linux-kernel - Re: [PATCH v3 00/14] vt: implement proper Unicode handling

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Message-ID: <2025042609-diagnoses-whinny-36b1@gregkh>
Date: Sat, 26 Apr 2025 11:24:17 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Nicolas Pitre <nico@...xnic.net>
Cc: Jiri Slaby <jirislaby@...nel.org>, Nicolas Pitre <npitre@...libre.com>,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 00/14] vt: implement proper Unicode handling

On Fri, Apr 25, 2025 at 11:13:40AM -0500, Nicolas Pitre wrote:
> 
> 
> > Le 25 avr. 2025 à 09:29, Greg Kroah-Hartman <gregkh@...uxfoundation.org> a écrit :
> > 
> > On Thu, Apr 17, 2025 at 02:45:02PM -0400, Nicolas Pitre wrote:
> >> The Linux VT console has many problems with regards to proper Unicode
> >> handling:
> >> 
> >> - All new double-width Unicode code points which have been introduced since
> >>  Unicode 5.0 are not recognized as such (we're at Unicode 16.0 now).
> >> 
> >> - Zero-width code points are not recognized at all. If you try to edit files
> >>  containing a lot of emojis, you will see the rendering issues. When there
> >>  are a lot of zero-width characters (like "variation selectors"), long
> >>  lines get wrapped, but any Unicode-aware editor thinks that the content
> >>  was rendered properly and its rendering logic starts to work in very bad
> >>  ways. Combine this with tmux or screen, and there is a huge mess going on
> >>  in the terminal.
> >> 
> >> - Also, text which uses combining diacritics has the same effect as text
> >>  with zero-width characters as programs expect the characters to take fewer
> >>  columns than what they actually do.
> >> 
> >> Some may argue that the Linux VT console is unmaintained and/or not used
> >> much any longer and that one should consider a user space terminal
> >> alternative instead. But every such alternative that is not less maintained
> >> than the Linux VT console does require a full heavy graphical environment
> >> and that is the exact antithesis of what the Linux console is meant to be.
> >> 
> >> Furthermore, there is a significant Linux console user base represented by
> >> blind users (which I'm a member of) for whom the alternatives are way more
> >> cumbersome to use reducing our productivity. So it has to stay and
> >> be maintained to the best of our abilities.
> >> 
> >> That being said...
> >> 
> >> This patch series is about fixing all the above issues. This is accomplished
> >> with some Python scripts leveraging Python's unicodedata module to generate
> >> C code with lookup tables that is suitable for the kernel. In summary:
> >> 
> >> - The double-width code point table is updated to the latest Unicode version
> >>  and the table itself is optimized to reduce its size.
> >> 
> >> - A zero-width code point table is created and the console code is modified
> >>  to properly use it.
> >> 
> >> - A table with base character + combining mark pairs is created to convert
> >>  them into their precomposed equivalents when they're encountered.
> >>  By default the generated table contains most commonly used Latin, Greek,
> >>  and Cyrillic recomposition pairs only, but one can execute the provided
> >>  script with the --full argument to create a table that covers all
> >>  possibilities. Combining marks that are not listed in the table are simply
> >>  treated like zero-width code points and properly ignored.
> >> 
> >> - All those tables plus related lookup code require about 3500 additional
> >>  bytes of text which is not very significant these days. Yet, one
> >>  can still set CONFIG_CONSOLE_TRANSLATIONS=n to configure this all out
> >>  if need be.
> >> 
> >> Note: The generated C code makes scripts/checkpatch.pl complain about
> >>      "... exceeds 100 columns" because the inserted comments with code
> >>      point names, well, make some inlines exceed 100 columns. Please make
> >>      an exception for those files and disregard those warnings. When
> >>      checkpatch.pl is used on those files directly with -f then it doesn't
> >>      complain.
> >> 
> >> This series was tested on top of v6.15-rc2.
> > 
> > I've taken the first version of this, should I revert all of them and
> > then apply these, or do you want to send a diff between this and what is
> > in the tty-next tree?
> Please remove what you have and replace with this v3. Will be much cleaner this way. 

Ok, just did that, thanks.

greg k-h