Five findings from the araminta+hoshe round. Tapering now fires only on
a TRUE upstream source: the course's first raw world point is tested
against the canvas's own world bounds (conservative 1m epsilon) —
exact detection because the server crop keeps one point beyond the
window (layer_proxy crop_course_to_window lo = first_in-1, contract
documented), so crop passthroughs draw the old flat full-width cut and
never a false headwater. The averaged-normal joint is replaced by a
real mitre (half_w/cos(theta/2) recovered trig-free via the bisector
normal), clamped by a 2x mitre limit AND 0.45x the shorter adjacent
segment — restoring true perpendicular width at bends (the 29% pinch at
confluences is gone) and preventing the hairpin bowtie; the winding doc
now states the actual bounded guarantee. Antialiasing restored via the
hybrid: only the varying-width taper head draws as a ribbon; the
constant-width ~85% of every course keeps the original antialiased
draw_polyline (byte-identical for untapered courses), split at an
interpolated arc-length point sharing position and width — junction
capture evidence in .cache/screenshots/t1175-fix-round/. Flat-fill
single-element color array. Suite 24 -> 48 tests.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
jpmschweitzerandClaude Fable 5
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