[PATCH v2 00/40] Use ASCII subset instead of UTF-8 alternate symbols
Mauro Carvalho Chehab
mchehab+huawei at kernel.org
Sat May 15 01:22:39 PDT 2021
Em Fri, 14 May 2021 10:06:01 +0100
David Woodhouse <dwmw2 at infradead.org> escreveu:
> On Fri, 2021-05-14 at 10:21 +0200, Mauro Carvalho Chehab wrote:
> > Em Wed, 12 May 2021 18:07:04 +0100
> > David Woodhouse <dwmw2 at infradead.org> escreveu:
> >
> > > On Wed, 2021-05-12 at 14:50 +0200, Mauro Carvalho Chehab wrote:
> > > > Such conversion tools - plus some text editor like LibreOffice or similar - have
> > > > a set of rules that turns some typed ASCII characters into UTF-8 alternatives,
> > > > for instance converting commas into curly commas and adding non-breakable
> > > > spaces. All of those are meant to produce better results when the text is
> > > > displayed in HTML or PDF formats.
> > >
> > > And don't we render our documentation into HTML or PDF formats?
> >
> > Yes.
> >
> > > Are
> > > some of those non-breaking spaces not actually *useful* for their
> > > intended purpose?
> >
> > No.
> >
> > The thing is: non-breaking space can cause a lot of problems.
> >
> > We even had to disable Sphinx usage of non-breaking space for
> > PDF outputs, as this was causing bad LaTeX/PDF outputs.
> >
> > See, commit: 3b4c963243b1 ("docs: conf.py: adjust the LaTeX document output")
> >
> > The afore mentioned patch disables Sphinx default behavior of
> > using NON-BREAKABLE SPACE on literal blocks and strings, using this
> > special setting: "parsedliteralwraps=true".
> >
> > When NON-BREAKABLE SPACE were used on PDF outputs, several parts of
> > the media uAPI docs were violating the document margins by far,
> > causing texts to be truncated.
> >
> > So, please **don't add NON-BREAKABLE SPACE**, unless you test
> > (and keep testing it from time to time) if outputs on all
> > formats are properly supporting it on different Sphinx versions.
>
> And there you have a specific change with a specific fix. Nothing to do
> with whether NON-BREAKABLE SPACE is ∉ ASCII, and *certainly* nothing to
> do with the fact that, like *every* character in every kernel file
> except the *binary* files, it's representable in UTF-8.
>
> By all means fix the specific characters which are typographically
> wrong or which, like NON-BREAKABLE SPACE, cause problems for rendering
> the documentation.
>
>
> > Also, most of those came from conversion tools, together with other
> > eccentricities, like the usage of U+FEFF (BOM) character at the
> > start of some documents. The remaining ones seem to came from
> > cut-and-paste.
>
> ... or which are just entirely redundant and gratuitous, like a BOM in
> an environment where all files are UTF-8 and never 16-bit encodings
> anyway.
Agreed.
>
> > > > While it is perfectly fine to use UTF-8 characters in Linux, and specially at
> > > > the documentation, it is better to stick to the ASCII subset on such
> > > > particular case, due to a couple of reasons:
> > > >
> > > > 1. it makes life easier for tools like grep;
> > >
> > > Barely, as noted, because of things like line feeds.
> >
> > You can use grep with "-z" to seek for multi-line strings(*), Like:
> >
> > $ grep -Pzl 'grace period started,\s*then' $(find Documentation/ -type f)
> > Documentation/RCU/Design/Data-Structures/Data-Structures.rst
>
> Yeah, right. That works if you don't just use the text that you'll have
> seen in the HTML/PDF "grace period started, then", and if you instead
> craft a *regex* for it, replacing the spaces with '\s*'. Or is that
> [[:space:]]* if you don't want to use the experimental Perl regex
> feature?
>
> $ grep -zlr 'grace[[:space:]]\+period[[:space:]]\+started,[[:space:]]\+then' Documentation/RCU
> Documentation/RCU/Design/Data-Structures/Data-Structures.rst
>
> And without '-l' it'll obviously just give you the whole file. No '-A5
> -B5' to see the surroundings... it's hardly a useful thing, is it?
>
> > (*) Unfortunately, while "git grep" also has a "-z" flag, it
> > seems that this is (currently?) broken with regards of handling multilines:
> >
> > $ git grep -Pzl 'grace period started,\s*then'
> > $
>
> Even better. So no, multiline grep isn't really a commonly usable
> feature at all.
>
> This is why we prefer to put user-visible strings on one line in C
> source code, even if it takes the lines over 80 characters — to allow
> for grep to find them.
Makes sense, but in case of documentation, this is a little more
complex than that.
Btw, the theme used when building html by default[1] has a search
box (written in Javascript) that could be able to find multi-line
patterns, working somewhat similar to "git grep foo -a bar".
[1] https://github.com/readthedocs/sphinx_rtd_theme
> > [1] If I have a table with UTF-8 codes handy, I could type the UTF-8
> > number manually... However, it seems that this is currently broken
> > at least on Fedora 33 (with Mate Desktop and US intl keyboard with
> > dead keys).
> >
> > Here, <CTRL><SHIFT>U is not working. No idea why. I haven't
> > test it for *years*, as I din't see any reason why I would
> > need to type UTF-8 characters by numbers until we started
> > this thread.
>
> Please provide the bug number for this; I'd like to track it.
Just opened a BZ and added you as c/c.
> > Now, I'm not arguing that you can't use whatever UTF-8 symbol you
> > want on your docs. I'm just saying that, now that the conversion
> > is over and a lot of documents ended getting some UTF-8 characters
> > by accident, it is time for a cleanup.
>
> All text documents are *full* of UTF-8 characters. If there is a file
> in the source code which has *any* non-UTF8, we call that a 'binary
> file'.
>
> Again, if you want to make specific fixes like removing non-breaking
> spaces and byte order marks, with specific reasons, then those make
> sense. But it's got very little to do with UTF-8 and how easy it is to
> type them. And the excuse you've put in the commit comment for your
> patches is utterly bogus.
Let's take one step back, in order to return to the intents of this
UTF-8, as the discussions here are not centered into the patches, but
instead, on what to do and why.
-
This discussion started originally at linux-doc ML.
While discussing about an issue when machine's locale was not set
to UTF-8 on a build VM, we discovered that some converted docs ended
with BOM characters. Those specific changes were introduced by some
of my convert patches, probably converted via pandoc.
So, I went ahead in order to check what other possible weird things
were introduced by the conversion, where several scripts and tools
were used on files that had already a different markup.
I actually checked the current UTF-8 issues, and asked people at
linux-doc to comment what of those are valid usecases, and what
should be replaced by plain ASCII.
Basically, this is the current situation (at docs/docs-next), for the
ReST files under Documentation/, excluding translations is:
1. Spaces and BOM
- U+00a0 (' '): NO-BREAK SPACE
- U+feff (''): ZERO WIDTH NO-BREAK SPACE (BOM)
Based on the discussions there and on this thread, those should be
dropped, as BOM is useless and NO-BREAK SPACE can cause problems
at the html/pdf output;
2. Symbols
- U+00a9 ('©'): COPYRIGHT SIGN
- U+00ac ('¬'): NOT SIGN
- U+00ae ('®'): REGISTERED SIGN
- U+00b0 ('°'): DEGREE SIGN
- U+00b1 ('±'): PLUS-MINUS SIGN
- U+00b2 ('²'): SUPERSCRIPT TWO
- U+00b5 ('µ'): MICRO SIGN
- U+03bc ('μ'): GREEK SMALL LETTER MU
- U+00b7 ('·'): MIDDLE DOT
- U+00bd ('½'): VULGAR FRACTION ONE HALF
- U+2122 ('™'): TRADE MARK SIGN
- U+2264 ('≤'): LESS-THAN OR EQUAL TO
- U+2265 ('≥'): GREATER-THAN OR EQUAL TO
- U+2b0d ('⬍'): UP DOWN BLACK ARROW
Those seem OK on my eyes.
On a side note, both MICRO SIGN and GREEK SMALL LETTER MU are
used several docs to represent microseconds, micro-volts and
micro-ampères. If we write an orientation document, it probably
makes sense to recommend using MICRO SIGN on such cases.
3. Latin
- U+00c7 ('Ç'): LATIN CAPITAL LETTER C WITH CEDILLA
- U+00df ('ß'): LATIN SMALL LETTER SHARP S
- U+00e1 ('á'): LATIN SMALL LETTER A WITH ACUTE
- U+00e4 ('ä'): LATIN SMALL LETTER A WITH DIAERESIS
- U+00e6 ('æ'): LATIN SMALL LETTER AE
- U+00e7 ('ç'): LATIN SMALL LETTER C WITH CEDILLA
- U+00e9 ('é'): LATIN SMALL LETTER E WITH ACUTE
- U+00ea ('ê'): LATIN SMALL LETTER E WITH CIRCUMFLEX
- U+00eb ('ë'): LATIN SMALL LETTER E WITH DIAERESIS
- U+00f3 ('ó'): LATIN SMALL LETTER O WITH ACUTE
- U+00f4 ('ô'): LATIN SMALL LETTER O WITH CIRCUMFLEX
- U+00f6 ('ö'): LATIN SMALL LETTER O WITH DIAERESIS
- U+00f8 ('ø'): LATIN SMALL LETTER O WITH STROKE
- U+00fa ('ú'): LATIN SMALL LETTER U WITH ACUTE
- U+00fc ('ü'): LATIN SMALL LETTER U WITH DIAERESIS
- U+00fd ('ý'): LATIN SMALL LETTER Y WITH ACUTE
- U+011f ('ğ'): LATIN SMALL LETTER G WITH BREVE
- U+0142 ('ł'): LATIN SMALL LETTER L WITH STROKE
Those should be kept as well, as they're used for non-English names.
4. arrows and box drawing symbols:
- U+2191 ('↑'): UPWARDS ARROW
- U+2192 ('→'): RIGHTWARDS ARROW
- U+2193 ('↓'): DOWNWARDS ARROW
- U+2500 ('─'): BOX DRAWINGS LIGHT HORIZONTAL
- U+2502 ('│'): BOX DRAWINGS LIGHT VERTICAL
- U+2514 ('└'): BOX DRAWINGS LIGHT UP AND RIGHT
- U+251c ('├'): BOX DRAWINGS LIGHT VERTICAL AND RIGHT
Also should be kept.
In summary, based on the discussions we have so far, I suspect that
there's not much to be discussed for the above cases.
So, I'll post a v3 of this series, changing only:
- U+00a0 (' '): NO-BREAK SPACE
- U+feff (''): ZERO WIDTH NO-BREAK SPACE (BOM)
---
Now, this specific patch series address also this extra case:
5. curly commas:
- U+2018 ('‘'): LEFT SINGLE QUOTATION MARK
- U+2019 ('’'): RIGHT SINGLE QUOTATION MARK
- U+201c ('“'): LEFT DOUBLE QUOTATION MARK
- U+201d ('”'): RIGHT DOUBLE QUOTATION MARK
IMO, those should be replaced by ASCII commas: ' and ".
The rationale is simple:
- most were introduced during the conversion from Docbook,
markdown and LaTex;
- they don't add any extra value, as using "foo" of “foo” means
the same thing;
- Sphinx already use "fancy" commas at the output.
I guess I will put this on a separate series, as this is not a bug
fix, but just a cleanup from the conversion work.
I'll re-post those cleanups on a separate series, for patch per patch
review.
---
The remaining cases are future work, outside the scope of this v2:
6. Hyphen/Dashes and ellipsis
- U+2212 ('−'): MINUS SIGN
- U+00ad (''): SOFT HYPHEN
- U+2010 ('‐'): HYPHEN
Those three are used on places where a normal ASCII hyphen/minus
should be used instead. There are even a couple of C files which
use them instead of '-' on comments.
IMO are fixes/cleanups from conversions and bad cut-and-paste.
- U+2013 ('–'): EN DASH
- U+2014 ('—'): EM DASH
- U+2026 ('…'): HORIZONTAL ELLIPSIS
Those are auto-replaced by Sphinx from "--", "---" and "...",
respectively.
I guess those are a matter of personal preference about
weather using ASCII or UTF-8.
My personal preference (and Ted seems to have a similar
opinion) is to let Sphinx do the conversion.
For those, I intend to post a separate series, to be
reviewed patch per patch, as this is really a matter
of personal taste. Hardly we'll reach a consensus here.
7. math symbols:
- U+00d7 ('×'): MULTIPLICATION SIGN
This one is used mostly do describe video resolutions, but this is
on a smaller changeset than the ones that use "x" letter.
- U+2217 ('∗'): ASTERISK OPERATOR
This is used only here:
Documentation/filesystems/ext4/blockgroup.rst:filesystem size to 2^21 ∗ 2^27 = 2^48bytes or 256TiB.
Probably added by some conversion tool. IMO, this one should
also be replaced by an ASCII asterisk.
I guess I'll post a patch for the ASTERISK OPERATOR.
Thanks,
Mauro
More information about the linux-arm-kernel
mailing list