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Debug API reference

Updated Jun 20, 2026 3 min read

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The debug API is a frozen read-and-drive surface exposed as <code>FasterMotion.debug</code>. It ships so humans, support, agents, and integration tests can inspect running pages.

Core read methods

  • validate(): run live graph validation and return warning/error/info objects.
  • validateFmtion(json): run static structural checks before loading.
  • errors(): return recent runtime errors and drained runtime warnings.
  • nodes(filter?): inspect node snapshots by type or id prefix.
  • dump(): capture graph, backend, errors, scroll, pins, and node snapshots.

Surface-specific methods

  • inspect(selector): map DOM elements to graph drivers and computed state.
  • pins() and scroll(): inspect scroll and pin runtime state.
  • sceneWires(): inspect cross-scene texture wires.
  • textures(): inspect renderer texture stats.
  • skinnedMeshes() and getDeformedVertices(pathId): inspect rigged/deformed render state.

Physics and drive methods

  • Physics readers include physicsWorld(), physicsBody(id), physicsBodyIds(), physicsCollisionLog(), physicsBodyAt(x, y), physicsBodyGeometry(id), and physicsJoints().
  • Physics diagnostic drive methods include physicsForceUnpause(), physicsRestorePause(), and physicsBodySetVelocity().
  • scrollTo(target) mutates page scroll and resolves after graph evaluations settle.

Full method list

  • errors, nodes, pins, inspect, smInternal, scroll, tick, dump, validate, validateFmtion, sceneWires, physicsWorld, physicsBody, physicsBodyIds, physicsCollisionLog, physicsBodyAt, physicsBodyGeometry, physicsJoints, physicsForceUnpause, physicsRestorePause, physicsBodySetVelocity, scrollTo, textures, skinnedMeshes, getDeformedVertices

Verified runnable examples

This guide points to proof-backed sample coverage. The full ledger lives in Generated examples and proof log.

DOM: Scroll fade reveal

  • Source: faster-motion/demo/tests/dom/catalog/scroll-animations/fade-reveal/fade-reveal.domgraph.fmtion
  • Expected output: Sections fade and translate into place as their trigger elements enter the configured viewport range.
  • Validation: Schema validation passed. Runtime proof reports zero structural/runtime issues and 17 loaded nodes.
  • Desktop proof: generated-assets/faster-motion-docs/proofs/screenshots/dom-fade-reveal-desktop.png
  • Mobile proof: generated-assets/faster-motion-docs/proofs/screenshots/dom-fade-reveal-mobile.png

Canvas: Fill rule diagnostic

  • Source: faster-motion/demo/tests/canvas/fillrule-diagnostic/fillrule-diagnostic.fmtion
  • Expected output: A contained Canvas scene renders paired path cases so nonzero and evenodd fill handling can be compared visually.
  • Validation: Schema validation passed. Runtime proof reports zero blocking runtime issues and 10 rendered objects; the accepted metadata note is preserved in the proof ledger.
  • Desktop proof: generated-assets/faster-motion-docs/proofs/screenshots/canvas-fillrule-diagnostic-desktop.png
  • Mobile proof: generated-assets/faster-motion-docs/proofs/screenshots/canvas-fillrule-diagnostic-mobile.png

Guide-specific sample target: Debug console sample that runs validate, nodes filter, inspect selector, sceneWires, textures, and one physics reader.

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