Swimlane geometry

This package lays out the immutable diagrams/swimlane model. Inputs and output are explicit values. It imports no Mermaid or BPMN document module.

///|
test "measured lanes retain source order and expose checker findings" {
  let view = @model.Swimlane::new(
    "review",
    [
      @model.Node::new("A", lane="Customer"),
      @model.Node::new("B", lane="Support"),
    ],
    [@model.Connection::new("AB", "A", "B")],
    direction=LR,
    lanes=[@model.Lane::new("Customer"), @model.Lane::new("Support")],
  )
  let result = @layout.layout(view)
  let geometry = result.geometry.unwrap()
  let customer = geometry.shapes
    .iter()
    .find_first(s => s.id == "Customer")
    .unwrap()
  let support = geometry.shapes
    .iter()
    .find_first(s => s.id == "Support")
    .unwrap()
  assert_true(customer.box.y < support.box.y)
  assert_eq(geometry.connections[0].connection.id, "AB")
  assert_eq(
    @layout.check(geometry, @layout.palette(@theme.Theme::classic().light)),
    [],
  )
  assert_eq(
    @layout.layout(view, limits=@layout.Limits::new(work=1)).geometry,
    None,
  )
}

layout walks nested scopes with an explicit stack. It measures labels, keeps empty lanes, packs unowned nodes separately and ranks condensed cycles. Local scope directions are independent of the global flow direction. Reversing flow never reverses source lane order or connection identities. Minimum-length hints reserve additional rank gaps. Disconnected children retain declaration order.

Each vector silhouette and edge port share outline. Routing uses bounded orthogonal search around unrelated shapes and label boxes. Return edges, self-loops and parallel handoffs retain distinct paths and ports. Visible edges that cross a collapsed boundary attach to that ancestor while their stored connection keeps its logical endpoints. Hidden internal edges are omitted. Invisible connections constrain placement but do not paint or animate.

Limits::new(minimum_approach=24.0) reserves every straight endpoint corridor before routing middle segments or placing connection labels. This prevents an earlier edge from blocking a later marker approach. Return and parallel routes use separate collinear channels, while transverse crossings remain available for display bridges. Compact symbols with external labels use a clear side; concave silhouettes retain their actual outline attachment. Larger minima increase the automatic scope spacing. Existing route points remain available separately from the renderer's final styled paths.

Side ports follow the other endpoints' cross-axis order, with declaration order breaking ties for parallel identities. The bounded grid search indexes obstacle rows and columns and caches segment checks. Optional channels keep room beside existing spans for safe bends and bridges; actual endpoint coordinates stay fixed.

Limits::new defaults to 10,000 elements, 50,000 connections, depth 256, 1,000,000 work units and 16 Mi UTF-16 output units. Ownership or reference errors, unsupported shapes and exhausted work return no partial geometry. Routing can fail explicitly when those bounds cannot find a clear path.

check reports Overlap, Fit, Size, Contrast, Containment, Endpoint and Limit findings. Intended container ownership is permitted. It does not move or repair supplied geometry. Use palette on the shared theme palette to apply the exact ink shades used by the swimlane painter. Derived SVG numbers have at most three fractional digits and are stable on all four backends.