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From: Peck@RADC-MULTICS.ARPA.UUCP
Newsgroups: comp.sys.atari.st
Subject: RE: query re: text scrolling in windows; text mode
Message-ID: <870208210354.251475@RADC-MULTICS.ARPA>
Date: Sun, 8-Feb-87 16:03:00 EST
Article-I.D.: RADC-MUL.870208210354.251475
Posted: Sun Feb  8 16:03:00 1987
Date-Received: Wed, 11-Feb-87 05:42:05 EST
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 35


  The reason I have found for not scrolling the text in windows is that
the GEM system doesn't support text very well.
  By not very well, I mean, it doesn't do scrolling for you, it doesn't handle
window wraparound at the end of a line, and its generally not text
orientated (unfortunately).  After using GEM for awhile and trying to do
things with it, you come to the startling conclusion that GEM was taken
from some programmer's scratch directory somewhere after he through it
away.  In general, things are done very strangely.
  Anyway, uniterm, the vt52 emulator and others (not degas though)
completely ignore GEM and go through the BIOS which is a collection of
lowlevel system subroutines that either are the drivers or communicate
with the drivers. (I'm not sure, but someone will say for sure.) It
turns out that the BIOS video driver takes VT52 escape codes for cursor
control, screen clearing, etc.  That's why it was so easy to make a vt52
emulator.
  
  I don't know if anyone has actually tried to write code for a terminal
emulator in GEM, but if they could get a text-window management package
together that's speedy enough......

  According to _Programmer's Guide to GEM_ by Balma and Fitler, sez on
page 180:
  "It' importaint to note that GEM is very weak on text processing
functions: that is, functions which display blocks of text and manage
selection, insertion, and deletion of this text.  Apple's Macintosh, for
example. provides Text Edit Record functions to manipulate the entry,
selections, and display of large chunks of text; these kinds of
functions are not available from within GEM.  To develop a GEM word
processing application, for example, you must provide your own functions
to manage the display of blocks of text.  Discussion of the development
of these functions is beyond the scope of this text."
  Naturally, they don't say where to go to find a bigger scope either...

           rodney