[MPEG-OTSPEC] Vertical Writing: Character Orientations are Sometimes Uncontrollable

[David Singer]

I’m not an expert here, but it does seem to me that
* behavior should only be embedded in fonts if it is expected to vary between fonts; constant properties of characters that are independent of fonts should be expressed once
* it should be possible (e.g. by user-side style-sheet) to substitute a font (from the one the author expected or previewed with) and still get correct layout

> On Aug 7, 2020, at 19:41 , Eric Muller <eric.muller at efele.net> wrote:
> The link between layout engines and fonts is the 'vert' feature. So what Murata-san wants is for the 'vert' feature to behave according to some known fixed rules (of course, the UAX50 rules are an obvious choice, but by no means necessary), rather than the current situation where MS Mincho does it one way and Meiryo does it another way. I can only see two solutions, after having picked the rules: 1) we fix the fonts that do not follow the rules or 2) we switch to a new feature that specifically imposes the rules (and may be fallback to 'vert') . I suspect that 1) is not an option.

Which leads me to suspect that (2) is better than (1).

David Singer
Manager, Software Standards, Apple Inc.