beecast-player — the first-party beecast player

A self-contained, dependency-free player for asciicast recordings (v1, v2, and v3): a DOM-free asciicast parser and VT100/xterm-subset terminal emulator, a headless playback controller, and a thin DOM half with the default controls and <beecast-player> Web Component. The crate exposes the component as two string constants to inline — PLAYER_JS (one <script>) and PLAYER_CSS (one <style>); nothing is fetched at runtime, no workers, no fonts, no images.

This crate is the component's canonical home. The component was born in scsh's session browser and graduated here; scsh is now one downstream consumer among any others. beecast pages embed it through beecast-page; any other page or app that plays asciicast recordings consumes it from crates.io the same way.

Clean-room statement. Written from scratch against public format and protocol documentation only — the asciicast v1/v2/v3 format descriptions and the standard ECMA-48 / xterm control-sequence references. No asciinema-player source code was consulted, copied, or translated. MIT, like the rest of beecast, so every embedding page carries a single license.

Layout

The three JS files are concatenated at compile time into the one PLAYER_JS constant.

// Inline both constants whole; the page stays fully self-contained.
let js = beecast_player::PLAYER_JS;
let css = beecast_player::PLAYER_CSS;

Integration levels

1. Zero-config factory (legacy, still fully supported):

const player = BeeCastPlayer.create({ data: castText }, mountElement, {
  fit: 'both',
  controls: true,
  idleTimeLimit: 2,
  markers: [[t, 'label'], /* or */ { time: t, label: 'label', type: 'chapter' }],
  startAt: 12.5,
  speed: 1.5,
  autoPlay: true,
  fullscreenEl: el,
});
player.play();
player.pause();
player.seek(t);
player.setSpeed(2);       // in place — does not remount
player.getCurrentTime();  // recording seconds, synchronous
player.getState();        // snapshot: status, time, markers, terminal, …
player.subscribe(fn);     // immediate + changes; returns unsubscribe
player.append(text);      // live-follow
player.dispose();

2. Web Component (preferred for new browser embeddings):

<beecast-player fit="both" idle-time-limit="2"></beecast-player>
<script>
  const el = document.querySelector('beecast-player');
  el.load({ cast: castText, markers: [[0, 'Start']] });
  el.play();
  el.addEventListener('beecast-timeupdate', (e) => { /* e.detail.currentTime */ });
</script>

3. Headless controller (custom UI, tests, non-DOM hosts):

const controller = BeeCastController.create({
  data: castText,
  idleTimeLimit: 2,
  speed: 1,
  markers: [],
  clock: optionalClock, // { now, requestAnimationFrame, cancelAnimationFrame }
});
const stop = controller.subscribe((state, meta) => { /* render your UI */ });
controller.play();
controller.setSpeed(1.5);
controller.seek(42.5);
controller.append(chunk);
controller.dispose();

Compatibility notes (public vs internal)

Public today

• BeeCastVT: parseCast, appendCast, buildPacing, extendPacing, mapTime, Term, attribute bit constants, color256.
• BeeCastController.create(...) and its command/state/subscribe contract.
• BeeCastPlayer.create(...) methods: play, pause, toggle, seek, getCurrentTime, setSpeed, getState, subscribe, append, dispose.
• <beecast-player> element: properties/methods/events listed below.
• CSS variables listed in BeeCastPlayer.supportedCssVariables (semantic --beecast-* plus terminal --sp-*).

Readable but not public (migration window only — do not depend on these):

• player.playing, player.pacedPos, player.eventIdx, and other internals listed in BeeCastPlayer.nonPublicFields. Prefer getState().status === 'playing' or subscribe.

getCurrentTime() and seek() are synchronous. If a future source needs async seeking, that will be a separately named method — these contracts will not change silently.

Playback state

interface PlaybackState {
  status: 'idle' | 'playing' | 'paused' | 'ended';
  currentTime: number;      // recording seconds
  duration: number;
  speed: number;
  atLiveEdge: boolean;
  canAppend: boolean;
  markers: TimelineMarker[];
  terminal: TerminalSnapshot;
  dimensions: { columns: number; rows: number };
}

getState() returns a defensive snapshot. subscribe(listener) invokes the listener immediately with the current state, then on meaningful changes. High-frequency timeupdate notifications are coalesced to animation-frame rate; discrete events (seek, speedchange, durationchange, …) always deliver. The unsubscribe function is idempotent.

Events (CustomEvent on the player root / <beecast-player>)

Times are always recording time. Origins include 'api', 'keyboard', 'pointer', 'marker', 'source'.

Markers

Tuples [time, label] still work and are normalized. Preferred form:

interface TimelineMarker {
  id: string;
  time: number;
  type: 'chapter' | 'annotation' | 'event' | string;
  label: string;
  description?: string;
  color?: string;
  source?: 'cast' | 'sidecar' | 'integration';
  data?: unknown;
}

In-band m events get source: 'cast' and stable ids. Sidecar chapters use source: 'sidecar'.

Sources

type CastSource =
  | { type: 'text'; data: string }
  | { type: 'custom'; subscribe: (sink) => unsubscribe };

The base player never fetches because a string looks like a URL. Network-backed adapters are caller-supplied; generated pages use only inline text and perform zero network requests.

Theming

Stable semantic tokens:

--beecast-color-surface
--beecast-color-surface-raised
--beecast-color-text
--beecast-color-text-muted
--beecast-color-accent
--beecast-color-focus
--beecast-color-marker
--beecast-color-error
--beecast-control-height
--beecast-radius
--beecast-font-ui
--beecast-font-terminal

Built-in themes via data-theme="dark" | "light" | "system" on the player root (or the theme attribute on <beecast-player>). Terminal ANSI colors (--sp-c0…--sp-c15) remain independently themeable. Internal .sp-* classes are not a public API.

Controls configuration

controls: true | false | {
  play: true,
  seek: true,
  time: true,
  speed: true,
  chapters: true,
  fullscreen: true,
}

Accessibility

• Icon-only controls expose accessible names (aria-label) independent of title.
• Play/pause uses aria-pressed; speed options use aria-checked.
• Seek supports Arrow keys, Home, End, Page Up/Down.
• :focus-visible styles use --beecast-color-focus / accent.
• accessibility: 'snapshot' | 'off' — snapshot mode exposes the current terminal as off-screen preformatted text (not a live region, so playback does not flood assistive tech).
• prefers-reduced-motion disables overlay motion.

Keyboard when the player has focus: space play/pause · ←/→ seek ±5s · < / > speed down/up · [ / ] previous/next marker · c chapters · f fullscreen · Escape closes menus.

Time axis, layout, live-follow

The time axis is always recording time. Idle-time compression only affects pacing (long silences play back at most idleTimeLimit seconds long); seek, getCurrentTime, markers, and ?t= deep links all use the recording's own clock.

Layout. With fit set, the fixed-metric terminal scales down (never up) to the containing box's width — and, for fit: 'both', also to the mount's height when the embedding page gives it one. Whenever the terminal (scaled or not) ends up narrower than its pane, it is centered horizontally.

The big play button. While the recording sits at its very start, a large center play glyph — block characters shaped as a triangle — dims the screen behind it; one click starts playback. It never appears mid-recording.

Live-follow. Feed each new chunk of v2/v3 NDJSON to append(text). Chunk boundaries are free; partial trailing lines buffer until complete. A playhead at the live edge stays pinned (tail -f policy); a viewer who seeked back is never yanked forward. v1 append is a no-op.

The core half is exposed on BeeCastVT for embedders that need it without a mounted player.

Terminal emulation scope

The subset a tmux-hosted TUI actually exercises: cursor addressing (CUP/CUU/CUD/CUF/CUB/ CHA/VPA/CNL/CPL), erase (ED/EL/ECH), insert/delete (ICH/DCH/IL/DL), scroll (SU/SD, DECSTBM scroll regions, IND/RI/NEL), SGR (16/256/true color, bold, dim, italic, underline, inverse, strikethrough), alternate screen (?1049, ?47), cursor visibility (?25), autowrap with deferred wrap (?7), save/restore cursor (DECSC/DECRC, CSI s/u), DEC special graphics (ESC ( 0 line drawing, SO/SI), tab stops, OSC consumption (titles are parsed and ignored), and v3 in-band resize events. Unrecognized sequences are consumed and ignored — never rendered as text.

Testing

The DOM-free core and headless controller self-test under Node from cargo test (vt_core_node_selftest shells out to node and skips silently when Node is not installed): parsing, the emulator subset, live-follow appends, the pacing map, controller state transitions, subscribe/unsubscribe, setSpeed, seek, and marker normalization. Structural tests gate the bundle properties every self-contained embedding depends on — no </script, no workers, no CSS fetches, no third-party license marker, and a stable public API surface.

License

MIT (text in LICENSE, shipped with the crate) — the component, like the rest of beecast, is all first-party code.