Allowing DFLT to take languages

[Martin Hosken]

Dear Vlad,

Cross posted from Opentype list. So if you saw it there, there is no difference here :)

I would like to propose a content change to the OT spec.

In the section on Opentype Layout Common Table Formats, under Script List Table and Script Record, there is a paragraph that says:

If a Script table with the script tag 'DFLT' (default) is present in the ScriptList table, it must have a non-NULL DefaultLangSys and LangSysCount must be equal to 0. The 'DFLT' Script table should be used if there is not an explicit entry for the script being formatted.

I propose that the words "and LangSysCount must be equal to 0" be removed from the standard.

Rationale:

1. There is no technical reason for this limitation. All shaping engines support multiple languages for the DFLT script.
2. No applications (except OTS now) reject fonts on account of having a non-zero LangSysCount. This implies that this part of the standard is being ignored.
3. If DFLT is being used as a fallback shaper for a given script, as implied by the last sentence in the paragraph, then that text may also have languages associated with it, that need to be handled appropriately in the DFLT script just as they would for the actual script.

In summary, the ongoing inclusion of this restriction only causes problems and adds nothing of value to the standard. Hence I propose it be removed.

TIA,
Yours,
Martin