Re: GTK Progress bar: assistance pls.

[tom dbservice com]

Bin Chen wrote:
> å 2008-01-07äç 13:18 +0530ïvijayasarathy setsindia netåéï
> >         for(i=start_count;i<end_count;i++)
> >         {
> >                 //g_print("i = (%d)\n",i);
> >                 while(j<100000)//To kill time, keep counting until a
> > lakh
> >                         j++;
> >                 j = 0;//Make j 0 for the next loop.
> >                 //sleep(2);
> >                 pdata->fraction = (gdouble)i/(gdouble)(range);
> >
> >                 fflush(NULL);
> >                 //gtk_progress_bar_pulse (GTK_PROGRESS_BAR
> > (pdata->pbar));
> >                 //gtk_progress_bar_set_pulse_step(GTK_PROGRESS_BAR
> > (pdata->pbar),pdata->fraction );
> >                 gtk_progress_bar_set_fraction (GTK_PROGRESS_BAR
> > (pdata->pbar),
> > pdata->fraction);
> >         }//End for i = start_count to end_count
>
> For this code snippet, you update all your progress in the loop and not
> yield the control to gtk_main(), this is the problem.

IOW you don't let gtk draw the UI until you are done with the button  
callback. You should not block in the main gtk thread (the one where  
you called gtk_main() from). Always return as fast as possible from  
callbacks. Don't wait, don't block on anything.

> You should not write code like this, using a timer to update the
> progress bar instead of this loop, otherwise the drawing instruction
> will be pending due to your full control of CPU.

I suggest you use threads, they are easy to do with glib. When the  
user clicks the button, create a thread and give it the progress bar  
widget. In the thread do the loop and in ever iteration update the  
progress bar. Pay attention to thread safety, use thread  
synchronization primitives like mutexes (GMutex) when needed. I'm not  
very familiar with gtk and threads, but IIRC gtk isn't thread safe by  
default.

tom