Re: GtkNotebook problems

[Owen Taylor <otaylor redhat com>]

Damon Chaplin <damon@karuna.freeserve.co.uk> writes:

> I think there are a couple of problems with GtkNotebook (GTK+ 1.2.6):
> 
>  1) gtk_notebook_real_switch_page() currently queues a resize, but
>     for complicated layouts this can make page switching quite slow,

Really? Resizing is almost always pretty instantaneous.

>     and I don't really think it should be here.
> 
>     The Changelog mentions why this was done:
> 
>     Sat Aug 21 14:07:36 1999  Lars Hamann  <lars@gtk.org>
> 
> 	* gtk/gtknotebook.c (gtk_notebook_real_switch_page): queue_resize
> 	notebook after switch to avoid drawing problems.
> 	(Bug#856 Reported by: Theodore Roth <troth@netmagic.net>)
> 
>     Maybe there is a better solution to that problem.

The drawing and size allocation code in GtkNotebook is in very poor
state, and IMO needs complete rewriting. This wasn't a very good
solution to the problem in my opinion, but I didn't see anything
immediately better when I looked at the problem.

>  2) gtk_notebook_size_request() sometimes shows, hides, or unmaps child
>     widgets. I don't think this should be done here, and I think this may
>     be causing a problem I have where pages sometimes do not appear at all.

Well, with the way GTK+ 1.2 works, the map/unmap must be done here.
I don't believe that gtk_notebook_size_request() ever shows or
hides pages, though it does do that to tab labels.

The problem is that gtk_widget_real_show() has code like:

static void
gtk_widget_real_show (GtkWidget *widget)
{
  g_return_if_fail (widget != NULL);
  g_return_if_fail (GTK_IS_WIDGET (widget));
  
  if (!GTK_WIDGET_VISIBLE (widget))
    {
      GTK_WIDGET_SET_FLAGS (widget, GTK_VISIBLE);

      if (widget->parent &&
	  GTK_WIDGET_MAPPED (widget->parent) &&
	  !GTK_WIDGET_MAPPED (widget))
	gtk_widget_map (widget);
    }
}

So, if we show a non-current page of a shown notebook, it will get
mapped, so we need to unmap it again in the size_request.

There are basically possible two solutions we can take for GTK+-1.4:

 1) Use a GdkWindow per page. That way, we can just leave the
    child widget mapped and show/hide the GdkWindow.

 2) Add ::child_shown ::child_hidden signals/vfuncs to 
    gtk_container, move the gtk_widget_map(child)
    to gtk_container_real_child_shown(), and override
    that in GtkNotebook.

Regards,
                                        Owen