COLR: incorporate revised semantics for sweep gradients to align with CSS

[PeterCon]

In discussion with Google, it was found that the spec for sweep gradients was potentially confusing because of ways in which it diverged from the way sweep gradients are expressed in CSS and also in Skia. This was due to misunderstanding of the (unfortunately vague) Skia spec when COLR v1 formats were being defined. To minimize confusion, and since implementations for COLR v1 are still very early in their development, Microsoft and Google agreed to make a breaking change in the semantics for representation of sweep gradients.

Note: The formats for representing sweep gradients (PaintSweepGradient, PaintVarSweepGradient) do not need to change. The only change is to how member values are interpreted.

The draft changes from googlefonts/colr-gradients-spec#362 need to be incorporated into OT 1.9.1.

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Document Details

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• ID: be879f46-c026-4a9d-1156-a3c98ae8f429
• Version Independent ID: 28be1ce2-e487-b652-632f-e4dc5bb17f42
• Content: COLR - Color Table (OpenType 1.9) - Typography
• Content Source: typographydocs/opentype/spec/colr.md
• Product: typography
• GitHub Login: @PeterCon
• Microsoft Alias: alib

[PeterCon]

See the OT 1.9.1 alpha for draft revisions addressing this issue.

[PeterCon]

This is fixed in OT 1.9.1. See the OT 1.9.1 beta for draft revisions addressing this issue.