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From: sansom@trwrb.UUCP
Newsgroups: comp.sys.atari.st
Subject: Re: Setscreen
Message-ID: <1571@trwrb.UUCP>
Date: Thu, 29-Jan-87 22:55:00 EST
Article-I.D.: trwrb.1571
Posted: Thu Jan 29 22:55:00 1987
Date-Received: Sat, 31-Jan-87 07:21:34 EST
References: <1889@homxc.UUCP>
Reply-To: sansom@trwrb.UUCP (Richard Sansom)
Organization: TRW EDS, Redondo Beach, CA
Lines: 39

In article <1889@homxc.UUCP> jdn@homxc.UUCP (J.NAGY) writes:
>I have a problem which should be a piece of cake
>for you ST hackers out there.
>I want to write a simple TOS terminal communications
>program with a split screen.  In the upper half of the screen
>I will display the input from the RS-232 port.  At the same time,
>the user should be able to enter characters at the keyboard which
>will be stored in a buffer for later transmission. I want to
>display the typed data in the lower half of the screen while the
>upper half is displaying the data received at the RS232 port.
>What is the best way to do this?

What you want to do is possible (at least, I think it is ;-),
unfortunately, there is no easy way to do it.  The xbios Setscreen()
call will only allow you to change the entire screen's physical and/or
logical location in memory (it must be on a 256 byte boundry).  In
order to change the physical screen "on the fly" (that is, somewhere
between the top and bottom scan lines) you would need to change the
memory address the video scanner is using to scan the screen at the
instant (in the frame being drawn) you want your second screen to
appear.  This would involve extensive knowledge of the ST's video
chip (isn't it called the "shifter"?).  Unfortunately, again, there
has been no official documentation from Atari showing how to do this.
I imagine some individuals have managed to wrangle this info out of
Atari HQ, but I haven't (not that I've really tried).

Your best bet may be to do the screen manipulation yourself - either
using GEM & windows (slow), or TOS & the "glass terminal"/VT52 escape
sequences.  Good luck!

-Rich

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