@tldraw/editor/dist-esm/lib/hooks/useRefState.mjs.map

tldraw infinite canvas SDK (editor).

{
  "version": 3,
  "sources": ["../../../src/lib/hooks/useRefState.ts"],
  "sourcesContent": ["import { Dispatch, SetStateAction, useCallback, useRef, useState } from 'react'\n\n/**\n * A `useState` that uses a `ref` to keep the state in sync with the last value assigned to it.\n *\n * This is useful when creating side-effect state that behave correctly in react strict mode. The\n * obvious way to do this is to use `useState` within a `useEffect` like this:\n *\n * ```ts\n * const [state, setState] = useState(null)\n * useEffect(() => {\n *   const thing = createSideEffectThing()\n *   setState(thing)\n *   return () => thing.destroy()\n * }, [deps])\n * ```\n *\n * The problem with this is that when initially mounting in strict mode, react will:\n * - Call the initial effect and set state with an instance\n * - Call the cleanup function and destroy the instance\n * - Call the effect again and set state with a new instance\n * - Restore the state to the first instance\n *\n * Now, our effect and our state are out of sync: the effect is using the new instance, but the\n * state contains the old instance which has been destroyed.\n *\n * Using a `ref` is a solution, as it'll always keep the value last assigned to it, so it stays in\n * sync with the effect. That's no good for rendering though, as react won't trigger a re-render\n * when the contents of the ref changes.\n *\n * This hook solves this problem by using a `ref` to keep the value in sync with the effect, and\n * a `useState` to trigger a re-render when the value changes.\n *\n * @internal\n */\nexport function useRefState<T>(initialValue: T): [T, Dispatch<SetStateAction<T>>] {\n\tconst ref = useRef(initialValue)\n\tconst [state, setState] = useState(initialValue)\n\n\tif (state !== ref.current) {\n\t\tsetState(ref.current)\n\t}\n\n\tconst update: Dispatch<SetStateAction<T>> = useCallback((value) => {\n\t\tif (typeof value === 'function') {\n\t\t\tref.current = (value as any)(ref.current)\n\t\t} else {\n\t\t\tref.current = value\n\t\t}\n\n\t\tsetState(ref.current)\n\t}, [])\n\n\treturn [state, update]\n}\n"],
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}