typedef struct _AppData AppData;
 
struct _AppData
{
    HildonProgram *program; /* handle to application */
    HildonWindow *window; /* handle to app's window */
    osso_context_t *osso; /* handle to osso */
};

/* Creates and initialises a main_view */
MainView* interface_main_view_new( AppData *data )
{
    /* Zero memory with g_new0 */
    MainView* result = g_new0( MainView, 1 );
    ...
      /* Add hardware button listener to application */
    g_signal_connect(G_OBJECT(result->data->window),
        "key_press_event", G_CALLBACK(callback_key_press), result);
    ...
}

/* Callback for hardware keys */
gboolean callback_key_press(GtkWidget * widget, GdkEventKey * event, gpointer data)
{
    switch (event->keyval) {
    case GDK_Up:
        callback_up( NULL, data );
        return TRUE;
 
    case GDK_Down:
        callback_down( NULL, data );
        return TRUE;
 
    case GDK_Left:
        callback_left( NULL, data );
        return TRUE;
 
    case GDK_Right:
        callback_right( NULL, data );
        return TRUE;
 
    case GDK_Return: 
        callback_reset( NULL, data );
        return TRUE;
 
    case GDK_F6:
        callback_fullscreen( NULL, data );
        return TRUE;
 
    case GDK_F7: /* "Increase (zoom in)" */
        return FALSE;
 
    case GDK_F8:  /* "Decrease (zoom out)" */
        return FALSE;
 
    case GDK_Escape: /* "Cancel/Close" */
        return FALSE;
 
    }
    return FALSE;
}