On 1/12/13 10:46 AM, Leon Maurer wrote:
Howdy,
I'm running in to a problem where TkInter won't update the interface on
OS X. I've filed a bug (http://bugs.python.org/issue16941), but it was
suggested that I also send the message here, in case you have some
thoughts about what to do -- either a fix or a workaround.
Here's a small piece of code which has the problem:
https://mywebspace.wisc.edu/lnmaurer/web/updatebug/bugtest.py
The program is simple -- basically a big canvas with a some text in the
middle that counts up.
Here's a short quick-time movie showing the problem with that code:
https://mywebspace.wisc.edu/lnmaurer/web/updatebug/updatebug.mov
The screen-cast has three parts. First, it shows the program working as
it should. Then, I add a simple background image to the canvas (a black
rectangle), and the interface refuses to refresh at all; I get a
spinning beach ball wheel (although the cursor appears as the usual
black arrow in the screen-cast). Finally I increase the delay between
updates, and the interface again refreshes as it should.
You're running into a well-known and essentially unsolvable bug with Tk
on OS X, essentially integration between the event loop of Tk and
Cocoa's event loop. This is not a Tkinter issue, it's a Tk issue, and
it's essentially impossible to fix: the event loops of Tk and Cocoa are
very different and their integration is a fragile, leading at times to
the kinds of screen freeze/lockups you see. Increasing the delay between
events a bit, as you've done, is a recommended best practice, as it
gives the event loop time to spin and process the event queue; so you've
essentially already found the best solution for your problem.
I'm speaking here at the maintainer of Tk on the Mac; we've discussed
these issues on the Tcl-Mac mailing list, the MacPython list, and here,
and a lot of talented developers besides myself have looked at it. No
one has been able to solve the issue, it's simply an inherent artifact
that can only be worked around.
Thanks,
Kevin
----
Kevin Walzer
Code by Kevin
http://www.codebykevin.com
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