Function createVirtualizerBase

packages/angular-virtual/src/index.ts:28–82

(
  options: Signal<VirtualizerOptions<TScrollElement, TItemElement>>,
)

export * from './types'

function createVirtualizerBase<
  TScrollElement extends Element | Window,
  TItemElement extends Element,
>(
  options: Signal<VirtualizerOptions<TScrollElement, TItemElement>>,
): AngularVirtualizer<TScrollElement, TItemElement> {
  let virtualizer: Virtualizer<TScrollElement, TItemElement>
  function lazyInit() {
    virtualizer ??= new Virtualizer(options())
    return virtualizer
  }

  const virtualizerSignal = signal(virtualizer!, { equal: () => false })

  // two-way sync options
  effect(
    () => {
      const _options = options()
      lazyInit()
      virtualizerSignal.set(virtualizer)
      virtualizer.setOptions({
        ..._options,
        onChange: (instance, sync) => {
          // update virtualizerSignal so that dependent computeds recompute.
          virtualizerSignal.set(instance)
          _options.onChange?.(instance, sync)
        },
      })
      // update virtualizerSignal so that dependent computeds recompute.
      virtualizerSignal.set(virtualizer)
    },
    { allowSignalWrites: true },
  )

  const scrollElement = computed(() => options().getScrollElement())
  // let the virtualizer know when the scroll element is changed
  effect(
    () => {
      const el = scrollElement()
      if (el) {
        untracked(virtualizerSignal)._willUpdate()
      }
    },
    { allowSignalWrites: true },
  )

  let cleanup: () => void | undefined
  afterNextRender(() => (virtualizer ?? lazyInit())._didMount(), {
    phase: AfterRenderPhase.Read,
  })

  inject(DestroyRef).onDestroy(() => cleanup?.())

  return proxyVirtualizer(virtualizerSignal, lazyInit)
}

export function injectVirtualizer<
  TScrollElement extends Element,