[MPEG-OTSPEC] DSIG spec issue

[Levantovsky, Vladimir]

FWIW, the stripping of DISG is also a necessity for WOFF2. Due to transforms and data pre-processing / optimization steps applied as part of the WOFF2 encoding steps [that invalidate the DSIG], it is required that “the compliant WOFF2 encoder MUST remove the DSIG table from an input font data, prior to applying transformations and entropy coding steps.” (https://www.w3.org/TR/WOFF2/#table_format)

I’d say let’s deprecate DSIG once and for all.

Vlad


From: mpeg-otspec <mpeg-otspec-bounces at lists.aau.at> On Behalf Of Peter Constable
Sent: Wednesday, August 26, 2020 9:53 AM
To: Bobby de Vos <bobby_devos at sil.org>; Dave Crossland <dcrossland at google.com>; mpeg-otspec <mpeg-otspec at lists.aau.at>
Subject: Re: [MPEG-OTSPEC] DSIG spec issue

Office has a font service, serving fonts to (recent versions of) Office apps. My understanding is that they strip DSIG tables from fonts in the service. So, I would assume that recent versions of Office shouldn’t require DSIG tables to enable features in Latin fonts, though I haven’t confirmed that.

This is all product commentary: it can inform whether DSIG may still be relevant for fonts, though of course doesn’t belong in the spec itself.


Peter

From: Bobby de Vos <bobby_devos at sil.org<mailto:bobby_devos at sil.org>>
Sent: Wednesday, August 26, 2020 6:01 AM
To: Peter Constable <pgcon6 at msn.com<mailto:pgcon6 at msn.com>>; Dave Crossland <dcrossland at google.com<mailto:dcrossland at google.com>>; mpeg-otspec <mpeg-otspec at lists.aau.at<mailto:mpeg-otspec at lists.aau.at>>
Subject: Re: [MPEG-OTSPEC] DSIG spec issue


In addition to triggering the OpenType icon, a DSIG was (is?) needed in older versions of Microsoft Word to process some OpenType features in Latin script fonts.

https://github.com/googlefonts/fontbakery/issues/1845#issuecomment-564383952<https://protect-us.mimecast.com/s/Wqy2CwpA5KsGM0Z7IqyVTq>

As recently as Office 2013 this was the case, and Office 2013 has not reached end of life yet.
On 2020-08-25 8:01 p.m., Peter Constable wrote:
I think at one time, yes, but I don’t think that’s been relevant since Windows 7.


Peter

From: mpeg-otspec <mpeg-otspec-bounces at lists.aau.at><mailto:mpeg-otspec-bounces at lists.aau.at> On Behalf Of Dave Crossland
Sent: Tuesday, August 25, 2020 6:09 PM
To: mpeg-otspec <mpeg-otspec at lists.aau.at><mailto:mpeg-otspec at lists.aau.at>
Subject: Re: [MPEG-OTSPEC] DSIG spec issue

Wasn't there something about needing a DSIG table to trigger the OpenType icon in Windows Explorer?

--
Bobby de Vos
bobby_devos at sil.org<mailto:bobby_devos at sil.org>
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