Windows python/Pmw-tkinter problem

[Bruce Davis]

I'm having a problem on windows (both 2000 and XP) with a multi-threaded
tkinter gui application. The problem appears to be a deadlock condition
when a child thread pops up a
Pmw dialog window in the context of a main window. The problem does not
occur on HPUX or Linux. The following simple example code illustrates
the problem and the work around
I've come up with; However, I'd like, very much, to get rid of the kludgy
work around.

Running the following program without input options works (my work around)

WindowsProblem.py

Running the program with a '-r' option causes a deadlock condition and the
program hangs.

WindowsProblem.py -r

Anyone had a similar problem or know of a solution/patch for this problem?

Thanks,

-Bruce Davis

BTW I'm currently using Python 2.3.2 - the problem also occurs on Python
2.2. And, again, there is no need for the work around on HPUX or Linux. This
seems
to be a windows type of thing.


#!/usr/bin/env python

import thread, threading, Pmw, time, sys
from Tkinter import *
class mainWindow:

def __init__(self, root, winKludge):
self.root = root

# Create a simple frame with one button
fr = Frame(self.root)
button= Button(fr, text='Click to exit', command=self.NOP)
button.grid(row=0, column=0)
fr.grid(row=0, column=0)

# start a worker thread so as not to block the main window thread.
thread.start_new_thread(workerThread, (root, winKludge))

def NOP(self):
self.root.destroy()

def workerThread(parent, winKludge):
# sleep a while and pop up a dialog window.
time.sleep(2.0)
pu = popup(parent, winKludge)
pu.show()
class popup:

def __init__(self, root, winKludge):
self.root = root
self.winKludge = winKludge
if self.winKludge and sys.platform=='win32':
self.kludgeMutex = threading.Lock()
self.kludgeMutex.acquire()
self.condEvent = threading.Condition()
self.condEvent.acquire(1)
root.after_idle(self.windowsKludge)
self.condEvent.wait(30.0)
self.condEvent.release()
self.win = Pmw.MessageDialog(root,
separatorwidth=4,
message_text='Test',
buttons=('Click to exit',),
command=self.callBack,
)
self.win.withdraw()

def windowsKludge(self):
# need to block the main window thread to prevent the program hang
when creating the popup
self.condEvent.acquire(1)
self.condEvent.notify()
self.condEvent.release()
self.kludgeMutex.acquire()

def show(self):
if self.winKludge and sys.platform=='win32':
self.kludgeMutex.release()
self.root.after_idle(self.win.activate)
self.wait()
else:
self.win.activate(globalMode='nograb',
geometry='centerscreenalways')

def quitter(self):
if self.winKludge and sys.platform=='win32':
self.condEvent.acquire(1)
self.condEvent.notify()
self.condEvent.release()
self.win.deactivate()

def wait(self, timeOut=2000):
self.condEvent.acquire(1)
self.condEvent.wait(timeOut)
self.condEvent.release()

def callBack(self, result):
self.quitter()


if __name__ == '__main__':

usageStr="""

WindowsProblem [r] [h]
Simple program to demonstrate a problem that occurs on windows (2000 and
XP)
and a work around. The program works without the work around on HPUX and
Linux boxes.
Input options:
-h - displays this help message
-r - reproduce the problem

Without the -r option, there is no problem.
With the -r option, the window appears to deadlock and hang forever.

"""

import getopt
try:
optlist,args = getopt.getopt(sys.argv[1:],"hr")
except getopt.error,info:
Print (usageStr)
sys.exit(1)

winKludge = 1
for opt in optlist:
if opt[0] == '-h':
print usageStr
sys.exit(0)
elif opt[0] == '-r':
winKludge = 0

# Create the main window
root = Tk()
mainWindow(root, winKludge)
root.mainloop()