Two items the inter-staff solve deferred turned out to be one thing -- and it was
not the "metric-vs-solver tension" I filed it as. The catalog was right; the
engraver was non-conforming.
req:qmc:vertical has always defined the realized inter-staff gap as the separation
"between the adjacent CONTENT EXTENTS the band separates". vertical_raw measured
the separation between the two bands' glyph `members`, because until primitive
band ownership (efaebb9) a band listed no strokes or curves to own. A staff's
outermost ink is usually not a glyph. On two_staff_close_content the solve cleared
the declared 2.0 gap exactly, while the glyph-ink gap was 5.06 -- so the axis
reported |5.06-2|/2 = 1.53, saturated to 1.0, and fired a Standard-tier floor
warning on a correct layout. The metric was charging the solver for the ledger and
slur ink it had made room for. Axis now reads 2.7e-7; the warning is gone.
Two design calls worth naming:
- The geometry is read back from the BAKED output, not from the solve's own
staff_ext. Reading back solver intent would make the axis circular and blind
to exactly the bug class that bit twice this week; now a shift the bake fails
to apply to some primitive class surfaces as a real deviation. CastLayout
gained stroke_system/curve_system for it -- a stroke carries no spring slot,
so system_of_slot cannot answer for it.
- The solve now targets the preferred_height of the InterStaffGap band
to_constrained emitted for that staff pair, not VerticalBand::inter_staff_gap's
default. That is what makes the band a height model rather than a constant:
solve and metric agree by construction, not by both calling one constructor.
NO version move. Formula, contributing units, anchor, and normalization are
unchanged -- only a wrong measurement was. This is the P12-I11 precedent
(engrave-side resolution), not P12-I12 (which redefined spacing_distortion's unit
and did move the catalog). The catalog gains a clarification of what "content
extent" means, since before band ownership that reading was arguably
unimplementable, which is why the defect survived. Its stale rationale (still
claiming the vertical spring solve is deferred) is refreshed, and the axis's
inter-system half is recorded as a genuine trade-off against page_fill_efficiency
rather than a defect, so it is not re-filed as a bug.
Measurement-only: no layout change, ENGRAVER_VERSION stays 11, zero golden churn.
Mutation-verified: reverting vertical_raw to glyph-only measurement scores 1 and
fails the new assertion. Gate green, QMC PDF rebuilds clean.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Levi Neuwirth
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