Frametop: a multi-screen desktop and universal 3D mouse for the Steam Frame

Several KDE Plasma screens floating in SteamVR, each a real monitor of any
resolution and shape, shown by our own compositor (ft-screens), with a
layout, wrist pinning, and visibility modes; a Bluetooth mouse that drives
all of SteamVR as a room-anchored 3D pointer (input relay, ft-pointer
helper, ft_pointer SteamVR driver); two settings apps; and Bluetooth LE
fixes. Installs on the headset with ./install.sh.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

session/keep-apps.sh

@@ -0,0 +1,35 @@
+#!/bin/bash
+# Runs on the Frame host just before the desktop stops (desktops.sh stop). Moves the
+# programs started inside the desktop out of its systemd unit (frametop-desktop) into a
+# scope of their own, so stopping the unit (which kills everything left in it) only ends
+# the desktop itself. Windows still close: a GUI app exits when its compositor goes.
+# Background work started from the desktop keeps running: servers, agents, tmux, builds.
+unit=frametop-desktop.service
+cg=$(systemctl --user show -p ControlGroup --value "$unit" 2>/dev/null)
+[ -n "$cg" ] && [ -r "/sys/fs/cgroup$cg/cgroup.procs" ] || exit 0
+
+# The desktop's own processes stay in the unit and stop with it: the session, KWin,
+# Plasma, and the session services it started (portals, input methods, kded, wallet...).
+own='^(frametop-sessi|dbus-|startplasma|plasma|kwin|Xwayland|ksmserver|krdpserver|Xvnc|xfreerdp|ft-layout|'
+own+='kded|kactivitymanage|kaccess|kglobalaccel|kscreen|kwalletd|ksecretd|polkit-kde|org_kde_|baloo|'
+own+='xembedsniproxy|gmenudbusmenu|DiscoverNotifie|kimpanel|ibus|xdg-|at-spi|dconf-service|fusermount|agent)'
+keep=()
+while read -r pid; do
+  comm=$(cat "/proc/$pid/comm" 2>/dev/null) || continue
+  [[ $comm =~ $own ]] && continue
+  # ft-screens' launcher (distrobox enter, podman exec) stays too.
+  tr '\0' ' ' < "/proc/$pid/cmdline" 2>/dev/null | grep -q -e 'ft-screens' -e 'ft-layout' -e 'frametop-session' && continue
+  keep+=("$pid")
+done < "/sys/fs/cgroup$cg/cgroup.procs"
+[ ${#keep[@]} -gt 0 ] || exit 0
+
+scope=frametop-apps-$(date +%s).scope
+if busctl --user call org.freedesktop.systemd1 /org/freedesktop/systemd1 org.freedesktop.systemd1.Manager \
+    StartTransientUnit 'ssa(sv)a(sa(sv))' "$scope" fail 3 \
+    PIDs au "${#keep[@]}" "${keep[@]}" \
+    Description s "Programs started in the Frametop desktop, kept past its restart" \
+    CollectMode s inactive-or-failed 0 >/dev/null; then
+  echo "kept ${#keep[@]} process(es) in $scope"
+else
+  echo "couldn't move the desktop's programs out of $unit; they stop with it" >&2
+fi