26 Jun
2013
26 Jun
'13
6:35 p.m.
On Wed, Jun 26, 2013 at 03:06:36PM +0100, Peter Coghlan wrote:
(Over the years I have seen many so-called VT100
emulators on PCs and Macs that
made no attempt whatever to implement scrolling regions.)
Like the DEC GIGI (VK100)! That was a surprise -- DEC's own terminal won't
work with EDT (in spite of being generally ANSIsh when not in ReGIS mode).
OK I just did some testing on a real DEC VT100 in local mode (it's not
cabled to anything that could display those files), and found that if
either parameter to ESC [ Pa ; Pb r is out of range (.GT. 24) or if they're
not in order (i.e. Pa .GE. Pb -- note that the scroll region must be at least
2 lines so Pa .EQ. Pb is invalid too), the command is ignored and doesn't
even home the cursor. Thanks for making me check this -- will fix E11!
However, either or both parameter may be defaulted (i.e. 0 or missing, and
the ; can be left out if Pb is defaulted). Pa defaults to 1 and Pb defaults
to 24 (or presumably EOS on larger screens). So that's probably what you
should use if you're trying to set the range from some known line down to
the unknown end of screen w/o knowing what that is. (EDT in particular is
big into using defaults since it makes output faster, so this is definitely
legit -- any VT100 emulator that can't handle defaulted parameters will
break with lots of DEC's own software.)
John Wilson
D Bit