feat: "Gaming on NVIDIA" replaces the SteamOS conversion on NVIDIA PCs

gamescope's gaming mode shows a corrupted picture on NVIDIA (NVIDIA bug 5240452), also nested in KDE and in a KWin-only
session. With an NVIDIA GPU the conversion (gaming, boot, single, glyphs) is hidden unless already on, and nvidia takes its
place: Steam installed when missing and started at login on the Plasma desktop (user unit), with the sub-option bigpicture
for Big Picture or the normal window. The kernel parameters and early NVIDIA modules (RTX 20 series or newer) are kept as
part of it. tests/nvidia-test.sh covers the component and the menu rules against a fake GPU.

lib/backend.sh

@@ -148,6 +148,8 @@ backend_apply() {
     # The same rules as the menu's toggles.
     [[ "${WANTED[single]:-0}" == 1 ]] && WANTED[gaming]=1
     [[ "${WANTED[gaming]:-0}" == 0 ]] && { WANTED[single]=0; WANTED[boot]=0; }
+    [[ "${WANTED[bigpicture]:-0}" == 1 ]] && WANTED[nvidia]=1
+    [[ "${WANTED[nvidia]:-0}" == 0 ]] && WANTED[bigpicture]=0
     [[ "${WANTED[poweroff]:-0}" == 1 ]] && WANTED[machine]=1
     [[ "${WANTED[machine]:-0}" == 0 ]] && WANTED[poweroff]=0
     [[ "${WANTED[kpin]:-0}" == 1 ]] && WANTED[machine]=1

lib/login-manager.sh

@@ -109,7 +109,6 @@ gaming_enable() {
     esac
     create_desktop_shortcut
     steam_enable
-    nvidia_enable || return 1
     os_name_enable || return 1
 }
 
@@ -125,7 +124,6 @@ gaming_disable() {
     steam_disable
     krevert gaming
     os_name_disable
-    nvidia_disable
     ok "The PC boots to the normal login screen again (from the next boot)."
 }
 

lib/menu.sh

@@ -5,12 +5,12 @@
 
 # Menu order. Components are turned on in this order and off in reverse;
 # gaming must come first (single user builds on it).
-COMPONENTS=(gaming boot theme glyphs single launcher steamgame notify vram cec machine poweroff kpin hdmi bios)
+COMPONENTS=(gaming boot nvidia bigpicture theme glyphs single launcher steamgame notify vram cec machine poweroff kpin hdmi bios)
 # One-off actions rather than on/off components: never preselected, never
 # re-applied, not listed as on or off.
 ACTIONS=(bios)
 # Sub-options, shown indented under their parent and only while it's ticked.
-declare -A PARENT=([boot]=gaming [steamgame]=launcher [poweroff]=machine [kpin]=machine [hdmi]=machine [bios]=machine)
+declare -A PARENT=([boot]=gaming [bigpicture]=nvidia [steamgame]=launcher [poweroff]=machine [kpin]=machine [hdmi]=machine [bios]=machine)
 # Never preselected on a first run: booting into the desktop is a choice,
 # gamescope is the default; HDMI-CEC is opt-in (it can wake the machine or
 # upset other devices on the TV, even on SteamOS), except on a Steam Machine,
@@ -25,7 +25,7 @@ NO_PRESELECT=(boot cec kpin hdmi)
 # FEATURE_BASELINE.
 FEATURE_BASELINE=2.1.0
 declare -A FEATURE_VERSION=(
-    [gaming]=2.9.7 [boot]=2.1.0 [theme]=2.1.0 [glyphs]=2.1.0 [single]=2.1.0
+    [gaming]=2.9.0 [boot]=2.1.0 [nvidia]=2.9.7 [bigpicture]=2.9.7 [theme]=2.1.0 [glyphs]=2.1.0 [single]=2.1.0
     [launcher]=2.1.0 [cec]=2.7.0 [machine]=2.9.0 [poweroff]=2.2.0 [vram]=2.3.0 [notify]=2.5.0 [steamgame]=2.5.1
     [kpin]=2.1.0 [hdmi]=2.1.0
 )
@@ -33,6 +33,8 @@ declare -A FEATURE_VERSION=(
 declare -A LABEL=(
     [gaming]="SteamOS conversion: boot into gaming mode, Steam on the desktop"
     [boot]="Boot into the desktop instead of gaming mode"
+    [nvidia]="Gaming on NVIDIA: Steam on the desktop, started at login"
+    [bigpicture]="Steam starts in Big Picture: the controller-friendly Steam (untick: Steam's normal window)"
     [theme]="Install SteamOS theme: Vapor look (cachyos-vapor)"
     [glyphs]="Install Steam Deck/Machine icons: Deck button icons in gaming mode"
     [single]="Single user mode: no password, lock screen or log out (SDDM)"
@@ -51,6 +53,11 @@ declare -A CURRENT WANTED
 
 component_available() {
     case "$1" in
+        # gamescope's own session is broken on NVIDIA: the conversion is replaced by "Gaming on NVIDIA" there (shown
+        # anyway when it's already on, so it can be turned off).
+        gaming|boot|single|glyphs) ! nvidia_present || gaming_status ;;
+        nvidia) nvidia_available ;;
+        bigpicture) bigpicture_available ;;
         machine|poweroff) machine_available ;;
         vram) vram_available ;;
         steamgame) steamgame_available ;;
@@ -141,6 +148,7 @@ component_selectable() {
 
 detect_components() {
     local c any=false
+    for c in "${COMPONENTS[@]}"; do CURRENT[$c]=0; WANTED[$c]=0; done
     for c in "${COMPONENTS[@]}"; do
         component_available "$c" || continue
         if "${c}_status"; then CURRENT[$c]=1; any=true; else CURRENT[$c]=0; fi
@@ -270,6 +278,9 @@ toggle_component() {
     if [[ "$c" == gaming && "${WANTED[gaming]}" == 0 ]]; then WANTED[single]=0; WANTED[boot]=0; fi
     # Where to boot to is part of the conversion, too.
     if [[ "$c" == boot && "${WANTED[boot]}" == 1 ]]; then WANTED[gaming]=1; fi
+    # Big Picture is opt-out: ticked along with "Gaming on NVIDIA".
+    if [[ "$c" == nvidia ]]; then WANTED[bigpicture]=${WANTED[nvidia]}; fi
+    if [[ "$c" == bigpicture && "${WANTED[bigpicture]}" == 1 ]]; then WANTED[nvidia]=1; fi
     # The power-off fix is opt-out: ticked along with Steam Machine support.
     if [[ "$c" == machine ]]; then WANTED[poweroff]=${WANTED[machine]}; fi
     if [[ "$c" == poweroff && "${WANTED[poweroff]}" == 1 ]]; then WANTED[machine]=1; fi

lib/nvidia.sh

@@ -1,22 +1,99 @@
 #!/bin/bash
-# NVIDIA fix for gaming mode, part of the SteamOS conversion
-# (gaming_enable/gaming_disable). gamescope drives the display itself
-# through DRM/KMS; with NVIDIA that needs kernel modesetting and the
-# framebuffer driver (nvidia-drm.modeset=1 nvidia-drm.fbdev=1) and the
-# driver in the initramfs, or the screen shows a corrupted image.
-# Does nothing without a supported NVIDIA GPU (RTX 20 series or newer) that has
-# its driver installed.
+# Gaming on NVIDIA PCs: the SteamOS conversion (gamescope session) isn't offered there, because gamescope's DRM session shows a
+# corrupted picture on NVIDIA (NVIDIA's open bug 5240452: modes above 2560x1440@120). `nvidia` is the replacement: Steam on the
+# Plasma desktop, installed when missing and started at login; `bigpicture` (a sub-option) makes it start in Big Picture.
+# On a supported card (RTX 20 series or newer, `nvidia_supported`) it also sets up what NVIDIA's Wayland/DRM stack wants:
+# nvidia-drm.modeset=1 and fbdev=1 on the kernel command line and the NVIDIA modules in the initramfs. That didn't cure
+# gamescope's picture (the driver already reported both `Y`), but it is the standard setup and may be needed.
 # Sourced by steamify.sh; not meant to be run on its own.
 
+NVIDIA_UNIT=steamify-steam-autostart.service
 NVIDIA_PARAMS="nvidia-drm.modeset=1 nvidia-drm.fbdev=1"
-NVIDIA_INITRAMFS_CONF=/etc/mkinitcpio.conf.d/90-steamify-nvidia.conf
+NVIDIA_INITRAMFS_CONF=${NVIDIA_INITRAMFS_CONF:-/etc/mkinitcpio.conf.d/90-steamify-nvidia.conf}
 # The script and pacman hook that keep the initramfs file right at every kernel change.
 NVIDIA_SCRIPT=${NVIDIA_SCRIPT:-/usr/local/libexec/steamify-nvidia-initramfs}
 NVIDIA_HOOK=${NVIDIA_HOOK:-/etc/pacman.d/hooks/85-steamify-nvidia-initramfs.hook}
+# The running kernel's command line; the tests point this at a file.
+NVIDIA_CMDLINE=${NVIDIA_CMDLINE:-/proc/cmdline}
 # The DRM devices in sysfs; the tests point this at a fake tree.
 NVIDIA_DRM_DIR=${NVIDIA_DRM_DIR:-/sys/class/drm}
 
+nvidia_unit_file() { echo "$HOME/.config/systemd/user/$NVIDIA_UNIT"; }
+
 nvidia_present() {
+    # An NVIDIA GPU (PCI vendor 0x10de, display class) whose driver provides
+    # nvidia_drm. nouveau has none, and gamescope is not a problem there.
+    local d
+    for d in "$NVIDIA_DRM_DIR"/card[0-9]*/device; do
+        [[ "$(cat "$d/vendor" 2>/dev/null)" == 0x10de ]] || continue
+        [[ "$(cat "$d/class" 2>/dev/null)" == 0x03* ]] || continue
+        modinfo nvidia_drm >/dev/null 2>&1 && return 0
+    done
+    return 1
+}
+
+# Shown on NVIDIA PCs, unless the SteamOS conversion is already on there (it
+# has to be turned off first: both would start Steam at login).
+nvidia_available() { nvidia_present && ! gaming_status 2>/dev/null; }
+bigpicture_available() { nvidia_available; }
+
+nvidia_status() {
+    pacman -Q steam >/dev/null 2>&1 && [[ -f "$(nvidia_unit_file)" ]] &&
+        user_systemctl is-enabled -q "$NVIDIA_UNIT" 2>/dev/null
+}
+
+nvidia_write_unit() {
+    # nvidia_write_unit [args]: the autostart unit, Steam started with those arguments.
+    local unit; unit="$(nvidia_unit_file)"
+    mkdir -p "$(dirname "$unit")"
+    service_file steamify-steam-autostart.service ARGS="$1" > "$unit" || { err "Writing $unit failed."; return 1; }
+    user_systemctl daemon-reload
+}
+
+nvidia_enable() {
+    info "Gaming on NVIDIA: Steam on the desktop, started at login..."
+    if ! pacman -Q steam >/dev/null 2>&1; then
+        sudo pacman -S --needed --noconfirm steam || { err "Installing Steam failed."; return 1; }
+        state_set nvidia installed_pkgs steam
+    fi
+    # Keeps what the Big Picture option set up; a first run starts Steam normally.
+    local args=""; bigpicture_status && args=-gamepadui
+    nvidia_write_unit "$args" || return 1
+    user_systemctl enable "$NVIDIA_UNIT" >/dev/null 2>&1 || { err "Enabling $NVIDIA_UNIT failed."; return 1; }
+    nvidia_kernel_enable || return 1
+    ok "Steam starts at your next login."
+}
+
+nvidia_disable() {
+    local pkgs unit; unit="$(nvidia_unit_file)"
+    user_systemctl disable --now "$NVIDIA_UNIT" >/dev/null 2>&1
+    rm -f "$unit"
+    user_systemctl daemon-reload
+    pkgs="$(state_get nvidia installed_pkgs)"
+    # Only what Steamify installed; games and the Steam folder stay.
+    # shellcheck disable=SC2086 # a list of package names
+    [[ -n "$pkgs" ]] && sudo pacman -Rns --noconfirm $pkgs >/dev/null 2>&1
+    state_clear nvidia
+    nvidia_kernel_disable
+    ok "Steam no longer starts at login."
+}
+
+bigpicture_status() { grep -qs -- '-gamepadui' "$(nvidia_unit_file)"; }
+
+bigpicture_enable() {
+    # The unit comes from nvidia_enable (it runs first); without it there is nothing to change.
+    [[ -f "$(nvidia_unit_file)" ]] || return 0
+    nvidia_write_unit -gamepadui && ok "Steam starts in Big Picture at your next login."
+}
+
+bigpicture_disable() {
+    [[ -f "$(nvidia_unit_file)" ]] || return 0
+    nvidia_write_unit "" && ok "Steam starts in its normal window at your next login."
+}
+
+# --- Kernel parameters and early modules (a supported card only)
+
+nvidia_supported() {
     # A supported NVIDIA GPU: PCI vendor 0x10de, display class, its kernel
     # driver installed, and not older than the RTX 20 series, decided like the
     # VRAM booster does (vram_nvidia_legacy_id: chwd's legacy card lists, every
@@ -53,7 +130,7 @@ nvidia_param_set() {
     # The kernel treats "nvidia_drm" and "nvidia-drm" alike: CachyOS' own
     # setup may already have written the underscore spelling.
     local f re; f="$(nvidia_boot_file)"; re="${1//nvidia-drm/nvidia[-_]drm}"
-    grep -qwE -- "$re" /proc/cmdline 2>/dev/null ||
+    grep -qwE -- "$re" "$NVIDIA_CMDLINE" 2>/dev/null ||
         { [[ -n "$f" ]] && grep -qwE -- "$re" "$f" 2>/dev/null; }
 }
 
@@ -107,8 +184,8 @@ nvidia_boot_has_params() {
     sudo grep -rqs 'nvidia-drm.modeset=1' "$target"
 }
 
-nvidia_enable() {
-    nvidia_present || return 0
+nvidia_kernel_enable() {
+    nvidia_supported || return 0
     local f changed=0 p; f="$(nvidia_boot_file)"
     if nvidia_params_missing; then
         if [[ -z "$f" ]]; then
@@ -154,7 +231,7 @@ nvidia_enable() {
     return 0
 }
 
-nvidia_disable() {
+nvidia_kernel_disable() {
     local f changed=0; f="$(nvidia_boot_file)"
     if [[ -n "$f" ]] && grep -q "$NVIDIA_PARAMS" "$f" 2>/dev/null; then
         sudo sed -i "s/ \?$NVIDIA_PARAMS//" "$f"