STIX fonts should use the ssty feature

[davidmjones]

From the Open Type MATH document:

"Script Style This feature provides glyph variants adjusted to be more suitable for use in subscripts and superscripts. These script style forms should not be scaled or moved in the font; scaling and moving them is done by the math handling client. Instead, the ssty feature should provide glyph forms that result in shapes that look good as superscripts and subscripts when scaled and positioned by the Math engine. When designing the script forms, the font developer may assume that MATH.MathConstants.ScriptPercentScaleDown and MATH.MathConstants.ScriptScriptPercentScaleDown will be the scaling factors used by the Math engine. This feature can have a parameter indicating the script level: 1 for simple subscripts and superscripts, 2 for second level subscripts and superscripts (that is, scripts on scripts), and so on. (Currently, only the first two alternates are used). For glyphs that are not covered by this feature, the original glyph is used in subscripts and superscripts. Recommended format: Alternate Substitution table (Single Substitution if there are no second level forms). There should be no context."

This is for example needed to get the right size of prime characters. See https://bugzilla.mozilla.org/show_bug.cgi?id=442637.

Apparently, some MATH fonts only enables that feature when the Math script tag is set. See http://www.microsoft.com/typography/otspec/scripttags.htm and https://bugzilla.mozilla.org/show_bug.cgi?id=953385.

Reported by: fred-wang

Original Ticket: stixfonts/tracking/48

[davidmjones]

This issue is targeted to be fixed in version 2.0.0 which is currently under development.

Original comment by: stipub

[davidmjones]

http://fred-wang.github.io/MathFonts/STIX/#scriptedop_ssty

Original comment by: fred-wang

[davidmjones]

• status: open --> closed-fixed

Original comment by: stipub

[davidmjones]

We believe that this issue has been addressed in version 2.0.0.

Original comment by: stipub