From: Thomas Wolff <towo@towo.net>
To: cygwin@cygwin.com
Subject: Re: [ANNOUNCEMENT] Updated: dash-0.5.8-3
Date: Tue, 14 Feb 2017 20:29:00 -0000 [thread overview]
Message-ID: <0da58793-0b76-1f13-aca3-06ed6aa83dc3@towo.net> (raw)
In-Reply-To: <6488d88d-f6b8-674d-692c-8372977a4707@redhat.com>
Am 14.02.2017 um 20:56 schrieb Eric Blake:
> On 02/14/2017 01:40 PM, Thomas Wolff wrote:
>>> No. We're talking about a function in the master side of the tty, while
>>> the applications started in the terminal are on the slave side.
>> I am not familiar with the concept of setting termios properties on
>> either the master or slave side of a pty. I've only ever set them in the
>> client application, including my tests about IUTF8 which worked. Would
>> setting on the master side imply it's set for the clients implicitly,
>> and can it be changed later, e.g. when mintty character encoding is
>> being changed from the Options dialog?
>> And you say the function of erasing characters on BS is in the master
>> side? To be honest, this confuses me. I thought it's a client function,
>> like readline() would perform if used (apparently not by dash), which is
>> kind of an enhanced version of the tty cooked mode and used to work even
>> without the new flag, right?
> The readline source code does not mention IUTF8; and neither bash nor
> dash need to reference it, because if the tty handling code sets it
> correctly for what the terminal is going to display, then the clients
> that are read()ing from the tty never even see BS in cooked mode (the
> master side of the terminal handles BS before the read() completes in
> the slave, if I'm understanding it correctly).
This does not comply with my (limited) understanding of pty stuff. In
mintty, forkpty will create a master/slave pty; mintty feeds it on the
master side, while the client program (usually a shell) reads from the
slave side. Mintty never handles BS for input, it simply feeds it into
the pty. "Line disciplines" like cooked mode must be handled on the
slave side.
>>> iutf8 is set in Linux by default and by most terminal applications ionly
>>> reset if the LC_CTYPE setting in the environment of the terminal
>>> application is not set to the utf8 codeset. This is determined at
>>> terminal startup, not by the inferior processes runnin in the terminal.
>>> The applications still can set iutf8 via termios control (or stty(1)).
>> Will you patch stty as well to address the new flag?
> Already patched; coreutils-8.26-2 was promoted to current yesterday.
>
>>> For mintty I just thought it might be helpful to honor the character set
>>> setting in its options and to default to iutf8 if it's not set.
>> Sure, but it would be better to find a solution that implicitly works in
>> all terminals. Isn't it possible to handle this in forkpty()/openpty()?
> Does forkpty()/openpty() currently pay attention to environment
> variables to even know what encoding is currently in use?
Don't know, but maybe it simply should for this purpose, for a
widely-useful solution.
> And what's to
> say that the environment used to fork the master side will match the
> locale settings of the slave process that connects to the pty, so how do
> we know whether to default IUTF8 on or off based solely on the slave's
> environment, when it is the master that is handling BS and therefore the
> master's character encoding that matters for how much BS should erase ?
See above; the master isn't handling BS. But there should be no such
inconsistency in the case of mintty because master and slave are forked
from common initial code. I think this consideration is only relevant
for reattaching programs like screen.
------
Thomas
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next prev parent reply other threads:[~2017-02-14 20:29 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-27 23:40 Eric Blake (cygwin)
2017-01-24 15:58 ` Houder
2017-01-25 1:28 ` Steven Penny
2017-01-25 13:37 ` Houder
2017-01-25 20:31 ` cyg Simple
2017-01-28 14:36 ` Houder
2017-01-26 0:14 ` Steven Penny
2017-01-28 13:44 ` Houder
2017-01-31 10:04 ` Corinna Vinschen
2017-01-31 13:16 ` Corinna Vinschen
2017-01-31 15:02 ` Houder
2017-01-31 15:33 ` Corinna Vinschen
2017-01-31 15:42 ` Eric Blake
2017-02-01 8:46 ` Houder
2017-01-31 17:54 ` Houder
2017-02-01 9:17 ` Corinna Vinschen
2017-02-13 22:03 ` Thomas Wolff
2017-02-14 8:45 ` Corinna Vinschen
2017-02-14 19:40 ` Thomas Wolff
2017-02-14 19:56 ` Eric Blake
2017-02-14 20:29 ` Thomas Wolff [this message]
2017-02-14 20:35 ` Thomas Wolff
2017-02-15 22:19 ` Thomas Wolff
2017-02-16 12:49 ` Corinna Vinschen
2017-02-16 20:32 ` Thomas Wolff
2017-02-17 7:36 ` Thomas Wolff
2017-02-17 9:43 ` Corinna Vinschen
2017-02-17 22:30 ` Thomas Wolff
2017-02-18 22:46 ` Thomas Wolff
2017-02-20 9:11 ` Corinna Vinschen
2017-02-20 21:08 ` Thomas Wolff
2017-02-20 9:07 ` Corinna Vinschen
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