Add an OpenType Math version: Source Serif Pro Math

[be5invis]

So that SSP could be used in academic papers.

[frankrolf]

@be5invis Thank you for this suggestion.
A good start would be identifying characters to be created, and their purpose. In addition to that, links to reference material would be appreciated.

[dchenk]

Microsoft Word has a wonderful equation editor, which typesets mathematical and scientific symbols beautifully. But it looks good only with Cambria, because other fonts lack the necessary characters. It'd be great to do equation typesetting with SSP. :)

[be5invis]

@frankrolf I think we can start with the charset of Cambria Math.

[frankrolf]

Here is some related material:
http://typeculture.com/academic-resource/articles-essays/three-typefaces-for-mathematics/
http://www.tiro.com/Articles/Word_to_InD_Math.pdf

The character set of Cambria Math:
https://web.archive.org/web/20070724002846/http://www.tiro.nu/Articles/Cambria/Cambria_Math_Basic_Spec_V1.pdf

[KrasnayaPloshchad]

Here is some instructions from Microsoft:
https://docs.microsoft.com/en-us/typography/opentype/spec/math

Here are some instruction for necessary character set for Math font, published by Unicode Consortium:
https://www.unicode.org/reports/tr25/
https://www.unicode.org/notes/tn28/

There are some TeX engine can make use of OpenType Math technology to present math formulars, especially XeTeX and LuaTeX. Althrough LibreOffice doesn’t support OT Math natively, it’s still able to insert math formula via TexMaths, which can calling XeLaTeX to generete a formula, and you can specifying fonts if you set to use XeLaTeX.
Firefox can also make use of OT Math to render MathML, based on the HarfBuzz library. You will see the effect if you open this page in Firefox.

[RuixiZhang42]

In terms of the design, Minion Math’s website has two presentation slides from the designer:

• http://www.typoma.com/publ/20040430-bachotex.pdf
• http://www.typoma.com/publ/20041002-atypi.pdf

Some of the features I find important are

1. Optical sizes for first- and second-order sub/superscripts.
2. Real Math Italic instead of Text Italic (see also Real Math Italic? firamath/firamath#38 where I have compared three groups of typefaces).
3. Larger/legible but consistent math operators, see Mathematical operators fixed and redesigned alerque/libertinus#272
4. Not all math layout engines support kerning with OpenType math font (see Math font side bearing alerque/libertinus#273), so there is a hassle between side-bearing and glyph adjustment.

In terms of glyph coverage, the specimen of Minion Math is a good reference: http://www.typoma.com/data/MinionMath_Release_1_026.pdf

[amoschou]

The other professionally designed OpenType maths font which could be consulted/referenced is STIX Two Math (https://github.com/stipub/stixfonts) designed by Tiro Typeworks. Its glyph chart is at https://github.com/stipub/stixfonts/blob/master/docs/charts/StixTwoMath.pdf.

[twardoch]

The bulk of OpenType Math fonts consists of including serif roman, italic, bold and bold italic, plus sans roman, italic, bold and bold italic, plus a special double-striked alphabet, plus a script plus a fraktur. Then there are "generic" symbols that are effectively monoline. And only a comparably small part needs to be designed uniquely, or could be borrowed from another font and adapted.

A good reference for a basic OpenType Math glyph set is the TG Schola Math, based on the URW opensource version of Century Schoolbook — which is a design that’s a very distant cousin to Source Serif. Given that IBM Plex Serif is also a distant cousin, perhaps an effort could be made to make Source Serif Math and IBM Plex Serif Math together. I think many of the special symbols could have a shared design base. The sans counterparts would most likely come from the respective sans fonts (Source and Plex). We’d need to source a script and a fraktur (could be borrowed from STIX Two or from some existing OFL design).

[twardoch]

Link to TG Schola Math http://www.gust.org.pl/projects/e-foundry/tg-math/download/index_html#Schola_Math

[kauesena]

This font would be a great addition for mathematical typesetting. Is there still the intention of making SSP into a OpenType Math font? I would like to help.

[mdeff]

Characters to be designed, reference material, and other resources can be found at IBM/plex#250.

Work on IBM Plex is planned to start in Q1 2022, and Google is actively working on Noto Sans Math. As a scientist, I'm quite excited at the possibility to "soon" have multiple professionally developed OpenType Math typefaces in addition to Cambria Math and STIX Two Math. Thanks for your work on Source Serif!