[Info-vax] escape sequences, cursor positioning

[Steven M. Schweda]

From: =?ISO-8859-1?Q?Jan-Erik_S=F6derholm?=
 <jan-erik.soderholm at telia.com>

> SMS wrote:
> > JF Mezei wrote:
> > 
> >> DECTERM doesn't do display control characters. [...]
> > 
> >    I believe that mine do.  I've just been using
> > EDIT /TPU to look at a log file from  a
> > "SET HOST 0 /LOG" command, and I see a
> > whole collection of cute little [C/R] and [N/L]
> > characters on my screen.
> 
> Aren't they displayed by TPU, not by the DECTerm ?
> That is, when they are sent to DECTerm, they are not
> control characters but the actual characters "C", "/",
> "R" and "N", "/", "L".

   No, I mean single-cell characters which look roughly like:

      +--+      +--+
      |C |      |N |
      | R|      | L|
      +--+      +--+

   As for who's displaying them, well, TPU/EVE is telling the DECterm
what to do, and the DECterm is doing it.  According to my handy "VT 220
Programmer Pocket Guide", these are in the DEC Special Graphics
character set (with all the L- and T-shapes in different orientations,
and the horizontal lines at five different heights, and the rest of the
fun stuff).  Anyone doing serious VT100 graphics needs to know about
these (and the SO (%x0E) and SI (%x0F) characters to switch back and
forth between G0 and G1).  (It's all in the book, and I haven't really
cared since about 1985.  And thanks for reminding me.)

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

   Steven M. Schweda               sms at antinode-info
   382 South Warwick Street        (+1) 651-699-9818
   Saint Paul  MN  55105-2547