Re: Forcing expose before onscreen mapping

["Matt Hoosier" <mwhoosier gmail com>]

Tommi,

Excellent hint. With matchbox (or no window manager at all), just doing

 gtk_widget_realize (win);
 gdk_window_set_back_pixmap (win->window, NULL, FALSE);

does the trick.

Thanks

On 10/11/06, Tommi Komulainen <tommi komulainen iki fi> wrote:
> On 10/11/06, Matt Hoosier <mwhoosier gmail com> wrote:
> > When a GtkWindow first appears after gtk_widget_show() is called on
> > it, there is a moment during which it isn't yet rendered, and the X11
> > window's space is filled with all white background.
> >
> > I understand that this is an artifact of the normal allocate -> map ->
> > expose progression. Is there a way to force that the window already
> > has a rendered copy of itself available for the first refresh cycle,
> > so that applications don't flicker to/from white at startup?
>
> As I recall, windows can not be drawn on until they're mapped. But
> once they're mapped, they're also visible, usually.
>
> Hack that comes to mind, it may or may not help, could be to render
> the window to an offscreen pixmap prior to showing it. Currently it's
> a hack, there's better offscreen support in bugzilla, I think.
> Possibly something like the following:
>
> (On second thought gtk_widget_realize (window);
> gdk_window_set_back_pixmap (window->window, NULL, FALSE); alone might
> work, if I'm understanding the API docs correctly. Depends on window
> manager.)
>
>   gtk_window_iconify (window);
>   gtk_widget_show (window);
>
>   /* now the widgets should be in "visible enough" state, namely
> mapped, to be drawn correctly but hopefully not visible to the user */
>
>   /* render the widgets to an offsceen pixmap and set it as background pixmap */
>   pixmap = gdk_pixmap_new (..., window->allocation.width,
> window->allocation.height, ...);
>   fake_expose_event (window, pixmap);
>   gdk_window_set_back_pixmap (window->window, pixmap, FALSE);
>   g_object_unref (pixmap);
>
>   /* show the window and let it be drawn normally */
>   gtk_window_deiconify (window);
>   /* the following should probably be done after expose event */
>   gdk_window_set_back_pixmap (window->window, NULL, FALSE);
>
> /* found from gnome-control-center */
> static void
> fake_expose_event (GtkWidget *widget, GdkPixmap *pixmap)
> {
>         GdkWindow      *tmp_window;
>         GdkEventExpose  event;
>
>         tmp_window = widget->window;
>         widget->window = pixmap;
>
>         event.type = GDK_EXPOSE;
>         event.window = widget->window;
>         event.send_event = FALSE;
>         event.area = widget->allocation;
>         event.region = NULL;
>         event.count = 0;
>
>         gtk_widget_send_expose (widget, (GdkEvent *) &event);
>
>         widget->window = tmp_window;
> }
>
> --
> Tommi Komulainen                                 tommi komulainen iki fi
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