Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!ucbvax!bloom-beacon!ATHENA.MIT.EDU!swick
From: swick@ATHENA.MIT.EDU (Ralph R. Swick)
Newsgroups: comp.windows.x
Subject: Re: Callbacks in class structure.
Message-ID: <8912210052.AA24099@LYRE.MIT.EDU>
Date: 21 Dec 89 00:52:45 GMT
References: <1929@syma.sussex.ac.uk>
Sender: daemon@athena.mit.edu (Mr Background)
Organization: DEC/MIT Project Athena
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> Does it make sense to talk about callback lists as being a class property, as
> opposed to an instance property.

Perhaps it might from an abstract point of view, but Xt does not
directly support class resources.  In some cases, a widget implementation
can go to extra lengths to modify class data (e.g. in an initialize
procedure).  In the particular case of callbacks, though, the
current mechanism is intimately bound with instance data.
It would take a new interface to be able to support (shared) callback
lists in the class structure.

> In general, can resources be defined as class properties, as
> opposed to widget properties?

You can certainly use some of the lower-level resource routines
(e.g. XtGetSubvalues) to fill up class structures with things
that from nearly all external appearance look identical to
instance resources.  Interesting concept; I've never actually
considered it in this light.

> Do others feel that
> there should be a comp.windows.xt, as well as a comp.windows.x

Won't help me, and the equivalent mail list+gateway here at
expo would just add to our workload, but I'm not violently
opposed (sorry, Bob :-).