The pencil: a click-to-insert that composes the two inverses — staff_pitch_at
(the natural pitch at the height) and position_at (the grid-snapped onset) —
into a fresh CMN note (duration = grid step) in the staff's primary voice, and
makes room under the overwrite policy as one atomic transaction.
Make-room over the overlapping notes/rests of the voice: a fully-covered event
is deleted; one the new note partially overlaps is trimmed (a phase-3
ModifyEvent placement change); one the new note lands inside is split — the
original is trimmed to its head and its tail re-inserted. A split tail is a
clone of the original event's whole shape (a rest's visibility, a note's
articulations/dynamics/stem/grace) with fresh event and pitch ids, and any
authored spelling is carried onto the fresh pitches via RespellPitch (an
inferred spelling re-derives) — the same atomic copy insert_note_after_selection
does. The several ids minted in one intent advance local checked counters, since
the session high-water mark does not move until commit.
Refuses cleanly rather than corrupt: an overlapped tuplet member raises
OverlapsTuplet (ratio compensation is out of scope); an off-staff or non-metric
click, or a non-note/rest overlap, raises NoInsertTarget.
Tests (against valid_score's tuplet-free metric region; the rich fixture's only
metric region is a triplet): empty-space insert, full-cover overwrite, the split
structure, the split tail's shape fidelity and authored-spelling carry, the
tuplet refusal, and the non-metric refusal. A click_for_position helper inverts
position_at so a test targets an exact onset.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NAtEiJtt9yKVV1zjKYmZhS
Levi Neuwirth
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