Date: Fri, 19 Nov 1999 15:13:23 +1100 From: Gregory Bond <gnb@itga.com.au> To: "Ronald F. Guilmette" <rfg@monkeys.com> Cc: freebsd-bugs@FreeBSD.ORG Subject: Re: misc/14959: incomplete xterm termcap entry (see also bug gnu/5039) Message-ID: <199911190413.PAA08161@lightning.itga.com.au> In-Reply-To: Your message of Wed, 17 Nov 1999 23:27:12 -0800.
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> >Extending termcap (yet again!) with another set of tags for this
> >feature is probably not feasible.
> OK. I'll bite. Why not?
At least partly because the same functionality is not available in terminfo,
and terminfo is not extensible. Interestingly, terminfo -does- have a flag to
say "this terminal does or doesn't restore", but no way of turning this feature
on or off. ti/to (aka smcup/rmcup in terminfo) are more designed for things
like Tek terminals that need special handling to deal with cursor addressing
(remember, termcap was designed in the days when paper teletypes were not
uncommon Unix terminals!). E.g. from the terminfo man page:
This is also used for the Tektronix 4025, where smcup sets
the command character to be the one used by terminfo. If
the smcup sequence will not restore the screen after an
rmcup sequence is output (to the state prior to outputting
rmcup), specify nrrmc.
[I'm taking "terminfo" here to be the Solaris2.6 implementation, which is
probably pretty generc for SVR4 systems.]
A more solid reason extending termcap is not feasible is that it will be
impossible to get all the authors of all screen-based client programs to
support any such extension. And the user has a perfectly acceptable workaround
using two termcap entries and shell aliases/functions/scripts to select, on a
program by program basis, which behaviour they want.
>(I don't know any of the history, so I probably shouldn't comment, but...
>It really does seem strange to me that such a fundamental capability never
>earned its own pair of two-letter termcap abbreviations. How about terminfo?
>Are there special terminfo codes for screen save/restore? I haven't worked
>on SVR4 for quite awhile, so I can't remember.)
Because, as I said earlier, termcap was developed in the era when any form of
cursor addressing at all was a rare bonus, and semi-advanced features like
screen save/restore almost unheard of. And terminfo is in many ways just a
(poor) reimplementation of the termcap capabilities.
Greg,
who used to dream of a terminal that could do insert/delete line/char
when in full-screen mode.
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