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

[Eric Muller]

On 8/6/2020 3:11 AM, 梁海 Liang Hai wrote:
> The behavior specified by UAX #50 is a decent low-level default at 
> most, and can’t address all the use cases. Therefore fonts naturally 
> need to be diverse and address the flexibility required by typography.

I disagree with the second sentence, when interpreted anywhere close to 
"fonts can do anything". We need fonts to do their part. If a U+0041 A 
LATIN CAPITAL LETTER A is displayed by a "B", we can clearly blame the 
font and declare it useless for rendering text. Similarly if "MANZANITA" 
is displayed at "MAZNAZITA" by the font deciding to rotate N and Z, we 
are in trouble.

I also disagree with the second sentence as a consequence of the first. 
UAX50 is not in control of the orientation. The author, via markup, is 
in control (at least, wants to be; that's implicit in Murata-san's 
presentation). UAX50 is there only to make the life of the author 
simpler, by minimizing markup. You can think of running a transformation 
on documents that inject explicit markup, according to UAX50, wherever 
the author did not explicitly put it. That document would have a precise 
meaning regardless of UAX50.

The way I see the current situation is that we have many fonts that 
predate the need for the author to control the orientation regardless of 
the font, rather than the author reacting to the font. The later is 
acceptable in the print world, where layout is done at "factory" time, 
the author (in a broad sense) can see exactly what the reader will see, 
and can adjust his document to the font. It is problematic in the 
ebook/web world where the layout is done at "reading" time, with pieces 
or behaviors that the author does not always control (in particular 
fonts). In that world, we need fonts (and layout engines) that respect 
precisely the orientation chosen by the author (and of course document 
formats that let him or her express the desired orientation)

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.

Eric.