -- ignore it
>             pass
>         else:
>             try:
>                 col=root.send(name,'no-bgcolor')
>                 used.append(col)
>             except:
>                 pass
>     return used
> 
> def setscheme(root):
>     try:
>         bgcolor=os.environ['NONIUS_BGCOLOR']
>         Pmw.Color.setscheme(root,background=bgcolor)
>     except KeyError:
>         # Now sample all others, and see what is in use. Choose a new one.
>         u=usedcolors(root)
>         for col in :
>             if col in u:
>                 continue
>             break
>         else:
>             print "No free background color"
>             col="grey85"
>         Pmw.Color.setscheme(root,background=col)
>         root.tk.createcommand('no-bgcolor',lambda bgcolor=col: bgcolor )
>         os.environ['NONIUS_BGCOLOR']=col
>         
> def setup(idle=1):
>     import Tkinter,Pmw
>     Pmw.initialise(fontScheme='Pmw1',size=14)
>     root=Tkinter._default_root
>     setscheme(root)
>     import balloon # Automatically initializes...
>     # Set up idle task calls for "checkifcanceled"....
>     if idle:
>         import projtls
>         projtls._ltt.setidletask(root.update)
>     return root
>     
> 
> 
> -- 
> =====   rob at hooft.net          http://www.xs4all.nl/~hooft/rob/  =====
> =====   R&D, Nonius BV, Delft  http://www.nonius.nl/             =====
> ===== PGPid 0xFA19277D ========================== Use Linux! =========
> -- 
> http://www.python.org/mailman/listinfo/python-list
> 

-- 
Greg McFarlane     INMS Telstra Australia     gregm at iname.com