make virtual list more effecient using "reselect"

This commit is contained in:
Nolan Lawson 2018-03-04 13:37:55 -08:00
parent 562a58f030
commit 73861c4749
2 changed files with 51 additions and 1 deletions

View File

@ -1,5 +1,6 @@
import { mark, stop } from '../../_utils/marks' import { mark, stop } from '../../_utils/marks'
import { RealmStore } from '../../_utils/RealmStore' import { RealmStore } from '../../_utils/RealmStore'
import { reselect } from '../../_utils/reselect'
const VIEWPORT_RENDER_FACTOR = 3 const VIEWPORT_RENDER_FACTOR = 3
@ -21,9 +22,10 @@ virtualListStore.computeForRealm('scrollHeight', 0)
virtualListStore.computeForRealm('offsetHeight', 0) virtualListStore.computeForRealm('offsetHeight', 0)
virtualListStore.computeForRealm('itemHeights', {}) virtualListStore.computeForRealm('itemHeights', {})
virtualListStore.compute('visibleItems', virtualListStore.compute('rawVisibleItems',
['items', 'scrollTop', 'itemHeights', 'offsetHeight', 'showHeader', 'headerHeight'], ['items', 'scrollTop', 'itemHeights', 'offsetHeight', 'showHeader', 'headerHeight'],
(items, scrollTop, itemHeights, offsetHeight, showHeader, headerHeight) => { (items, scrollTop, itemHeights, offsetHeight, showHeader, headerHeight) => {
window.rawVisibleItemsComputed = (window.rawVisibleItemsComputed || 0) + 1
mark('compute visibleItems') mark('compute visibleItems')
if (!items) { if (!items) {
return null return null
@ -58,6 +60,8 @@ virtualListStore.compute('visibleItems',
return visibleItems return visibleItems
}) })
reselect(virtualListStore, 'visibleItems', 'rawVisibleItems')
virtualListStore.compute('heightWithoutFooter', virtualListStore.compute('heightWithoutFooter',
['items', 'itemHeights', 'showHeader', 'headerHeight'], ['items', 'itemHeights', 'showHeader', 'headerHeight'],
(items, itemHeights, showHeader, headerHeight) => { (items, itemHeights, showHeader, headerHeight) => {
@ -97,6 +101,14 @@ virtualListStore.compute('allVisibleItemsHaveHeight',
if (process.browser && process.env.NODE_ENV !== 'production') { if (process.browser && process.env.NODE_ENV !== 'production') {
window.virtualListStore = virtualListStore window.virtualListStore = virtualListStore
virtualListStore.observe('visibleItems', () => {
window.visibleItemsChangedCount = (window.visibleItemsChangedCount || 0) + 1
})
virtualListStore.observe('rawVisibleItems', () => {
window.rawVisibleItemsChangedCount = (window.rawVisibleItemsChangedCount || 0) + 1
})
} }
export { export {

38
routes/_utils/reselect.js Normal file
View File

@ -0,0 +1,38 @@
// Avoid re-renders by caching the most recent value of an array
// or an object, using an approach similar to https://github.com/reactjs/reselect.
// This avoids the issue where Svelte may keep re-rendering because it doesn't
// know if an object/array has changed or not.
import isEqual from 'lodash/isEqual'
if (process.browser && process.env.NODE_ENV !== 'production') {
window.reselectStats = {}
}
export function reselect (store, outputKey, inputKey) {
let prevValue
let nextValue
let count = 0
let countKey = `${outputKey}_reselectCount`
store.compute(countKey, [inputKey], input => {
if (process.browser && process.env.NODE_ENV !== 'production') {
window.reselectStats[inputKey] = window.reselectStats[inputKey] || {numInputChanges: 0, numOutputChanges: 0}
window.reselectStats[inputKey].numInputChanges++
}
if (!isEqual(prevValue, input)) {
nextValue = input
count++
}
return count
})
store.compute(outputKey, [countKey], () => {
if (process.browser && process.env.NODE_ENV !== 'production') {
window.reselectStats[inputKey].numOutputChanges++
}
prevValue = nextValue
nextValue = null
return prevValue
})
}