Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!sgi!msc@ramoth.SGI.COM
From: msc@ramoth.SGI.COM (Mark Callow)
Newsgroups: comp.windows.news
Subject: Re: Is "transform" in NeWS 1.1 OK ?
Summary: transform behaviour
Message-ID: <25826@sgi.SGI.COM>
Date: 31 Jan 89 01:52:34 GMT
References: <4495@natmlab.dms.oz>
Sender: daemon@sgi.SGI.COM
Organization: Silicon Graphics, Inc., Mountain View, CA
Lines: 37

In article <4495@natmlab.dms.oz>, ronb@natmlab.dms.oz (Ron Baxter) writes:
> 
> 	The following session with psh puzzles me and I wonder
> 	what I am missing.
> 
> 		executive
> 		Welcome to NeWS Version 1.1
> 		matrix currentmatrix pstack
> 		[1 0 0 1 0 0] 
The preceding line does nothing since the next thing you do is clear the
stack
> 		clear 100 200 transform pstack
> 		100 700 
> 		clear -20 -40 transform pstack
> 		-20 940 
> 		clear 50 70 itransform pstack
> 		50 830 
> 
> 	Since the CTM is an identity matrix I would have expected
> 	transform, itransform, etc to make no change to x and y.
> 	The LaserWriter behaves as I expected, so is this a NeWS 1.1
> 	funny?
The default CTM isn't the identity matrix.  It is the default matrix that
gives the user a coordinate system with a lower left origin and 72 units to
the inch on the output device.  Sun ignores the 72/inch requirement but
they do use the matrix to invert to get an upper left origin hence the
result you see.

N.B., If you had used the 3 operand transform

	100 200 [1 0 0 1 0 0] transform

on your Sun you would have got a typecheck error.  The 3 operand form isn't
implemented.  I recently implemented it on the Iris and it will be in our
next release.
--
	-Mark