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<div class="moz-cite-prefix">On 14092020 11:29 am, Peter Constable
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:MWHPR1301MB211297A75405E3954B3151EF86230@MWHPR1301MB2112.namprd13.prod.outlook.com">
<p class="MsoNormal"><span lang="EN-CA">Is the ‘curs’ feature
considered a required feature for Arabic or other
cursively-connecting scripts?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA"><o:p> </o:p>I would have
expected it’s required. It’s clear the intent is for
triggering cursive attachment positioning (GPOS type 3), and
<a
href="https://docs.microsoft.com/en-us/typography/script-development/arabic"
moz-do-not-send="true">Microsoft’s Arabic implementation
spec</a> lists it among features to be applied in GPOS
processing. But the
<a
href="https://docs.microsoft.com/en-us/typography/opentype/spec/features_ae#tag-curs"
moz-do-not-send="true">
description in the OTL feature registry</a> is worded in a
way that makes it sound optional, at the user’s discretion:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA"><o:p> </o:p>“</span><em><span
style="font-size:12.0pt;font-family:"Segoe
UI",sans-serif;color:#171717;background:white">UI
suggestion:</span></em><span
style="font-size:12.0pt;font-family:"Segoe
UI",sans-serif;color:#171717;background:white"> This
feature could be made active or inactive by default, at the
user’s preference.</span><span lang="EN-CA">”</span></p>
</blockquote>
<p>Based on Arabic fonts I have worked on or examined, I would say
this definitely should not be optionally active, and if present
the curs feature is expected to be applied by default. Indeed, a
lot of fonts simply break if curs is not applied.</p>
<p>If a font contains support for different kinds of Arabic layout,
e.g. a simplified layout with only horizontal connections and a
more sophisticated display with some amount of vertical
connections or cascading connections, then the curs support
required for the latter still needs to be applied by default, and
the differentiation of the layout styles would be implemented,
somehow, in GSUB, setting up the glyphs that either will or will
not require curs attachment in GPOS.</p>
<p>JH</p>
<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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