Focus behaviour on widget derived from a gtkentry

[Geert Janssens <info kobaltwit be>]

Hi,

I've been banging my head against the wall for some time now on this problem:
I have a widget that is derived from a GtkEntry. The derived widget basically 
does some additional validation checks during text entry, nothing more really.
If you like to see the complete code, you can browse it here:
http://svn.gnucash.org/trac/browser/gnucash/trunk/src/gnome-utils/gnc-amount-
edit.c

I am now having problems to set the focus on this widget programmatically. In 
this particular use case, the widget is added to a GtkAssistant, and during 
the prepare of the page showing this widget, I call a gtk_widget_grab_focus on 
it. This does nothing.
If I do the same with a plain GtkEntry on the same assistant page in the same 
prepare callback, this entry does get the focus. So I assume my custom widget 
is not handling things properly.

Based on another thread I found on the gtk-list list [1] I then tried adding a 
callback to the focus-in-event signal in gnc_amount_edit_init like so:

    g_signal_connect (G_OBJECT (gae), "focus-in-event",
                      G_CALLBACK (gnc_amount_edit_focus_in), NULL);

And the callback function simply call gtk_widget_grab_focus on the internal 
GtkEntry widget:

static gboolean gnc_amount_edit_focus_in (GNCAmountEdit *gae,
                                          GdkEvent      *event,
                                          gpointer       data)
{
    gtk_widget_grab_focus (GTK_WIDGET(&gae->entry));
    return FALSE;
}

Stepping through the code in a debugger shows me that the callback is really 
called, but it still doesn't set the focus.

I am sure I'm missing something, but I don't see it. Any hints ?

Geert

[1] http://www.mail-archive.com/gtk-list gnome org/msg02478.html