[Justfont] Internet Media type for font collections

[Chris Lilley <[e-mail]>]

Hello,

It is unclear in the current spec what Internet media Type to use for
Collections (previously, TrueType Collections but now expanded to
OpenType as well). I can see several possibilities, which have
different impacts on the spec.

a) Just use font/truetype for TTC.
+ avoids adding another type
- no way to indicate support for collections in an Accept header
- complicates specifying a fragment identifier (only sometimes legal)

consequences:
  need to add .ttc to the file types section
  change fragment identifiers to allow an optional fragment (but only
  if ttc)

Similarly, just use font/opentype for OTC (is .otc the usual filetype?)
(same pluses, minuses and consequences as for TTC)

b) Same as a) but add a parameter like collection="true" or something.
I don't like this option, partly because params are often awkward to
configure on servers and tend to be little used (or hard coded to
particular filetypes) and also because it has all the disadvantages of
a) regarding optional fragments.

c) Define two new media types, for TTC (TrueType outlines, no OpenType
layout) and for OTC (CFF or TTF outlines, OpenType Layout)
- two more types (but at least, no parameters)
+ easy to map to existing filetypes .ttc .otc
+ fragment identifier easy to specify (numeric, the n'th font in the
collection where n starts at one. If omitted, same as #1)
+ Easy to use in an Accept header

Option c) is my preferred option, would be interested to hear what
others think.

This refers to github issues:
   Media type for OpenType collections #6
   https://github.com/svgeesus/ietf-justfont/issues/6

    Fragment syntax for collections #7
    https://github.com/svgeesus/ietf-justfont/issues/7

although the main question for #7 is what media type to put the
fragment syntax onto. The actual syntax of #1, #2 is uncontroversial
and already used (but as a non-normative example) in CSS3 Fonts.

-- 
Best regards,
 Chris  Lilley
 Technical Director, W3C Interaction Domain