Re: [ft-devel] [FYI] MingLiU identifier

[mpsuzuki]

On Wed, 17 Nov 2010 07:55:17 -0500
David Bevan <address@hidden> wrote:
>> In general scope, I think, you raised a concern that
>> the checksum in TTF header is too simple (it's a sum
>> of 32-bit values of the table) to guarantee the identity.
>> It's reasonable.
>
>My concern is that the (small) tables may actually be
>the same in a variety of fonts.

Ah, I see. Your concern is not the conflict of the
checksum (or other hash value), but the conflict of
the table itself. To identify more correctly, other
tables (that are preserved in the subsetting) should
be compared... I'm understanding correctly?

>> If I check the fonts bundled to Microsoft Windows,
>> Mac OS (Classic & OS X), and distributed in GNU/Linux
>> distribution and I find no conflict, is it sufficient
>> guarantee? 
>
>That seems reasonable.

OK, I will try.

>> If not, I cannot access wider coverage
>> of the fonts, so, the possible solution would be...
>> 
>> 1) identify by family name comparison is used too,
>>    and add a fallback by sfnt table checksum.
>> 
>> 2) in addition to the tag-name of the table and
>>    the checksum, the length should be checked.
>>
>> 3) if it's still insufficient... should we use
>>    our own hash value instead of the checksum
>>    in sfnt header.
>
>Only 1) would address my concern.

1) is already implemented in my proof of concept patch.

http://lists.nongnu.org/archive/html/freetype-devel/2010-08/msg00019.html

Regards,
mpsuzuki