Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!genrad!panda!husc6!harvard!caip!lll-crg!lll-lcc!vecpyr!greg
From: greg@vecpyr.UUCP (Greg Millar)
Newsgroups: net.graphics
Subject: Re: VDI/CGI
Message-ID: <280@vecpyr.UUCP>
Date: Sun, 11-May-86 15:05:49 EDT
Article-I.D.: vecpyr.280
Posted: Sun May 11 15:05:49 1986
Date-Received: Tue, 13-May-86 02:04:58 EDT
References: <277@vecpyr.UUCP> <307@ulowell.UUCP>
Reply-To: greg@vecpyr.UUCP (Greg Millar)
Distribution: net
Organization: Visual Engineering Inc
Lines: 69
Keywords: CGI VDI GraphCap Device-drivers

miner@ulowell.UUCP (Richard Miner) wrote in response to my posting...

Greg then:
>>our GKS (with our vdi) and you want to add a new device driver, all you
>>have to do is add a new graphcap entry (sort of like a termcap entry)

Richard:
>This sounds like it will work nice for devices that you can just send
>ESC sequences or that have ASCII stream bindings, but what about parallel
>devices, or devices that have there [SIC] own graphics library?

>... the solution is to have a GKS or VDI/CGI WITH SOURCE!

Greg now:
Not true.  Many users can not afford source licences for COMMERCIAL, SUPPORTED,
DOCUMENTED, ETC software.  Not only that, users of applications using a GKS
most likely will not have source and may not even have a library to relink
to.  Here are some good reasons to do it this way:

	- No source needed (the GraphCap file is the driver source)

	- No libraries needed to add new drivers to applications

	- No need to re-port driver code from system to system

	- No need to relink all of the applications (on all of the systems
	  you are supporting) using graphics, everytime a new device is 
	  added to the library

	- You may have any number of devices available to your applications
	  at ANY time without your application getting bigger and bigger.
	  (Consider just 20 device drivers on line at 10-20Kb each = 200-400kb
	  extra code to haul around)

	- You may want several instances of a particular device driver on line.
	  For example (Imagen portrait, Imagen landscape, Imagen 240 dpi,
	  Imagen 300 dpi, Imagen Black & White, Imagen Gray scale, and all 
	  combinations!)  With coded device drivers this usually means that
	  many seperate device drivers to link in, with GraphCap it means
	  just changes a couple of fields and referencing a parent entry,
	  like termcap's "tc=". 

	- Don't need to know C or FORTRAN or whatever

	- Very fast device support turnaround and debugging (make the entry
	  and run)

	- etc, etc, etc


GraphCap does indeed support parallel devices, and devices that have 
library interfaces (like most workstations).  A full explanation was
not given in the original posting because (1) GraphCap is a large
and complicated software system that would take a very large article
to fully describe its functionality and use, (2) it was not intended
to be an advertisement.

If any of you would like more information from a source that has all
of the particulars, please respond to


		
			Greg Millar

			...{ucbvax,decwrl}!dual!vecpyr!greg
			Visual Engineering, Inc.  
			2680 N. First
			San Jose, CA 95134
			(408) 945-9055