Re: Updating GUI during long operation

[Allin Cottrell <cottrell wfu edu>]

On Thu, 25 Apr 2013, Kip Warner wrote:

> I will try adjusting the animation's framerate and seeing if I can 
> get the worker thread to give a breather to the main thread which 
> seems to be working when using an idle_add() callback to trigger 
> an event flush.

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();
    }
}

If my app is not operating in GUI mode the callback function pointer 
is NULL and is skipped; if it's in GUI mode the callback ensures 
that a spinner operates and the GUI doesn't look dead. I'm not doing 
anything fancy with threads; just every so many rounds of the 
numerical operation this callback is triggered, and it stops the GUI 
from looking dead.

Inside the numerical procedure I have something like

if (iter % k == 0 && activity_callback != NULL) {
    activity_callback();
}

Allin Cottrell