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machines.coaxmetal: sway kiosk so nested gamescope keeps its wayland backend
Replace the greetd gamescope-session (which required STROM_NO_GAMESCOPE and
rendered games directly in the session compositor) with greetd launching sway.
A game's nested gamescope prefers its wayland backend, which needs wlroots
protocols that cage (and, differently, an outer gamescope session) do not give
it. Under those it fell back to gamescope's SDL backend, whose Vulkan swapchain
remake loops and aborts on this RADV RENOIR iGPU (rendervulkan.cpp
vulkan_remake_swapchain) - crashing e.g. Baba Is You a couple seconds in. sway
exposes those protocols, so gamescope inits its wayland backend and never hits
the crashing SDL path. Every game keeps its own gamescope (render resolution,
in-game exit chord, bare-tty portability); no per-game workaround needed.
Also resolve STROM_FLAKE to the /home/strom/strom checkout when present (github
fallback) so changes can be tested on the box before pushing upstream.
author
lassulus
date
(Jul 25, 2026, 11:28 PM CEST)
commit
aaa1cbbc
aaa1cbbcb2269f80dcac56dc263a9712d9458ecf
parent
7698c37a
7698c37a0dcb24377d62afe6531b6744c3e87bc2
+55
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machines/coaxmetal/strom.nix
+55
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machines/coaxmetal/strom.nix
···
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...
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}:
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let
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# Run the patched launcher from the on-disk strom checkout at
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# /home/strom/strom (it carries STROM_NO_GAMESCOPE support until that lands
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# upstream). With the kiosk itself being a gamescope session (below), games
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# are launched as <slug>.no-gamescope so they render directly in the session
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# compositor instead of nesting a per-game gamescope.
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# Run the launcher + games from the on-disk strom checkout at
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# /home/strom/strom when it exists, else the public github flake (see the
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# STROM_FLAKE selection in strom-session below).
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#
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# Compositor: sway (wlroots) via greetd autologin - NOT cage, and NOT an outer
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# gamescope session. Each game still brings its own gamescope, nested ONCE
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# inside sway.
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#
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# Why sway and not cage: a game's nested gamescope prefers its WAYLAND backend,
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# which needs wlroots protocols that cage (a minimal kiosk compositor) does not
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# expose. Under cage gamescope's wayland backend fails ("Couldn't create
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# Wayland objects") and silently falls back to its SDL backend, whose Vulkan
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# swapchain remake loops and aborts on this RADV RENOIR iGPU
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# (rendervulkan.cpp vulkan_remake_swapchain) - that is what crashed Baba Is You
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# a couple seconds in. sway exposes those protocols, so gamescope inits its
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# wayland backend and never touches the crashing SDL path. (An outer gamescope
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# session instead double-nests gamescope-in-gamescope, which is worse.)
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# Keeping per-game gamescope preserves render resolution/scaling, the in-game
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# exit chord, and bare-tty portability - hence no STROM_NO_GAMESCOPE.
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strom-session = pkgs.writeShellScript "strom-session" ''
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set -u
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# xpadneo owns the Xbox pad's hidraw node, so force SDL (pygame launcher and
···
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# powered on after the launcher starts is never seen. Force SDL to poll
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# /dev/input instead, which reliably picks up pads as they connect/disconnect.
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export SDL_JOYSTICK_DISABLE_UDEV=1
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# Under cage the launcher window never reports input focus, and SDL suppresses
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# joystick (not keyboard) events while unfocused - so keyboard works but the
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# pad does not. Allow joystick events regardless of focus.
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# In the kiosk the launcher window may not report input focus, and SDL
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# suppresses joystick (not keyboard) events while unfocused - so allow
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# joystick events regardless of focus.
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export SDL_JOYSTICK_ALLOW_BACKGROUND_EVENTS=1
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# The kiosk compositor is already gamescope on DRM (see services.greetd
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# below), so tell the launcher to run games directly in it rather than
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# nesting a per-game gamescope (which double-nests and, on this GPU, storms
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# the Vulkan swapchain and crashes games like Baba Is You).
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export STROM_NO_GAMESCOPE=1
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# Resolve the strom flake once: prefer the on-disk checkout at
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# /home/strom/strom (edit + test there before pushing to github), and fall
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# back to the public flake when it is absent. The launcher runs from this
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# ref, and pkgs/launcher resolves each game's ref from STROM_FLAKE too (it
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# sets the default with := so this export wins).
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if [ -d /home/strom/strom ]; then
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STROM_FLAKE=/home/strom/strom
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else
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STROM_FLAKE=github:kraftwerk-gaming/strom
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fi
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export STROM_FLAKE
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# strom-run (the per-game supervisor) needs a delegated cgroup v2 so it can
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# mkdir a child cgroup and cgroup.kill the game tree atomically. The greetd
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# PAM session drops us into a root-owned logind session scope
···
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done
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# Relaunch whenever the couch launcher exits (gamepad B / Esc) so the kiosk
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# never drops to a blank screen. The loop runs inside the delegated scope so
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# every game inherits a writable cgroup; the gamescope compositor stays up
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# (it is the session's other child) across relaunches.
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# every game inherits a writable cgroup; sway stays up (the launcher is just
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# one of its clients) across relaunches.
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#
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# setpriv --ambient-caps=-all: the login session may carry an ambient
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# capability (e.g. cap_wake_alarm) that every child inherits. bwrap refuses
···
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--quiet --collect -- \
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${pkgs.util-linux}/bin/setpriv --ambient-caps=-all \
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${pkgs.bash}/bin/bash -c 'while true; do
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${config.nix.package}/bin/nix run /home/strom/strom#scripts.launcher
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${config.nix.package}/bin/nix run "$STROM_FLAKE#scripts.launcher"
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sleep 2
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done'
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'';
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# Bare wlroots kiosk: no window chrome, every toplevel fullscreen, no idle
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# blanking. Its whole reason to exist over cage is that it exposes the wlroots
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# protocols each game's nested gamescope needs for its wayland backend (see
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# the top-of-file note).
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sway-kiosk = pkgs.writeText "sway-kiosk.conf" ''
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default_border none
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default_floating_border none
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gaps inner 0
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gaps outer 0
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# Fullscreen every toplevel: the launcher grid and each game's gamescope.
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for_window [app_id=".*"] fullscreen enable
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for_window [class=".*"] fullscreen enable
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# No swaybar / no swayidle -> no bar, no DPMS blank (mains-powered kiosk).
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exec ${strom-session}
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'';
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in
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{
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# Dedicated, unprivileged kiosk user. Gamepad input comes through evdev
···
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];
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};
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# Kiosk autostart: a gamescope session on DRM (via greetd autologin),
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# replacing cage. gamescope presents straight to the display, so there is no
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# nested Wayland swapchain for RADV to storm on this Vega iGPU. greetd gives
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# the strom user a real seat/VT (DRM master) and a delegated user manager,
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# which the launcher's systemd-run --user --scope relies on for game cgroups.
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# Kiosk autostart: greetd autologins the strom user on tty1 into sway, which
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# runs the couch launcher as its sole fullscreen client. default_session
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# re-runs the same session if sway ever exits.
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services.greetd = {
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enable = true;
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settings =
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let
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session = {
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command = "${pkgs.gamescope}/bin/gamescope -- ${strom-session}";
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command = "${pkgs.sway}/bin/sway --config ${sway-kiosk}";
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user = "strom";
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};
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in
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{
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# initial_session autologins on boot with no prompt; default_session
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# re-runs it (also autologin) if the gamescope session ever exits.
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initial_session = session;
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default_session = session;
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};