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jaywhy13 is offline jaywhy13
2009-12-03 , 02:46
Posts: 80 | Thanked: 9 times | Joined on Oct 2007
#1
Is there a difference between

HildonWindow *window;
window = HILDON_WINDOW (hildon_window_new());

and

GtkWidget *window;
window = (hildon_window_new());

Essentially.. I'm trying to figure out why there's a need to do the whole HILDON_WINDOW(...) or GTK_CONTAINER(...)?

What's the real purpose of these functions? HILDON_WINDOW or GTK_CONTAINER?

Consider:
Code:
GtkWidget *window;
GtkWidget *button;

window = hildon_window_new ();
button = hildon_button_new_with_text (...);

gtk_container_add (GTK_CONTAINER (window),button);
The signature is:
void gtk_container_add (GtkContainer *container,GtkWidget *widget);
In this case, "window" is a pointer to type GtkWidget... so I'm guessing the GTK_CONTAINER serves as some kind of cast (Java background.. forgive me) to convert the GtkWidget to a GtkContainer? My reasoning is since... GtkContainer is a GtkWidget, you need more specificity since the function wants a container, not just any old widget. Is this correct?

Another example I don't quite get is this one...
g_signal_connect (G_OBJECT (window), "delete_event",
G_CALLBACK (gtk_main_quit), NULL);
The first parameter is supposed to be a pointer to type GObject... what role does G_OBJECT play here? If this is a cast operation... I'm not used to seeing casts goes this direction. Since GObject is the ultimate superclass.. why would you cast any subclass of GOBject back to GObject?
 
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