Struct Arrangement

pub struct Arrangement { /* private fields */ }

A planar subdivision as a doubly-connected edge list.

Handles stay valid across edits unless the element they name is removed, which is what makes incremental editing possible at all.

Implementations

impl Arrangement

pub fn from_polygon(corners: &[Point2]) -> Result<Self, BuildError>

Build a single bounded face from a closed polygon.

Corners are taken counter-clockwise; a clockwise ring is reversed so the bounded face is the one inside it. Silently accepting either winding is the right call here because “which side is inside” is unambiguous for a simple closed ring, and forcing callers to normalise first only moves the same code outward.

Errors

BuildError::DegenerateBoundary or BuildError::ZeroArea.

impl Arrangement

pub fn add_vertex(&mut self, position: Point2) -> VertexId

Add an isolated vertex.

Legal on its own: a vertex with no edges is a valid, if uninteresting, arrangement element, and building incrementally needs it.

pub fn split_edge( &mut self, edge: HalfEdgeId, at: Point2, ) -> Result<VertexId, EditError>

Split an edge at at, inserting a new vertex.

The point must lie on the segment. Both the edge and its twin are split, so the structure stays consistent.

Errors

EditError::PointNotOnEdge if at is not collinear with the edge or lies outside it.

pub fn drag_vertex( &mut self, vertex: VertexId, to: Point2, ) -> Result<(), EditError>

Move a vertex, refusing the move if it would break a face.

Errors

EditError::WouldSelfIntersect if any incident face would stop being simple. The arrangement is left unchanged in that case.

impl Arrangement

pub fn face_halfedges(&self, face: FaceId) -> Vec<HalfEdgeId>

Half-edges around a face’s boundary, counter-clockwise.

Returns empty for a face with no boundary (the unbounded face of an empty arrangement).

pub fn face_outline(&self, face: FaceId) -> Vec<Point2>

Corner positions of a face, counter-clockwise.

pub fn face_area(&self, face: FaceId) -> f64

Signed area of a face, positive when its boundary runs counter-clockwise.

The unbounded face has no meaningful area; it reports 0.0 rather than a negative number that a caller might sum into a total.

pub fn neighbour_across(&self, edge: HalfEdgeId) -> FaceId

The face on the other side of a half-edge.

Always defined: the unbounded face is a real face, so an edge on the outer boundary reports it rather than None.

pub fn bounded_faces(&self) -> impl Iterator<Item = FaceId> + '_

Every bounded face, in arena order.

Deliberately excludes the unbounded face: a caller asking for “the regions” almost never means the infinite one, and including it is the kind of default that produces a wrong total on the first use.

pub fn vertex_halfedges(&self, vertex: VertexId) -> Vec<HalfEdgeId>

Half-edges leaving a vertex, counter-clockwise around it.

pub fn degree(&self, vertex: VertexId) -> usize

Number of edges meeting at a vertex.

pub fn halfedge_origin(&self, edge: HalfEdgeId) -> VertexId

Vertex a half-edge leaves from.

pub fn halfedge_face(&self, edge: HalfEdgeId) -> FaceId

Face lying to the left of a half-edge.

impl Arrangement

pub fn audit(&self) -> ArrangementHealth

Check every structural invariant.

impl Arrangement

pub fn new() -> Self

An empty plane: one unbounded face, no vertices or edges.

pub const fn outer_face(&self) -> FaceId

The unbounded region surrounding every bounded face.

pub fn vertex_count(&self) -> usize

Number of vertices, including any left isolated by edits.

pub fn face_count(&self) -> usize

Number of faces, including the unbounded one.

pub fn halfedge_count(&self) -> usize

Number of half-edges; always twice the number of edges.

pub fn position(&self, vertex: VertexId) -> Point2

Position of a vertex.

Trait Implementations

impl Clone for Arrangement

fn clone(&self) -> Arrangement

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Arrangement

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Arrangement

fn default() -> Self

Returns the “default value” for a type.