fix(overlay): Linux X11/XWayland stacking, stale pause state, multi-copy selector (#101)

docs/architecture/README.md

@@ -19,6 +19,7 @@ The desktop app keeps `src/main.ts` as composition root and pushes behavior into
 
 - [Domains](./domains.md) - who owns what
 - [Layering](./layering.md) - how modules should depend on each other
+- [Subtitle Overlay Priming](./subtitle-overlay-priming.md) - visible-overlay subtitle startup flow
 - Public contributor summary: [`docs-site/architecture.md`](../../docs-site/architecture.md)
 
 ## Current Shape

docs/architecture/subtitle-overlay-priming.md

@@ -0,0 +1,83 @@
+<!-- read_when: changing visible overlay startup, Linux/X11 overlay window shape, mpv subtitle callbacks, or subtitle tokenization emission -->
+
+# Subtitle Overlay Priming
+
+Status: active
+Last verified: 2026-06-01
+Owner: Kyle Yasuda
+Read when: debugging subtitle state or blank Linux/X11 overlay windows when the visible overlay is shown or recreated
+
+Visible-overlay subtitle priming fills the overlay from mpv's current subtitle properties before
+waiting for the next live mpv subtitle event. This avoids a stale or blank overlay when the user
+manually shows the visible overlay while playback is already sitting on a subtitle.
+
+On Linux/X11, visible-overlay show and later mpv bounds refreshes restore the Electron window shape
+to the full current overlay bounds. Electron's `BrowserWindow.setShape()` applies a bounding shape,
+not an input-only region; stale shapes can leave a mapped 1920x1080 overlay with smaller X11 shape
+extents such as `800x600+0+0`, so renderer and websocket subtitle state are correct while bottom
+subtitles do not draw.
+
+## Entry Points
+
+- `src/main.ts` calls `primeCurrentSubtitleForVisibleOverlay()` when manual visible-overlay show
+  paths run.
+- `src/main.ts` calls `restoreVisibleOverlayWindowShapeForShow()` before visible-overlay show
+  actions on Linux, and `resetVisibleOverlayInputState()` restores a full shape instead of applying
+  an empty shape.
+- `src/main.ts` also restores the Linux/X11 shape after applying mpv overlay bounds, so a newly
+  created 800x600 hidden Electron window cannot keep clipping after it is resized to mpv geometry.
+- `primeCurrentSubtitleForVisibleOverlay()` delegates to
+  `primeVisibleOverlaySubtitleFromMpv()` in `src/main/runtime/current-subtitle-snapshot.ts`.
+- `restoreVisibleOverlayWindowShapeForShow()` delegates to `restoreLinuxOverlayWindowShape()` in
+  `src/main/runtime/linux-overlay-window-shape.ts`.
+- Inputs are callback deps, not globals: `getMpvClient`, `setCurrentSubText`,
+  `getCurrentSubtitleData`, `consumeCachedSubtitle`, `onSubtitleChange`,
+  `refreshCurrentSubtitle`, `emitSubtitle`, optional secondary-subtitle callbacks, and `logDebug`.
+
+## Primary Subtitle Flow
+
+1. Read the connected mpv client through `getMpvClient()`. Exit if no connected client.
+2. Request mpv `sub-text`. On failure, log a
+   `[visible-overlay-subtitle-prime] failed to read sub-text` debug line and exit.
+3. Normalize non-string `sub-text` to `''`, then call `setCurrentSubText(text)` so app state
+   matches mpv before any overlay emission.
+4. Empty text: call `onSubtitleChange(text)`, emit `{ text, tokens: null }`, then prime secondary
+   subtitles.
+5. Current cached payload: if `getCurrentSubtitleData()?.text === text`, call
+   `emitSubtitle(payload)` and `refreshCurrentSubtitle(text)`, then prime secondary subtitles.
+6. Tokenization cache hit: call `consumeCachedSubtitle(text)`, `onSubtitleChange(text)`, and
+   `emitSubtitle(cachedPayload)`, then prime secondary subtitles.
+7. Cache miss: call `refreshCurrentSubtitle(text)` and let normal tokenization emit the final
+   payload.
+
+In `src/main.ts`, both `onSubtitleChange` and `refreshCurrentSubtitle` pause
+`subtitlePrefetchService`, notify it with `onSeek(lastObservedTimePos)`, and then call the matching
+`subtitleProcessingController` method. This gives the visible overlay priority over background
+prefetch work and re-centers prefetch around the live playback time.
+
+## Emitted State
+
+- `emitSubtitle(payload)` maps to `emitSubtitlePayload(payload)`, which sends the normal
+  annotated subtitle payload to overlay windows and subtitle websocket listeners.
+- Secondary priming reads mpv `secondary-sub-text`, stores it in
+  `mpvClient.currentSecondarySubText`, and broadcasts `secondary-subtitle:set` to overlay windows.
+- If secondary `requestProperty` fails, the primary flow stays complete and only a debug line is
+  written.
+
+## Linux/X11 Window Shape
+
+- `restoreLinuxOverlayWindowShape()` reads `BrowserWindow.getBounds()` and calls `setShape()` with
+  one full-window rectangle: `{ x: 0, y: 0, width, height }`.
+- Restore the shape after `setBounds()`/mpv geometry updates, not only before showing the overlay.
+  Manual startup can create the hidden overlay at Electron's default 800x600 size before the window
+  tracker applies the real mpv bounds.
+- Do not use `setShape([])` as a passive reset for the visible overlay. On the tested X11/XWayland
+  path, empty or stale bounding shapes produced invisible or clipped subtitles even though the
+  overlay window remained mapped above mpv.
+- Pointer pass-through should continue to use `setIgnoreMouseEvents(true, { forward: true })` and
+  the Linux cursor-poll fallback, not bounding-shape clipping.
+
+## Config And Migration
+
+No config or schema migration. This workflow reuses existing mpv properties, overlay IPC events,
+subtitle tokenization cache, and prefetch controls.