OpenType Feature Format

Michael Jarboe

I was looking closer at an OpenType 'zero' feature for the slashed zero replacement and realized it was written out using each grouping bracketed rather than having each separate grouping designated as a class.

Written like

sub [zero zero.op zero.lt] by [slashzero slashzero.op zeroslash.lt] 

as opposed to

sub @zero1 by @zero2

I was just curious about this as it all gets decompiled so is it simply a case of the feature being easy enough to write out vs. using classes?

Erin McLaughlin

Yes, they're the same. Probably just a short enough list that someone didn't want to write a class.

Khaled Hosny

Both lines  are using classes, the first are just unnamed classes. But anyway it is just syntactic sugar, substitution lookups does not use classes, so both are the same as:

sub zero    by slashzero;
sub zero.op by slashzero.op;
sub zero.lt by zeroslash.lt;

María Ramos

The good thing about creating classes is that you can use it in different lookups, without having to write the groups down more than once. If you are just going to use that group just once then you don't need a class.