how=2 also clear the entire display

[ryuukk]

0 = clear display from cursor to end, therefore it needs history

however

2 = clear entire display

On windows when using git bash, clear didn't clear the entire display, it put back the history therefore you could always scroll back

If you use the provided terminal emulator (from msys), calling clear clear the entire display, so that's the proper behavior, same when using Windows Terminal

With this PR clear now behaves properly with Terminus

Fix #120, #340 and probable some other issues

There is also this line in the code base that looks suspicious:

https://github.com/randy3k/Terminus/pull/399/files#diff-1ff8d95a5f63ac2d193b501633246f1211a04d98c4ef04782ddd5a9a1dc327b3R390-R392

[randy3k]

It is working as intended. 2 should only erase the viewport and 3 would erase the scrollback history. See https://xtermjs.org/docs/api/vtfeatures/#csi

0 | Erase from the cursor through the end of the viewport.
-- | --
1 | Erase from the beginning of the viewport through the cursor.
2 | Erase complete viewport.
3 | Erase scrollback.

[ryuukk]

Who is right? xtermjs, or windows terminal, msys terminal and other tools?

[randy3k]

vt510 doesn't have the concept of scrollback history. We should unleast reference xterm. https://www.xfree86.org/current/ctlseqs.html

Of course, Windows terminal may have evolved differently as xterm and inconsistency is expected. Terminus would follow xterm's standard in case of having any inconsistency.

[randy3k]

By the way, it also depends on the clear program that you use. Some clear program will emit \e[3J and some will emit \e[2J.

[ryuukk]

Options from clear

Options:
  -T TERM     use this instead of $TERM
  -V          print curses-version
  -x          do not try to clear scrollback

If -x tries to not clear scrollback, what does not calling it with -x supposed to do according to clear?

it prints:

\033[H\033[2J\033[3J 

So 3 is there, why does terminus stops at 2?

Calling it with -x prints

\033[H\033[2J

So you may be right, however, terminus stopping at 2 and not handling 3, wich is present, is a bug right?

[randy3k]

printf '\033[H\033[2J\033[3J' does clear the scroll back history for me (in bash and zsh / macOS).

[raylucker]

I am using Windows, in cmd to clear the entire cmd I have to use "cls" instead of "clear". However, in terminus "cls" only scroll down to the cursor instead of clearing all the display.

[mataha]

I am using Windows, in cmd to clear the entire cmd I have to use "cls" instead of "clear". However, in terminus "cls" only scroll down to the cursor instead of clearing all the display.

That's because cls prints ASCII 0x0C (<FF> - form feed) unless cmd.exe is connected to stdout:

printf("\014"); // ^L
return 0;

Neither Windows Terminal nor conhost.exe implement CSI 3 J. CSI 2 J works as intended.