What is the current Unicode stance on subscripts and superscripts for mathematical use?

[Doug Ewell]

So, does that mean you don't think L2/18-206 will fly?

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<gd&r>

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Doug Ewell | Thornton, CO, US | ewellic.org

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-----Original Message-----
From: Unicore <unicore-bounces at unicode.org> On Behalf Of John Hudson via Unicore
Sent: Monday, June 22, 2020 10:48
To: unicore at unicode.org
Subject: Re: What is the current Unicode stance on subscripts and superscripts for mathematical use?

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Math layout and display needs to be able to handle essentially arbitrary

super- and subcript characters, and to do so at multiple levels of –script embedding, e.g. subscripts of superscripts. This requires specialised fonts as well as specialised layout engines. The method we use in OpenType math fonts, i.e. fonts containing a MATH table with extensive scaling and alignment data to be used by math layout engines, is to have variant full-size glyphs that are then scaled down to the superscript, subscript, superscriptscript, etc. sizes and positioned according to MATH table data and tolerances within the layout engines (e.g. some environments may allow for more vertically compressed positioning for inline equations).

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The set of variant glyphs provided for scaling to –script and –scriptscript size will vary depending on the font. If a font does not contain such variants for a given character, the layout engine will apply scaling (as defined in the MATH table) to the default glyph for that character.

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We're in the process of extending the STIX Two Math font with a large number of additional variants for –script and –scriptscript use, based on frequency analysis from the American Mathematical Society and other members of the STI Pub consortium. Latin and Greek letters are definitely among the most frequent superscript and subscript typeforms, but the overall list is very much larger, includes multiple styles of letters, as well as a variety of symbols and operators.

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J.

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John Hudson

Tiro Typeworks Ltd     <http://www.tiro.com> www.tiro.com

Salish Sea, BC         <mailto:tiro at tiro.com> tiro at tiro.com

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