Re: Problem in updating progress bar

[Diego Zuccato <diego otello alma unibo it>]

DC A wrote:
> What could be the reason for using gtk_events_pending() and 
> gtk_main_iteration() in the following code snippet:
> 
> 
> for( gflt=0; gflt<=1;  ){
>         gtk_progress_bar_update( (GtkProgressBar*)pbar, gflt );
>         //update
>         while (gtk_events_pending ())
>             gtk_main_iteration ();
>         gflt += 0.1;
>         sleep(1);
>        if ( gflt > 1 ) break;
>     }
> 
> why the code cannot update the progressbar without these two functions? I 
> saw the API but still it is not clear to me.
'Cause you're blocking the main loop (which handles all the updating).
But that sleep(1) still blocks for a whole second any action: your GUI
will act quite strangely!
Could be really better to handle a timeout/idle callback.
If all you have to do is some lengthy operation, you could use a thread
that does it and updates a "percentage indicator" (a shared variable).
In the main program (the GUI manager) you set up a timeout callback (the
timeout is up to you: from .1 to tenths of seconds) that reads the
shared variable and updates the progress bar. This way you won't have to
bother about locks: just DON'T do anything GUI-related in the calc thread.

BYtE,
 Diego.