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From: Peter Korsgaard <peter@korsgaard.com>
To: Edgar Bonet <bonet@grenoble.cnrs.fr>
Cc: buildroot@buildroot.org
Subject: Re: [Buildroot] [PATCH 1/1] support/testing/infra/emulator.py: prevent the commands from wrapping
Date: Sat, 09 Oct 2021 13:28:57 +0200	[thread overview]
Message-ID: <87fstav3ly.fsf@dell.be.48ers.dk> (raw)
In-Reply-To: <914a4374-e517-b730-c45f-f37ec8147649@grenoble.cnrs.fr> (Edgar Bonet's message of "Tue, 5 Oct 2021 19:17:58 +0200")

>>>>> "Edgar" == Edgar Bonet <bonet@grenoble.cnrs.fr> writes:

 > Traditional VT-10x terminals (and their emulators) have a "magic
 > margins" feature that enables the last character position to be updated
 > without scrolling the screen: whenever a character is printed on the
 > last column, the cursor stays over the character, instead of moving to
 > the next line.

 > The Busybox shell, ash, attempts to defeat this feature by printing
 > CF,LF right after echoing a character to the last column.[1] This
 > doesn't play well with emulator.py. The run() method of the Emulator
 > class captures the output of the emulated system and assumes the first
 > line it reads is the echo of the command, and all subsequent lines are
 > the command's output. If the line made by the command + shell prompt is
 > longer than 80 characters, then it is echoed as two or more lines, and
 > all but the first one are mistaken for the command's output.

 > We fix this by telling the emulated system that we are using an
 > ultra-wide terminal with 29999 columns. Larger values would be ignored
 > and replaced by the default, namely 80 columns.[2]

 > [1] https://git.busybox.net/busybox/tree/libbb/lineedit.c?h=1_34_0#n412
 > [2] https://git.busybox.net/busybox/tree/libbb/xfuncs.c?h=1_34_0#n258

 > Signed-off-by: Edgar Bonet <bonet@grenoble.cnrs.fr>
 > Reported-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
 > Co-authored-by: Yann E. MORIN <yann.morin.1998@free.fr>
 > ---
 >  support/testing/infra/emulator.py | 2 ++
 >  1 file changed, 2 insertions(+)

 > Note that I tested that the command

 >     stty columns 29999

 > does fix the wrapping behavior on an actual board, while using a serial
 > connection. I did not test the script emulator.py, as I am unfamiliar
 > with the testing infrastructure. Would someone volunteer to do that
 > test?

Committed to 2021.02.x, 2021.05.x and 2021.08.x, thanks.

-- 
Bye, Peter Korsgaard
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      parent reply	other threads:[~2021-10-09 11:29 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-05 17:17 [Buildroot] [PATCH 1/1] support/testing/infra/emulator.py: prevent the commands from wrapping Edgar Bonet
2021-10-05 20:01 ` Yann E. MORIN
2021-10-06  7:11   ` Thomas Petazzoni
2021-10-06 10:22     ` Edgar Bonet
2021-10-06 19:47       ` Yann E. MORIN
2021-10-06 19:56 ` Yann E. MORIN
2021-10-09 11:28 ` Peter Korsgaard [this message]

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