Examples

// apps/docs/examples/virtual/long-list.tsx'use client';
import {useState} from 'react';
import {Button} from '@workspace/active-ui/components/primitives/button';import {Input} from '@workspace/active-ui/components/primitives/input';import {Label} from '@workspace/active-ui/components/primitives/label';import {useVirtualAxis} from '@workspace/active-virtual/react';
const COUNT = 10_000;
/** Every seventh row wraps to a second line: the axis measures real heights. */function rowText(position: number): string {  const base = `Row ${(position + 1).toLocaleString('en')}`;  return position % 7 === 3    ? `${base}: a longer note that wraps to a second line in a narrow column, so this row is taller than its estimate.`    : base;}
/** 10,000 rows of varying height; only the rows in view (plus overscan) are in the DOM. */export default function LongList() {  const [container, setContainer] = useState<HTMLDivElement | null>(null);  const [target, setTarget] = useState('5000');  const {projection, controller, itemRef} = useVirtualAxis({    count: COUNT,    estimate: 32,    container,  });  return (    <div className="flex flex-col gap-3">      <form        className="flex flex-wrap items-end gap-2"        onSubmit={(event) => {          event.preventDefault();          const row = Number(target);          if (Number.isInteger(row) && row >= 1 && row <= COUNT)            controller.scrollToPosition(row - 1, {align: 'center'});        }}      >        <div className="flex flex-col gap-1.5">          <Label htmlFor="virtual-target">Row</Label>          <Input            id="virtual-target"            className="w-28"            inputMode="numeric"            value={target}            onChange={(event) => setTarget(event.target.value)}          />        </div>        <Button type="submit" variant="outline">          Go to row        </Button>      </form>      <div        ref={setContainer}        className="bg-background h-72 overflow-auto rounded-md border"        tabIndex={0}        aria-label="Ten thousand rows"        data-virtual-container      >        <div style={{height: projection.extent, position: 'relative'}}>          {projection.items.map((item) => (            <div              key={item.identity}              ref={itemRef(item.identity)}              className="border-b px-3 py-1.5 text-sm"              style={{                position: 'absolute',                top: 0,                left: 0,                width: '100%',                transform: `translateY(${item.offset}px)`,              }}              data-position={item.position}            >              {rowText(item.position)}            </div>          ))}        </div>      </div>      <p className="text-muted-foreground text-sm" aria-live="polite">        {projection.items.length} of {COUNT.toLocaleString('en')} rows in the        DOM      </p>    </div>  );}

// apps/docs/examples/virtual/keyed-prepend.tsx'use client';
import {useState} from 'react';
import {Button} from '@workspace/active-ui/components/primitives/button';import {useVirtualAxis} from '@workspace/active-virtual/react';
interface Message {  key: string;  text: string;}
function messages(from: number, count: number): Message[] {  return Array.from({length: count}, (_, index) => {    const n = from + index;    return {key: `m${n}`, text: `Message ${n}`};  });}
/** * A keyed list: loading older messages above the viewport does not move what * is on screen, because the axis anchors on a key and compensates the scroll. */export default function KeyedPrepend() {  const [container, setContainer] = useState<HTMLDivElement | null>(null);  const [items, setItems] = useState(() => messages(100, 50));  const {projection, itemRef} = useVirtualAxis({    keys: items.map((item) => item.key),    estimate: 36,    container,    // Keep the item at the top in place even when the list is scrolled to    // its very start, instead of following that edge.    startEdge: 'preserve',  });  const byKey = new Map(items.map((item) => [item.key, item]));  const first = Number(items[0]!.key.slice(1));  return (    <div className="flex flex-col gap-3">      <div className="flex flex-wrap items-center gap-2">        <Button          variant="outline"          disabled={first === 0}          onClick={() =>            setItems((list) => [              ...messages(Math.max(0, first - 20), Math.min(20, first)),              ...list,            ])          }        >          Load 20 older messages        </Button>        <span className="text-muted-foreground text-sm" aria-live="polite">          {items.length} messages, from {items[0]!.text}        </span>      </div>      <div        ref={setContainer}        className="bg-background h-60 overflow-auto rounded-md border"        tabIndex={0}        aria-label="Messages"        data-virtual-container      >        <div style={{height: projection.extent, position: 'relative'}}>          {projection.items.map((item) => (            <div              key={item.identity}              ref={itemRef(item.identity)}              className="border-b px-3 py-2 text-sm"              style={{                position: 'absolute',                top: 0,                left: 0,                width: '100%',                transform: `translateY(${item.offset}px)`,              }}            >              {byKey.get(String(item.identity))?.text}            </div>          ))}        </div>      </div>    </div>  );}