Re: GtkNotebook and callback

[TORRI Vincent <Vincent Torri math u-bordeaux fr>]

On Sun, 17 Nov 2002, Arno wrote:

> 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));

You have to pass the child of your page, not page itself (a 
GtkNotebookPage is not a GtkWidget). You can get the child of your current 
page with

  GtkWidget *child;
  child = gtk_notebook_get_nth_page (notebook, 
gtk_notebook_get_current_page (notebook));

>   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

What kind of result would you want to have ? You compute the difference of 
two adresses, so the result could be (almost) every number, I think.

regards

Vincent TORRI

> Thx ;)
> Arno
>
>
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-- 
TORRI Vincent
Mathematiques Appliquees Bordeaux                                                
Institut de Mathematiques                                                       
Universite Bordeaux 1                                                           
351 cours de la liberation                                                      
33 405 Talence cedex - France                                                   
                                                                                
Tel : 33 (0)5 57 96 21 42                                                       
Fax : 33 (0)5 56 84 26 26                                                       
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