Home Manager modules for the Steam Frame

Portal fix, Steam-session keyboard layout, VR keyboard patch, hidden
apps, clipboard-sync and a Firefox Flatpak launcher, all under
steamFrame.*, plus the outer-session user-services mechanism.

modules/session.nix

@@ -0,0 +1,72 @@
+# Shared settings for the two sessions on the Steam Frame, and the
+# user-services mechanism.
+#
+# The Frame runs the Steam/VR session (gamescope, systemd user manager, outer
+# D-Bus at <runtimeDir>/bus) and a nested Plasma desktop with its own
+# XDG_RUNTIME_DIR and private D-Bus. Modules that talk to the outer session use
+# `runtimeDir` / `userBus` explicitly.
+#
+# User services: `home-manager switch` usually runs from the nested desktop,
+# whose XDG_RUNTIME_DIR and D-Bus can't reach the user manager, so
+# home-manager's own reloadSystemd step is skipped ("User systemd daemon not
+# running"). The `steamFrameUserServices` activation entry does it instead,
+# pointed at the outer session: it always runs `systemctl --user
+# daemon-reload` (so changed unit files are picked up even when both lists are
+# empty), then starts the units in `userServices.start` and restarts those in
+# `userServices.restart`.
+{ config, lib, ... }:
+let
+  cfg = config.steamFrame;
+  units = lib.escapeShellArgs;
+in {
+  options.steamFrame = {
+    runtimeDir = lib.mkOption {
+      type = lib.types.str;
+      default = "/run/user/1000";
+      description = "XDG_RUNTIME_DIR of the outer (Steam/VR) session.";
+    };
+    userBus = lib.mkOption {
+      type = lib.types.str;
+      default = "unix:path=${cfg.runtimeDir}/bus";
+      defaultText = lib.literalExpression ''"unix:path=''${config.steamFrame.runtimeDir}/bus"'';
+      description = ''
+        Address of the outer session D-Bus. The user systemd manager and the
+        single running kwalletd6 are only reachable over this bus.
+      '';
+    };
+    outerBusEnv = lib.mkOption {
+      type = lib.types.str;
+      readOnly = true;
+      default = "env DBUS_SESSION_BUS_ADDRESS=${cfg.userBus}";
+      defaultText = lib.literalExpression ''"env DBUS_SESSION_BUS_ADDRESS=''${config.steamFrame.userBus}"'';
+      description = ''
+        Command prefix for launchers (desktop entry Exec= lines) that must use
+        the outer bus, e.g. so apps started from the nested desktop use the
+        one kwalletd6 instead of starting a second wallet on the private bus.
+      '';
+    };
+    userServices = {
+      start = lib.mkOption {
+        type = lib.types.listOf lib.types.str;
+        default = [ ];
+        example = [ "docker.service" ];
+        description = "User units started on switch if not already running (outer user manager).";
+      };
+      restart = lib.mkOption {
+        type = lib.types.listOf lib.types.str;
+        default = [ ];
+        example = [ "vr-keyboard.service" ];
+        description = "User units restarted on every switch (outer user manager).";
+      };
+    };
+  };
+
+  config.home.activation.steamFrameUserServices = lib.hm.dag.entryAfter [ "reloadSystemd" ] (''
+    export XDG_RUNTIME_DIR=${lib.escapeShellArg cfg.runtimeDir} DBUS_SESSION_BUS_ADDRESS=${lib.escapeShellArg cfg.userBus}
+    run /usr/bin/systemctl --user daemon-reload
+  '' + lib.optionalString (cfg.userServices.start != [ ]) ''
+    run /usr/bin/systemctl --user start ${units cfg.userServices.start}
+  '' + lib.optionalString (cfg.userServices.restart != [ ]) ''
+    run /usr/bin/systemctl --user restart ${units cfg.userServices.restart}
+  '');
+}