Fwd: UAX#50 conformance: Is it possible to update existing fonts without causing damage to existing non-CSS applications?

---------- Forwarded message ---------
From: MURATA Makoto <eb2m-mrt@asahi-net.or.jp>
Date: 2019年11月25日(月) 13:35
Subject: UAX#50 conformance: Is it possible to update existing fonts
without causing damage to existing non-CSS applications?
To: Nat McCully <nmccully@adobe.com>
Cc: Taro Yamamoto <tyamamot@adobe.com>, Florian Rivoal <florian@rivoal.net>,
fantasai <fantasai@inkedblade.net>, MURATA Makoto (FAMILY Given) <
eb2m-mrt@asahi-net.or.jp>


Nat,

I am wondering what is needed from font people
(including the upcoming Joint Working Group of SC34
and SC29 about OpenType) about vertical writing.

First, here is my understanding of the issue.

Interactions between fonts and applications have
been vague historically.  They are not based on any
written contracts.  Font developers implement
OpenType features without knowing whether they are
used by applications; application programmers
implement text rendering without knowing whether
fonts provide relevant OpenType features.

Meanwhile, recent OWP requires fidelity among
different web browsers.  In other words, users
expect that different web browsers on different
platforms provide reasonably similar results.  Such
fidelity is hampered by vague interactions of
fonts and applications, however.

In particular, the Japanese publishing industry
requires fidelity among different EPUB readers as
far as character rotation in vertical writing is
concerned.  If enough fidelity is not available,
Japanese publishers dare to use character-like
images.

To provide more fidelity, CSS specifications start
to say more about fonts.  In particular, CSS
Writing Modes require that the vert feature of
OpenType must be enabled for upright typesetting.
CSS Writing Modes further mentions the vrtr feature
for sideways typesetting.  The choice of upright
and sideways by default is done by UAX#50 rather
than the vrt2 feature.  I also think that we have
to move away from vague interactions and establish
contracts between applications and fonts.

But OpenType fonts equipped with the vert feature
already exist.  In my understanding, such fonts do
not necessarily do what CSS Writing Modes expect.
CSS people hope that existing OpenType fonts are
updated as required by CSS Writing Modes.

I have discussed with Yamamoto-san of Adobe.  He
strongly feels that it is impossible to update
existing fonts without causing damage to existing
non-CSS applications.  I assume that his opinion is
based on discussions internal to Adobe.

If existing fonts cannot be updated as required by
CSS Writing Modes and UTS#50, what should we do?
I am wondering if we should introduce yet another
feature (maybe "cssVert").

Regards,
Makoto (promoting the JWG for OpenType from the SC34 side)


-- 
Regards,
Makoto