Function useDeclaredCursor

src/ink/hooks/use-declared-cursor.ts:25–73

({
  line,
  column,
  active,
}: {
  line: number
  column: number
  active: boolean
})

 * explicitly after render.
 */
export function useDeclaredCursor({
  line,
  column,
  active,
}: {
  line: number
  column: number
  active: boolean
}): (element: DOMElement | null) => void {
  const setCursorDeclaration = useContext(CursorDeclarationContext)
  const nodeRef = useRef<DOMElement | null>(null)

  const setNode = useCallback((node: DOMElement | null) => {
    nodeRef.current = node
  }, [])

  // When active, set unconditionally. When inactive, clear conditionally
  // (only if the currently-declared node is ours). The node-identity check
  // handles two hazards:
  //   1. A memo()ized active instance elsewhere (e.g. the search input in
  //      a memo'd Footer) doesn't re-render this commit — an inactive
  //      instance re-rendering here must not clobber it.
  //   2. Sibling handoff (menu focus moving between list items) — when
  //      focus moves opposite to sibling order, the newly-inactive item's
  //      effect runs AFTER the newly-active item's set. Without the node
  //      check it would clobber.
  // No dep array: must re-declare every commit so the active instance
  // re-claims the declaration after another instance's unmount-cleanup or
  // sibling handoff nulls it.
  useLayoutEffect(() => {
    const node = nodeRef.current
    if (active && node) {
      setCursorDeclaration({ relativeX: column, relativeY: line, node })
    } else {
      setCursorDeclaration(null, node)
    }
  })

  // Clear on unmount (conditionally — another instance may own by then).
  // Separate effect with empty deps so cleanup only fires once — not on
  // every line/column change, which would transiently null between commits.
  useLayoutEffect(() => {
    return () => {
      setCursorDeclaration(null, nodeRef.current)
    }
  }, [setCursorDeclaration])

  return setNode
}