linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Andrey Utkin <andrey_utkin@fastmail.com>
To: Adam Borowski <kilobyte@angband.pl>
Cc: "Manuel Schölling" <manuel.schoelling@gmx.de>,
	plagnioj@jcrosoft.com, tomi.valkeinen@ti.com, jslaby@suse.cz,
	gregkh@linuxfoundation.org, linux-fbdev@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v7 0/3] console: Add persistent scrollback buffers for all VGA consoles
Date: Mon, 28 Nov 2016 00:02:15 +0000	[thread overview]
Message-ID: <20161128000215.GQ11418@dell-m4800.home> (raw)
In-Reply-To: <20161127231548.GA29376@angband.pl>

On Mon, Nov 28, 2016 at 12:15:48AM +0100, Adam Borowski wrote:
> On Sun, Nov 27, 2016 at 09:37:30PM +0000, Andrey Utkin wrote:
> > I've just patched next-20161125 with this set and given it a run.
> > 
> > Scrollback persistence works fine, just as in earlier versions.
> > 
> > This time I didn't forget to test clear operation.
> > 
> > The only important concern is that after logout, the scrollback is not
> > wiped by /bin/login or /sbin/agetty (not sure who of them is responsible
> > for that). What do you see on your workstations in this case?
> 
> If you're on Debian or a derivative, that's clear_console.  It uses a
> switch-vt-then-back hack which obviously doesn't work with scrollback
> persistence.  Reported as https://bugs.debian.org/845177 -- I'll molest the
> maintainer if the patch doesn't get applied soon, so we can have the fix in
> time for stretch (then Ubuntu zesty).

I'm on Gentoo.

> Because of a sad lack of a time machine, old systems will use clear_console
> with that hack until they die, that's why
> CONFIG_VGACON_SOFT_SCROLLBACK_PERSISTENT defaults to n; in a few years it'll
> be ok to flip it.
> 
> > I guess we need to do something of the following:
> >  - catch some control character sequences to wipe the scrollback
> 
> \e[3J
> 
> >  - indicate (by some flag) some feature capability for this
> 
> Terminfo calls this flag "E3".
> 
> >  - request update in terminfo database or whatever, to let ncurses know
> >    that it is capable of scrollback wiping by some control charater
> >    sequences
> 
> Already there for quite a while.
> 
> > clear(1) doesn't wipe the scrollback at all, it is still reachable, all
> > of it.
> 
> It does for me on the console.  The man page says:
> 
> # clear clears your screen if this is possible, including its scrollback
> # buffer (if the extended "E3" capability is defined).  clear looks in the
> # environment for the terminal type and then in the terminfo database to
> # determine how to clear the screen.
> 
> Because of its reliance on terminfo, you need to have TERM=linux in your
> environment; also, screen/tmux obviously breaks this.

I wonder whether my ncurses is not bleeding-edge enough, or I have some
non-standard config. Anyway, thanks for explanation.

> > echo -e "\e[3J" seems to wipe the scrollback, but if you do it several
> > times in a row, every time you (or at last I do) get your prompt a bit
> > lower, so after many times you end up with blank screen and the prompt
> > at the bottom of the screen.
> 
> Yeah, none of \e[J subcommands move the cursor at all.  As you use echo
> without -n, you move two lines lower, and even with -n the command you typed
> takes a line.  You want to move the cursor explicitly, add "\e[H".

Thanks for explanation.

  parent reply	other threads:[~2016-11-28  0:02 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20161118005309.GC26324@dell-m4800.home>
2016-11-20 21:58 ` [PATCH v5 0/2] console: Add persistent scrollback buffers for all VGA console Manuel Schölling
2016-11-20 21:58   ` [PATCH v5 1/2] console: Move scrollback data into its own struct Manuel Schölling
2016-11-20 21:58   ` [PATCH v5 2/2] console: Add persistent scrollback buffers for all VGA consoles Manuel Schölling
2016-11-20 22:23     ` kbuild test robot
2016-11-21 20:17     ` Adam Borowski
2016-11-22 16:56       ` Manuel Schölling
2016-11-23 17:33         ` Adam Borowski
2016-11-27 16:51           ` [PATCH v7 0/3] " Manuel Schölling
2016-11-27 16:51             ` [PATCH v7 1/3] console: Move scrollback data into its own struct Manuel Schölling
2016-11-27 16:51             ` [PATCH v7 2/3] console: Add callback to flush scrollback buffer to consw struct Manuel Schölling
2016-11-27 16:51             ` [PATCH v7 3/3] console: Add persistent scrollback buffers for all VGA consoles Manuel Schölling
2016-11-27 21:37             ` [PATCH v7 0/3] " Andrey Utkin
2016-11-27 23:15               ` Adam Borowski
2016-11-27 23:30                 ` Jakub Wilk
2016-11-28  0:02                 ` Andrey Utkin [this message]
2016-11-28 21:28               ` Manuel Schölling
2016-11-29 10:01                 ` Andrey Utkin
2016-11-29 10:44                   ` Adam Borowski
2016-11-29 16:35                   ` Manuel Schölling
2016-12-01 21:03                   ` Manuel Schölling
2016-12-01 21:31                     ` Andrey Utkin
2016-11-27 23:53             ` Adam Borowski
2016-11-28 21:23               ` Manuel Schölling
2016-11-23 17:33       ` [PATCH v5 2/2] " Manuel Schölling
2016-12-04 10:53 [PATCH v7 0/3] " Manuel Schölling
2016-12-06 10:02 ` Greg KH
2016-12-06 16:32   ` Manuel Schölling

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20161128000215.GQ11418@dell-m4800.home \
    --to=andrey_utkin@fastmail.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=jslaby@suse.cz \
    --cc=kilobyte@angband.pl \
    --cc=linux-fbdev@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=manuel.schoelling@gmx.de \
    --cc=plagnioj@jcrosoft.com \
    --cc=tomi.valkeinen@ti.com \
    --subject='Re: [PATCH v7 0/3] console: Add persistent scrollback buffers for all VGA consoles' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).