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Re: [css-writing-modes] Propose to weaken upright rendering of horizontal-only scripts

From: Koji Ishii <kojiishi@gmail.com>
Date: Tue, 19 May 2015 18:42:00 +0900
Message-ID: <CAN9ydbV8-Zb+Ra5mu2vS5CF31LMFRELU11nzT-caWXeW1PLD0Q@mail.gmail.com>
To: fantasai <fantasai.lists@inkedblade.net>
Cc: "www-style@w3.org" <www-style@w3.org>
Talked with fantasai, and allow me to clarify the intention better.

I'm not asking UAs choose to fallback in sideways arbitrarily, but I
suppose there are some characters that we really don't know how to
render in upright. Unicode Regional Indicator Symbol Letter for

So I'd like the spec allow UA not to render in upright. fantasai told
me that, even if the spec says "MUST", such behaviors could be
accepted by directors. That solves my primary concern, but then it
sounds like it's "SHOULD" to me.

Note that I tested Blink, WebKit, and Trident, all of them have some
characters they cannot render as of today. Gecko, unfortunately, my
test script did not work, I'll see when it's fixed.


On Tue, May 19, 2015 at 1:20 PM, fantasai <fantasai.lists@inkedblade.net> wrote:
> On 04/29/2015 04:40 AM, Jonathan Kew wrote:
>> On 28/4/15 19:02, Koji Ishii wrote:
>>> I’d like to propose to weaken spec words when rendering
>>> horizontal-only scripts in upright.
>>> One in text-orientation: upright, the proposed change is from:
>>>   characters from horizontal-only scripts are rendered upright
>>> to:
>>>   characters from horizontal-only scripts should be rendered upright
>> I don't think this should be weakened to a "should", as this
>> would allow an implementation to ignore the 'upright' value and
>> render Latin (etc) characters as if it were 'mixed' or
>> 'sideways-right'. We shouldn't leave room for that to be claimed
>> as a conforming implementation of text-orientation:upright.
>>> Then in the definition of “upright characters”[2], from:
>>>   characters from horizontal cursive scripts (such as Arabic) are
>>>   shaped in their isolated forms when typeset upright
>>> to:
>>>   characters from horizontal cursive scripts (such as Arabic) should
>>>   be shaped in their isolated forms when typeset upright
>>> or we could be more descriptive how we’d like to weaken.
>> Again, I'd prefer not to weaken in this way; I think it's clear that
>> cursive horizontal scripts, when typeset in vertical upright mode,
>> should use isolated forms rather than their normal (horizontal)
>> cursive joining. (Firefox Nightly currently gets this wrong, but
>> should be fixed very shortly.)
> Fwiw, I agree completely with Jonathan here.
>> What's less clear, IMO, is how to handle the complex Indic scripts
>> where reordering and clustering behavior is involved.
> Yes, this is a fair criticism. I think the default behavior should
> be to break the text into grapheme clusters, and render each upright
> individually. For cases where this is known to be incorrect, and
> more correct rules are known (e.g. per-syllable), then those rules
> override this default rule.
>>> The motivation is that I know little about if every single
>>> horizontal-only script can really render upright with this
>>> definition. I know there are people who knows it better than me, but
>>> a discussion of Jonathan and Behdad[3] indicated me that there are
>>> more we need to study, and I’m afraid to define it normatively with
>>> our current knowledge.
>> I agree there are gaps in our knowledge of how best to render some
>> scripts in this mode, but rather than weakening the current spec
>> text, which I think is OK as far as it goes, perhaps we should
>> just have a note that the behavior of complex scripts such as
>> Indic and SE Asian in vertical upright is not clearly defined yet.
> Again, agreed. And we should add that note. :)
> ~fantasai
Received on Tuesday, 19 May 2015 09:42:27 UTC

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