Re: Updating GUI during long operation

[Kip Warner <kip thevertigo com>]

On Thu, 2013-04-25 at 22:53 -0400, Allin Cottrell wrote:
> I have a situation which might, perhaps, be akin to yours. From the 
> GUI, my app calls an iterative numerical procedure that can be quite 
> time consuming. Without any special treatment, this causes the GUI 
> to appear "frozen" and unresponsive, as if something had gone wrong.
>
> My solution was to introduce a "breather", as you call it. I 
> installed a callback function, to be called every k iterations of 
> the numerical procedure (for a suitable value of k). The callback 
> simply looks like this:
>
> static void gui_show_activity (void)
> {
>      while (gtk_events_pending()) {
>          gtk_main_iteration();
>      }
> }

Hey Allin. Thanks a lot for your help. It's similar to my situation, but
unfortunately in my case the demanding work is in a secondary thread
where events_pending() / main_iteration() don't seem to do anything from
the secondary thread. I'm guessing because it's a separate event queue
in each thread and we're really not suppose to be doing GUI operations
outside the main thread anyways. 

So I tried using idle_add() in the worker thread to have a callback
invoked periodically from within the main thread which in turn does
exactly what your gui_show_activity() function does, but the problem is
that the callback calls itself recursively until the stack blows up
because main_iteration() call invokes the callback again since the last
invocation was never removed off the queue yet. Almost got it. Arg.

-- 
Kip Warner -- Software Engineer
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http://www.thevertigo.com