pinafore/routes/_utils/AsyncLayout.js
2018-01-27 10:46:52 -08:00

50 lines
1.2 KiB
JavaScript

// Use intersection observer to calculate rects asynchronously
import { getRectFromEntry } from './getRectFromEntry'
class AsyncLayout {
constructor(generateKeyFromNode) {
this._onIntersectionCallbacks = {}
this._intersectionObserver = new IntersectionObserver(entries => {
entries.forEach(entry => {
let key = generateKeyFromNode(entry.target)
this._onIntersectionCallbacks[key](entry)
})
})
}
observe(key, node, callback) {
if (!node) {
return
}
if (this._intersectionObserver) {
this._onIntersectionCallbacks[key] = (entry) => {
callback(getRectFromEntry(entry))
this.unobserve(key, node)
}
this._intersectionObserver.observe(node)
}
}
unobserve(key, node) {
if (key in this._onIntersectionCallbacks) {
return
}
if (!node) {
return
}
if (this._intersectionObserver) {
this._intersectionObserver.unobserve(node)
}
delete this._onIntersectionCallbacks[key]
}
disconnect() {
if (this._intersectionObserver) {
this._intersectionObserver.disconnect()
this._intersectionObserver = null
}
}
}
export { AsyncLayout }