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Re: [css-text] Shaping Isolation and Layout Separation of Inlines

From: fantasai <fantasai.lists@inkedblade.net>
Date: Mon, 18 Aug 2014 18:29:26 -0700
Message-ID: <53F2A876.1040505@inkedblade.net>
To: John Daggett <jdaggett@mozilla.com>
CC: WWW International <www-international@w3.org>, www-style@w3.org
On 08/18/2014 06:02 PM, John Daggett wrote:
>
> fantasai wrote:
>
>>> Not sure what the intended purpose of this text is but I guess the
>>> first question is whether it's necessary or not.
>>
>> We got requests to clarify when Arabic joining is broken or not
>> broken at an inline boundary. For example, some implementations
>> breaking joining even when there's no style change. This is clearly
>> bad. As another example, in another implementation joining was
>> preserved even when margin/border/padding was nonzero, which created
>> problems for a set of inlined list items that were now pretending to
>> be all part of the same word.
>
> I don't think it's an easy task to come up with a good definition of whether shaping is broken or not at inline boundaries, at least not one that will actually be useful for implementations to use as a guideline. Better to consider what's optimal and what's not. Breaking at presentational style changes (e.g. color) shouldn't happen. But any property change that affects positioning (e.g. nonzero margin/border/padding) or alters an input to shaping will potentially affect the output of shaping. Whether it does or not will depend on underlying implementation details.
>
> I'm not sure specifying this in great detail helps implementations that really need to understand the scripts that they are dealing with in the first place. Giving them general guidelines to follow is better I think.

I think there are three classes of guidelines here, actually:

   1. Must not break shaping. (No style change case. You have no excuse.)
   2. Should not break shaping, if possible. YMMV depending on
      implementation/font technology. Less breakage = better.
   3. Must break shaping.

And I think we should be able to give interoperable results
on 1 and 3.

~fantasai
Received on Tuesday, 19 August 2014 01:29:56 UTC

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