GtkNotebook and callback

[Arno <dark-arno ifrance com>]

Hello,

I make a callback on my GtkNotebook :
g_signal_connect (G_OBJECT (notebook), "switch_page",
           G_CALLBACK (notebook_changed_cb),
           NULL);

And in my fonction I do :
notebook_changed_cb (GtkNotebook *notebook, GtkNotebookPage *page,
            guint numero_page, gpointer data)
{
 const gchar *text;

 text = gtk_notebook_get_menu_label_text(notebook, GTK_WIDGET(page));
 printf("Label: %s\n", text);
}

But I have a little pb when I use this solution:
(check_tsr:592): GLib-GObject-WARNING **: invalid uninstantiatable type 
`(null)' in cast to `GtkWidget'

(check_tsr:592): Gtk-CRITICAL **: file gtknotebook.c: line 4905 
(gtk_notebook_get_menu_label_text): assertion `GTK_IS_WIDGET (child)' failed
Label: (null)


It said that it could cast my GtkNotebookPage to a widget. So I search 
in the code source and I do this :

struct _GtkNotebookPage
{
 GtkWidget *child;
 GtkWidget *tab_label;
 GtkWidget *menu_label;
 GtkWidget *last_focus_child;    /* Last descendant of the page that 
had focus */

 guint default_menu : 1;    /* If true, we create the menu label ourself */
 guint default_tab  : 1;    /* If true, we create the tab label ourself */
 guint expand       : 1;
 guint fill         : 1;
 guint pack         : 1;

 GtkRequisition requisition;
 GtkAllocation allocation;

 guint mnemonic_activate_signal;
};

void
notebook_changed_cb (GtkNotebook *notebook, GtkNotebookPage *page,
            guint numero_page, gpointer data)
{
 const gchar *text;

 printf("Page: %p,   Child:%p\n", page, page->child);
 printf("Diff: %d\n", (int)page->child - (int)page);
 text = gtk_notebook_get_menu_label_text(notebook, 
GTK_WIDGET(page->child));
 printf("Label: %s\n", text);
}

And I obtain :

Page: 0x80c8e00,   Child:0x80c8be8
Diff: -536
Label: List of packets


With this solution I obtain the name of the current menu but I need to 
copy the struct _GtkNotebookPage from the source to my project. I don't 
think that it's the good solution. So if you could help me. I use GTK2.

Also, I don't understand why (int)page->child - (int)page) equal to -536

Thx ;)
Arno


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