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

IntersectionPointBuilder — result points (port of JTS IntersectionPointBuilder)

Phase 2b of the OverlayNG port (design doc §3). A port of operation/overlayng/IntersectionPointBuilder.java: extracts Point results from an Intersection of non-point inputs, at nodes incident on edges of BOTH inputs where none of the incident edges is itself in the result (i.e. the inputs meet at an isolated point). isAllowCollapseLines is always true here (non-strict), so the boundary-collapse guard in isEdgeOf is elided.

Returns the result points as coordinate tuples; the driver wraps them. Nothing here is exported.

function _build_points(g::OverlayGraph{P, T}) where {P, T}
    edges = g.edges
    points = T[]
    for ne in graph_node_edges(g)
        if _is_result_point(edges, ne)
            push!(points, node_point(g.arr, he_origin(edges, ne)))
        end
    end
    return points
end

Port of isResultPoint: a node incident on edges of both inputs, none of them in the result.

function _is_result_point(edges, node_edge::Integer)
    is_edge_of_a = false
    is_edge_of_b = false
    e = Int32(node_edge)
    while true
        oe_in_result(edges, e) && return false
        lbl = oe_label(edges, e)
        is_edge_of_a |= _is_edge_of(lbl, 0)
        is_edge_of_b |= _is_edge_of(lbl, 1)
        e = he_onext(edges, e)
        e == node_edge && break
    end
    return is_edge_of_a && is_edge_of_b
end

@inline _is_edge_of(lbl::OverlayLabel, i::Integer) = is_boundary(lbl, i) || is_line(lbl, i)

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