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<div class="moz-cite-prefix">On 21082020 8:21 pm, Dave Crossland
wrote:<br>
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<blockquote type="cite"
cite="mid:CAOgqPYe_PvyiuyQnrMB=F5WVTzShn-2KfHEv5s1GQLggbZd0Dw@mail.gmail.com">
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<div dir="ltr">On Fri, Aug 21, 2020, 4:55 PM Andrew Glass <<a
href="mailto:Andrew.Glass@microsoft.com"
moz-do-not-send="true">Andrew.Glass@microsoft.com</a>>
wrote:<br>
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<blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px
solid rgb(204,204,204);padding-left:1ex">I agree with John,
existing engines need to be maintained so long as existing
fonts would not be 100% compatible if shaped via USE. That
is certainly the case for Indic 1 & 2 tags, hence the
goal of supporting Indic 3 via USE. <br>
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<div dir="auto">I'm confused - it seems from a discussion on
another thread (below) that "indic 3" was an idea floated a a
few years ago, but it's been at a dead stop for a while... Is
that right?</div>
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<div dir="auto">I'm guessing because of the regression risk to
existing working fonts?</div>
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<p>No. The whole point of defining new script tags would be to avoid
compatibility issues for existing fonts, in the same way that
assigning the Indic 2 tags avoided breaking existing fonts using
Indic 1 shaping.</p>
<p>At the first OTWG meeting in April 2014—a whole day of which
ended up being mostly about USE, which at that stage wasn't
implemented in any shipping products—Andrew suggested the future
possibility of passing already supported scripts like Devanagari,
Bengali, etc. to USE. At the time, I recall some questions about
what benefit there would be to this, given that working solutions
for those scripts already existed, but I don't remember who asked
that. Andrew suggested some reasons, but I can't recall what they
were. Andrew?<br>
</p>
<p>It was some time later, when Ned implemented USE in Core Text,
that he included the option to use unofficial Indic 3 tags to pass
scripts to USE. I did some experiments with this, notably with
Kannada fonts, which turned out to need radically different OTL in
order to work in USE. So I'm not in any rush to commit to spending
time doing Indic 3 implementations for fonts that already work
fine with Indic 2. [Note that in addition to registering the tags,
USE data for the characters would need to be agreed; as I recall,
there was a HarfBuzz issue related to that with proposed values.]<br>
</p>
<p>I think there are two reasons why registering the Indic 3 tags
has stalled: the general reason that everything else has stalled,
and the specific reason that there isn't a very compelling case to
inspire font makers to do something radically different when what
they're doing already works.<br>
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<p>JH<br>
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<pre class="moz-signature" cols="72">--
John Hudson
Tiro Typeworks Ltd <a class="moz-txt-link-abbreviated" href="http://www.tiro.com">www.tiro.com</a>
Salish Sea, BC <a class="moz-txt-link-abbreviated" href="mailto:tiro@tiro.com">tiro@tiro.com</a>
NOTE: In the interests of productivity, I am currently
dealing with email on only two days per week, usually
Monday and Thursday unless this schedule is disrupted
by travel. If you need to contact me urgently, please
use some other method of communication. Thank you.</pre>
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