Re: vt.c small patch

[Owen Taylor <otaylor redhat com>]

Cristiano De Michele <demichel na infn it> writes:

> On Wed, 2002-04-17 at 16:01, Owen Taylor wrote:
> > 
> > Cristiano De Michele <demichel na infn it> writes:
> > 
> > > Hi Owen,
> > > ah yes this is how to reproduce what I think is a problem :):
> > > open an xterm and run for example vim or emacs -nw when you exit 
> > > the screen before entering such apps is got back,
> > > gnome-terminal instead put all output of that apps into the buffer.
> > > With my patch GT behaves as xterm (or rxvt)
> > > check and let me know,
> > 
> > This probably has something to do with your termcap, since it
> > works perfectly for me. What sort of system are you using? What
> > is the TERM environment variable set to?
> > 
> > Regards,
> >                                         Owen
> > 
> > 
> Dear Owen,
> I don't think so, I've just checked looking into the termcap file given
> with xterm-164  and the escape sequences for te/ti capabilities are
> [?1049h and [?1049l so I think the actual unpatched vt.c is wrong.
> I also attached the termcap file,

Hmmm, this seems to be a XFree86 xterm'ism. To quote from Dickey's ChangeLog:

  Patch #90 - 1998/12/13 - XFree86 3.9Nq

  Implement new escape sequence, private mode 1049, which combines the
  switch to/from alternate screen mode with screen clearing and cursor
  save/restore. Unlike the existing escape sequence, this clears the
  alternate screen when switching to it rather than when switching to
  the normal screen, thus retaining the alternate screen contents for
  select/paste operations.

  When I implemented the popup menu entry to toggle between the normal
  and alternate screens, I considered only pasting from the normal
  screen to the alternate; this improvement allows either direction.  #
  Changed the termcap and terminfo for xterm-xfree86 and xterm-8bit to
  use the new 1049 private mode.

The termcap from ncurses on my system uses 1047 and 1048. It seems like
it shouldn't do any harm to support 1049 in addition. But it looks like
your patch doesn't get the screen clearing behavior right. (Or in fact
clear the alternate screen at all.)

The vte emulator that Nalin is hacking on is cool (and a little backwards)
in that it actually reads the termcap entry and uses those escape sequences;
which should fix this sort of problem, where the 'xterm' termcap entry
is different on every system.

Regards,
                                        Owen