Gaze: install our eye tracker, prefer it, and say why a calibration dot wasn't taken

A user on a fresh install got "Calibration failed: only 0 of 21 dots" with
no reason. The installer never installed our tracker, so gaze used
SteamVR's, and the only way SteamVR's tracker rejects a dot is losing an
eye for most of the look. The panel just showed a red ring.

- install.sh: step 9/10 installs our tracker (gaze/tracker/install.sh)
  after gaze mode, yes by default; it needs sudo, so --yes runs it only
  when sudo won't prompt. If it fails, gaze keeps SteamVR's tracker.
  Configs that still say GAZE_TRACKER=steam (the old template) are asked
  whether to switch.
- GAZE_TRACKER=auto, the new default: ours when it's installed (the
  frame grabber, its unit, and ft-eyes' Python), else SteamVR's.
  ft-gazed rechecks every second, so installing it switches over. Input
  Settings lists Own tracker first as recommended, and says how to
  install it when it's missing (checking the host's /etc through
  /run/host from the dev container).
- The calibration panel has a note line, orange over the instructions:
  why a dot wasn't taken (an eye lost, a blink, the eyes disagreeing for
  SteamVR's tracker, from steady_samples' new drop counts; ft-eyes' reply
  for ours), what a click is still waiting for after 1.5 s, and a failed
  calibration's most common reason, which the Gaze page shows too.
  steady_samples keeps the same samples as before (checked on 2037
  windows of recordings); a lost eye is named before a blink, since its
  openness reads 0.

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

gaze/ft-gazed

@@ -3,8 +3,12 @@
 
 Two settings in ~/.config/frametop.conf (the Gaze page of Frametop Input Settings), read
 again when the file changes:
-  GAZE_TRACKER=steam|own   SteamVR's eye tracker (default), or our own (gaze/tracker/ft-eyes,
-                           ft-gaze's source "own"; this service runs it, see below)
+  GAZE_TRACKER=auto|own|steam
+                           our own eye tracker (gaze/tracker/ft-eyes, ft-gaze's source "own";
+                           this service runs it, see below) or SteamVR's. auto (the default)
+                           is ours when it's installed (gaze/tracker/install.sh: the frame
+                           grabber, and ft-eyes' Python in this checkout), else SteamVR's; it
+                           switches when ours is installed or removed.
   GAZE_EYE=auto|left|right the eye bias (gazecal.EyeWeights): auto weights each eye by how far
                            off it was at your recent nudges; left or right counts that eye twice
                            as much as the other. Either eye alone carries the gaze when the
@@ -119,6 +123,7 @@ EYES_PROG = REPO / "gaze" / "tracker" / "ft-eyes"  # our own tracker
 EYES_PYTHON = REPO / "gaze" / "tracker" / "build" / "venv" / "bin" / "python"  # numpy, OpenCV (build.sh)
 EYES_SOCKET = "\0ft_eyes"                      # its control socket
 EYES_CAMS = Path("/dev/shm/frametop-eyes-cams")  # the frames it reads (frametop-eyegrab.service)
+EYEGRAB = (Path("/etc/frametop/ft-eyegrab"), Path("/etc/systemd/system/frametop-eyegrab.service"))  # tracker/install.sh
 CONF = Path.home() / ".config" / "frametop.conf"
 CALIBRATION = STATE / "calibration.json"
 LESSONS = STATE / "pointer-lessons.json"
@@ -126,6 +131,7 @@ LESSON_LOG = STATE / "pointer-lessons.jsonl"
 SOURCES = ("action", "mmap1", "mmap2", "left", "right")  # the ones with a calibration here
 SIDES = ("left", "right")  # ft-gaze's order, and the sources for each eye alone
 TRACKERS = ("steam", "own")
+TRACKER_SETTINGS = ("auto",) + TRACKERS
 BIASES = ("auto", "left", "right")
 NUDGE_MAX = 55.0  # degrees: POINTER_GAZE_NUDGE_MAX's default, the largest lesson taken
 HISTORY = 12.0    # seconds of the gaze sent, to find a lesson's look (the helper sends it up to 10 s later)
@@ -153,8 +159,14 @@ def log(msg):
     print(f"ft-gazed: {msg}", file=sys.stderr, flush=True)
 
 
+def own_installed():
+    """Is our own tracker installed: its frame grabber, and ft-eyes' Python here?"""
+    return all(p.exists() for p in EYEGRAB) and EYES_PYTHON.exists()
+
+
 def read_settings():
-    """(tracker, eye bias, nudge max) from frametop.conf, defaults for anything missing or unknown."""
+    """(tracker, GAZE_TRACKER, eye bias, nudge max) from frametop.conf, defaults for anything
+    missing or unknown. The tracker is "steam" or "own": auto picks ours when it's installed."""
     conf = {}
     try:
         for line in CONF.read_text().splitlines():
@@ -164,13 +176,15 @@ def read_settings():
                 conf[k.strip()] = v.strip().lower()
     except OSError:
         pass
-    tracker = conf.get("GAZE_TRACKER", "steam")
+    setting = conf.get("GAZE_TRACKER", "auto")
+    setting = setting if setting in TRACKER_SETTINGS else "auto"
+    tracker = setting if setting != "auto" else "own" if own_installed() else "steam"
     bias = conf.get("GAZE_EYE", "auto")
     try:
         nudge = min(max(float(conf.get("POINTER_GAZE_NUDGE_MAX", NUDGE_MAX)), 1.0), 110.0)  # the helper's range
     except ValueError:
         nudge = NUDGE_MAX
-    return tracker if tracker in TRACKERS else "steam", bias if bias in BIASES else "auto", nudge
+    return tracker, setting, bias if bias in BIASES else "auto", nudge
 
 
 def mtime(path):
@@ -185,7 +199,7 @@ class Service:
         self.override, self.verbose, self.to = source, verbose, to
         self.source = source or "mmap1"  # the older path's source
         STATE.mkdir(parents=True, exist_ok=True)
-        self.tracker, self.bias, self.nudge_max = read_settings()
+        self.tracker, self.tracker_setting, self.bias, self.nudge_max = read_settings()
         self.conf_mtime = mtime(CONF)
         self.models = {name: Correction() for name in SOURCES}
         self.mode = DEFAULT_MODEL
@@ -246,9 +260,12 @@ class Service:
 
     def load_settings(self):
         self.conf_mtime = mtime(CONF)
-        tracker, bias, self.nudge_max = read_settings()
+        tracker, self.tracker_setting, bias, self.nudge_max = read_settings()
         if (tracker, bias) != (self.tracker, self.bias):
-            log(f"tracker {tracker}, eye bias {bias}" + (f" (--source {self.override} wins)" if self.override else ""))
+            auto = ""
+            if self.tracker_setting == "auto":
+                auto = " (auto: ours is installed)" if tracker == "own" else " (auto: ours isn't installed)"
+            log(f"tracker {tracker}{auto}, eye bias {bias}" + (f" (--source {self.override} wins)" if self.override else ""))
             self.tracker, self.bias = tracker, bias
             for w in self.weights.values():
                 w.bias = bias
@@ -733,7 +750,8 @@ class Service:
             st.update(calibration_samples=cal.get("dots", 0), calibration_made=cal.get("made"),
                       lessons=max(len(m) for m in w.misses), own_running=bool(own),
                       own_reseat=any(e.get("reseat") for e in own.get("eyes", {}).values()))
-        st.update(eyes_process=self.eyes_proc is not None, eyegrab=EYES_CAMS.exists())
+        st.update(eyes_process=self.eyes_proc is not None, eyegrab=EYES_CAMS.exists(),
+                  tracker_setting=self.tracker_setting, own_installed=own_installed())
         st.update({"ft_gaze": self.proc is not None, "sample_age_s": round(time.monotonic() - self.last_sample, 2)
                    if self.last_sample else None, "headset_on": self.steam.wearing(),
                    "headset_on_since": self.steam.worn(), "last": [round(v, 2) for v in self.last] if self.last else None,
@@ -749,7 +767,8 @@ class Service:
         if mtime(CALIBRATION) != self.cal_mtime:
             self.load_calibration()
             self.refit()
-        if mtime(CONF) != self.conf_mtime:
+        if mtime(CONF) != self.conf_mtime or (self.tracker_setting == "auto"
+                                              and own_installed() != (self.tracker == "own")):
             self.load_settings()
         want = self.eyes_wanted()
         if want and not self.eyes_proc and time.monotonic() >= self.eyes_restart_at: