feat(embedded-mpv): Linux port of the frame-copy rendering engine (headless EGL) (#1171)

* feat(embedded-mpv): Linux frame-copy helper via headless EGL

Port the frame-copy engine's native layer to Linux (PORTING.md items 1-4):

- frame_helper_gl.h: platform GlContext abstraction. macOS keeps the CGL
  path (moved verbatim); Linux acquires an EGL display in order
  surfaceless-Mesa -> default display -> GBM render node, binds a 3.2 core
  desktop-GL context surfaceless (1x1 pbuffer fallback), and hands mpv
  eglGetProcAddress. The helper's own GL calls link against glvnd
  libOpenGL, so no display server is required.
- frame_shm.h: portable frame_shm_now_ns() (CLOCK_MONOTONIC) shared by the
  helper and the reader addon, replacing the macOS-only
  clock_gettime_nsec_np(CLOCK_MONOTONIC_RAW); producer and consumer stay on
  the same clock.
- embedded_mpv_frame_reader.c: real implementation now also on __linux__
  (the code was already POSIX apart from the clock call).
- binding.gyp: OS==linux executable branch for iptvnator_mpv_helper linking
  system libmpv (-lmpv) + EGL/OpenGL/gbm, with rpaths for $ORIGIN/lib and
  the build-time library dir. The in-process addon still does not link
  libmpv - the ban only binds in-process, the helper is out of process.
- build-embedded-mpv.js: system-dev fallback on Linux (LIBMPV_INCLUDE_DIR
  or /usr/include) so a distro libmpv-dev install builds without staging a
  vendored runtime; a pre-set LINUX_NATIVE_LIBRARY_DIR now wins over the
  vendored lib dir.

Verified on Ubuntu 25.04 / i7-1165G7 (Iris Xe): lavfi smoke per PORTING.md
(idle->loading->playing snapshots at 4 Hz, aspect-fit generation bump
g1 1280x720 -> g2 960x720 for a 4:3 source), reader probe 60 fps at
1080p60 with 0 torn reads, clean quit with no leaked processes or shm.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* feat(embedded-mpv): enable the frame-copy engine gates on Linux

Flip the TypeScript side of the Linux port (PORTING.md item 5). A shared
dependency-free predicate, isFrameCopyPlatformSupported() (linux any-arch,
darwin arm64-only), now backs all four gates so they cannot drift:

- main.ts: the persisted Settings toggle promotes to the env flag on Linux
  too (this runs before window creation and controls the sandbox relax).
- EmbeddedMpvNativeService.isFrameCopyEngineActive/isFrameCopyAvailable.
- EmbeddedMpvFrameCopyAdapter.isSupported.

getSupport() ordering: the frame-copy branch moves above the Linux-only
native-engine prerequisites - the X11/Xwayland display-server check and
the system-mpv-on-PATH probe only bind the --wid native engine, while the
frame-copy helper renders offscreen (headless EGL) and links libmpv
itself. createSession() also skips resolving the native window handle for
frame-copy sessions, which the adapter ignores anyway, so native-Wayland
sessions no longer trip the window-handle assertion.

Settings copy: the i18n frame-copy description now says macOS (Apple
Silicon) and Linux in all 18 languages; stale macOS-only doc comments in
the settings/support interfaces updated alongside.

Tests: platform-gate matrix for the adapter (darwin arm64/x64, linux
x64/arm64, win32) and service specs covering Linux activation under
native Wayland, macOS arm64 staying active, macOS x64 staying native, and
the skipped window handle for frame-copy sessions.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* chore(packaging): CI + package guards for the Linux frame-copy helper

- build-and-make.yaml: install libegl-dev/libgl-dev/libgbm-dev on the
  Linux runner (the helper's EGL backend needs them now that the helper
  target builds on Linux), and verify the built helper exists and DOES
  link libmpv - the inverse of the addon's no-libmpv rule, which still
  holds and stays validated.
- electron-after-pack.cjs: strip iptvnator_mpv_helper from packaged Linux
  apps. It links the build host's system libmpv, which end-user systems
  cannot be assumed to have; the support probe treats the missing helper
  as frame-copy-unavailable (dev-build-only engine until the
  bundled-runtime staging milestone).
- frame_helper_gl.h: log the chosen EGL display tier to stderr (the
  adapter mirrors helper stderr), so bring-up problems on exotic setups
  are diagnosable.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* docs(embedded-mpv): document the Linux frame-copy port

- architecture doc: frame-copy section covers Linux (EGL display tiers,
  build deps, package strip), Linux support matrix notes the frame-copy
  exception to the X11 + system-mpv requirements, Linux measured baseline.
- RESULTS.md: Ubuntu 25.04 / i7-1165G7 (Iris Xe) measurement rows via the
  production helper + reader probe; viewport-size claim reproduced.
- PORTING.md: Linux marked done with pointers to what changed; Windows
  remains the open port and its perf gate the open decision.
- CLAUDE.md + tools/embedded-mpv/README.md: platform scope, Linux dev
  build requirements, system-headers fallback, helper strip.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* test(embedded-mpv): commit the Linux frame-copy measurement probe

linux-frame-probe.mjs reproduces the RESULTS.md Linux rows: spawns the
production helper, attaches the frame-reader addon to the announced shm
generation, and reports new-frame fps, copy wall time, produce->copy age,
torn reads and pixel spread. Usage documented in RESULTS.md.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(embedded-mpv): address multi-agent review findings on the Linux port

Confirmed findings (each verified by 3 adversarial reviewers):

- CI would fail to link the helper: -lOpenGL needs the unversioned glvnd
  libOpenGL.so, shipped only by libopengl-dev, which neither the runner
  images nor the previous apt line provide. Added to the workflow and to
  every documented Linux build-dep list.
- The new 'test -x' dist guard could never pass: webpack's dist asset
  copy drops file modes (helper arrives as 0644). The guard is now
  'test -f'; electron-after-pack.cjs restores the execute bit on packaged
  helpers (also fixes packaged-macOS spawns); the support probe now
  requires X_OK, so a mode-stripped helper reads as frame-copy-unavailable
  and falls back to native instead of failing spawn with EACCES.
- The Settings frame-copy toggle was unreachable in exactly the Linux
  states the port targets: the native-Wayland and missing-system-mpv
  unsupported payloads omitted frameCopyAvailable, and toggle visibility
  derives solely from it. Both returns now advertise availability.

Also from review:

- build-embedded-mpv.js keeps the old graceful-skip contract when the new
  system-dev fallback finds libmpv-dev but the GL/EGL/gbm dev stack is
  missing (previously such machines skipped; a hard electron-build
  failure was a regression).
- createSession derives the window-handle skip from the dispatched addon
  instead of re-evaluating the engine gate, so the two cannot disagree.
- The render thread logs the GL renderer string (surfaceless Mesa can
  silently pick llvmpipe on non-Mesa-primary systems; now diagnosable —
  verified 'Mesa Intel Iris Xe' on this machine).
- Specs pin the new semantics: frameCopyAvailable advertised while native
  is unsupported (Wayland / no mpv), frame-copy supported without a
  system mpv, and the handle-skip test disposes its session through the
  owning adapter.
- Docs: PORTING.md file map reflects the frame_helper_gl.h seam for the
  Windows porter; helper-strip removal correctly gated on milestone 4
  (bundled libmpv), not milestone 3; RESULTS.md preamble notes the
  RAW->MONOTONIC clock change; stale '(macOS)' scope comments updated.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(embedded-mpv): address Greptile/Codex review comments

- Sandbox gate requires a usable helper (Greptile P1, security): the
  main.ts env promotion now also probes for an executable
  iptvnator_mpv_helper before relaxing the window sandbox — a stale
  opt-in on packaged Linux (helper deliberately stripped) or after a
  cleaned native build no longer costs a sandboxless launch for an
  engine that cannot activate. Helper discovery (addon candidate paths +
  X_OK probe) moved into embedded-mpv-frame-copy-platform.util.ts,
  shared by main.ts and the service; the service keeps thin instance
  wrappers so tests can stub per scenario. New util spec pins the
  platform matrix, candidate resolution, and the execute-bit semantics.
- Stale frame-copy artifacts on skipped builds (Codex P2): cleanOutput()
  now also removes iptvnator_mpv_helper and
  embedded_mpv_frame_reader.node, so a failed/skipped rebuild cannot
  leave a previous helper advertising frame-copy support against a
  runtime the build just declared unavailable.
- Multiarch default lib dir (Greptile P1, partially refuted): -l
  resolution never depended on our -L (the compiler's built-in search
  paths include the Debian/Ubuntu multiarch dir — proven by the green CI
  run linking with a nonexistent -L dir), but the system-dev fallback
  now defaults to /usr/lib/<multiarch-triple> when present so the -L
  flag and the helper's baked rpath point somewhere real.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(embedded-mpv): harden Linux frame-copy port

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

.github/workflows/build-and-make.yaml

@@ -68,7 +68,7 @@ jobs:
               if: matrix.os == 'linux'
               run: |
                   sudo apt-get update
-                  sudo apt-get install --no-install-recommends -y rpm libarchive-tools flatpak flatpak-builder appstream libx11-dev libxext-dev libmpv-dev mpv pkg-config
+                  sudo apt-get install --no-install-recommends -y rpm libarchive-tools flatpak flatpak-builder appstream libx11-dev libxext-dev libmpv-dev mpv pkg-config libegl-dev libgl-dev libopengl-dev libgbm-dev
 
                   # Configure Flatpak
                   # 1. Add the Flathub repository (source of runtimes)
@@ -336,6 +336,18 @@ jobs:
                           ldd dist/apps/electron-backend/native/embedded_mpv.node
                           exit 1
                       fi
+                      # The frame-copy helper is the inverse: a separate process
+                      # that MUST link libmpv (dev-mode engine; stripped from
+                      # packages until the bundled-runtime staging lands).
+                      # test -f, not -x: the webpack dist asset copy drops file
+                      # modes; consumers restore the bit (after-pack) or require
+                      # it via the X_OK support probe.
+                      test -f dist/apps/electron-backend/native/iptvnator_mpv_helper
+                      if ! ldd dist/apps/electron-backend/native/iptvnator_mpv_helper | grep -q 'libmpv'; then
+                          echo "::error::Linux frame-copy helper must link libmpv"
+                          ldd dist/apps/electron-backend/native/iptvnator_mpv_helper
+                          exit 1
+                      fi
                       ;;
                   esac