Scene Invariants

Five pure functions that check PLACEMENT INVARIANTS in a rendered scene: no unwanted overlap, a visibility floor, 'sits on its declared plane', scale consistency across zoom levels, and 'did this actually move over time'. Each is shaped (snapshot, config) => Violation[].

THE BOUNDARY, STATED FIRST. This library does not render anything and does not measure anything. It has no DOM, no canvas, no screenshot capture, and no I/O of any kind -- not even a clock. You measure your own rendered scene however you already do, build a plain snapshot object, and hand it over. That is what makes it usable against a game engine, a canvas app, a DOM layout or a chart library without adopting any of them.

THE SILENT FAILURE. A label rendered behind another element, a marker floating slightly off its plane, an icon that stops scaling with its layer at one zoom level -- none of these throw. The renderer did exactly what it was told. The scene is a correct render of an incorrect arrangement, and the only detector most teams have is someone happening to look at that zoom level on that data.

Checking invariants rather than pixels is what makes this survive a redesign: a screenshot test fails when anything changes, so it is disabled; an invariant fails only when the arrangement is actually wrong.

VERIFIED: 44 tests, measured by running the suite.

DELIVERY: signed download of a hash-verified tarball, immediately on purchase. Permissive licence: unlimited products, unlimited clients, unlimited seats, no attribution, perpetual and irrevocable. One restriction, do not republish the source as source.

Interface

What you call, and what comes back. Types and signatures only — the implementation ships with the source.

  export function checkLiveness( snapshot: LivenessSnapshot, config: LivenessConfig, ): Violation[];
  export function checkOverlap( snapshot: OverlapSnapshot, config: OverlapConfig, ): Violation[];
  export function checkPlaneContainment( snapshot: PlaneContainmentSnapshot, config: PlaneContainmentConfig, ): Violation[];
  export function checkScaleConsistency( snapshot: ScaleConsistencySnapshot, config: ScaleConsistencyConfig, ): Violation[];
  export function checkVisibilityFloor( snapshot: VisibilityFloorSnapshot, config: VisibilityFloorConfig, ): Violation[];

  export type ViolationKind = "violation" | "unknown" | "exemption";