Inter process communication using Tk/send hangs on suspended processes

[Rob W. W. Hooft]

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
    


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=====   rob at hooft.net          http://www.xs4all.nl/~hooft/rob/  =====
=====   R&D, Nonius BV, Delft  http://www.nonius.nl/             =====
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