Bug 203768 – Safari/WebKit not rendering glyph substitution (GSUB) correctly in variable fonts

• Component: Text
• Status: RESOLVED DUPLICATE

[Stephen Nixon]

Created attachment 382639 [details]
screenshot of website demonstrating Safari mishandling GSUB in variable font

Interactive HTML bug report: https://arrowtype.github.io/recursive/gsub-bug-and-hack_fix-safari/index.html

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Summary:

Glyph substitution (GSUB) in variable fonts occurs when a character's shape is changed in a non-compatible way. Put simply, GSUB is when shape changes dramatically, rather than gradually, along an axis.

GSUB does work with multiple characters, BUT it fails if a string contains only one character.

This behavior is problematic for any websites that are demonstrating font design, or in any user-editable text field that may have 1 character at any given time, which may require GSUB to be activated to correct display.

As of Nov 1, 2019, this test fails in:

• Safari on macOS, Version 12.1.1 (14607.2.6.1.1)
• Safari Technology Preview, Release 95 (Safari 13.1, WebKit 14609.1.7)
• Safari in iOS 13.1.3

[Myles C. Maxfield]

*** This bug has been marked as a duplicate of bug 186804 ***

[Stephen Nixon]

Thanks for sorting this as a duplicate, Myles! Good to realize you already knew about it.