Re: Update progress bar without returning to main loop?

[Toralf Lund <toralf procaptura com>]

Murray Cumming wrote:

> > > Should there perhaps also be an example illustrating the approach I
> > > eventually took to resolve my problem (see my other posts...)
> > >
> > > It's really just a matter of replacing
> > >
> > > wait_on_system();
> > >
> > > with
> > >
> > > pb->gdk_window()->process_updates(false);
> > >
> > > in the example, I believe.
> > >      
>
> I'm sceptical that this can really work well enough, but I would have to
> do some research/experiments to find out, if I found time.
>  
It works!

I believe this is the right and proper way of forcing queued redraw 
requests to be handled out immediately, which is something the toolkit 
generally can and should allow. I mean, how to do this was quite hard to 
find in the API documentation, but that does not mean it's an 
undocumented feature; it's actually there if you know where to look. 
From the Gtk::Widget doc,

int Gtk::Widget::send_expose 	( 	GdkEvent*  	/event/ 	 )  	

 	

Very rarely-used function.

This function is used to emit an expose event signals on a widget. This 
function is not normally used directly. The only time it is used is when 
propagating an expose event to a child NO_WINDOW widget, and that is 
normally done using Gtk::Container::propagate_expose() 
<http://www.gtkmm.org/docs/gtkmm-2.4/docs/reference/html/classGtk_1_1Container.html#a17>.

If you want to force an area of a window to be redrawn, use 
gdk_window_invalidate_rect() or gdk_window_invalidate_region(). To cause 
the redraw to be done immediately, follow that call with a call to 
gdk_window_process_updates().





I'm more sceptical to docs that suggesti to users that you have to use 
event loop constructs and/or threads in order to do something as simple 
as this. Not that there is anything wrong with Bob's example as such, 
it's just that it shows the way to program *if you want to respond to 
user input while the job progresses*. It you don't, then I daresay 
running an event loop is overly complex and/or simply wrong.

- T