Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!uunet!mcsun!ukc!dcl-cs!dik
From: dik@comp.lancs.ac.uk (Mr R. M. Bentley)
Newsgroups: comp.lang.smalltalk
Subject: Smalltalk coordinates to screen coordinates
Message-ID: <1089@dcl-vitus.comp.lancs.ac.uk>
Date: 31 Oct 90 15:15:50 GMT
Reply-To: dik@dcl-cs.UUCP (Mr R. M. Bentley)
Organization: Department of Computing at Lancaster University, UK.
Lines: 28

I am trying to implement a C-program which displays a colored raster
image on the screen as a Smalltalk method. The point to position the
image is passed to the C function as parameters to the primitive method.

I am having trouble mapping the local co-ordinates used in Smalltalk to
refer to the Smalltalk display within the Sunview window to absolute 
display coordinates. 

What I really want to be able to do is position a colored image within a
View. I can get the local origin of the View (using insetDisplayBox) but
I need to be able to translate this to global screen co-ordinates for the
primitive function. 

As far as I can see, I have two options: 

	1. Modify the co-ordinates in Smalltalk before passing to the
	   primitive.

        2. Use SunView to locate the Smalltalk window origin and add this
	   as a constant in the C function to the parameters passed from
	   Smalltalk.

Currently we're using pixrect onto the frame buffer, opening ("/dev/fb").
I'm told that this problem can be resolved if anyone knows if smalltalk
provides a handle to its pixrect. (I am using Smalltalk 2.5).

If anyone knows if either of the two approaches is feasible and how to go
about it, I would be very grateful for advice/assistance.