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From: linton@marktwain.rad.sgi.com (Mark Linton)
Newsgroups: comp.windows.interviews
Subject: Re: components of World
Message-ID: <1991May9.161230.23058@fido.wpd.sgi.com>
Date: 9 May 91 16:12:30 GMT
References: <19378@crdgw1.crd.ge.com>
Sender: news@fido.wpd.sgi.com (Usenet News Admin)
Reply-To: linton@marktwain.rad.sgi.com (Mark Linton)
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Lines: 35

In article <19378@crdgw1.crd.ge.com>, taylorp@sunstar.crd.ge.com (Patrick D. Taylor) writes:
|> I have a few questions about Scene and World in InterViews 2.6.
|> 
|> I want to get a list of components which have been inserted into the world.
|> According to the man page for Interactor, the GetComponents() member
|> function should return a list of the interactor's components if the
|> interactor is a Scene.  Scene does not implement GetComponents(), nor does
|> World, which is a Scene.  So World::GetComponents() is actually
|> Interactor::GetComponents(), which does nothing.  How do I get the
|> components of the World scene?
|> 
|> Also, the man page for Scene specifies that "when a scene is deleted, it
|> should delete all its component interactors.  The World scene does not do
|> this.  Why not?

You have clearly stated why World should not be a scene subclass,
which is the change we made in 3.0.  World is really just an interface
to the display/root window.

|> What I want to be able to do is insert an arbitrary number of interactors
|> into a world.  Each interactor has a quit button which removes it from the
|> world.  When all of the interactors have been removed, the program should
|> terminate.  Thus, my main event loop would be something like:
|> 
|> 	do {
|> 	  Read(event);
|> 	  event.target->Handle(event);
|> 	  n = number of components left in world;
|> 	} while (n > 0);
|> 
|> Any suggestions?

One approach is to have a list of all the components; the other has a count.
When you insert into the world, add to the list/count; subtract when you remove.
It is common to have an "application" object that manages this state.