Re: Howto make a gtkbutton send a "changed" signal?

[David NeÄas <yeti physics muni cz>]

On Tue, Dec 01, 2009 at 09:59:07AM +0100, Till Harbaum wrote:
> i am changing the UI of an existing app for mobile usage in a way that i replace
> some gtkentry's with some gtkbuttons which the use some alternate input method.
>
> I want to keep as much of the application as it is and one of the things the app expects
> is that this particular widget emits a "changed" event whenever its contents changes.
>
> So i'd like to enable my gtkbutton to emit a "changed" event, but i don't find any examples
> on how to achieve that. How do i "attach" a new signal to an existing widget type?

If you agree that what you are trying to do is silly and you are
desperate, you are allowed to read on.

I'm not sure what it means `contents changed' for a button.  So I
respond to "clicked".  But you can emit the signal in response to
"notify::label" (i.e. the change of the label) or whatever it means
`contents changed' for you.

Yeti

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#include <gtk/gtk.h>

static void
emit(GObject *object, gpointer user_data)
{
    guint id = GPOINTER_TO_UINT(user_data);
    g_signal_emit(object, id, 0);
}

static void
changed(GObject *object)
{
    g_print("signal \"changed\" emitted on instance %p (%s)\n",
            object, G_OBJECT_TYPE_NAME(object));
}

int
main(int argc, char *argv[])
{
    GtkWidget *window, *button;
    guint id;

    gtk_init(&argc, &argv);
    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);

    id = g_signal_new("changed", GTK_TYPE_BUTTON,
                      G_SIGNAL_RUN_FIRST, 0, NULL, NULL,
                      g_cclosure_marshal_VOID__VOID, G_TYPE_NONE, 0);

    button = gtk_button_new_with_label("Click Me!");
    g_signal_connect(button, "clicked", G_CALLBACK(emit), GUINT_TO_POINTER(id));
    g_signal_connect(button, "changed", G_CALLBACK(changed), NULL);
    gtk_container_add(GTK_CONTAINER(window), button);
    gtk_widget_show_all(window);

    gtk_main();

    return 0;
}
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