[MPEG-OTSPEC] VARC, glyf, and TT-instructions

[Greg Hitchcock]

Through a combination of the GETINFO instruction and the INSTCTRL instruction, glyphs or fonts can make educated decisions about whether to apply instructions under different circumstances such as rotations, stretching, &c. Typically we recommend in the pre-program to disable hints under rotation, but if someone comes up with a clever algorithm for handling this, that is an option.

GregH

From: mpeg-otspec <mpeg-otspec-bounces at lists.aau.at> On Behalf Of Skef Iterum via mpeg-otspec
Sent: Friday, January 26, 2024 11:33 AM
To: Laurence Penney <lorp at lorp.org>
Cc: mpeg-otspec <mpeg-otspec at lists.aau.at>
Subject: Re: [MPEG-OTSPEC] VARC, glyf, and TT-instructions

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On 1/24/24 23:47, Laurence Penney wrote:
On 25 Jan 2024, at 01:25, Skef Iterum via mpeg-otspec <mpeg-otspec at lists.aau.at><mailto:mpeg-otspec at lists.aau.at> wrote:
There is a distinction between whether the text path itself is skewed or
rotated and whether a component in a composite is skewed or rotated.
Asking around it seems as though with the existing glyf components
instructions are not automatically turned off when "compositing", but
perhaps that info is wrong.

Either way, though, that seems like something the specification should
clarify.
I asked similar questions when I was getting my head around TT hinting, and recall being told that skewed or rotated components were not hinted. The person I asked would most likely have been Greg Hitchcock.

Josh Hadley on our team got curious about this and did an experiment or two
in VTT. As far as we can tell there is no automatic disabling of hints when using
"not nice" transformations, at least in that tool. We can provide a specific
example or two if anyone needs them.

It's possible that the "client side" implementations work differently than the
development tools but designers are likely to take the guidance of those tools
unless there is very strong conventional wisdom pointing in a different
direction.

Skef
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