ports/153942: Tmux patch breaks backspace in tmux command mode

[Brandon Low]

>Number: 153942
>Category: ports
>Synopsis: Tmux patch breaks backspace in tmux command mode
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-ports-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Thu Jan 13 01:30:08 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator: Brandon Low
>Release: FreeBSD 8.1-RELEASE-p2 amd64
>Organization:
none
>Environment:
System: FreeBSD erudite.lostlogicx.com 8.1-RELEASE-p2 FreeBSD 8.1-RELEASE-p2 #1: Mon Jan 10 20:27:03 PST 2011 ro...@erudite.lostlogicx.com:/usr/obj/usr/src/sys/GENERIC amd64

>Description:
Due to the patch file /usr/ports/sysutils/tmux/files/patch-tty-keys.c the backspace key does not work in <C-b>: mode (tmux command mode).

>How-To-Repeat:
cd /usr/ports/sysutils/tmux
make clean install
tmux
<C-b>:
type anything, then try to backspace

>Fix:
For me, removing the file /usr/ports/sysutils/tmux/files/patch-tty-keys.c and running make uninstall; make clean install on tmux fixed the problem for me, but I don't know why the patch existed in the first place, I can only assume that its existance was to fix a bug for another user.

>Release-Note:
>Audit-Trail:
>Unformatted:
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[Anonymous]

The following reply was made to PR ports/153942; it has been noted by GNATS.

From: Anonymous <swe...@gmail.com>
To: Brandon Low <lost...@lostlogicx.com>
Cc: bug-fo...@freebsd.org
Subject: Re: ports/153942: Tmux patch breaks backspace in tmux command mode
Date: Thu, 13 Jan 2011 07:32:05 +0300

Brandon Low <lost...@lostlogicx.com> writes:

> Here's an email that I received from the maintainer of tmux about this
> issue, indicating that it should be safe to remove the patch nowadays:
>
> the reason they did that is because at least some freebsd versions have
> xterm etc generate ^H by default and have ^H as verase in termios (stty)
>
> tmux always sends ^? as backspace to programs inside, but earlier
> versions did not change the termios inside to set verase to ^?
>
> new versions do, so outside can have verase=^H, tmux will detect that is
> backspace (from termios) and translate it to ^? inside as well as

And this magic translation has a bug, you can't disable it. Run from
inside tmux

$ stty erase '^H'

then try to use backspace key or Ctrl-H in ncurses apps. It'd still
produce '^?'. That's because there's actually no way to type '^H'.
Any other erase character would work fine.

> setting verase to ^? in new windows so applications inside tmux use the
> right thing
>
> this is all because terminfo kbs is too unreliable and so many
> applications just blindly accept ^? anyway

'^H' is also a valid character for Ctrl-H. Without tty-keys.c patch
there is one keycode less as both Ctrl-H and Ctrl-? produce '^?'.
And any (default) keybinding with '^H' doesn't work.

>
> since your terminal on freebsd sends ^? (and termios is ^? too) either
> you're using a terminal which uses that by default, you changed the
> xterm deleteIsDEL property (like everyone else does), or freebsd changed
> their default