ArtPlayer/packages/artplayer-plugin-danmuku/ARCHITECTURE.md

Danmuku maintenance map

The compatibility reference is the actual npm 5.3.0 package. Its archive, historical declarations, earlier exports and failure evidence are indexed in refactor/baselines/danmuku-release.json and danmuku-contract.md at the repository root. Do not infer runtime contracts from the old declaration file.

Module responsibilities

Module	Responsibility
src/index.js	Plugin factory, facade getters, bound methods, setting and heatmap composition
src/danmuku.js	Internal instance, method return identity, configuration/load commits, event and lifecycle wiring
src/config.js	Fresh defaults, validation schema, configuration comparison and normalization
src/input.js	Input forms, replacement ownership, independent append operations, cancellation and synchronous callback reentry
src/bilibili-parser.js	Pure legacy-compatible XML fields, mode mapping and entity decoding
src/bilibili.js	Fetch and response text, one parser Worker per request, fallback, settlement and Blob URL cleanup
src/scheduler.js	One RAF or asynchronous frame, cancellation generations, preparation ownership and failure recovery
src/renderer.js	Owned node allocation, preparation, geometry snapshots, placement, pause/resume styling and disposal
src/queue.js	Ordered state pools, eligibility and state transitions
src/worker-client.js	Track Worker lifecycle, a shared response dispatcher, unique request IDs and pending requests
src/worker.js	Track placement Worker; a separate protocol from the XML parser Worker
src/setting.js	Settings coordinator, configuration controls, mount and fullscreen layout
src/setting-template.js	Existing template HTML and static icon values
src/setting-slider.js	Slider index, pointer and rotation behavior
src/setting-send.js	Pending send, original error outlet and lock countdown
src/setting-lifecycle.js	Exact subscription/proxy disposal, cancellation and conditional host-property restoration
src/setting-style.js	Shared document style and one pending DOMContentLoaded installation
src/heatmap.js	Owned control, progress stops, subscriptions and per-instance gradient
src/heatmap-sampling.js	Sorted-time bin counts with historical numeric boundaries
src/heatmap-geometry.js	Legacy point normalization, caller-visible point writes and SVG curve calculation

The package is undergoing staged migration. PKG-DANMUKU-03 separates input and configuration responsibilities in JavaScript; PKG-DANMUKU-04 separates scheduling and track requests; PKG-DANMUKU-05 separates rendering and UI resources; PKG-DANMUKU-06 converts all owned modules and Worker messages to TypeScript and validates installed consumers. This intermediate structure is not the final TypeScript or release acceptance.

Contracts to retain

• The registrar returns its facade synchronously. emit() and load() return Promises resolving to the internal Danmuku instance, which differs from that facade. config/hide/show/reset return that same internal instance synchronously; mount() returns undefined. Keep the three live getters.
• load() and load(undefined) replace only after input succeeds. load(target) appends without updating option.danmuku. Independent appends may complete in either order and can append after a replacement.
• Arrays enter synchronously. Empty initial input emits show -> config -> reset -> loaded before registration returns. Nonempty input inserts the first item before the first await, then awaits each emit() in order. A later invalid item leaves earlier accepted items present.
• A new replacement supersedes an older replacement. Destroy cancels all input operations. Cancelled public loads resolve to the same internal instance; they do not emit late loaded/error events or write stale rows. The input Promise itself may be uncancellable; observe its eventual rejection locally.
• Invoke a loader function without an explicit receiver. Invoke the filter through the current option so its receiver remains that option. Check load ownership again after callbacks and reset events, including synchronous callbacks that start another replacement.
• Keep input normalization observable: accepted objects receive missing mode, style and color before filtering, and the queue receives a shallow copy. Explicit time zero is preserved; missing time and NaN default to current time + 0.5. The historical validator accepts NaN as a number, so preserving zero must not accidentally remove that fallback. Positive infinity remains positive infinity; negative values, including negative infinity, clamp to zero.
• Function and Promise configuration changes use identity. Structurally equal ordinary values retain the historical JSON comparison behavior. Validate and normalize a prospective option before replacing the current option; invalid updates cannot corrupt it. Configuration does not implicitly reload input.
• Keep XML entity order, unpadded hexadecimal colors, numeric conversions, extension fields and existing mode mapping. An empty XML document is a valid empty result. Fetch/text failures must reach the public load's single error outlet and reject it; automatic initial loading observes that rejection.

Scheduling ownership

Keep at most one pending RAF or asynchronous preparation frame. Native play and playing both invoke the existing start path and retain its events, but must not create competing loops. Ready items precede wait items; wait selection retains the current-time +/- 0.1 second window and state-pool order. Keep the existing track algorithm and geometry fields until separately reviewed.

Pause, reset, successful replacement input commit, hide, seeking, destroy and replacing the beforeVisible callback invalidate unfinished preparation. Cancellation races the user Promise so an unresolved callback cannot prevent later work. A frame owns its allocated node; check that node identity before recycling it, and check the generation after each await or callback. Existing emit/stop nodes survive hide, seeking and callback changes; reset retains its explicit reset behavior.

Seek does not implicitly reset already displayed or paused comments. Date.now still measures wall-clock lifetime, excluding paused time. With synchronous playback enabled, new comments sample speed/playbackRate when allocated; active comments retain their assigned remaining seconds. Do not change these timing rules as incidental cleanup.

A rejected beforeVisible reports its original error once and excludes that item from further attempts in the current run. Explicit start, reset, an invalidation or replacement callback permits another attempt if the item is still eligible. False results retain their ordinary next-frame evaluation. Other items can continue after a rejection. Error-listener failures are observed locally and logged instead of creating a detached rejected RAF Promise.

A track Worker fault rejects its pending requests with the original error, disposes that Worker and reports one error, then halts internal scheduling. It does not fabricate a public stop event. A later start/reset rebuilds the Worker; repeated failure waits for another explicit recovery opportunity. Cancelled internal requests resolve { id, result: undefined } instead of remaining pending forever. Normal responses preserve { id, result }.

Recovery error listeners run synchronously and can call destroy, stop, reset, hide or start again. After recovery, the outer start must recheck destruction, stop and fault state, its cancellation generation and its start-attempt identity before continuing paused rows, scheduling or emitting start. Generation checks protect reset/hide and other invalidation; the attempt identity also protects a nested start that succeeds without changing the generation. Do not let the outer call revive stopped rows or add a second start event after a nested recovery. Ordinary repeated starts still retain their historical events and internal return identity. Recovery tests restore a working Worker factory before a single nested action; they do not manufacture an infinite retry loop.

Install the shared handler before sending requests. IDs are unique across requests and Worker replacement, including multiple requests in one millisecond. Late, unknown and duplicate replies do not settle a different request.

Verification and remaining work

yarn test:danmuku runs frozen historical contracts/failures and candidate input, parser, scheduler and Worker regressions. The historical helper and archives must remain frozen; candidate tests use test/helpers/danmuku-candidate.js and may select built artifacts through ARTPLAYER_DANMUKU_ARTIFACT. The input tests compare NaN and both infinities against frozen source and real npm main/legacy artifacts. Preserve those historical assertions alongside the explicit-zero correction when changing numeric normalization.

test/browser/danmuku-input.spec.js uses native video and Blob Workers against published and candidate cores. Run its source, main and legacy variants after the normal package build. Browser evidence distinguishes local XML/fault fixtures from the real Bilibili service, and Windows WebKit from Safari devices.

test/browser/danmuku-scheduler.spec.js verifies native callback cancellation, three modes, strict dense geometry, one request per prepared item, native pause/seek/rate and visible-node reuse. Preserve both geometric and protocol assertions; unique IDs alone do not prove non-overlapping tracks.

Long-run native load behavior still requires PKG-DANMUKU-07. Check task evidence and the risk register before changing completion or release status; short native regressions are not package-wide stability acceptance.

Rendering and UI resources

The scheduler owns whether work may proceed; the renderer owns the actual nodes. Destroy removes those nodes even when the core retains its HTML. It does not remove unrelated children. Replacement loading retains the historical whole-layer clear and starts a fresh node pool. Keep cancellation identity checks in the scheduler/renderer boundary when moving preparation logic. Replacement also removes owned nodes moved outside the layer before releasing their ownership records. Unrelated nodes outside the layer are left in place.

Setting registers its destruction boundary before creating UI. Initialization failure releases its own resources; the factory also rolls back the previously created Danmuku and Worker, preserving the original error. Store exact art subscriptions and proxy disposers. On old cores, use events.remove when the disposer remains registered; calling only the returned function can leave a registry entry. A disposal failure must not prevent other owned cleanup.

Pending beforeEmit is raced against destruction. Preserve its option receiver and strict true acceptance. Ordinary send inserts synchronously, clears input and starts the existing countdown; observing the emitted Promise must not delay that UI behavior. Retain console.error('Error emitting danmuku:', error) as the existing send-error outlet. Destruction prevents late input writes and timers.

Mount and fullscreen move the same Setting node. Destroy removes only that node. Dataset and display writes restore the preceding owner/original value only while the current value is still owned. Shared mounts must retain the surviving instance, and subsequent user writes must survive. The injected stylesheet is document-wide, stays available to other instances and retains import-time installation. Pending DOMContentLoaded installation is shared and released once it runs; it is not an instance leak.

Heatmap owns its control and listeners. Removal/replacement detaches them and must not remove a newer same-name control. The gradient ID is instance-specific; the first available heatmap-solids and local heatmap-start/heatmap-stop hooks remain, including repeated bundle evaluation. Zero or invalid sampling uses a positive default, and invalid dimensions/duration render no SVG. Preserve fractional step progression and strict-left/inclusive-right time bins. The original points event clones only the outer array and mutates inner y values; preserve that observable behavior, including repeated updates.

Issue #958 is a separate density defect from the earlier zero-step/cleanup fixes. Automatic queue sampling keeps the historical 128-unit Y domain until its transformed peak exceeds 32 units. Above that threshold, use four times the peak as the upper domain and constrain endpoints/Bezier controls to the bottom quarter of the chart. Constraining the control polygon bounds the whole cubic; merely clipping SVG overflow would retain the tall, flattened block. This is a visual correction for sampled high density, not a change to queue counts or timing. Small unfitted curves keep their exact old path, including small Bezier overshoot; the 25px bound applies to fitted charts, not every possible custom option.

Copy own enumerable option fields once, as the historical Object.assign did; do not reread getters or treat inherited axis fields as overrides. Finite explicit Y axes and nonempty custom points bypass fitting and preserve old paths and caller-visible writes. A resize/loaded event resamples the queue as before. test/danmuku-heatmap.test.js retains historical paths and tests dense bins, peak differences, control bounds and option property semantics. test/browser/danmuku-heatmap-density.spec.js verifies 16000 uniform, clustered and mixed rows using native SVG bounds, playback, progress and resizing against both cores in Chromium/Firefox/WebKit. This is heatmap validation; it is not a 16000-visible-DOM-danmuku throughput or long-duration heap benchmark (task07).

test/danmuku-setting.test.js uses Linkedom and real published core utilities for template parsing, selectors, events and lifecycle tests. Linkedom has no layout; its measured rectangles are controlled inputs, not browser evidence. test/browser/danmuku-resources.spec.js covers native external/shared mounts, pending sends, timers, retained-core HTML, initialization rollback and independent heatmaps. Run it with the scheduler/input specs for source and built artifacts. Dedicated recovery/new-continuation cases establish a ready item as a test precondition; obsolete gates and NaN use the actual media clock at 0.25 rate. These lifecycle preconditions do not establish stress-load timestamp delivery. The renderer resource cases also begin with an explicitly eligible row, then require native Worker completion and visible DOM before testing replacement or destruction. The separate pause/seek/rate case observes the original ready getter without changing its result and records bounded native media-time/queue samples to distinguish eligibility misses from placement failures.