What is the time frame for USE shapers to provide support for CV+C ?

[Asmus Freytag (c) via Unicode]

On 8/7/2019 5:08 PM, Andrew Glass wrote:
>
> Shaping domain names is a new requirement. It would be good to 
> understand the specific cases that are falling in the gap here.
>
Domain names are simply strings, but the protocol enforces normalization 
to NFC. In some situations, it might be possible for a browser, for 
example, to have access to the user-provided string, but I can see any 
number of situations where the actual string (as stored in the DNS) 
would need to be displayed.

For the scenario, it does not matter whether it's NFC or NFD, what 
matters is that some particular un-normalized state would be lost; and 
therefore it would be bad if the result is that the string can no longer 
be rendered correctly.

In particular, as the strings in question would be identifiers, where 
accurate recognition is prime.

A./

> *From:*Unicode <unicode-bounces at unicode.org> *On Behalf Of *Asmus 
> Freytag via Unicode
> *Sent:* 07 August 2019 14:19
> *To:* unicode at unicode.org
> *Subject:* Re: What is the time frame for USE shapers to provide 
> support for CV+C ?
>
> What about text that must exist normalized for other purposes?
>
> Domain names must be normalized to NFC, for example. Will such strings 
> display correctly if passed to USE?
>
> A./
>
> On 8/7/2019 1:39 PM, Andrew Glass via Unicode wrote:
>
>     That's correct, the Microsoft implementation of USE spec does not normalize as part of the shaping process.
>
>     Why? Because the ccc system for non-Latin scripts is not a good mechanism for handling complex requirements for these writing systems and the effects of ccc-based normalization can disrupt authors intent. Unfortunately, because we cannot fix ccc values, shaping engines at Microsoft have ignored them. Therefore, recommendation for passing text to USE is to not normalize.
>
>     By the way, at the current time, I do not have a final consensus from Tai Tham experts and community on the changes required to support Tai Tham in USE. Therefore, I've not been able to make the changes proposed in this thread.
>
>     Cheers,
>
>     Andrew
>
>     -----Original Message-----
>
>     From: Richard Wordingham<richard.wordingham at ntlworld.com>  <mailto:richard.wordingham at ntlworld.com>  
>
>     Sent: 07 August 2019 13:29
>
>     To: Richard Wordingham via Unicode<unicode at unicode.org>  <mailto:unicode at unicode.org>
>
>     Cc: Andrew Glass<Andrew.Glass at microsoft.com>  <mailto:Andrew.Glass at microsoft.com>
>
>     Subject: Re: What is the time frame for USE shapers to provide support for CV+C ?
>
>     On Tue, 14 May 2019 03:08:04 +0100
>
>     Richard Wordingham via Unicode<unicode at unicode.org>  <mailto:unicode at unicode.org>  wrote:
>
>         On Tue, 14 May 2019 00:58:07 +0000
>
>         Andrew Glass via Unicode<unicode at unicode.org>  <mailto:unicode at unicode.org>  wrote:
>
>             Here is the essence of the initial changes needed to support CV+C.
>
>             Open to feedback.
>
>                *   Create new SAKOT class
>
>             SAKOT (Sk) based on UISC = Invisible_Stacker
>
>                *   Reduced HALANT class
>
>             Now only HALANT (H) based on UISC = Virama
>
>                *   Updated Standard cluster mode
>
>             [< R | CS >] < B | GB > [VS] (CMAbv)* (CMBlw)* (< < H | Sk > B | SUB
>
>                 [VS] (CMAbv)* (CMBlw)*)* [MPre] [MAbv] [MBlw] [MPst] (VPre)*
>
>                 (VAbv)* (VBlw)* (VPst)* (VMPre)* (VMAbv)* (VMBlw)* (VMPst)* (Sk
>
>                 B)* (FAbv)* (FBlw)* (FPst)* [FM]
>
>         This next question does not, I believe, affect HarfBuzz.  Will NFC
>
>         code render as well as unnormalised code?  In the first example above,
>
>         <TONE-2, SAKOT, LOW YA> normalises to <SAKOT, TONE-2, LOW YA>, which
>
>         does not match any portion of the regular expression.
>
>     Could someone answer this question, please?  The USE documentation ("CGJ handling will need to be updated if USE is modified to support
>
>     normalization") still implies that the USE does not respect canonical equivalence.
>
>     Richard.
>

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