[mpeg-OTspec] [OpenType] TrueType-flavored ".otf"

[Ken Lunde]

John,

You wrote:

>> While we're on the subject of "Recommendations for OpenType Fonts," some of my recent work with TrueType has demonstrated that virtually all modern TrueType-capable environments no longer depend on or adhere to the "First Four Glyphs in Fonts" portion, specifically that GIDs 1 through 3 can be arbitrary glyphs. Only GID+0 (.notdef) must be present and must also function as the ".notdef" glyph. This reality brings TrueType in better line with PostScript-based fonts in which only GID+0 must be present and function as the ".notdef" glyph.
> 
> There remain workflow issues in this regard, and I've found it easier to 
> bring PS fonts in line with the old TTF requirement than the other way 
> round. The only time a client for CFF fonts has actually requested that 
> we not apply the first-four-glyphs rule was when we made fonts for 
> Adobe, which required us to manually rewrite the first part of the cmap 
> tables (using TTX at that time) after generating fonts from VOLT. While 
> the first-four-glyphs rule might no longer be a requirement for any 
> consuming software, does it do any harm at all?

Of course, there's no harm, but continuing to include such recommendations, particularly when they're no longer being enforced, doesn't seem to make much sense today. Consider converting PostScript-based fonts into TrueType. I work primarily with very large (in terms of the number of glyphs) CID-keyed fonts, and for such fonts, only CID+0 (GID+0) is fixed. All other glyphs are arbitrary. The benefit is that the GIDs can be preserved during the conversion process, which allows many of the tables, such as GSUB, GPOS, and cmap to name a few, to be used as-is. By enforcing GIDs 1 through 3, it requires that these tables be touched. Preserving GIDs makes the conversion cleaner, and *much* easier to test.

For font editing applications, a "preserve GIDs" option would be useful when opening a PostScript-based font then saving it as a TrueType font.

Anyway, we were on the subject of "Recommendations for OpenType Fonts," so this comment seemed timely and worthwhile to discuss.

Regards...

-- Ken