[MPEG-OTSPEC] Some research on TT instructions and cubics

[Liam R. E. Quin]

On Sat, 2023-09-23 at 18:37 +0100, Jonathan Kew wrote:
> 
> IMO: I think the spec should *either* state that if the glyph data 
> violates these "must" requirements, nothing will be rendered for that
> glyph; *or else* it should clearly specify how "anomalous" cases --
> such as the CUBIC flag being set on a single off-curve point -- are
> to be processed, so that implementations produce a consistent result.

I’m fine with adding more text, and with seeing the spec tightened up;
that's why it's a draft, of course.

> One possible way forward, for example, would be to specify that for
> any contour where the CUBIC flag is used in violation of the rules
> given, all CUBIC flags must be ignored and the contour processed
> entirely according to legacy TrueType quadratic behavior.

That would be a possible implementation strategy given the current
draft, of course, and may be the best choice to make it easy to move to
using the GLYF table with existing font data.

liam



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