Hi!
Well...you CAN do things to a GUI from a thread in Tkinter, but not
on Windows (and, of course, not on Linux, Solaris or OSX just because
you're not supposed to in the first place).
I had, in essence:
Stop = False
def TickleButton(But):
while Stop == False:
sleep(.25)
But.update()
return
StopBut = None
def drawForm():
global StopBut
Entry fields, Labels, Buttons, Texts, etc...
StopBut = Button(text = "Stop", command = change Stop to True)
return
# Do stuff and output info to a Text field or draw on a Canvas.
def doSomethingLongAndTedious():
start_new_thread(TickleButton, (StopBut))
Do lots of stuff while checking the value of Stop when appropriate.
When finished Stop = True
return
At some point call drawForm() and bring up the form (usually a menu
command in my case).
At some point call doSomethingLongAndTedious() (usually from a GO
button on the form in my case).
Everything works fine, except on Windows. If the Button is on a form
(form=a Frame with buttons, fields, Labels, etc.) that has a Text
widget or a Canvas widget with Scrollbars (vertical in my case)
attached to them everything is fine UNTIL the Text or Canvas gets
full enough with output from the operation in the long and tedious
function) to activate the Scrollbars. Then at that instant
everything grinds to a severe halt (you have to practically use the
Task Manager to kill the program). It's odd that it's OK on *NIXs,
but not on Windows. I wouldn't know if it is a Tkinter problem, or a
Python problem, or just a Scrollbar problem, or what (I'm not that
smart). Is it ever going to be possible to do things like this?
What with multiple core CPUs and many threads and stuff now upon us
Tkinter is beginning to show signs of death, which is too bad since
it runs like crazy everywhere with minimal fuss.
So I'm back to just calling But.update() every once-in-a-while in the
programs. It works OK, but not as well as I'd like. It's tricky
figuring out in each long and scary function when to do the update
(don't want to do it too often or it slows things down, but don't
want to do it too slowly or the user thinks nothing is happening when
they click the Stop button -- my Stop buttons go from red/NORMAL when
running to yellow when the user clicks on them then to default color/
DISABLED when the long and tedious function actually gets to a safe
stopping point).
Bob
On the EeePC signals thing, it doesn't look like the programs get any
signals when the lid is closed and the Linux goes into standby (which
makes some sense -- the programs aren't really supposed to know that
anything happened when you go into standby), but there are little one-
liner text files that get changed from things like "Lid: open" to
"Lid: closed" that I can poll (again, polling! :) to see when the
lid has been closed and shutdown the serial ports in time...maybe. I
haven't gotten back to that program to implement it yet.
On Jan 23, 2008, at 03:50, [EMAIL PROTECTED] wrote:
>
> Hello Bob,
>
> You wrote:
>> Is there anything that is OK for a thread to do to the GUI? Like
>> would just calling .update() on a Button() be OK? It seems to work,
>> but is it OK?
>
>> I'm calling it on a "Stop" button, specifically, in the thread every
>> quarter second, instead of peppering the code with updates() to give
>> the button a chance to set it's IntVar value and then stop everything
>> when the code gets around to checking that.
>
>> From what I remember everybody says: Don't do that!
> Some refs I found googling for 'tkinter and threads':
>
> A clear warning
> http://mail.python.org/pipermail/tkinter-discuss/2005-February/
> 000313.html
> (the cited reference is dead, though)
> In the following answer is a small example using threading.
>
> Another example using thread and Queue (from effbot):
> http://effbot.org/zone/tkinter-threads.htm
>
> I have used a solution from Mark Lutz (Programming Python/O'Reilly)
> but just for popup dialogs that block the GUI while a thread
> is running (communicating via a simple variable).
> This might be applicable to your scenario, too.
>
> In a socket testing application I have used 'after' in the GUI thread
> to look at a common buffer if new data have arrived.
>
>
> BTW have you found some info regarding your signals problem?
>
> Hope this helps,
> Matthias Kievernagel
> (mkiever/at/web/dot/de)
> _______________________________________________
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> Tkinter-discuss@python.org
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>
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