SelectPanel: Add story to load more items on scroll

packages/react/src/SelectPanel/SelectPanel.dev.stories.tsx

@@ -1,7 +1,7 @@
 import {TriangleDownIcon} from '@primer/octicons-react'
 import type {Meta} from '@storybook/react-vite'
 import type React from 'react'
-import {useState} from 'react'
+import {useState, useEffect, useRef} from 'react'
 
 import Box from '../Box'
 import {Button} from '../Button'
@@ -406,3 +406,66 @@ export const AllVariants = () => {
     </>
   )
 }
+
+const NUMBER_OF_ITEMS = 500
+const lotsOfItems = Array.from({length: NUMBER_OF_ITEMS}, (_, index) => {
+  return {
+    id: index,
+    text: `Item ${index}`,
+    description: `Description ${index}`,
+    leadingVisual: getColorCircle('#a2eeef'),
+  }
+})
+
+export const LotsOfItems = () => {
+  const [selected, setSelected] = useState<ItemInput[]>([])
+  const [filter, setFilter] = useState('')
+  const filteredItems = lotsOfItems.filter(item => item.text.toLowerCase().startsWith(filter.toLowerCase()))
+  const [open, setOpen] = useState(false)
+  const timeBeforeOpen = useRef<number>()
+  const timeAfterOpen = useRef<number>()
+  const [timeTakenToOpen, setTimeTakenToOpen] = useState<number>()
+
+  const onOpenChange = () => {
+    timeBeforeOpen.current = performance.now()
+    setOpen(!open)
+  }
+
+  useEffect(() => {
+    if (open) {
+      timeAfterOpen.current = performance.now()
+      if (timeBeforeOpen.current) setTimeTakenToOpen(timeAfterOpen.current - timeBeforeOpen.current)
+    }
+  }, [open])
+
+  return (
+    <>
+      <p>
+        Time taken to render {NUMBER_OF_ITEMS} items: {timeTakenToOpen || '(click "Select Labels" to open)'}
+      </p>
+
+      <FormControl>
+        <FormControl.Label>Labels</FormControl.Label>
+        <SelectPanel
+          title="Select labels"
+          placeholder="Select labels"
+          subtitle="Use labels to organize issues and pull requests"
+          renderAnchor={({children, ...anchorProps}) => (
+            <Button trailingAction={TriangleDownIcon} {...anchorProps} aria-haspopup="dialog">
+              {children}
+            </Button>
+          )}
+          open={open}
+          onOpenChange={onOpenChange}
+          items={filteredItems}
+          selected={selected}
+          onSelectedChange={setSelected}
+          onFilterChange={setFilter}
+          width="medium"
+          height="large"
+          message={filteredItems.length === 0 ? NoResultsMessage(filter) : undefined}
+        />
+      </FormControl>
+    </>
+  )
+}

packages/react/src/SelectPanel/SelectPanel.examples.stories.tsx

@@ -1,4 +1,4 @@
-import React, {useState, useMemo} from 'react'
+import React, {useState, useMemo, useRef, useEffect} from 'react'
 import type {Meta} from '@storybook/react-vite'
 import {Button} from '../Button'
 import type {ItemInput} from '../deprecated/ActionList/List'
@@ -10,6 +10,8 @@ import FormControl from '../FormControl'
 import {Stack} from '../Stack'
 import {Dialog} from '../experimental'
 import styles from './SelectPanel.examples.stories.module.css'
+import Checkbox from '../Checkbox'
+import Label from '../Label'
 
 const meta: Meta<typeof SelectPanel> = {
   title: 'Components/SelectPanel/Examples',
@@ -474,3 +476,115 @@ export const WithDefaultMessage = () => {
     </FormControl>
   )
 }
+
+const NUMBER_OF_ITEMS = 500
+const lotsOfItems = Array.from({length: NUMBER_OF_ITEMS}, (_, index) => {
+  return {
+    id: index,
+    text: `Item ${index}`,
+    description: `Description ${index}`,
+    leadingVisual: getColorCircle('#a2eeef'),
+  }
+})
+
+export const RenderMoreOnScroll = () => {
+  const [selected, setSelected] = useState<ItemInput[]>([])
+  const [open, setOpen] = useState(false)
+  const [renderSubset, setRenderSubset] = React.useState(true)
+
+  const [filter, setFilter] = useState('')
+  const filteredItems = lotsOfItems.filter(item => item.text.toLowerCase().startsWith(filter.toLowerCase()))
+
+  const [numberOfItemsInSubset, setNumberOfItemsInSubset] = useState(50)
+  const subsetOfFiltereredItemsToRender = filteredItems.slice(0, renderSubset ? numberOfItemsInSubset : NUMBER_OF_ITEMS)
+
+  useEffect(function loadMoreItemsOnScrollEnd() {
+    const scrollContainer = document.querySelector('#select-labels-panel-dialog [role="listbox"]')?.parentElement
+
+    const handler = (event: Event) => {
+      const container = event.target as HTMLElement
+      if (container.scrollTop === container.scrollHeight - container.offsetHeight) {
+        // has scrolled to bottom
+        setNumberOfItemsInSubset(numberOfItemsInSubset + 50)
+      }
+    }
+
+    // eslint-disable-next-line github/prefer-observers
+    if (scrollContainer) scrollContainer.addEventListener('scroll', handler)
+    return () => scrollContainer?.removeEventListener('scroll', handler)
+  })
+
+  /* perf measurement logic start */
+  const timeBeforeOpen = useRef<number>()
+  const timeAfterOpen = useRef<number>()
+  const [timeTakenToOpen, setTimeTakenToOpen] = useState<number>()
+
+  const onOpenChange = () => {
+    if (!open) timeBeforeOpen.current = performance.now()
+    setOpen(!open)
+  }
+
+  useEffect(
+    function measureTimeAfterOpen() {
+      if (open) {
+        timeAfterOpen.current = performance.now()
+        if (timeBeforeOpen.current) setTimeTakenToOpen(timeAfterOpen.current - timeBeforeOpen.current)
+      }
+    },
+    [open],
+  )
+  /* end */
+
+  return (
+    <form>
+      <FormControl>
+        <FormControl.Label>Render subset of items on initial open</FormControl.Label>
+        <FormControl.Caption>
+          {renderSubset ? 'Loads more items on scroll' : `Loads all ${NUMBER_OF_ITEMS} items at once`}
+        </FormControl.Caption>
+        <Checkbox
+          checked={renderSubset}
+          onChange={() => {
+            setRenderSubset(!renderSubset)
+            setTimeTakenToOpen(undefined)
+            setNumberOfItemsInSubset(50)
+          }}
+        />
+      </FormControl>
+      <p>
+        Time taken (ms) to render initial {renderSubset ? 50 : NUMBER_OF_ITEMS} items:{' '}
+        {timeTakenToOpen ? <Label>{timeTakenToOpen.toFixed(2)} ms</Label> : '(click "Select Labels" to open)'}
+      </p>
+      <p>
+        Known bug: Scroll resets to top when the items change. Works well with feature flag{' '}
+        <Label>primer_react_select_panel_remove_active_descendant</Label>
+      </p>
+
+      <FormControl>
+        <FormControl.Label>Labels</FormControl.Label>
+        <SelectPanel
+          title="Select labels"
+          placeholder="Select labels"
+          subtitle="Use labels to organize issues and pull requests"
+          renderAnchor={({children, ...anchorProps}) => (
+            <Button trailingAction={TriangleDownIcon} {...anchorProps} aria-haspopup="dialog">
+              {children}
+            </Button>
+          )}
+          open={open}
+          onOpenChange={onOpenChange}
+          items={subsetOfFiltereredItemsToRender}
+          selected={selected}
+          onSelectedChange={setSelected}
+          onFilterChange={setFilter}
+          width="medium"
+          height="large"
+          message={filteredItems.length === 0 ? NoResultsMessage(filter) : undefined}
+          overlayProps={{
+            id: 'select-labels-panel-dialog',
+          }}
+        />
+      </FormControl>
+    </form>
+  )
+}