why do constructors return GtkWidget?

[Emmanuel Touzery <emmanuel touzery free fr>]

Hello,

    I otherwise have a good understanding of GTK and can build 
relatively big programs, but I have a poor understanding of gobject. I 
use it to make my own gobjects in C but I don't understand all the 
implementation details.

    In particular, I don't understand why is it normal for GTK widget 
"constructors" to return GtkWidget and not their real type.

    For instance I would expect:

gtk_menu_item_new ()

    To return GtkMenuItem*. But it doesn't, it returns GtkWidget*.

    And then gtk_menu_shell_append() takes a GtkWidget*, not 
GtkMenuItem*. And it seems it's not because you could put any widget 
there, the documentation says "The GtkMenuItem to add".

    It's annoying for me because I find that putting the real types in 
my code makes it easier to follow (rather than everything being a 
GtkWidget*), but if I go that route, I must constantly up and downcast...

    From my limited understanding of gobject I would think those 
widgets could return and take the real type and all will work well? am I 
wrong? or are those historical reasons?

emmanuel