Re: printf and refresh drawing area

[Russell Shaw <rjshaw netspace net au>]

Fabrice Chinjoie wrote:
> Hi,
>
> I want to see a semi circle moving into a drawing area.
>
> That's what I do :
>
>  gdk_draw_rectangle (widget->window,
>              widget->style->white_gc,
>              TRUE,
>              0, 0,
>               widget->allocation.width,
>               widget->allocation.height);
>
>  gdk_draw_arc(widget->window,
>           widget->style->black_gc,
>           TRUE,
>           X,
>           Y,
>           dcircle,
>           dcircle,
>           angle*64,
>           180*64);
> change angle value...
>
> This code is called by : timeout_handler =g_timeout_add(1000, 
> update_angle,widget);
>
> When I'm doing this, the drawing area doesn't change. But... If I put a 
> printf(" angle %d \n",angle) after the gdk_draw_arc in the first 
> function. it works and I can see my semi circle move.
> Any idea about this?
> Thanks.

You should put these drawing functions in the "expose" event handler,
so it gets drawn whenever X sees the window coverage has changed.

http://www.gtk.org/tutorial/ch-scribble.html

Whenever your drawing changes, you can trigger your own expose event.