@react-facet/deferred-mount

React Facet is a state management for performant game UIs. For more information on how to use this package check the official documentation available at https://react-facet.mojang.com/.

This package allows you to defer the mounting of a component to the next frame. By wrapping components on a big list you can keep the frame time low while everything is mounted.

When the DeferredMountProvider is used, it requires that there is at least one descendent as a DeferredMount or DeferredMountWithCallback, otherwise it will wait forever as deferring.

Example

In the example below it will mount:

• Mounting: nothing
• First Frame: First
• Second Frame: First and Second
• Third Frame: First, Second and Third

The useIsDeferring hook allows to check what is the status of the deferred mounting (by returning a Facet) so we can, for example, show a spinner.

const SampleComponent = () => {
  const isDeferringFacet = useIsDeferring()

  return (
    <>
      <fast-text text={useFacetMap((isDeferring) => (isDeferring ? 'deferring' : 'done'), [], [isDeferringFacet])} />
      <DeferredMount>
        <div>First</div>
      </DeferredMount>
      <DeferredMount>
        <div>Second</div>
      </DeferredMount>
      <DeferredMount>
        <div>Third</div>
      </DeferredMount>
    </>
  )
}

render(
  <DeferredMountProvider frameTimeBudget={16}>
    <SampleComponent />
  </DeferredMountProvider>,
  document.getElementById('root'),
)

The frameTimeBudget prop allows the tweaking of how much time the library has available to do work on a given frame (by default it targets 60fps).

Deferring Asynchronous Renders

Some components may need to wait some time before they can be considered fully rendered (for example if they are fetching data). For these cases you should use DeferredMountWithCallback with the useNotifyMountComplete hook.

Example

const DelayedComponent = () => {
  const notifyMountComplete = useNotifyMountComplete()
  const [data, setData] = useState()

  useEffect(() => {
    fetch('mock-api').then((data) => {
      setData(data)
      notifyMountComplete()
    })
  }, [notifyMountComplete])

  return <div>{data}</div>
}

render(
  <DeferredMountProvider>
    <DeferredMountWithCallback>
      <DelayedComponent />
    </DeferredMountWithCallback>
  </DeferredMountProvider>,
  document.getElementById('root'),
)