Module cancel

Cooperative cancellation for long geometry operations.

Why cooperative

GeomError::Cancelled existed in the error enum but nothing could produce it: there was no way to ask for cancellation. The variant was aspirational, and an aspirational cancellation contract is worse than none, because callers plan around it.

This is a plain atomic flag, not an async runtime. Geometry providers are synchronous and CPU-bound; a token they poll costs one relaxed atomic load at whatever granularity they declare.

Safety of cancellation

Cancellation is safe, never partial. A provider returns either a complete result or GeomError::Cancelled. It must never return a half-cut mesh, because a partial solid is indistinguishable from a valid one downstream and corrupts every quantity derived from it.

Structs

CancellationToken

A shared cancellation flag.

Enums

CancellationGranularity

How finely a provider polls its cancellation token.