Substrate

Browser events → typed intents.

The substrate is the input-side layer that turns browser events (beforeinput, keydown, mousedown, pointermove, composition, paste, drop) into typed intents. It is the only place in @spine-editor/dom that owns browser event listeners.

Entry point

The substrate is internal to createSpineDomRuntime(...). Supporting modules live in packages/dom/src/substrate/, including input, mouse, selectionchange, and navigation/clipboard/lifecycle subtrees.

Responsibilities

  • Translate input — map each event to an Intent and dispatch it through the engine.
  • Cancel native behavior — preventDefault() on events the engine handles.
  • Own composition state — suspend keyboard intents during IME composition (see IME).
  • Forward pointer events — mouse/touch → selection updates via the selection mapping layer.
  • Attach input evidence — for supported shortcuts, the substrate may read committed semantic state to say "this was Space after #"; the planner still decides whether that becomes a heading.

Non-responsibilities

The substrate does not:

  • Mutate the document directly.
  • Decide final semantic meaning (planner rules handle that).
  • Write the DOM beyond reading event targets.