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

On Mon, Aug 18, 2014 at 6:29 PM, fantasai <fantasai.lists@inkedblade.net> wrote:
> 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.

And, for some languages, #2 can be subdivided further, such as the
"give the correct Arabic letter form, even if you can't shape them
properly" topic.

~TJ

Received on Tuesday, 19 August 2014 01:44:27 UTC