Re: Call a function after showing something in a DrawingArea

[Christoph Bersch <bersch uni-muenster de>]

Hi John!

John Cupitt schrieb:
> On 1/3/06, Christoph Bersch <bersch uni-muenster de> wrote:
> > I want to write a program, that draws something in a DrawingArea, and calls a
> > function after _showing_ the changes in the DrawingArea:
> >
> > 1) call function draw_something()
> > 2) show the changes
> > 3) call a function measure()
> > 4) return to step 1)
>
> I would use a timeout. Set it to run every 20ms (or whatever interval
> you want), and do something like:
>
> static int number_of_ticks = 0;
>
> my_timeout_callback( ...
> {
>   number_of_ticks += 1;
>   if( number_of_ticks & 1 )
>     // queue a redraw of our drawingarea
>     gtk_widget_queue_draw( ..
>   else
>     measure();
>
>   return( TRUE );
> }

Great, this seems to work :-)

> There's no guarantee that the draw will occur before the measure, but
> it probably will for most reasonable machines. But of course that's
> always true for X.

As long as it works for X, it's ok for me.

I thought, that a call of gtk_widget_draw() might be better than
gtk_widget_queue_draw_area(), as it draws immediately, although it is
deprecated.

So how could a call of gtk_widget_draw() be replaced in new code (I
don't fully understand the part belonging to this function in the
documentation). Could it be something like

gdk_window_invalidate_rect ();
gdk_window_process_updates ();
?

Thanks
Christoph