Svelte

Live before-and-after

Executed source

Imported verbatim with ?raw from every implementation file shown below. Playback timing and FLIP controls come from the shared demo harness.

main.tsRuntime.svelteRow.svelte

src/svelte/main.tsTypeScript · 17 linesCopy

import { mount, tick, unmount } from "svelte";
import { writable } from "svelte/store";

import { mountFrameworkDemo, type DemoFrameState, type DemoRuntime } from "../shared/demo.js";
import Runtime from "./Runtime.svelte";

await mountFrameworkDemo("Svelte", (target, initialState): DemoRuntime => {
  const frame = writable<DemoFrameState>(initialState);
  const component = mount(Runtime, { props: { frame }, target });
  return {
    destroy: () => unmount(component),
    update: async (nextState) => {
      frame.set(nextState);
      await tick();
    },
  };
});

src/svelte/Runtime.svelteSvelte · 40 linesCopy

<script lang="ts">
  import { createLikftc } from "@vp-tw/likftc/svelte";
  import { untrack } from "svelte";
  import { derived, type Readable } from "svelte/store";

  import {
    createAfterRows,
    createBeforeRows,
    type DemoFrameState,
  } from "../shared/demo.js";
  import Row from "./Row.svelte";

  let { frame }: { frame: Readable<DemoFrameState> } = $props();

  const items = untrack(() => derived(frame, (state) => state.items));
  const entries = untrack(() => createLikftc(items, { getId: (item) => item.id }));
  let beforeRows = $derived(createBeforeRows($frame));
  let afterRows = $derived(createAfterRows($frame, $entries));
</script>

<div class="runtime-grid">
  <article class="runtime-panel">
    <small>WITHOUT</small>
    <h3>Logical ID key</h3>
    <ol data-list="before">
      {#each beforeRows as row (row.key)}
        <Row {row} />
      {/each}
    </ol>
  </article>
  <article class="runtime-panel">
    <small>WITH @LIKFTC/SVELTE</small>
    <h3>Presence identity</h3>
    <ol data-list="after">
      {#each afterRows as row (row.key)}
        <Row {row} />
      {/each}
    </ol>
  </article>
</div>

src/svelte/Row.svelteSvelte · 20 linesCopy

<script lang="ts">
  import { describeRow, type DemoRenderedRow } from "../shared/demo.js";

  let { row }: { row: DemoRenderedRow } = $props();
</script>

<li
  class="runtime-row"
  data-collision={String(row.kind === "collision")}
  data-id={row.item.id}
  data-key={row.keyText}
  data-kind={row.kind}
  data-phase={row.kind === "exiting" ? "exiting" : "current"}
  data-slot={row.slot}
>
  <b>{row.item.id.toUpperCase()}</b>
  <span>{row.item.label}</span>
  <code>{row.keyText}</code>
  <em>{describeRow(row.kind)}</em>
</li>

The store resets its identity state when the last subscriber disconnects. Active subscribers share one transactional source subscription.