focus trap in tkinter

[kyosohma at gmail.com]

On Apr 9, 8:27 am, "vigac... at gmail.com" <vigac... at gmail.com> wrote:
> Hi all,
>
> I'm trying to write a simple tkinter program, then this problem popped
> up. The followin code will describe the problem.
>
> ------------------------------------------
>
> import Tkinter
>
> class countdown(Tkinter.Frame):
>         def __init__(self, master = None):
>                 Tkinter.Frame.__init__(self, master)
>                 self.ticker = Tkinter.Label(self)
>                 self.pack()
>                 self.ticker.pack()
>                 self.ticker["text"] = "foo"
>                 self.master.bind("<FocusIn>", self.__focus_in)
>                 self.master.bind("<FocusOut>", self.__focus_out)
>                 self.master.wm_attributes("-topmost", 1)
>
>         def __focus_in(self, detail):
>                 self.master.wm_attributes("-alpha", 1)
>
>         def __focus_out(self, detail):
>                 self.master.wm_attributes("-alpha", 0.8)
>
> if ("__main__" == __name__):
>         root = Tkinter.Tk()
>         app = countdown(master = root)
>         app.mainloop()
>
> ------------------------------------------
>
> My aim is to set the alpha property of the toplevel window to 0.8 when
> it lose focus, and set it back to 1 when it regain focus, pretty
> simple. But the problem is, whenever wm_attributes() is called, a new
> focus event is generated, and then wm_attributes() will be called
> again, then the program runs into endless loop of receiving focus
> events. Simply run above code will see what's going on.
>
> I tried to disable FocusIn event in the event handlers, by calling
> self.master.unbind(), but it doesn't work.
>
> I also tried to bind FocusIn and FocusOut event to the frame, the
> label widgets, instead of the toplevel window, but both frame and
> label widgets doesn't receive focus event, even after I set their
> takefocus properties to 1.
>
> There should be a way to make it work, just I didn't find it. Any
> input?
>
> Best regards!

I found some info on focus events in a previous post:
http://mail.python.org/pipermail/python-list/2000-January/021226.html

Maybe it will give you an idea.

Lundh's site has a lot of event information on it:
http://effbot.org/tkinterbook/tkinter-events-and-bindings.htm

If you were using wxPython, you'd do an event.Skip(), but I can't seem
to find that functionality in Tkinter. Maybe you'll have better luck.
Hopefully a Tkinter guru will come to the rescue.

Sorry I wasn't more help.

Mike