NOTE: This functionality is experimental and may change at any time.

EdgeSourceInfo — per-ring/line source topology (port of JTS EdgeSourceInfo)

Phase 2a of the OverlayNG port (design doc §2.7, §3 amendment 3). Records the topological information carried by one source linework (a polygon ring or a line) from a single input geometry: which input it came from, its dimension, its ring role, and — for area rings — the signed depth_delta.

One EdgeSourceInfo exists per RelateSegmentString, indexed by the segment string's position in the arrangement's segstrings. A NodedEdge reaches its source info through NodedEdge.string_idx; nothing is copied per noded edge (design §2.1 invariant 5), so nothing can desynchronize.

Everything here is internal to GeometryOps — nothing is exported.

"""
    EdgeSourceInfo

Source topology of one input linework (port of JTS `EdgeSourceInfo`): `index`
(`0` = A, `1` = B), `dim` (`DIM_A` for a ring, `DIM_L` for a line), `is_hole`
(ring role), and `depth_delta` (the signed side-labelling delta of an area ring,
`0` for a line). Consumed by the edge merger to build `OverlayLabel`s.
"""
struct EdgeSourceInfo
    index       :: Int8
    dim         :: Int8
    is_hole     :: Bool
    depth_delta :: Int8
end

The depth delta of one area ring, derived ONCE from the material-interior authority (design §2.7). JTS EdgeNodingBuilder.computeDepthDelta assigns the canonical delta +1 to a ring in "Exterior-on-Left" orientation and flips to -1 otherwise; equivalently (Edge.locationLeft/Right) a positive delta means Left = EXTERIOR, Right = INTERIOR — i.e. the material interior lies on the RIGHT. So depth_delta = material_interior_on_left ? -1 : +1, computed on the ring's stored order and matching that convention exactly. Folding the hole flip into _ring_material_interior_on_left keeps relate / overlay / extents in agreement by construction.

function _ring_depth_delta(m::Manifold, pts::Vector, is_hole::Bool; exact)
    return _ring_material_interior_on_left(m, pts, is_hole; exact) ? Int8(-1) : Int8(1)
end

Build the source info for one segment string. Area rings carry a depth delta; lines carry none (dim == DIM_L, depth_delta == 0).

function _edge_source_info(m::Manifold, ss::RelateSegmentString; exact = True())
    index = ss.is_a ? Int8(0) : Int8(1)
    if ss.dim == DIM_A
        is_hole = _ss_is_hole(ss)
        return EdgeSourceInfo(index, DIM_A, is_hole, _ring_depth_delta(m, ss.pts, is_hole; exact))
    end

    return EdgeSourceInfo(index, DIM_L, false, Int8(0))
end

The per-string source-info table of an arrangement, aligned to segstrings (so sources[NodedEdge.string_idx] is the noded edge's source info).

function _edge_source_infos(m::Manifold, arr::NodedArrangement; exact = True())
    return [_edge_source_info(m, ss; exact) for ss in arr.segstrings]
end

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