Re: font features in CSS

fantasai wrote:

> Right. We don't have toggles. We do have presence=ON, absence=OFF for
> many things. However, it seems we're dealing with a tri-state here,
> not a boolean: ON, OFF, and DEFAULT.

OpenType Layout features can be categorised as:

On by default; cannot be turned off (e.g. <rlig> or the core Arabic and 
Indic script shaping features).

On by default; can be turned off (e.g. <liga>)

Off by default; can be turned on (e.g. <dlig>


For those that can be turned on, most would be expected to be 
user-triggered, but some could be heuristically invoked. For example, 
the <case> feature might be triggered by all-caps setting.

JH