[pygtk] Re: progressbar for file managing

[Fabian Braennstroem]

Hi John,

John Dennis schrieb am 04/17/2007 07:53 PM:
> On Tue, 2007-04-17 at 21:15 +0000, Fabian Braennstroem wrote:
>> Thanks for your advice! I tried to adjust your lines a bit, but I
>> was not successful:
>>
>>     def progress_pulse(self):
>>         if self.load_in_progress:
>>             self.progress.pulse()
>>             return True                 # call again
>>         else:
>>             return False                # do not call again
>>
>>
>>
>>     def on_load_data(self , state ):
>>         if state == 'start':
>>             self.load_in_progress = True
>>             self.progress.pulse()
>>             gobject.timeout_add(1, self.progress_pulse)
>>         if state == 'stop':
>>             self.load_in_progress = False
>>
>>     def callback(self, widget, data=None):
>>         i=0
>>         n=100
>>
>>         self.on_load_data('start')
>>
>>         shutil.copytree(file1,"/home/fab/test_copy2")
>>
>>         self.on_load_data('stop')
>>
>>
>> The progressbar starts to run, if the directory already exists and
>> 'shutil' stops with an error message; if the copying works than
>> there is no progressbar movement... strange. Do you know, what I am
>> doing wrong?
> 
> It's the same thing I told you originally, you can't both perform a
> synchronous copy and update the GUI at the same time. You also have to
> understand how the GTK event loop works.
> 
> Timeout callbacks are processed in the event loop. Your copy routine is
> processed in the event loop. They cannot proceed in parallel because the
> event loop is sequential. 
> 
> In one iteration of the event loop your copy routine installs a timeout
> callback with load_in_progress=True, does the copy, then sets
> load_in_progress=False. Sometime later the event loop gets to your
> timeout handler and calls it. But guess what the value of
> load_in_progress is?
> 
> I'm guessing the reason it works in an error condition is because
> copytree raises an exception which you don't catch (its caught by the
> event loop instead), thus you never set load_in_progress to False, then
> when the event loop calls your timeout handler load_in_progress is True
> and you pulse. BTW, 1 millisecond timeout is way too short.
> 
> You can cause the event loop to run during the copy with something like
> this:
> 
> while gtk.events_pending():
>    gtk.main_iteration(False)
> 
> But this has to be done inside the copy operation, or you have to
> structure the copy to be performed in chunks (e.g. idle_add()). But you
> can't do what you want to do if the copy operation is completely
> synchronous in one call (as copytree is) and you only have one thread.

Thanks for your help! I will try it ...
The chunks copy sounds pretty slow to me, but probably every file
manager is doing it, if it got any progressbar.

Greetings!
Fabian