enricobuehler
bc9201d136
Three things, one delivery path — a Fedora/Nobara box getting the patched gamescope. **The pin moves 8c676c39 -> 5fb8dce4** (3.16.25-1 -> 3.16.25-11). The commit that matters is ff6b924, `rendervulkan: fall back to XBGR2101010 when XRGB2101010 is unsupported`: it probes `linearTilingFeatures` for STORAGE+SAMPLED and captures as XBGR2101010 where A2R10G10B10 linear storage is unavailable — which is every NVIDIA. That covers the paths that are upstream's rather than ours: the RGB intermediate `paint_pipewire()` acquires when the stream is YCbCr, and AVIF screenshots. #143 fixed our own node host-side; this is the other half, and its commit message asked for exactly this bump. All six patches rebased. Only 0006 conflicted: upstream's f8be7ee added `vulkan_has_drm_modifiers_for_features()` immediately above the `g_device` declaration our patch turns into a reference — both kept. 0003 and 0005 come out byte-identical; 0006 also picks up the `--zero-commit --no-signature` form 0001-0005 already used. **Patch 0001 now offers `xBGR_210LE` BEFORE `xRGB_210LE`**, mirroring the host-side `HDR_FORMAT_ORDER` rationale on the producer end. A consumer takes the first pod it can use, and we were handing third-party consumers (OBS and friends) the one format NVIDIA fills byte-reversed under a correct-looking label. Deliberately NOT done by calling upstream's `vulkan_get_rgb10_capture_format()`, which is what pw_pods.rs proposes: that symbol landed after 3.16.25, so it would break `packaging/nix/gamescope.nix` — which applies these patches to whatever gamescope nixpkgs pins — with an opaque C++ error instead of a patch conflict. The reorder gets the same outcome on any base. Note added there so the next reader does not "fix" it. **And the RPM was never signed.** `Sign RPMs` runs right after `Build RPM`; the gamescope RPM is built ~90 steps later, behind its own ~10-minute cache, so it missed the signing pass entirely — every punktfunk-gamescope RPM ever published went out unsigned. The repo file we tell users to install carries `gpgcheck=1`, so `dnf install punktfunk-gamescope` failed with "The package is not signed" on every Fedora and Nobara box. The package was in the channel the whole time and could not be installed from it, which is worse than absent: the notes and the docs-site both say it is there. `sign-rpms.sh` now takes explicit paths (defaulting to `dist/*.rpm` as before) and a second pass signs this one before publish, fail-closed on a tag like the first. Verified on Nobara 44 (VM 123, RTX 5070 Ti passthrough), canary 0.27.0-0.ci12611.g516a2954: * Builds clean in the fc44 CI image; banner `3.16.25-17-ga87390d+pfhdr4` (11 upstream + our 6), so the marker the host probes still reads 4 — no capability moved, hence pkgrel 3 and `.pfhdrN` staying put. * `pw-cli enum-params` on the live node: BGRx, NV12, **xBGR_210LE (81), xRGB_210LE (80)** — 8-bit consumers still negotiate bit-for-bit, 10-bit now leads with the safe one. * All four patched flags present, `--pipewire-composite-external-overlay` included. * Patch 0006 confirmed working by comparison, which is the only way to see it: the new build exits 0 where both the pre-0006 `+pfhdr2` build and the stock 3.16.23.2 abort with 134. * Signing fix proven with a throwaway key: `Signature: (none)` -> `digests signatures OK`. * Host health on the canary: synthetic spike 300/300 encoded, loopback 300 recovered, 0 mismatches. One unexplained one-off: the very first headless run after install segfaulted at exit (SIGSEGV, after "Primary child shut down!"). Not reproduced in 11 subsequent runs across every flag combination, so it is recorded rather than diagnosed — the binary is stripped and there is no symbolised core.
12 KiB
punktfunk-gamescope — gamescope with 10-bit HDR PipeWire capture
Upstream gamescope's built-in PipeWire node is SDR-only: build_format_params() offers BGRx
and NV12, and paint_pipewire() hardcodes a Gamma-2.2 composite with the SDR screenshot LUT
set. An HDR game therefore reaches every capture consumer already tone-mapped down — which is
why the punktfunk gamescope backend has always streamed 8-bit, even though games can render
HDR on a headless gamescope today (--hdr-enabled --hdr-debug-force-support).
The patches here add the missing half, and nothing else. See
punktfunk-planning/design/gamescope-hdr-virtual-output.md for the full design.
| Patch | What | Upstream? |
|---|---|---|
0001-pipewire-offer-10-bit-BT.2020-PQ-capture-formats-HDR.patch |
Offer SPA xRGB_210LE/xBGR_210LE with MANDATORY SMPTE ST.2084 + BT.2020 props, map them to DRM_FORMAT_XRGB2101010/XBGR2101010, and composite them with g_ScreenshotColorMgmtLutsHDR + EOTF_PQ |
Yes — offered against gamescope#2126 |
0002-pipewire-optionally-composite-the-cursor-into-the-ca.patch |
--pipewire-composite-cursor (off by default): paint the pointer into the capture stream, using the same MouseCursor::paint call the scanout composite uses |
Yes — independently useful to any consumer with no cursor of its own |
0003-headless-advertise-the-virtual-display-s-mode-and-re.patch |
Give CHeadlessConnector a real GetModes() + GetValidDynamicRefreshRates() from the resolved -W/-H/-r, report GAMESCOPE_SCREEN_TYPE_EXTERNAL so update_mode_atoms publishes the list, and add --custom-refresh-rates |
Yes — a headless session that cannot report its own mode is a plain bug |
0004-pipewire-optionally-composite-the-external-overlay-i.patch |
--pipewire-composite-external-overlay (off by default): paint the external overlay layer (mangoapp — the fps/stats readout) into the capture stream |
Yes — same shape as the cursor patch, same argument |
0005-punktfunk-stamp-the-version-banner-with-pfhdrN.patch |
Append +pfhdr<N> to the --version banner |
No — ours only, retired when the functional patches above land upstream |
0006-punktfunk-never-destroy-the-Vulkan-device-or-output-.patch |
Give g_device and g_output storage that is never destroyed, so their destructors cannot call a Vulkan driver glibc has already unloaded at exit() |
Yes — a plain static-destruction-order bug, not punktfunk-specific |
Why the headless patch matters
A headless gamescope is how a streaming host gives a game a display: the caller passes the
client's exact mode and expects the session to run at it. It does — but it never told anyone.
CHeadlessConnector returned an empty span from both GetModes() and
GetValidDynamicRefreshRates() and reported GAMESCOPE_SCREEN_TYPE_INTERNAL, so
update_mode_atoms() deleted GAMESCOPE_DISPLAY_MODE_LIST_EXTERNAL (no resolution list) and
wlserver_send_gamescope_control() fell through to a one-entry refresh list built from
g_nOutputRefresh (no refresh list). With -r absent that entry is Init()'s 60 Hz default, so a
client on a 120 Hz panel was told its display was 60 Hz — and games capped themselves to it. Field
report 2026-08-08: "gamescope only shows 60hz and there's no other option".
Why the cursor patch matters more than it looks
gamescope keeps the pointer out of its PipeWire node — it lives on a hardware plane for scanout —
so punktfunk has always reconstructed it from XFixes and blended it into every frame host-side.
That blend is what forces the encode path onto its compute colour-conversion arm: the zero-copy
RGB-direct encode source (VK_VALVE_video_encode_rgb_conversion) hands the captured buffer to a
fixed-function front end with no blend stage. Painting the cursor into the node removes the reason
for the blend, and with it a full-frame pass per frame — a gamescope session becomes the first one
that can be genuinely zero-copy end to end.
Why the marker exists
punktfunk decides a session's shape before the virtual display exists: the bit depth at
handshake time (irrevocable — a PQ stream handed to an 8-bit encoder is a deliberate hard error),
and whether the host must composite the cursor before the encoder is even opened. Both answers
must therefore be static properties of the resolved binary, not optimistic negotiations. The host
runs <gamescope> --version once per boot and reads the revision — see gamescope_patch_level()
in crates/pf-vdisplay/src/vdisplay/linux/gamescope/discovery.rs.
The number is a monotonic patch-set revision, so one probe answers every capability:
| Level | Adds |
|---|---|
+pfhdr1 |
10-bit BT.2020/PQ capture formats |
+pfhdr2 |
…and --pipewire-composite-cursor |
+pfhdr3 |
…and the headless connector advertises its mode + --custom-refresh-rates |
+pfhdr4 |
…and --pipewire-composite-external-overlay |
Bump it whenever a patch adds or changes something the host must know about before it spawns.
A patch that only fixes a crash does not bump it: 0006 (the exit-time Vulkan teardown fix)
changes nothing the host probes for, so the level stays +pfhdr4 and the rebuild ships as a
pkgrel bump instead — exactly the split the PKGBUILD's own comment describes. Bumping the level
for a bugfix would be worse than useless: it would advertise a capability tier that does not exist
and strand hosts that gate on it.
⚠️ The two indirect spawn modes (the GAMESCOPE_BIN wrapper for gamescope-session-plus, and the
SteamOS PATH shim) pass these flags through PF_HDR_ARGS, so they share one dependency: if the
session ignores GAMESCOPE_BIN/PATH and execs the distro's gamescope, it gets neither the HDR
formats nor the cursor flag. HDR fails loudly there (the capture negotiation times out and latches
an SDR downgrade) — but a missing cursor would be silent, because the host was told the compositor
would paint the pointer and so painted none itself.
Both managed paths therefore verify after spawn: once the session's node appears,
verify_managed_spawn_flags reads the running compositor's /proc/<pid>/cmdline and refuses the
session if a flag we passed isn't there. The plan is fixed by then (cursor_blend feeds the encoder
open, which precedes the display), so the session cannot be corrected in place — instead the
capability is latched off for the process and the spawn fails, and the retry resolves a correct SDR
host-composited session. One rejected attempt per boot, then it converges.
The check fails open at every ambiguity: no flags expected, or no readable gamescope in
/proc, says nothing. Only a compositor we can see, missing a flag we can name, fails.
Which binary the host runs
Resolution order, applied identically by the bare spawn, the GAMESCOPE_BIN wrapper
(gamescope-session-plus) and the SteamOS PATH shim:
PUNKTFUNK_GAMESCOPE_BIN— absolute path overridepunktfunk-gamescopeonPATHgamescope
So installing this build under the name punktfunk-gamescope is enough; nothing replaces the
distro's gamescope.
Building
Pinned upstream: 5fb8dce4 (master, 2026-08-03 — 3.16.25-11-g5fb8dce). The patches apply
cleanly to that commit; they touch src/pipewire.cpp, src/steamcompmgr.cpp,
src/rendervulkan.cpp, src/rendervulkan.hpp and src/meson.build only.
The bump from 8c676c39 is deliberate: it brings upstream's vulkan_get_rgb10_capture_format()
(ff6b924), which probes linearTilingFeatures for STORAGE+SAMPLED and falls back to
DRM_FORMAT_XBGR2101010 on devices that cannot do linear-tiled A2R10G10B10 — i.e. every
NVIDIA. That covers the paths that are upstream's rather than ours: the RGB intermediate
paint_pipewire() acquires when the stream is YCbCr, and AVIF screenshots. Our own 10-bit RGB
node is covered by patch 0001, which offers xBGR_210LE first for the same reason.
git clone https://github.com/ValveSoftware/gamescope.git
cd gamescope
git checkout 5fb8dce4
git submodule update --init --recursive # or let meson fetch the subprojects
git am /path/to/punktfunk/packaging/gamescope/patches/*.patch
meson setup build/ --prefix=/usr -Dpipewire=enabled
ninja -C build/
# install as punktfunk-gamescope, NOT as gamescope
install -Dm755 build/src/gamescope /usr/bin/punktfunk-gamescope
Build dependencies
They are gamescope's, not ours, and they vary by distro. Two shortcuts that work:
# Fedora / Bazzite (inside a toolbox/distrobox — the host is immutable)
sudo dnf install -y dnf-plugins-core meson ninja-build glslc
sudo dnf builddep -y gamescope
sudo dnf install -y xorg-x11-server-Xwayland-devel # NOT pulled by builddep; wlroots needs it
# Arch / SteamOS — see the makedepends in ./PKGBUILD
⚠️ dnf builddep gamescope resolves Fedora's packaged gamescope, which is older than the master
we pin, so it can come up short. xorg-x11-server-Xwayland-devel is the one that actually bit
(2026-07-28, Fedora 43): without it wlroots' configure fails with Neither a subproject directory nor a xserver.wrap file was found, several minutes into an otherwise clean run. If a different
one surfaces, meson names it — install and re-run with --srcdir so the clone is not repeated.
gamescope needs CAP_SYS_NICE for its realtime priority; the distro packages set it on their
own binary. Mirror it if you install ours system-wide:
setcap 'CAP_SYS_NICE=eip' /usr/bin/punktfunk-gamescope
How each channel ships it
Four packaging paths, one build recipe — build-punktfunk-gamescope.sh — because the two things
that are easy to get wrong (which patches get applied, and whether wlroots is linked statically)
must not be decided twice.
| Channel | Built by | Notes |
|---|---|---|
| Bazzite / Fedora Atomic | .gitea/workflows/rpm.yml → build-sysext.sh --gamescope |
Inside the matching Fedora container, per major — the binary is soname-coupled to its base exactly like the RPM |
| Arch / SteamOS | .gitea/workflows/arch.yml → makepkg on ./PKGBUILD |
Its own pkgbase in the same pacman repo; pacman -S punktfunk-gamescope |
| NixOS | packaging/nix/gamescope.nix (an overrideAttrs on nixpkgs' gamescope) |
The one path that does NOT call the script — nixpkgs already solves the submodules, and a nix closure names every library it links |
| Anything else | the script, by hand | See Building above |
Both CI builds are cached on packaging/gamescope/** and best-effort. Cached because this
tree depends on nothing else in the repo, so a normal push restores a binary instead of spending
ten minutes on someone else's C++; best-effort because punktfunk works without it (SDR on the
gamescope backend, which is what every release before this one did) and a hiccup building gamescope
must not cost the packages those workflows exist to publish. A failed build emits a ::warning::
and is never cached, so the next run retries.
Note what is NOT in that table: the .deb. Debian/Ubuntu boxes build it by hand for now.
Verifying the patch on a box (P0 exit)
punktfunk-gamescope --version # must contain +pfhdr4
punktfunk-gamescope --backend headless -W 1920 -H 1080 -r 60 \
--hdr-enabled --hdr-debug-force-support --pipewire-composite-cursor -- vkcube &
pw-dump | grep -A40 '"gamescope"' # node offers xRGB_210LE / xBGR_210LE
The stream is only 10-bit once a consumer asks for it: the formats are listed last, so any consumer that negotiates the 8-bit stream today keeps negotiating it bit-for-bit.
Rebase policy
The functional patch is two files and mirrors code that already exists in-tree (the HDR AVIF screenshot path), so it rebases cheaply. We pin the gamescope commit we ship; when upstream takes it, both patches are dropped and the host's capability probe becomes a plain version floor.