Re: DSIG and other issues

My understanding of the thread is that some or all versions of MS Office
(quite possibly only MS Word) make a decision regarding whether to use
OpenType Layout features for Latin and other simple scripts based on the
presence of a DSIG table in a TrueType-outlines OpenType font.

My personal conclusion is that this has no implications on webfonts and as
such should be ignored.

My recommendation is that the spec be changed, to recommend that if the
original font had a DSIG table, then all signatures in the DSIG table be
removed.  Ie. an encoder is encouraged to keep an a DSIG table with zero
signatures.  That's a valid table that is only eight bytes.  (00 00 00 01
00 00 00 00).

behdad


On Wed, May 21, 2014 at 1:26 PM, Levantovsky, Vladimir <
Vladimir.Levantovsky@monotype.com> wrote:

> On Tuesday, May 20, 2014 10:17 PM Chris Lilley wrote:
>
> On Wednesday, May 21, 2014, 12:33:06 AM, Vladimir wrote:
>
> >  It is not
> > clear whether only certain applications are affected, or any that use
> > the underlying Win API, but this is something we may need to
> > investigate because of the WOFF2 spec recommendation to remove DSIG
> > because it will be compromised  by pre-processing and reconstruction
> > steps. What we may consider instead (or in addition to) is to remove
> > the DSIG table while encoding a font and recreate a dummy DSIG (if the
> > original font had it) to preserve font compatibility with Win API.
>
> That is a) gross and b) will be removed again by the font validators that
> are commonly used to check downloaded fonts.
>
> Okay, I should have made myself clear and explain what I had in mind in
> more details. One possible way to remedy the problem is to:
> - indicate whether the original font had DSIG table or not. If yes, the
> DSIG presence would be recorded by the encoder in the table directory but
> without the actual DSIG table present (which is similar to the way we treat
> the 'loca' table today);
> - if DISG was present in the original font, the decoder would have to
> resign the font according to the algorithms specified by the DSIG table
> specification (http://www.microsoft.com/typography/otspec/dsig.htm).
>
> I believe this approach should be perfectly compatible with the spec and
> with the current implementations.
>
> Thank you
> Vlad
>
>