[behdad]

Full COLRv1 instances must clamp alpha to [0, 1], while rotation and skew angles must preserve their periodic effect when variation takes them outside the stored F2Dot14 range. Skera previously used the same signed-width clamp for all of these fields, changing rotations above 360 degrees.

Clamp solid and gradient alpha only after full instancing. Preserve the unclamped base in partial instances because retained axes can bring it back into range. Normalize rotation and skew angles modulo 720 degrees before narrowing to F2Dot14, matching HarfBuzz's periodic representation.

Validation: focused color instancing tests, clippy, rustfmt, and typos pass. A synthetic two-axis font checks positive and negative alpha, gradient stops, and partial-then-full recovery of a base alpha of 1.5. A fresh HarfBuzz reference checks rotations above the stored angle range. The new angle test fails before this change.

The synthetic font was generated with fontTools FontBuilder; its weight and width rows respectively increase and decrease the first alpha. It is also used for a HarfBuzz regression fix.

Stacked on #2282.

Readers use read-fonts directly. write-fonts handles font assembly and owned table rebuilding; Skera retains its direct serializers and repacker. There is no separate generated Skera table tree.

[behdad]

Self-review in progress: full-instance alpha clamping and preserving an out-of-range but representable partial base are appropriate; rotation/skew wrapping by 720 degrees preserves their periodic effect within F2Dot14.

The new angle helper still adds 0.5 in float32 before flooring. It needs the same widened rounding boundary now moved into #2282. I will add a condition-independent scalar-product case that produces 0.5's immediate float32 predecessor, then use the shared helper. I am also checking partial alpha values beyond F2Dot14's storage range; keeping a base such as 1.5 does not by itself establish that larger intermediate values survive serialization.

[behdad]

Superseded by the rebuilt, consolidated instancing stack in #2416–#2423. MATH and name-table overrides remain separately covered by #2415 and #2411.