Setting the Scrolling Region on VT100's VT220's VT320's VT420's, VT510's etc. - test-drb@ccmp.vtda.org

3 Jul 2013

I sent the following to alt.sys.pdp11 just in case anyone could
use the information.  If there is anything that is incorrect, please
advise.  It is a summary of the information received from the
classiccmp list and John Wilson.  There were no replies from
usenet, but someone might find the information useful and the
post will be archived in a different location.

Jerome Fine

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Just in case anyone is interested, the solution was provided on
the classiccmp list.  The major problem was with respect to how
default parameters are handled in addition to a misunderstanding
with regard to line numbers which are invalid or out of range in
the Scrolling Region request.

<TOP> and <BOT> are replaced by decimal digits from "0"
to "9".  <ESC> is replaced by the octal 33 character.

(a)  If any parameter is omitted, a default is always supplied.
For the Scrolling Region request, the format is:
           <ESC>[<TOP>;<BOT>r
where <TOP> is the higher (smaller) line number to be used
and <BOT> is the lower (larger) line number to be used.  If
<TOP> is missing or is "0", then "1" is used instead.  If
<BOT>
is missing or is "0", the the line number for the bottom of the
screen is used instead. In addition, <BOT> must exceed
<TOP> by at least one.  If <BOT> is not greater than <TOP>
by at least one OR <BOT> exceeds the number of lines for the
screen, the request is ignored.

(b) At least 3 characters, including leading zeros, "0", are
allowed for any parameter, and probably any reasonable
number of leading zeros are allowed in practice.

I have not, myself, verified the above information, but it has been
tested by a few other individuals and is probably reliable.

If anyone has read this far, then the solution seems quite obvious:
<ESC>[16r
can be used and the line at the bottom of the screen will be used
as the default.  For a DEC  VT100 with AVO, <BOT> will be
defaulted to "24".  For any other DEC  VT100 compatible terminal,
such as the VT420 and VT510 which support up to 48 lines, <BOT>
may be defaulted to "48" or line number 48 at the bottom of the
screen when the VT420 terminal is set to that many lines.

For Ersatz-11, I normally run in FULL  SCREEN mode using the
DOS variant.  My video card is then set for and used with a screen
of either 80 columns by 50 lines  OR  132 columns by 44 lines.
<BOT> is then "50" for the former and "44" for the latter.  The
Win32 variant of Ersatz-11 also supports up to 255 columns by
255 lines.  Since my video card and monitor combination usefully
supports only up to 198 columns by 60 lines, my maximum initial
setting is:  E11 /CONSIZE:124x60 or 124 columns by 60 lines.
When a WIDE screen is requested, the number of columns expands
to 198 columns by 60 lines (where 198.4 is truncated from 1.6 * 124).
In both cases, <BOT> is "60" or line number 60 at the bottom of the
emulated VT100 screen.

If anyone has any additional questions, please ask.

Jerome Fine

...
 Jerome H. Fine wrote: 
...
  I have a simple request for anyone who is has a real
DEC  VT100
 or compatible terminal (VT100, VT220, VT320, VT420, VT510)
 and especially VT100 software emulations, either as standalone
 software or as part of a PDP-11 emulator such as Ersatz-11.

 In respect of the latter, I have been using the Ersatz-11 PDP-11
 emulator to support VT100 emulation with more than 24 lines
 for a few years.  In particular, as part of the implementation,
 when the Range Escape Sequence is used to begin the Scrolling
 Region at a line less than 24 for the TOP and a line at the bottom
 of the screen for the BOTTOM, I use:

 <ESC>[16;255r

 to scroll between line 16 and the bottom of the screen.  For
 real DEC VT100 terminals with the AVO option, there is
 ONLY one size for the number of lines, namely 24 lines.

 Since I can't ATTACH files to be sent to a newsgroup,
 below are two files which can be used to erase the screen,
 set the scrolling region to line 16 at the top and line 99 or line 255,
 respectively, at the bottom of the screen.  If the any VT100
 (compatible) terminal or emulated VT100 terminal set for 24 lines
 is able to handle setting the scrolling region in this manner, each
 file with FIFTY lines should begin starting to display "Line 1 of File"
 of the file on line 12 of the "terminal" and "Line 2 of File" on line
16
 of the "terminal" the  and end up showing approximately six lines of
 the file at the bottom of the screen as the previous lines of the file
 scroll off the TOP of the scrolling region (at line 16 of the terminal)
 with just "Line 1 of File" remaining on line 12 of the "terminal".

 I would very much appreciate learning the results of sending
 both files to a DEC (or emulated) VT100 terminal.  If they act
 the same was as Ersatz-11, the results will be identical with using
 24 in place of 99 or 255.

 Jerome Fine

 P.S.  When the file is transferred to the system, replace <ESC>
 with octal 33!!!!!!!!!!!!!!!!!!!!  KED can be used under RT-11.
 The user eliminates each <ESC> and enters TWO <ESC>
 characters instead.  Alternatively, if you can remember the
 first line correctly, you can enter the complete file in about
 2 minutes by duplicating (cut and paste) the other 49 lines.

 -------------------------------------------------------------------------

 <ESC>2J<ESC>[12;1HLine 1 of File<ESC>[16;99r<ESC>[16;1H
 Line 2 of File
 [Snip]
 Line 50 of File
 -------------------------------------------------------------------------

 <ESC>2J<ESC>[12;1HLine 1 of File<ESC>[16;255r<ESC>[16;1H
 Line 2 of File
 [Snip]
 Line 50 of File
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