Behdad Esfahbod behdad at behdad.org
Fri May 16 21:07:12 CEST 2014

On 14-05-16 11:52 AM, Simon Daniels MSFT wrote:
> As mentioned DSIG is currently the defined way to differentiate between an
> OpenType font and a TrueType font, and some apps use the presence of the table
> to treat the font differently than a regular TrueType font. By definition all
> OpenType CFF fonts are OpenType, so DSIG isn’t needed.

Thanks everyone for your replies.  So, from what I've read now, my
understanding is that the main functional different is that Word and possibly
other Office apps (which versions) will not expose GSUB/GPOS functionality if
the font has TrueType outlines and no DSIG table.

> Any proposal to deprecate DSIG would need to come up with a bullet proof
> mechanism to differentiate between TrueType and OpenType,

I disagree!  OpenType is by design backward-compatible with TrueType.  Ie. an
OpenType font without GSUB/GPOS is indistinguishable from a TrueType font.
They are by definition the same.  *Why* would one care about the distinction


> and not break app
> behavior, or user expectations - eg. how would a customer react if a font
> identified as OpenType today, became a TrueType font tomorrow if the new spec
> defined OpenType as being a font that includes GSUB or GPOS? What would we
> then call an OpenType CFF font that didn’t include GPOS or GSU?
> Regardless I would be interested in seeing a proposal written up.
> Cheers, Si


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