Re: PR/30978 CVS commit: src/lib/libcurses

[Valery Ushakov <uwe%stderr.spb.ru@localhost>]

The following reply was made to PR lib/30978; it has been noted by GNATS.

From: Valery Ushakov <uwe%stderr.spb.ru@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: PR/30978 CVS commit: src/lib/libcurses
Date: Sat, 6 Oct 2018 06:32:00 +0300

 On Sat, Oct 06, 2018 at 04:19:43 +0300, Valery Ushakov wrote:
 
 > As I expected the new curses is broken with TERM=sun.  Emitting that
 > character into the lower-right corner causes the line to wrap and,
 > consequenly, the screen contents to scroll up, messing up the display.
 
 IIRC the common hack^Wsolution for this is to use insertion, either
 smir/rmir or ich1 (or ich).
 
 E.g. the following will print "AZ" at the lower-right corner on both
 TERM=vt100 and TERM=sun
 
   tput clear
 
   # this is intended to be in the lower right corner
   # but emit it one column before
   tput cup $(expr $LINES - 1) $(expr $COLUMNS - 2)
   echo -n Z
   sleep 5
 
   # re-emit the character that was overwritten by the above
   # shifting 'Z' to its target position at the lower right corner
   tput cup $(expr $LINES - 1) $(expr $COLUMNS - 2)
   tput smir    # enter insert mode - nop is not present
   tput ich1    # insert 1 character - nop is not present
   echo -n A
   tput rmir    # end insert mode - nop is not present
 
   tput cup 0 0
   sleep 5
 
 Presence of :xn:LP: in termcap just tells you that you can avoid this
 song and dance and just write to the lower-right corner directly, so
 it's a micro-optimization and if these capabilities are not present,
 the display will still be correct at the cost of a few more bytes sent
 to the terminal.
 
 -uwe