[ft-devel] Apple offset scaling

[Alexei Podtelezhnikov]

Hi Toshiya and Werner,

It is well known that offsets in composite or compound glyphs were
treated differently by AAPL and MSFT. The former scales them the
latter does not

This page describes offset scaling
https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6glyf.html#COMPOUNDGLYPHS
It is hard to comprehend and there are unfortunate mistakes in this description.

This page in the section "Compound glyphs with rotated components"
provides important additional details
https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6AATIntro.html
It actually becomes quite clear what was intended for 45-degree
rotations with double-scaling, which was later dropped.

George Williams contributed code to support this
http://lists.nongnu.org/archive/html/freetype-devel/2002-07/msg00084.html
It is apparent that George gave up on fixing mistakes in the first
page and went with his own solution, which for any simple rotation
would not scale offset at all. This sounds reasonable but it is not
what was intended in the specifications.

Do you have fonts to test?

Thank you,
Alexei