WebKit does not activate small-caps for AAT fonts

[Dominik Röttsches (drott)]

1) Go to https://codepen.io/anon/pen/VEoVOp
2) Observe and compare letter shapes in first against second line, third against fourth line

Expected result:
Letter shapes for the word CURSIVE for first and second line differ, as the first and third line should activate and use the small-caps glyphs contained in the Apple Chancery font.

Actual result:
Letter shapes identical between first and second line, the first line has "swashy" glyph terminals for U R V I, while it shouldn't since the small-caps glyphs do not have such ornamental terminals.
Letter shapes differ for 3rd and 4th line since actual small caps are used for OpenType GSUB based small-caps.

This is probably due to small-caps feature detection not recognising the feature in AAT fonts, so WebKit proceeds to synthesise small-caps.

[Dominik Röttsches (drott)]

Created attachment 353596 [details]
WebKit rendering, no small-caps activation for Chancery

[Dominik Röttsches (drott)]

Created attachment 353597 [details]
Expected result, small caps activated for Chancery

[Brent Fulgham]

Safari and Firefox agree on behavior here, Chrome seems to get the expected output.

[Radar WebKit Bug Importer]

<rdar://problem/96321004>