Trim: firefox launcher, debugger-arm migration, comments and docs

- firefox: the prefs.js patterns built once; the extension link condition
  without the redundant desktopFix (it implies a pref).
- install.sh steamvr-debugger-arm: no second copy of the old-marker
  migration (cleanup, run on every switch before the arm unit exists,
  already does it).
- steam-ui-patches: shorter state option description; lib's description
  mentions extraArgs.
- README: uiPatches.patches fields in the options table (moved from
  docs/ui-patches.md); docs/ui-patches.md: the finder helpers;
  docs/steamvr-debugger.md: repeated sentences removed.

modules/cleanup/check.nix

@@ -203,11 +203,9 @@ pkgs.runCommand "cleanup-check" { nativeBuildInputs = [ cleanup pkgs.jq ]; } ''
   arm() { bash ${../../install.sh} steamvr-debugger-arm; }
   fresh e
   printf '{\n   "steamvr" : {}\n}\n' > $V
-  touch $S/steamvr-debugger                          # old marker: migrated
   echo activating > $STUB/state
   res=$(arm); echo "$res"
   [ "$(cat $S/steamvr-debugger.armed)" = absent ] || fail "armed"
-  gone $S/steamvr-debugger
   [ "$(jq -c .VRWebHelper $V)" = '{"DebuggerEnabled":true}' ] || fail "arm: $(cat $V)"
   there $root/run/steam-frame-nix/steamvr-debugger-restore
   [ "$(grep -c daemon-reload $STUB/log)" = 1 ] || fail "arm reload"

modules/firefox.nix

@@ -1,25 +1,18 @@
 # Firefox Flatpak (org.mozilla.firefox) launcher.
-# - prefs and vrFullscreenFix are default prefs (pref(), the default branch:
-#   never written to prefs.js, so removing one leaves nothing behind). Firefox
-#   reads defaults/pref/*.js from its system config dir, /app/etc/firefox in
-#   the Flatpak, the mount point of the org.mozilla.firefox.systemconfig
-#   extension. The user installation's "unmaintained extension" dir
-#   ($XDG_DATA_HOME/flatpak/extension/<id>/<arch>/<branch>) provides it: a
-#   home-manager link to a store dir, which Flatpak mounts itself (the
-#   sandbox needn't see /nix).
+# - prefs and vrFullscreenFix are default prefs (pref(): never written to
+#   prefs.js, so removing one leaves nothing behind) in defaults/pref/ of the
+#   org.mozilla.firefox.systemconfig extension (/app/etc/firefox), provided
+#   as the user installation's "unmaintained extension"
+#   ($XDG_DATA_HOME/flatpak/extension/<id>/<arch>/<branch>): a Home Manager
+#   link to a store dir, which Flatpak mounts itself (the sandbox needn't see
+#   /nix).
 # - vrFullscreenFix: in the Steam session gamescope focuses a fullscreen X11
 #   window but never shows it (Firefox looks frozen). ignore-widgets keeps
 #   fullscreen inside the window.
 # - desktopProfile: the sessions have separate buses/displays, so a second
 #   Firefox can't reach the running one and hits the profile lock; the nested
-#   desktop gets its own profile (a normal Firefox profile: browser data).
-#   Fullscreen works there, so the launcher undoes the fix in that profile
-#   only while its Firefox runs: a user.js link to the extension's
-#   steam-frame-nix-desktop-user.js (a sandbox path; dangling on the host),
-#   made right before Firefox starts and removed, with the value Firefox
-#   stored from it in prefs.js, once it has exited (firefox/launcher.nix).
-#   Leftovers (a crash) and what older versions wrote into profiles (user.js
-#   copies and links) are removed by steam-frame-nix-cleanup (on switch).
+#   desktop gets its own profile, where fullscreen works: the launcher undoes
+#   the fix there while its Firefox runs (firefox/launcher.nix).
 # The entry shadows the Flatpak's (same ID), keeping MIME associations, and is
 # seen by the "+" menu (which reads only ~/.local/share/applications).
 # defaultBrowser: without a default the portal picks the first installed
@@ -122,7 +115,7 @@ in {
 
     # stable: the branch the launcher runs (the extension point has no
     # version, so it takes the app's branch).
-    xdg.dataFile = lib.optionalAttrs (defaultPrefs != { } || desktopFix) {
+    xdg.dataFile = lib.optionalAttrs (defaultPrefs != { }) {   # desktopFix implies a pref
       "flatpak/extension/org.mozilla.firefox.systemconfig/aarch64/stable".source = sysconfig;
     } // {
     "applications/org.mozilla.firefox.desktop".text = ''

modules/firefox/launcher.nix

@@ -26,14 +26,15 @@ writeShellScript "firefox-launcher" (''
 '' + lib.optionalString desktopFix ''
   js=${lib.escapeShellArg desktopJs}
   u=$prof/user.js
+  pats=${lib.escapeShellArg (lib.concatMapStringsSep "\n" (k: "user_pref(${builtins.toJSON k},") desktopKeys)}
   # Firefox holds .parentlock open while it uses a profile (the sandbox sees
   # the profile at the same path).
   inUse() { find /proc/[0-9]*/fd -lname "$prof/.parentlock" -print -quit 2>/dev/null | grep -q .; }
   ours() { [ -L "$u" ] && [ "$(readlink "$u")" = "$js" ]; }
   sfn_unlink() {
     ours && ! inUse || return 0
-    if [ -f "$prof/prefs.js" ] && grep -qF -f <(printf '%s\n' ${lib.escapeShellArgs (map (k: "user_pref(${builtins.toJSON k},") desktopKeys)}) "$prof/prefs.js"; then
-      grep -vF -f <(printf '%s\n' ${lib.escapeShellArgs (map (k: "user_pref(${builtins.toJSON k},") desktopKeys)}) "$prof/prefs.js" > "$prof/prefs.js.sfn" || true
+    if [ -f "$prof/prefs.js" ] && grep -qF "$pats" "$prof/prefs.js"; then
+      grep -vF "$pats" "$prof/prefs.js" > "$prof/prefs.js.sfn" || true
       cat "$prof/prefs.js.sfn" > "$prof/prefs.js"
       rm -f "$prof/prefs.js.sfn"
     fi

modules/steam-ui-patches.nix

@@ -70,15 +70,10 @@ let
         default = false;
         description = ''
           Give the patch one persistent JSON value (e.g. choices made in its
-          UI), kept by the service in
-          $XDG_STATE_HOME/steam-frame-nix/ui-patches/<name>.json across
-          SteamVR restarts and reboots: the page reads it with
-          `window.__sfuiStore.get(name)` and writes it with
-          `window.__sfuiStore.set(name, value)` (see injector.mjs). The file
-          is kept when the patch is disabled or removed (the choices come
-          back when it is enabled again) and removed by
-          `steam-frame-nix-cleanup --all` (also run by `install.sh
-          uninstall`).
+          UI): `window.__sfuiStore.get(name)` / `.set(name, value)` in the
+          page, kept in $XDG_STATE_HOME/steam-frame-nix/ui-patches/<name>.json
+          across SteamVR restarts, reboots and disabling the patch; removed
+          by `steam-frame-nix-cleanup --all`.
         '';
       };
     };
@@ -106,9 +101,9 @@ in {
     defaultText = lib.literalMD "the helpers of `modules/lib`";
     description = ''
       Patch helpers from modules/lib/default.nix: `mkPatch { name, src,
-      signatures ? …, opts ? { } }` (calls `src` as
-      `(find, sigs, opts, hooks) => …`; see there), plus `finders`, `hooks`
-      (paths) and `signatures` (parsed signatures.json).
+      signatures ? …, opts ? { }, extraArgs ? [ ] }` (calls `src` as
+      `(find, sigs, opts, hooks, ...extraArgs) => …`; see there), plus
+      `finders`, `hooks` (paths) and `signatures` (parsed signatures.json).
     '';
   };