P2.1 CurveSegmentString — nodes only (OV-P2 / Bar 2)

[grootstebozewolf]

Stacked on cursor/cc-nest-annulus-0a09 @ d33b0cb (draft #15). Do not merge this into #7. This is OV-P2 / Bar 2, not OV-P1. Does not merge #12 / #13 / #15 / #7. Does not push to feature/sfa-curve-rgr or master.

Sentence

The noder is the named-miss suite, one assembly rule at a time. Nodes first. Densify is never a noder.

What this is

P2.1 is CurveSegmentString, not a free-floating CircularNoder of raw Coordinate[].

A package-private curve-module string: one piece is a straight chord or a circular arc (control triple / centre-radius-sweep — the same atom TwoNodeClip.Edge already is). A package-private CurveSegmentNoder intersects those strings and returns the discrete node set, or null.

Lives in org.locationtech.jts.operation.overlayng.curve (same package as TwoNodeClip) so intersectCircles / isOnSweep / line–circle stay package-private. org.locationtech.jts.noding.curve would need a public bridge; that is P2.5-shaped. Not a core SegmentString / Noder. Not N-SS.

Pins

Fixture	Nodes
R1.5 two-disc	(3.5, ±√12.75) — bit-identical to TwoNodeClip.intersectCircles
R1.6-2 disc-vs-plain	(0, ±5) — same segment–circle hits
H-SHELL-2	(±3, 4)
H-FOUR even-n	(±√24, ±1)
H-SHELL-N even-n	(±1, 0), (±1, √24)
H-SHELL-N-ODD	(±1, 0) + tangent (0, 5) — the tangent is a node

MIXED is the first miss. H-SHELL-N-MIXED (collinear overlap) stays null. So do pinch (H-ANNULUS-TANGENT) and holes (H-SHELL-HOLE-CROSS, H-SHELL-HOLE-X). No overlap-as-edge (P2.2). No faces. No hole punch (P2.3). No two-hole (P2.4). No public core noder (P2.5).

TwoShellClip pair hits now go through CurveSegmentString.intersect — one place for the math, kits still assemble faces.

What this is not

• Not P2.2 overlap-as-edge
• Not P2.3 bite vs hole
• Not P2.4 two-hole arrangement
• Not P2.5 / N-SS
• Not a snap-rounding noder
• Not densify-then-node flagged as exact
• Not a merge into feature/sfa-curve-rgr / PR SFA/SQL-MM curve awareness: Curve rename, arc-aware operations, OverlayNGCurve ratchet (#1195 RGR series) #7 / locationtech master

Verify

mvn -pl modules/curve -am test -DfailIfNoTests=false -Dcheckstyle.skip=true -Dpmd.skip=true \
  -Dtest=CurveSegmentStringTest,CompoundCurveShellOverlayTest,CircularArcOverlayTest,CircularDiscOverlayTest,CircularDiscPolygonOverlayTest,OverlayNGCurvePhase0Test,OverlayNGCurveRatchetTest,OverlayNGCurvePerfGateTest
bash dev/check-no-curved.sh
mvn -pl modules/curve checkstyle:check
mvn -pl modules/curve pmd:check

All green after this revision:

• CurveSegmentStringTest 11 / 0
• CompoundCurveShellOverlayTest 24 / 0
• CircularArcOverlayTest 11 / 0
• CircularDiscOverlayTest 12 / 0
• CircularDiscPolygonOverlayTest 7 / 0
• OverlayNGCurvePhase0Test 19 / 0
• OverlayNGCurveRatchetTest 44 / 0
• OverlayNGCurvePerfGateTest 78 / 0 (15% slack)
• mvn -pl modules/curve test: 600 tests, 0 failures
• Naming-guard OK; Checkstyle 0 violations; PMD check on jts-curve succeeded

Slack stays 15%. Overlay name is OverlayNGCurve. No new public API.