Add handleSpeedChange hook to site handler API#1457
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Problem ------- PR #1185 proposed fixing YouTube subtitle desync by monkey-patching window.setTimeout globally and adding a second MAIN-world content script to the manifest. The fix worked but the approach was wrong: global timer patching is fragile, the delay%10 heuristic depends on YouTube internals, and it bypassed the existing site handler system that was designed for exactly this kind of site-specific adaptation. Root cause ---------- When VSC sets video.playbackRate directly, YouTube's internal subtitle scheduler doesn't know about it. YouTube schedules caption refreshes based on its own assumed playback rate, so at high speeds the video outruns the captions. The real fix is to let site handlers participate in speed changes so they can sync with a site's custom player API. But the handler system had no hook for it — despite being the extension's primary operation. Design ------ The site handler API already had handleSeek (total replacement — the handler owns the operation, base class provides default behavior, overrides replace it entirely). Speed changes had no equivalent: all three places that assigned video.playbackRate did so directly, bypassing the handler system. This change adds handleSpeedChange(video, speed) following the same pattern: BaseSiteHandler.handleSpeedChange(video, speed) Default: video.playbackRate = speed SiteHandlerManager.handleSpeedChange(video, speed) Delegates to current handler All video.playbackRate assignments now route through this hook: - ActionHandler.setSpeed() — the primary speed change path - EventManager cooldown restore — site pushed back during cooldown - EventManager fight-back — site reset speed, extension restores it Fight-back safety: handleSpeedChange is always called inside the cooldown window. The cooldown guard at the top of handleRateChange prevents re-entry, so even if a handler's implementation triggers a ratechange event, it won't loop. What this enables ----------------- A YouTube handler override can now sync with YouTube's player: handleSpeedChange(video, speed) { video.playbackRate = speed; const player = document.querySelector('#movie_player'); if (player?.setPlaybackRate) player.setPlaybackRate(speed); } This makes YouTube's subtitle scheduler aware of the real speed — no timer hacking, no manifest changes, no global patches. That override is left for a follow-up; this commit provides the infrastructure. Cleanup ------- Removed YouTubeHandler.onPlayerStateChange() — dead code, defined but never called from anywhere. Handler API surface after this change ------------------------------------- Lifecycle: initialize(doc), cleanup() Discovery: shouldIgnoreVideo(video), getVideoContainerSelectors(), detectSpecialVideos(doc) UI: getControllerPosition(parent, video) Playback: handleSpeedChange(video, speed), handleSeek(video, sec) See docs/custom-player-handler.md for the full developer guide. Files changed ------------- src/site-handlers/base-handler.js — new handleSpeedChange method src/site-handlers/index.js — delegation in manager src/core/action-handler.js — setSpeed routes through handler src/utils/event-manager.js — fight-back routes through handler src/site-handlers/youtube-handler.js — remove dead onPlayerStateChange docs/custom-player-handler.md — developer guide tests/unit/site-handlers/ — 7 tests covering all paths
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Route all video.playbackRate assignments through the site handler
system, matching the existing handleSeek pattern. This gives site
handlers a clean way to sync speed changes with custom player APIs
(e.g. YouTube subtitle sync per #1185) without global monkey-patching.
video.playbackRate)
cooldown, custom override)