[MPEG-OTSPEC] comments wrt wide glyph ID proposal

[Simon Cozens]

On 12/12/2023 02:54, Peter Constable wrote:
> This may be an opportunity to deprecate certain formats from use in 
> wide-GID fonts. E.g., GSUB type 5 and GPOS type 7 (contextual) were 
> effectively obsoleted when the chaining contextual formats were added. 

My understanding is that OFF often contains multiple ways of doing the 
same thing, to give font producers opportunities to produce the most 
efficient binary representation. (for example, cmap subtables). These 
"obsolete" layout table formats can be used for the same purpose; 
fontTools has code to select the most efficient representation of 
chaining subtable and I've used it to knock quite a few bytes of fonts 
which make heavy use of chaining rules.

So I don't see a reason for taking these away; even if you want to do 
that, the change is not germane to wide glyph IDs. I'm in favour of 
keeping the scope of the change focused.

Simon