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From: sutela@polaris.utu.fi (Kari Sutela)
Newsgroups: comp.sys.amiga.tech
Subject: GfxBase->NormalDPMX and aspect ratio???
Message-ID: <1990Aug11.144404.18432@utu.fi>
Date: 11 Aug 90 14:44:04 GMT
Sender: sutela@utu.fi (Kari Sutela)
Organization: University of Turku, Finland
Lines: 22

I'm currently planning a small application in which I need to be able
to calculate the aspect ratio of the default WB-screen. The program
would be a simple Turtle-graphics system which would open a window on
the WB-screen and serve as an ARexx-function-host accepting turtle-graphics
related function calls.

Reading through the Includes&AutoDocs I found the variables
GfxBase->NormalDPMX and GfxBase->NormalDPMY which, I guess, would be
the supported way of retrieving the aspect ratio. The problem is that
I don't quite understand the meaning of these fields (the comment in
Includes&AutoDocs is a bit vague - what does "1/2 width WB" mean???).
Am I correct in assuming that the values tell me how many pixels/meter
there are on a non-interlaced lores (320-wide) screen? The values I found
(both were betweem 1200 and 1300 - can't remember exactly) on my PAL system
seem to support this. Nevertheless, using a lores screen as basis for DPMX
seems a bit strange, so I have some doubts about this.

So, a short explanation on these fields would be appreciated. BTW, how does
one's monitor affect the aspect ratio (or does it? - I just don't seem to
understand how video-hardware works :-)?

Kari Sutela	sutela@polaris.utu.fi