Optical size API, hooked up to CoreText (was Support AAT trak table)

[drott]

Part of crbug.com/627609 seems to be about trak table support for the San Francisco font. We currently lack support for this in hb-coretext.

[drott]

Discussed with Behdad: resolution would be to shape at intended point size using the CTFont, so that CoreText can apply correct advance width tracking. On the Blink side, we calculate a pt size from the CSS pixels, using the fixed 96dpi assumed screen pixel density of the CSS reference pixel.

[drott]

Behdad, any update? We're receiving some requests in Chrome to prioritise this. Thank you!

[behdad]

A few weeks...

[aziz]

Any update on this? Chrome still has major kerning issues rendering "San Fransisco" font on macOS

[behdad]

Soonish.. :)