chromium-fourier r2 + firefox-fourier 150.0.1 + KWIN_PIVOT.md

chromium-fourier:
- patch 3/3 nv12-external-oes-on-modifier-external-only.patch — adds
  NativePixmapEGLBinding::ModifierRequiresExternalOES helper, extends
  OzoneImageGLTexturesHolder::GetBinding to honor EGL external_only
  flag for NV12 dmabufs on panfrost / panthor. Validated on ohm
  (RK3566 hantro mainline 6.19.10): bbb_1080p30_h264.mp4 plays at
  34.7 % combined CPU vs ~131 % pre-patch baseline (~3.8x).
- PKGBUILD pkgrel 1->2, source array + sha256sums + prepare() hook for
  patch 4, patch numbering 1/2,2/2 -> 1/3,2/3,3/3.
- NEXT.md appended with 2026-04-28 section: patch 4 design, validation
  log, KWin GL_ALPHA bug pinpoint (preexisting since 2026-03-06,
  affects every wayland video client; unrelated to chromium-fourier),
  device-renumbering note (/dev/video1 = encoder post-reboot).
- KWIN_PIVOT.md: 4-phase plan to identify and patch KWin's
  glTexImage2D(internalFormat=GL_ALPHA) site, ohm-only test plan,
  scope discipline.
- patches/ now tracked (compiler-rt-adjust-paths, enable-v4l2,
  wayland-allow-direct-egl-gles2, nv12-external-oes); the dead-end
  chromeos-pipeline-bypass.patch removed.

firefox-fourier:
- 4 patches (gfxinfo v4l2 stateless fourccs, libwrapper hwdevice ctx,
  ffmpegvideo v4l2-request route, prefs v4l2-request default).
- PKGBUILD bumped to firefox 150.0.1, Arch toolchain glue patches
  layered in, mozconfig with --without-wasm-sandboxed-libraries for
  ALARM, package() launcher fix (rm -f symlink before cat > to avoid
  ENOENT through the dangling /usr/local symlink mach install drops).
- 150.0.1-1-aarch64.pkg.tar.zst built on boltzmann (95 MB), pending
  fresnel power-on for V4L2 stateless validation on RK3399.

arch/chromium-fourier/KWIN_PIVOT.md

@@ -0,0 +1,181 @@
+# KWin pivot — fix the `glTexImage2D(GL_ALPHA)` stall
+
+## What we know
+
+KWin 6.6.4-1 on Arch Linux ARM (Plasma 6.6.4-1, mesa 26.0.5-1, libdrm
+2.4.131-1) on ohm (PineTab2 / RK3566 / panfrost) silently corrupts its
+GL command queue mid-frame whenever a wayland client posts a video
+buffer. The journal carries a rolling stream of:
+
+```
+kwin_wayland: 0x4: GL_INVALID_VALUE in glTexImage2D(internalFormat=GL_ALPHA)
+kwin_wayland: 0x4: GL_INVALID_OPERATION in glTexSubImage2D(invalid texture level 0) × N
+```
+
+`GL_ALPHA` is not a valid `internalFormat` for `glTexImage2D` under
+**OpenGL ES 3.x** (it was the GLES1.x single-channel alpha format;
+GLES3 deprecates it for sized formats — `GL_R8`, `GL_LUMINANCE8_ALPHA8`,
+etc.). Once the texture allocation fails, the `glTexSubImage2D` calls
+that should populate it all error at level 0. KWin keeps retrying the
+same broken upload every frame, never recovers, and the present-callback
+path that depends on that texture stops acking client frames. Every
+wayland video client deadlocks on the missing ack.
+
+First occurrence in this box's journal: **2026-03-06** — the bug
+predates any chromium-fourier work by roughly seven weeks.
+
+## Triangulation already in hand
+
+| Client | Outcome |
+|---|---|
+| chromium-fourier 149-r2 (with patch 3/3) | plays ~3 s @ 34.7 % CPU then renderer/GPU park in `futex_do_wait` |
+| chromium-fourier 149-r2 (without patch 3/3) | plays ~10 s (slower path delays surfacing) then identical deadlock |
+| VLC | `cannot convert decoder/filter output to any format supported by the output` → `could not initialize video chain` |
+| mpv `--vo=null --hwdec=v4l2request` | `Could not create device.` (mpv-side bug, separate, unrelated) |
+| ffmpeg `-hwaccel v4l2request -i bbb -f null -` | plays through clean at 36 fps; hardware path is healthy |
+
+Decode path is healthy on this hardware. The wall is exclusively the
+compositor's GL backend.
+
+## Constraint: ohm is the only test box on hand
+
+ampere (RK3588 / panthor) is in the boxes-from-Shenzhen pile, currently
+DOWN. fresnel (RK3399 / Pinebook Pro) is offline. boltzmann (Rock 5
+ITX+ build host) doesn't run KWin. We do every step on ohm; we accept
+the wifi flakiness and the occasional reboot.
+
+## Phase 1 — Reproduce outside chrome and bound the trigger (1 evening)
+
+Goal: a deterministic, headless-or-near-headless reproduction that
+doesn't require launching a 800-MB browser.
+
+1. **Smallest-possible client.** Build a 50-line C wayland client that
+   creates a `wp_linux_dmabuf_v1` buffer, pumps frames at 30 fps, and
+   exits when KWin first errors. Use `weston-simple-dmabuf-egl` from
+   the `weston` package as a starting template — already does exactly
+   this but without our specific format/modifier matrix.
+2. **Vary the format/modifier matrix.** Run the smallest-possible
+   client with each of: NV12 + LINEAR, NV12 + AFBC, NV12 + AFRC,
+   AR24 + LINEAR, XR24 + LINEAR. We already know NV12 paths trigger;
+   confirming AR24/XR24 do *not* trigger localizes the bug to KWin's
+   YUV import path (vs a generic dmabuf import bug).
+3. **Vary the buffer dimensions.** Some KWin texture-cache paths
+   allocate fixed-size internal scratch textures; non-power-of-two,
+   non-multiple-of-16, or specifically odd-aspect cases sometimes
+   trigger paths that healthy aspect ratios skip. Test 1920×1080,
+   1280×720, 854×480, 640×360 and a deliberately weird 1366×768.
+4. **Vary KWin scene type.** Switch
+   `kwin_wayland --scene-type=opengl` vs `--scene-type=opengl-es`
+   (current default on this hardware). If the bug only fires under
+   GLES, that's a strong signal — the offending site is in a
+   GLES-only fallback.
+
+By the end of Phase 1 we should have a one-line `weston-simple-dmabuf-egl
+-format=NV12 -modifier=…` that triggers the GL_ALPHA error within
+seconds, plus a yes/no answer to "does AR24 also trigger".
+
+## Phase 2 — Identify the call site (1–2 evenings)
+
+The crime scene is somewhere in `kwin/src/scene/*` or
+`kwin/src/effects/*`. Suspects, ranked:
+
+- **`SurfaceItemWayland::createPixmapTexture` → `GLTexture::create`
+  with `GL_ALPHA`.** This is the most likely path: KWin allocates a
+  fallback per-plane texture when the dmabuf import path can't take
+  the buffer whole. NV12 has a Y plane (single-channel) and a CbCr
+  plane (two-channel); historically the Y plane has been allocated as
+  `GL_ALPHA` in software fallbacks. If the EGL dmabuf import returned
+  `EGL_BAD_ATTRIBUTE` for `external_only` modifiers and KWin fell
+  through to per-plane, this is exactly where it would land.
+- **`BlurEffect::initBlurTexture` / `BackgroundContrastEffect::*`.**
+  Single-channel noise textures for blur dither. Less likely (these
+  fire on every frame regardless of video clients) but listed for
+  completeness.
+- **Window-decoration text glyph cache.** Qt's QGLTexture historically
+  requested `GL_ALPHA` for monochrome glyph atlases. Plasma 6 should
+  have moved to `GL_RED` long ago, but a stale code path in a
+  third-party theme or systray icon could still hit it.
+- **Cursor texture upload via `wl_shm_pool` + ARGB8888.** KWin's
+  cursor scene sometimes uploads via glTexImage2D — but the format
+  there is `GL_RGBA`, not `GL_ALPHA`. Probably not the suspect.
+
+Tooling to identify *which*:
+
+1. **`apitrace trace --api egl kwin_wayland …`** then
+   `apitrace dump trace.trace | grep -B5 GL_ALPHA`. Apitrace gives
+   us the C++ call stack at the offending site if KWin was built with
+   debug symbols.
+2. **`MESA_GL_DEBUG=context KWIN_GL_DEBUG=1 kwin_wayland --replace`**
+   plus `glDebugMessageCallback` already installed in KWin's
+   `OpenGLBackend` will print the source/type/severity for each
+   `GL_INVALID_VALUE`. Whether the file/line in the message includes
+   the user-space caller depends on Mesa's debug-extension support;
+   on panfrost it usually does include the GL function name and an
+   ID, but not the C++ source — that is what apitrace adds.
+3. **Build kwin from source** (`extra/kwin` PKGBUILD on Arch ARM,
+   patch in `-DDEBUG=ON`, `-DCMAKE_BUILD_TYPE=Debug`) so the call
+   stacks resolve to file:line.
+
+## Phase 3 — Write the patch (½ evening once Phase 2 is done)
+
+If the offender is a `GL_ALPHA` allocation in a GLES3 context, the
+fix is mechanical:
+
+```diff
+- glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, width, height, 0,
+-              GL_ALPHA, GL_UNSIGNED_BYTE, data);
++ glTexImage2D(GL_TEXTURE_2D, 0, GL_R8, width, height, 0,
++              GL_RED, GL_UNSIGNED_BYTE, data);
+```
+
+…and adjust the consuming shader's swizzle:
+
+```diff
+- gl_FragColor = vec4(texture2D(s, uv).a, …);
++ gl_FragColor = vec4(texture2D(s, uv).r, …);
+```
+
+If the offender is a per-plane fallback in the dmabuf import path
+(suspect #1 above), the patch is larger because the right fix is to
+*not fall through to the broken path* — handle the `external_only`
+case by binding `GL_TEXTURE_EXTERNAL_OES` instead. That mirrors the
+chromium-fourier patch 3/3 done at the chromium layer; symmetry says
+KWin should do the same in its `glTexImage` consumer.
+
+## Phase 4 — Ship and upstream (1 evening)
+
+1. **Local Arch package** as `kwin-fourier` under
+   `marfrit-packages/arch/kwin-fourier/`, sibling to chromium-fourier
+   and firefox-fourier. PKGBUILD inherits from `extra/kwin`, drops
+   in our patch, bumps `pkgrel`. Same `provides=kwin conflicts=kwin`
+   pattern.
+2. **Validate on ohm** by running the chromium-fourier 149-r2 build +
+   the bbb sample for a minute uninterrupted. Success = no GL_ALPHA
+   in the journal, no stall, smooth playback at the 34.7 % CPU
+   number from the chromium validation.
+3. **Upstream** via:
+   - File a `kwin` bug on bugs.kde.org with: apitrace fragment, our
+     hardware (Mali-G52 panfrost on RK3566 mainline), exact mesa
+     version, repro steps via `weston-simple-dmabuf-egl` if Phase 1
+     produced one.
+   - Push an MR to invent.kde.org/plasma/kwin against `master`.
+4. **Document** the fix in `chromium-fourier/docs/dmabuf-zero-copy.md`
+   so the next person who lands on the same wall finds the breadcrumb
+   trail.
+
+## What success looks like
+
+`chromium-fourier-149-r2` on ohm under KWin Wayland plays
+`bbb_1080p30_h264.mp4` end-to-end at the 34.7 % CPU figure already
+recorded by the architectural validation, with zero `GL_INVALID_VALUE`
+in the journal during playback. That number is the goal of the entire
+chromium-fourier campaign for RK3566 — it is currently blocked on a
+bug that has nothing to do with chromium.
+
+## Scope discipline
+
+We do not turn this into "audit the entire KWin GLES backend." If
+Phase 2 surfaces additional latent GL_INVALID_* errors that don't
+matter for video playback, we note them in the bug report and move
+on. The pivot is explicitly "remove this single wall so the
+chromium-fourier patch series can ship a working stack on RK3566."