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Re: [ft-devel] Starting work on the OpenType code


From: mpsuzuki
Subject: Re: [ft-devel] Starting work on the OpenType code
Date: Thu, 7 Apr 2005 19:36:36 +0900

Dear FT Maintainers

Now I'm starting to work for AAT/TrueTypeGX validator, in conjunction
with Masatake Yamato. The discussion about the future of OT validator
is interesting. Please let me ask a silly question about the policy of
validation.

Taking a glance on OT validator, its error status is only
FT_INVALID_FORMAT (when version is undefined) or FT_INVALID_DATA
(everything except of FT_INVALID_FORMAT). I think the data structure
of OpenType tables are designed to be simple and these 2 error status
is enough.

In the case of GX extensions, the tables are much complexed, and
validation result can be more varied. For example:

1) all data declared/defined by index/header were red,
   but unnessessary paddings are found.

2) all data declared/defined by index/header were red,
   but required/advised 32bit alignment is violated.

The handling of case 1) is questionable. There's no violation against
GX spec, but there might be poor implementation which expects only the
meaningful data are combined without padding.

The validation result should be defined from the viewpoint of font
format specification? Or, the validator should consider the fragile
font driver?

Regards,

mpsuzuki



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