Re: Using existing cairo context for GtkDrawingArea

[Ivan Baldo <ibaldo adinet com uy>]

   Hello.
   You can't AFAIK.
   GTK is double buffered, for every expose event, it draws to a 
different place. When you draw on the expose event, you are not drawing 
into the visible area of the screen, when the expose event is finished, 
GTK switches the drawing you just did offscreen to appear on the screen 
instead of the old one.
   So you must create a new Cairo context for every expose event, but 
don't worry, this is highly optimized and no time is wasted on the new 
context for every expose event.
   If you are having performance problems, you may try to use a cache 
for some parts of your drawing, you can use the 
cairo_surface_create_similar function for that, you can create a Cairo 
context for that surface and draw things there, then you can use that 
surface on the Cairo context of the expose event. You can cache mostly 
static things and the more dynamic ones you can draw in the expose event.
   HTH, goodbye.


El 07/12/06 20:37, asubedi escribió:
> Hi,
>
> I am trying to create a Graph widget using Cairo. I am using Ruby, but
> you can reply in any language you prefer.
>
> In the examples I have seen about using cairo in gtk application, most
> create a cairo context from GtkDrawingArea in the handler of expose
> event. However, I would like to create a cairo context independent of
> GtkDrawingArea, and would like to use that context in GtkDrawingArea's
> expose handler.  How can I do that?
> _______________________________________________
> gtk-app-devel-list mailing list
> gtk-app-devel-list gnome org
> http://mail.gnome.org/mailman/listinfo/gtk-app-devel-list
>
>   

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