The rendered slurs were wrong in three independent ways, all visible in the
two-staff and three-staff goldens.
1. Side. SlurDirection::Auto always arced above. The single-voice rule is
OPPOSITE the stems -- all stems up puts the slur under the noteheads, all
down puts it over them, and a mixed-stem span (which has no notehead side)
goes above. Every Auto slur over a stem-up passage was drawn through its own
stems. This is why stem direction had to land first: with every stem pointing
up, "opposite the stems" means nothing.
2. Endpoints. They sat at staff_top + gap -- a constant offset from the STAFF,
not from the notes -- so a slur between two C6s hung below its own noteheads
and crossed their ledger lines. They now sit a gap outside the endpoint
column's ink, at the notehead's centre. Where the stem points the same way as
the slur, that ink includes the stem, so the endpoint clears the stem tip.
3. Clearance. The apex was span-proportional and blind, so a note between the
endpoints poked straight through the arc. ColumnInk -- per staff, per column:
top, bottom, stem direction, notehead centre -- is the obstacle field. The
control points sit on the chord at thirds, so x is exactly linear in t and
the arc's departure from the chord is 3*lift*t*(1-t); a column at t needing d
more clearance forces an apex of at least d/(4*t*(1-t)).
An authored height is a floor, not a ceiling: clearance may raise it, so obeying
an author cannot draw a slur through a note. An authored direction still wins.
Obstacles are measured at the notehead CENTRE, the same x the endpoints use. The
first cut used the raw column x, which skews t and silently over-lifts: the
two-staff slur cleared its C6 by 4.05 spaces where 3.5 was needed. The clearance
test now asserts an upper bound as well as a lower one.
SLUR_INSET is gone. Endpoints at the notehead centres are what its 0.6-space
"tuck" approximated for the start point -- and got wrong for the end, where it
tucked a full notehead width to the LEFT of the final note.
Four mutations verified: always-above, staff-relative endpoints, no clearance
pass, and obstacles at the column x. The staff-relative-endpoint mutation PASSED
at first -- the tests asserted only "above the staff" / "below the staff", which a
staff-relative endpoint satisfies by construction. The exact-endpoint assertion
exists because that mutation survived.
Projection change, so no version moves; goldens churn.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Every stem in the engine pointed up, on the notehead's right, at a constant
octave. A C6 three ledger lines above the staff grew an upward stem shooting past
everything -- visible in the two_staff and three_staff renders. It is also why the
slurs are wrong: an Auto slur is placed OPPOSITE the stems, so no correct side
could be chosen while every stem pointed the same way. Stems are therefore a
prerequisite for the slur fix, not merely adjacent to it.
- Direction: away from the middle line, decided by the head furthest from it,
ties going down (the convention for a note on the line, and for a chord that
straddles it evenly).
- Attachment: the side it points -- an up-stem at the lowest head's right edge,
a down-stem at the highest head's left. Read from the head's own bounding box
rather than the rounded NOTEHEAD_STEM_X: for noteheadBlack those are 1.1807
and 0, and 1.1807 is Bravura's real stemUpSE (1.18). The old 1.15 was a
rounding -- it accounts for the whole of ten_measure's churn, where every stem
moved right by 0.031 and nothing else moved at all.
- Length: an octave from the outer head, but drawn out to the middle line when
the note lies beyond it, so no stem dangles in the ledger field.
No version moves. This is the PROJECTION changing, not a solver: to_constrained
emits different geometry from the same graph, so ENGRAVER_VERSION's promise (same
input => same output) is untouched. Every golden churns, stub and engrave alike,
because stems are constrained-stage geometry.
Locked by a_stem_points_away_from_the_middle_line_and_reaches_it, which re-pitches
a generated score across four octaves -- the corpus generator writes only low
notes, so nothing in the suite had ever exercised a down-stem. Mutation-verified:
restoring always-up plus fixed-octave fails it.
Parked, found on the way: BRAVURA_METRICS' notehead anchors are unusable as
written. They name stemUpNW/stemDownSE -- the corners an up- and down-stem never
attach to -- and their x of 1180 reads like 1.18 staff spaces written in
thousandths rather than the table's 1/1024 units (1.18 sp = 1208). Nothing
consumes them except metrics_hash, so correcting them would move the
GlyphCatalogIdentity every conformance claim declares. That makes three parked
candidates; the house rule opens a batch pass at three.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Groundwork for inter-staff band-height renegotiation (the last vertical-spring
piece): a fixture whose two staves' content nearly collides at the engraver's
fixed staff pitch, so the pending solve has something meaningful to separate.
two_staff_close_content: a one-measure, two-staff (treble/treble) metric score.
The top staff descends into low ledger notes (down to C2); the bottom staff
climbs into high ledger notes (up to C6) under a slur that arcs further above
them. In the constrained frame the top staff's content occupies y ≈ [-8, +4]
and the bottom staff's ≈ [-12, -5], overlapping in [-8, -5] — the C2 ledgers
collide with the C6 + slur. Invariant-clean; 8 notes, 1 slur, 41 strokes
(the heavy ledgering), 1 curve.
Registered in the render-svg acceptance suite; its goldens (this commit) show
the CURRENT overlapping layout — slice 2 (the solve) will update the engrave
golden to show the staves separated. Invariant test added. 946 tests, clippy 0,
docs -D warnings, conformance 8/8.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Levi Neuwirth