Re: gobject introspection

[Johan Dahlin <johan gnome org>]

> But the real reason why I'm posting here is to ask how the different
> language bindings handle unions (in particular GdkEvent). The
> introspection prototype currently doesn't handle unions at all, apart
> from the fact that fields are supposed to have struct offset
> information, so unions could be modeled by describing the overlapping
> fields. CORBA does seem to have a concept of discriminated union,
> which would probably cover the GdkEvent case, but trying to describe
> arbitrary anonymous unions in the middle of structs sounds like adding 
> a lot of complexity. It would be very tempting to just require
> accessors to make those kinds of C-specific things bindable.
>
> So, how do language bindings handle GdkEvent currently ?
>  
In Python there is only one GdkEvent class, which looks differently 
depending on the
actual event.

So for example event.type is a member which is always accessible while 
event.button is only accessible for GdkEventButton.

You can also create new events and assign members of them, that looks 
very similar to the C API:

 event = gtk.gdk.Event(gtk.gdk.BUTTON_PRESS)
 event.button = ...

Ideally, subclassing would be used, a main gdk.Event class and a 
subclass for each type in the union.

Currently the events are not handled by the code generator. In a future 
version of PyGTK they might be.

Johan Dahlin