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Re: Proposal for isolation characters in Unicode and the unicode-bidi:isolate and unicode-bidi:plaintext definitions

From: Aharon (Vladimir) Lanin <aharon@google.com>
Date: Mon, 23 Jul 2012 09:52:14 +0300
Message-ID: <CA+FsOYYaj_NC2NtzTrGPgwT1ynRq7qbz7hycBo49Ko=FQ-RoxA@mail.gmail.com>
To: Asmus Freytag <asmusf@ix.netcom.com>
Cc: Matitiahu Allouche <matitiahu.allouche@gmail.com>, Glenn Adams <glenn@skynav.com>, "'Martin J. Dürst'" <duerst@it.aoyama.ac.jp>, W3C style mailing list <www-style@w3.org>, public-i18n-bidi@w3.org
Thanks Asmus, that's what I was going to say.

On Sun, Jul 22, 2012 at 8:08 PM, Asmus Freytag <asmusf@ix.netcom.com> wrote:

>  If the desire for isolates is to allow the safe insertion of unrelated
> text, then the rules have to be such that no matter which characters the
> embedded text contains, it may not have any effect on the formatting of
> text around it.
>
> The one exception would be unmatched BDI/PDI, Instead of a sticking a
> single BDI/PDI pair around the text to be inserted, the inserting
> implementation would have to either add balancing BDI or PDI characters in
> front / back to balance the insertion, or, depending on context, perhaps
> disallow (filter) such characters from inserted text. With either strategy,
> the insertion could be self-contained.
>
> Filtering BDI/PDI from user input would seem a natural option when
> constructing a message from a template with short, user-specified,
> insertions, and is cheaper to implement than "rebalancing".
>
> The symmetric approach would require the implementation to balance
> "classical" embeddings and overrides in insertions (filtering would be a
> much less desirable option, as we expect overrides, in particular, to be
> quite legitimate in those types of user input).
>
> If not balanced, the sequence
>     [BDI]Having fun[PDF][PDI]
> would close any open overrides and thus affect the text following the
> insertion.
>
> Matis algorithm below does not seem to help with this case.
>
> A./
>
>
> On 7/22/2012 9:20 AM, Matitiahu Allouche wrote:
>
>  Aharon Lanin wrote:****
>
> "…some user codes their name as "Having fun[RLO]", it will cause the rest
> of the paragraph in which this user's name appears to come out backwards.
> However, putting each user name in an isolate will prevent that - but only
> if option 2 is used. The symmetrical approach does not have that property."
> ****
>
> The sequence is:    [BDI]Having fun[RLO][PDI] ****
>
> In option 3 (symmetric approach), the handler for PDI will detect that
> there is an unbalanced RLO and will close it.****
>
> The algorithm is: ****
>
> -        When encountering PDI, go back to the last BDI and close every
> open scope since the last BDI.****
>
> -        When encountering PDF, go back to the last LRE/RLE/LRO/RLO and
> close every open scope since that last formatting character.****
>
> In the last 2 sentences, "scope" includes embeddings, overrides and
> isolates.****
>
> ** **
>
> I also very much favor keeping CSS in sync with Unicode formatting
> characters behavior, and vice versa. I think this can be achieved with
> option 3 no less than with option 2.****
>
> ** **
>
> ** **
>
> Shalom (Regards),  *Mati*****
>
> ** **
>
> *From:* Aharon (Vladimir) Lanin [mailto:aharon@google.com<aharon@google.com>]
>
> *Sent:* Saturday, July 21, 2012 10:10 PM
> *To:* Matitiahu Allouche
> *Cc:* Glenn Adams; Martin J. Dürst; W3C style mailing list;
> public-i18n-bidi@w3.org
> *Subject:* Re: Proposal for isolation characters in Unicode and the
> unicode-bidi:isolate and unicode-bidi:plaintext definitions****
>
> ** **
>
> The idea behind the choice of options 2 is that an isolate would protect
> its surroundings against extra or missing PDFs in it contents. For example,
> if I have a site that displays the name of a user, and some user codes
> their name as "Having fun[RLO]", it will cause the rest of the paragraph in
> which this user's name appears to come out backwards. However, putting each
> user name in an isolate will prevent that - but only if option 2 is used.
> The symmetrical approach does not have that property. Also note that the
> current specification of CSS isolates (separate bidi paragraphs) also has
> this property, so retaining it means that changing the CSS spec to use
> Unicode isolates will have fewer visible effects. In all honesty, this is
> the part that appeals to me most about option 2.****
>
> ** **
>
> ** **
>
> On Fri, Jul 20, 2012 at 7:21 PM, Matitiahu Allouche <
> matitiahu.allouche@gmail.com> wrote:****
>
> I am late joining this discussion, because I did not see really compelling
> arguments in favor of option 1 rather option 2 or vice versa.****
>
> Just to add to the fun, I want to suggest a third option: in the case of
> improperly  nested embeddings/overrides/isolates, both PDF **and** PDI
> will close all unmatched controls.****
>
> Going back to examples a and b:****
>
> a: RLI LRE PDI PDF****
>
> b: RLE LRI PDF PDI****
>
>  ****
>
> In example a, the PDI will close the RLI and the LRE, PDF does nothing.***
> *
>
> In example b, the PDF will close the LRI and the RLE, PDI does nothing.***
> *
>
> If nothing else, this option has the merit of symmetry.****
>
> However, I am not in mad love with it, and I can live with either one of 1
> or 2.****
>
>  ****
>
>  ****
>
> Shalom (Regards),  *Mati*****
>
>  ****
>
> *From:* Glenn Adams [mailto:glenn@skynav.com]
> *Sent:* Monday, July 09, 2012 5:07 PM
> *To:* Aharon (Vladimir) Lanin
> *Cc:* Martin J. Dürst; W3C style mailing list; public-i18n-bidi@w3.org
> *Subject:* Re: Proposal for isolation characters in Unicode and the
> unicode-bidi:isolate and unicode-bidi:plaintext definitions****
>
>  ****
>
>  ****
>
> On Mon, Jul 9, 2012 at 12:28 AM, Aharon (Vladimir) Lanin <
> aharon@google.com> wrote:****
>
> > I don't understand your logic. You say option 2 offers greater forward
> compatibility,****
>
> > but then say you are choosing 2 because forward compatibility is NOT
> important.****
>
>  ****
>
> Not because it isn't important, but because in certain cases is LESS
> important than another consideration. It's a trade-off.****
>
>  ****
>
> In other words, I think that well-formed documents, i.e. ones where
> isolates and embeddings/overrides are properly nested, should display as
> well as possible on systems that do not support isolates. That is why the
> proposal has been modified to include PDI. On the other hand, when it comes
> to essentially broken documents, where embeddings/overrides and isolates
> are not properly nested, I think it is more important to let isolates do
> their job and isolate the missing and extra PDFs in the apps that do
> support isolates than to make the document display as similarly as possible
> on old and new apps, when apps that don't understand isolates can't
> possibly display the document 100% as intended anyway.****
>
>  > I think backward compatibility is more desirable, i.e., a system that
> knows nothing of****
>
> > isolates should work without modification,****
>
>  By definition, it can't display the document 100% as intended. We
> introduce PDI is so its disability is limited to displaying isolates
> incorrectly (but then limit this to when isolates and embeddings/overrides
> are properly nested).****
>
>  > and yet option 2 requires PDI to close an embedding/override,****
>
>  Only when the isolate began before the embedding/override. If we have LRE
> RLI PDI PDF, the PDI only closes the isolate, not the embedding.****
>
>  That stills leaves that case where pre-PDI implementations would behave
> differently than PDI aware implementations, since the former would not
> close the embedding/override at the same position. I believe that may be a
> problem, and should be avoided.****
>
>
>
Received on Monday, 23 July 2012 06:53:49 GMT

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