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Re: [css-text][css-writing-modes] Line breaking around Emoji, Gaiji, U+FFFC, and text-combine-horizontal

From: Koji Ishii <kojiishi@gmail.com>
Date: Mon, 26 Jan 2015 20:31:30 +0900
Message-ID: <CAN9ydbVqt72Ar29VH2FWrKXKNg9Bixcuz9XOXCbx8mf7pebSNg@mail.gmail.com>
To: fantasai <fantasai.lists@inkedblade.net>
Cc: "www-style@w3.org" <www-style@w3.org>
Thank you for the great summary.

On Mon, Jan 26, 2015 at 7:29 AM, fantasai <fantasai.lists@inkedblade.net> wrote:
>
> 1. text-combine-upright
> -----------------------
>
>    Result of text-combine-upright should break as ID, not as U+FFFC.
>    Current spec requires treating as actual contents for line-breaking.
>    So there is some misunderstanding of the text;
>    unclear whether there is an issue here to fix.
>
>    Proposal A: Leave spec as-is: TCY treated as its own text.
>    Proposal B: Make TCY always treated as ideographic character.

Hm, the change was made in 2012[1]. I merely remember we discussed,
but don't remember why we changed.

Though I lost that context, thinking now, I think B works the best.

> 2. UAX#14 Rules for Atomic Inlines Problematic
> ----------------------------------------------
>
>    Changing the rule order for UAX#14 is a difficult tailoring.
>    Spec should just create a special rule for atomic inlines.
>
>    Proposal A: Change spec wording to fix this.
>    Proposal B: Change spec wording to fix issue #3.
>
>    Remaining Issue: Should U+FFFC match images?

Not very clear the diff between A and B. Can you clarify?

I think the first thing we need to resolve here is that, do we honor
web-compat or what it should be?

We had what we think it should be in the LC. Then the issue #4[2] came
up, and at that point we took web-compat, but we missed to measure the
impact of the fix, and here we're now.

If we honor web-compat here, then there are a few options how to make
it happen. So options are:

Proposal A: Take what we think it should be and sacrifice web-compat
(i.e., won't fix issue #4)
Proposal B: Take web-compat by re-ordering UAX#14 rules (the current text)
Proposal C: Take web-compat by special handing replaced elements
outside the UAX#14
Proposal D: Take web-compat, but any other good way to do it?

The feedback from Unicode/ICU folks is that the current B isn't good.

Maybe we're talking the same? I couldn't read what you meant by your A and B.

> 3. Images as Emoji / Gaiji Should Break as ID
> ---------------------------------------------
>
>    Images used as emoji/gaiji need to break as ID in CJK contexts.
>
>    Proposal A: Add new property in L4 to switch behaviors.
>    Proposal B: Treat all images as ID.
>
>    Ideographic characters (ID class) can break in most places,
>    but not around certain punctuation like commas, enclosing
>    parens, or non-breaking characters (GL) like nbsp.
>    This behavior is, afaict, 100% more sensible than the current
>    behavior. The question is, is it Web-compatible?

This depends on issue 2 above. If we resolve to B or C or D, that
means a fix after the LC prevents what we wanted in the LC. This
property is to opt-out the fix and bring back the behavior we defined
in the LC, so I think we need this in the Level 3. It was impossible
to predict such fix will be made after the LC.

Given that, in that case, its initial value must represent the legacy
behavior. I'm good with either a string or a value to switch to the
new, desired behavior.

> Koji, did I miss anything?
>
> [There was a mention of a ruby issue on line breaking, but that
> has its own thread, so won't address here.]

Nope, thank you for the great summary. The ruby issue on line breaking
was resolved as Xidorn agreed to follow the current spec, so no worry
now.

[1] https://github.com/w3c/csswg-drafts/commit/42e60e0e7e3fb12fd799a9cca26a12426f3d9c35
[2] http://dev.w3.org/csswg/css-text-3/issues-lc-2013#issue-4

/koji
Received on Monday, 26 January 2015 11:31:57 UTC

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