[MPEG-OTSPEC] STAT instances, fvar instances and auto optical sizing

[Adam Twardoch]

1. Let's say a font has the wght axis with the STAT instances "Light",
"(Regular)" (elided) and "Bold". It again has the opsz axis with the STAT
instances "Small", "(Text)" and "Display".

The fvar instances permute those, so:
- Shall Light
- Light
- Display Light
- Small
- Regular (from elided fallback)
- Display
- Small Bold
- Bold
- Display Bold

2. Let’s say a desktop app implements behavior like CSS
"font-optical-sizing: auto", i.e. the app automatically chooses an "opsz"
value based on the font size (let’s disregard the question of specific
units).

3. Let's say the app implements a STAT-based style selection UI, with one
drop-down per STAT axis. In this model, it seems that the opsz drop-down,
should list Small, Text, Display AND should have an extra entry "Auto"
which makes it work like "font-optical-sizing: auto". Do you agree? I think
that's reasonable enough. Then, if any of the other opsz entries are
chosen, opsz would be frozen at the associated STAT value.

4. But what should be done in a model that lists fvar instances as styles?
Every fvar instance IS tied to some opsz value. So would the recommended UX
be that there is some kind of "checkbox" somewhere that basically says
"Font size chooses optical size" or something, and THEN choosing the
"Small" style vs. the "Display" style would have no visual effect?


-- 
Adam Twardoch
http://www.twardoch.com/


-- 
Adam Twardoch
http://www.twardoch.com/
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