quasar/src/composables/private.use-scroll-target/use-scroll-target.js

Build high-performance VueJS user interfaces (SPA, PWA, SSR, Mobile and Desktop) in record time

import { ref, watch, onBeforeUnmount } from 'vue'

import { listenOpts } from '../../utils/event/event.js'

export default function useScrollTarget(props, configureScrollTarget) {
  const localScrollTarget = ref(null)
  let scrollFn

  function changeScrollEvent(scrollTarget, fn) {
    const fnProp = `${fn !== void 0 ? 'add' : 'remove'}EventListener`
    const fnHandler = fn !== void 0 ? fn : scrollFn

    if (scrollTarget !== window) {
      scrollTarget[fnProp]('scroll', fnHandler, listenOpts.passive)
    }

    window[fnProp]('scroll', fnHandler, listenOpts.passive)

    scrollFn = fn
  }

  function unconfigureScrollTarget() {
    if (localScrollTarget.value !== null) {
      changeScrollEvent(localScrollTarget.value)
      localScrollTarget.value = null
    }
  }

  const noParentEventWatcher = watch(
    () => props.noParentEvent,
    () => {
      if (localScrollTarget.value !== null) {
        unconfigureScrollTarget()
        configureScrollTarget()
      }
    }
  )

  onBeforeUnmount(noParentEventWatcher)

  return {
    localScrollTarget,
    unconfigureScrollTarget,
    changeScrollEvent
  }
}