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From: pete@violet.berkeley.edu (Pete Goodeve)
Newsgroups: comp.sys.amiga.programmer
Subject: Re:  Intuition Image structure rendering utilities
Message-ID: <1991Mar29.074440.13711@agate.berkeley.edu>
Date: 29 Mar 91 07:44:40 GMT
References: <1214@muleshoe.cs.utexas.edu> <1991Mar27.080423.22023@agate.berkeley.edu> <dillon.5617@overload.Berkeley.CA.US>
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In  <dillon.5617@overload.Berkeley.CA.US> (27 Mar),
Matthew Dillon (dillon@overload.Berkeley.CA.US) writes:
>
>     Probably the best way to implement this sort of stuff is through
>     dynamically linked object modules.

Nope, I don't think I agree with you there, Matt.  Dynamically loaded
modules are a nice idea all right, but I don't think they're so suitable
for this purpose.

The problem as I see it is flexibility.  Unless you have a good match
between the symbols in your program and the dynamically loaded stuff
(in both directions) you're going to have some nasty hanging references.
When you write your "top-level" program you have to make sure that you've
satisfied ALL the references that the dynamic stuff might need.  And
different Renderers would probably have different requirements.  Could
get messy.

With something like ppIPC on the other hand, both ends of the link are
much more independent.  You can expand facilities at one end without
immediately worrying about the other.  A renderer can do the best it
can, even if there are some parts of the request it doesn't recognize.
At the other end, the client doesn't have to be concerned with advanced
features of the renderer that it doesn't need (or the author didn't
even know about).  As long as the interface (message format) is properly
defined and observed, everything should work fine.

Another advantage of a separate process is that it can be serving more
than one client at a time, as opposed to code that is loaded into a
program.  An off-the-top-of-the-head example: suppose you had a renderer
that could handle anims, but a paint program (with access to the renderer)
that couldn't, and a showanim display module.  You could flip between
viewing the anim, and grabbing frames of it for retouching, without
reloading anything.

                                        -- Pete --