linux-kernel - Re: [PATCH] Fix backspace on wrapped lines in console (virtual terminal)

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Date:	Tue, 23 Sep 2008 14:39:48 -0600
From:	Joe Peterson <joe@...rush.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>, hpa@...or.com
Subject: Re: [PATCH] Fix backspace on wrapped lines in console (virtual terminal)

Joe Peterson wrote:
> I have worked up a new patch (attached) for review.

After discussing this with Thomas Dickey (maintainer of xterm), and
running vttest on both xterm and vt, I have generated an even newer
patch for review.  This replaces previous patches in this thread.

xterm only "fixes" the backspace behavior if both reverse wrap and
autowrap modes are enabled.  Although the "fix" is required for accurate
erasure of characters on wrapped lines (and therefore is really nice
when using Linux), the vttest results are not what it expects test 1
(cursor movement).  I do not have a VTxxx to test, but I assume vttest
is true to the hardware.

It makes sense, therefore, to retain the older behavior in vt unless
reverse wrap (which did not exist in the hardware) is enabled.  This
makes the patch true to vttest (and presumably the hardware) as well the
same as xterm in this respect.

							Thanks, Joe

P.S.  If anyone has a VTxxx, it would be interesting to know what
happens with autowrap mode on when backspace is hit after a character is
typed in the rightmost column.  If the cursor moves back, and the 2nd to
last character is then erased, this means the VTxxx behavior will match
the patched vt and xterm (when reverse wrap is not on - i.e. using
standard modes).

View attachment "vt-add-reverse-wrap-mode.patch" of type "text/plain" (2583 bytes)