Re: [PATCH] example for gtk-demo demonstrating offscreen-rendered widgets with reflection-effect

[Mirco Müller <macslow bangang de>]

Am Montag, den 24.12.2007, 22:08 -0500 schrieb Matthias Clasen:

> I have some pedantic comments on the patch, but more importantly, I'd like to
> have a better understanding of
> 
> +  /* if we don't do this, the reflection gets not updated at the right
> +    * time */
> +    gtk_widget_set_double_buffered (window, FALSE);
> 
> If compositing and double-buffering don't work well together, we ought to have
> a good explanation of this in the docs...

	What's causing the reflection not to be updated correctly, if double
buffering is enabled for the top-level window, is a mystery to me still.

	I tried a lot of different things before the solution you see in the
patch was the one I settled for, because it was the only one I got
working.

	For example having double buffering enabled and connecting
window_expose_event() to the expose-event of backbutton, entry and
applybutton like...

        g_signal_connect_after (backbutton,
                                "expose-event",
                                G_CALLBACK (window_expose_event),
                                (gpointer) window);
        
        g_signal_connect_after (entry,
                                "expose-event",
                                G_CALLBACK (window_expose_event),
                                (gpointer) window);
        
        g_signal_connect_after (applybutton,
                                "expose-event",
                                G_CALLBACK (window_expose_event),
                                (gpointer) window);

... with a slightly changed window_expose_event() looking like...

        static gboolean
        window_expose_event (GtkWidget *widget,
                             GdkEventExpose *event
                             gpointer data)
        {
          GtkWidget *child;
          GtkWidget *window = (GtkWidget*) data;
          cairo_t *cr;
          cairo_matrix_t matrix;
          cairo_pattern_t *mask;
          GtkStyle *style;
        
          /* get our child... here the event-box */ 
          child = gtk_bin_get_child (GTK_BIN (window));
        
          /* create a cairo context to draw to the window */
          cr = gdk_cairo_create (window->window);
        
          /* redirect output for double-buffering */
          cairo_push_group (cr);
        
          /* write/paint over everything else */
          cairo_set_operator (cr, CAIRO_OPERATOR_OVER);
        
          /* set clip-region to windows dimensions */
          cairo_rectangle (cr,
                           (gdouble) window->allocation.x,
                           (gdouble) window->allocation.y,
                           (gdouble) window->allocation.width,
                           (gdouble) window->allocation.height);
          cairo_clip (cr);
        
          /* get theme background-color and clear/paint the context with it */
          style = gtk_widget_get_style (window);
          gdk_cairo_set_source_color (cr, &style->bg[GTK_STATE_NORMAL]);
          ...

... does not work. Widgets just don't update as I would expect.

Best regards...

Mirco