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From: blarson@skat.usc.edu (Bob Larson)
Newsgroups: comp.unix.wizards
Subject: Re: termcap "sg#0" capability
Message-ID: <4932@oberon.USC.EDU>
Date: Fri, 30-Oct-87 20:00:36 EST
Article-I.D.: oberon.4932
Posted: Fri Oct 30 20:00:36 1987
Date-Received: Thu, 5-Nov-87 06:01:46 EST
References: <847@quacky.UUCP>
Sender: nobody@oberon.USC.EDU
Reply-To: blarson@skat.usc.edu (Bob Larson)
Organization: USC AIS, Los Angeles
Lines: 44
Keywords: magic cookies

In article <847@quacky.UUCP> rmg@mips.UUCP (Richard M. Geiger) writes:
>I have a question about the semantics of the "sg" terminal capability.

>The BSD 4.3 termcap(5) manual page describes "sg" thus:
>>      sg    num          Number of garbage chars left by so or se (default 0)
>       ...
>>      The sequences to enter and
>>      exit standout mode are given as so and se, respectively.  If
>>      the code to change into or out of standout mode leaves one
>>      or even two blank spaces or garbage characters on the
>>      screen, as the TVI 912 and Teleray 1061 do, then sg should
>>      be given to tell how many characters are left.

>Notice that the manual page specifies a default of 0 for the sg
>attribute.  I initially interpreted this to mean that a terminal
>description with an explicit sg#0 should be equivalent to one with no
>sg capability given.

Terminals without standout glitch put the charcter attribute specified
on each character printed between the attribute start and attribute
end sequences.  Cursor motion may or may not be allowed.

Terminals with standout glitch use the character attribute specified
between the character position of the attribute start magic cookie and
the attribute end magic cookie (or the end of the screen).

Now how does one describe a terminal to termcap that uses magic
cookies that take no screen positions?  If you have a line in reverse
vidio, and want to change characters in the middle, you can not
treat this the same as no standout glitch.

I use sg#0 to denote the third type of terminal to MicroGnuEmacs (mg).  A
non-obvious problem with this is what happens when you print
characters to the end of line then send the code to end the attribute,
position to the first character of the next line, then do a clear to
end of line.  (Answer on one terminal I have: the rest of the screen
winds up in reverse vidio.)  mg avoids printing to the end of line on
sg#0 reverse lines to avoid this.

Is there a better way to do this?
--
Bob Larson		Arpa: Blarson@Ecla.Usc.Edu
Uucp: {sdcrdcf,cit-vax}!oberon!skat!blarson		blarson@skat.usc.edu
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