Reliable trapping of SIGINT or Ctrl-C when using tkinter

[Lloyd Zusman]

I'm using Python 1.5 under Redhat Linux 5.0. I'm trying to figure out
the best way to trap a SIGINT (or Ctrl-C) when using tkinter. To
illustrate the problem I have, do the following ...

-- Build Python-1.5 with tkinter enabled.

-- Go into the Demo/tkinter/guido directory under the Python-1.5
build tree.

-- Type "python imageview.py image-file", where "image-file" is the
full pathname of a displayable image.

-- Once the image pops up, make sure that the window focus is
held by the xterm window from which the "python ..." command
was just now invoked.

-- Hit Ctrl-C.

At this point, nothing happens. The Ctrl-C seems to be ignored.
But now ...

-- Without hitting any more keys on the keyboard, set the window
focus to the displayed image window.

As soon as that window gets the focus, the Ctrl-C takes effect.

My question is this: is there any way to restructure the
"imageview.py" program so that it will respond to SIGINT (Ctrl-C)
immediately, without having to set the window focus to the displayed
image first?

Thanks in advance for any help you folks can give me.

--
Lloyd Zusman
l...@asfast.com

[Guido van Rossum]

What you're seeing is caused by the way signal handlers are handled.
You're stuck in the Tcl/Tk main loop, and signal handlers are only
handled by the Python interpreter. A quick workaround is to use
after() to schedule a dummy function to be called once a second or so
-- this will make it *appear* that your signal is handled in a timely
manner.

--Guido van Rossum (home page: http://www.python.org/~guido/)