On Fri, Feb 28, 2003 at 08:56:04AM -0600, Jon Nelson wrote:
> To make progress bars work, I use the following code:
>
> while gtk.events_pending():
> gtk.mainiteration(0)
>
> And here is where I get into trouble.
>
> Assume the FIFO is still readable (perhaps I haven't read all of the
> data, or perhaps new data has arrived).
>
> It appears that gtk.mainiteration will call read_from_fifo *again*,
> which calls handle_fifo, which may result in calling mainiteration,
> which may result in read_from_fifo being called, which ....
Why not just use a global variable to lock this? Something like
self.block_read = 1
and then set this just before your mainiteration loop. Then check for it
inside read_from_fifo and only perform the actual read if you aren't
blocked.
> I've tried the following approaches:
>
> 1. don't call handle_fifo directly, use an idle function (same problem)
> 2. don't call handle_fifo directly, use a timeout function (same
> problem)
> 3. [incorrectly] use gtk.threads_{enter,leave} <- many scary locks.
> Wrong approach.
> 4. in handle_fifo, call gtk.input_remove(self.fifo_tag) and set
> self.fifo_tag appropriately, and later re-enable it when my work is
> done. <- why doesn't this work?
I think this isn't really related to threads at all, but IMBW.
> After the Queue has been populated, in read_from_fifo:
>
> old = gtk.events_pending
> def duh(*args):
> return 0
> gtk.events_pending = duh
> self.handle_fifo()
> gtk.events_pending = old
I think the lock would work in the same way as this, but a bit cleaner.
> 1. is there a better way to do this?
> 2. why doesn't #4 above work?
Possibly because of the order things are being processed inside GTK. I
would have to have a look at the input handling code but that comes to
mind as a definite possibility.
> What is the difference between calling mainiteration with blocking 0 or
> 1 (yeah, yeah, it "blocks". What does that *mean*?)
I think it blocks till an event has been triggered via GTK+.
> I gotta say. This was a monster stumper for me. Took me like 4 hours
> to figure it out.
Isn't coding fun?
Take care,
--
Christian Reis, Senior Engineer, Async Open Source, Brazil.
http://async.com.br/~kiko/ | [+55 16] 261 2331 | NMFL
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