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From: mlandau@bbn.com (Matt Landau)
Newsgroups: comp.windows.x
Subject: Re: Abstracting the Windowing System Interface
Message-ID: <13460@granite.BBN.COM>
Date: 2 Feb 90 20:40:34 GMT
References: <9002011637.AA04472@devnull.sun.com>
Sender: news@bbn.com
Lines: 55

dshr@SUN.COM (David Rosenthal) writes:
>> The secret to Andrew's window-system-portability is that it defined a
>> portable graphics layer that mapped well onto multiple window systems. 

>The secret to Andrew's portability to X11 is that X11 was designed from the
>start to be capable of supporting Andrew because some of the people who
>designed WM also helped design X11.  If you want to make this case,
>you need some less contrived example.

There are one or two other examples.  

At BBN, the multimedia communications group (of which I'm a part) has its 
own toolkit for producing window-based applications.  Our toolkit also
implements its own abstractions for windows, events and event processing, 
menus, dialogs, and other user-interface components, for both input and
output.  

Although our toolkit was originally written to run on top of SunWindows
(yes, it predates the SunView programming interface), we've since ported
it to X11, and in general applications simply recompile and run.  It's
true that we don't take advantage of ALL of the bells and whistles of X,
but in fact we manage to make very good use of many of them.  

What's most important is that you view the abstract toolkit as an evolving 
entity that you can modify as you port to other underlying window systems.
For instance, as we've ported our toolkit to X11, we've added new several
abstractions and semantics to make the fit better (window groups, a model
for transient vs. non-transient windows, etc.), then gone back and added 
the same abstractions to the Sun-specific version of the toolkit.  In most 
cases, the result is that BOTH versions of the toolkit are improved by
such additions.

As proof of the fact that you CAN build a generic window system toolkit
that's more than a toy, I will point out that we build our BBN/Slate 
product on top of this toolkit.  Slate is multimedia document communications
system that includes a document editor (documents contain text in English 
and other languages, graphics, monochrome and color images, spreadsheets, 
charts and graphs, voice annotations, and generic enclosures), mail reader
and interface to the local mail system, and realtime conferencing system
that allows multiple sites connected by TCP to examine and edit documents
simultaneously in real-time.  Both the user-interface components and the
underlying conferencing architecture are implemented within our toolkit,
and both run under SunView and X11 with no application-level source code
changes.  So it can be done :-)

[Before anyone asks, I'll head off some questions:  No, you can't get the 
toolkit sources -- they're considered proprietary software by BBN.  Yes,
you can buy Slate -- contact BBN Software Products Corp. for details and
prices, 'cause I'm an engineer and not a salesman :-)  No, it's not based
on Andrew, although the two systems have some similarities and we've done
some work with the Andrew folks in a reseach context.  If you have other
questions, email me directly rather than cluttering up the newsgroup.]
--
 Matt Landau		    		Dancing with the Ice Weasels
 mlandau@bbn.com