Prerequisite for the visible-slice engraving milestones (I-1+): give the
score graph the clef/key data the engrave pipeline needs for clef-relative
staff positioning and key-signature rendering, replacing the Chapter-7
TimeAnchor-only placeholders.
epiphany-core:
- ClefShape { G, F, C, Percussion } — each family's reference pitch (G4 / F3 /
middle C4) pins the staff-position mapping.
- Clef { shape, line, octave_shift } — the SMuFL family, the staff line its
reference pitch sits on (1 = bottom line), and an octave transposition; with
treble/bass/alto/tenor constructors and a treble Default. Generalizes to any
C-clef line and octave-transposing clefs.
- KeySignature — circle-of-fifths position, validated -7..=7: a private field
behind KeySignature::new (Option) + fifths(), and a custom Codec that rejects
an out-of-range count on decode (Reconstruct, as PowerOfTwo / Tempo do).
- ClefChange now carries clef: Clef; KeySignatureChange carries key: KeySignature.
- Codec (cstyle_enum_codec / struct_codec / the validating KeySignature impl),
lib.rs re-exports, a round-trip test over every shape x line x octave and every
fifths value, and an out-of-range decode-rejection regression test.
Zero blast radius: nothing constructed these with data (clef/key sequences are
always empty) and invariants only read .anchor, so existing Score bytes, hashes,
and goldens are unchanged. Fixtures get populated and the engrave pipeline reads
the data in I-1.
Gates: build/fmt/clippy -D warnings clean; cargo test --workspace green;
conformance_suite scale 1 passes. Stages only epiphany-core; the pre-existing
Agent-I working tree (engrave/layout-ir/render-svg + .gitignore) stays unstaged.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Levi Neuwirth
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