Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!sgi!msc
From: msc@canth.SGI.COM (Mark Callow)
Newsgroups: comp.windows.news
Subject: Re: Questions about windowing systems
Summary: inverse transformations
Message-ID: <21621@sgi.SGI.COM>
Date: 9 Sep 88 03:55:37 GMT
References: <8809072114.AA17658@ondine.LOCAL>
Sender: daemon@sgi.SGI.COM
Organization: Silicon Graphics Inc, Mountain View, CA
Lines: 30

In article <8809072114.AA17658@ondine.LOCAL>, greid@adobe.UUCP writes:
> 
> The Display PostScript system from Adobe provides all the power of the
> PostScript imaging model and font library and still lets you take
> advantage of a standard windowing environment like X windows. It is, in
> a sense, the best of both worlds:
> 
> 	* Full and complete implementation of the PostScript language
> 	  plus many extensions for speed and highly interactive use.

Since Display PostScript deals only with output, the application has
to implement inverse transformations so that when a user selects
something she's looking at in Display PostScript space, the application
can tell what it was.  All input from X comes in screen space.

I'm sure you can have Display PostScript perform the inverse
transformation but that seems to mean a round trip to the
server in addition to the trip the screen-space input already
took getting back from the server.

This makes interactive applications kind of hard.

I could be completely wrong.  There may be some extension I'm not
aware of that takes care of this.  I hope I am wrong.  Let me know.

	-Mark
--
From the TARDIS of Mark Callow
msc@sgi.sgi.com, ...{ames,decwrl,sun}!sgi!msc
"There is much virtue in a window.  It is to a human being as a frame is to
a painting, as a proscenium to a play.  It strongly defines its content."