Motion capture: camera selection dropdown

Replace camera index spinbox with a combo listing detected cameras by
name. On Linux enumerates /dev/video* and reads device names from sysfs
(fast, no probing). Fallback probes cv2.VideoCapture indices 0-7 on
other platforms. Simulation entry always appended as last option.

Also adds explicit simulation mode (index -1) to tracker.start() and a
rescan button (⟳) in both the main window and the Settings > Plugins
widget.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

3 files changed, 128 insertions, 20 deletions

diff --git a/plugins/motion_capture/plugin.py b/plugins/motion_capture/plugin.py
index d4bf497..e5d37c7 100644
--- a/plugins/motion_capture/plugin.py
+++ b/plugins/motion_capture/plugin.py
@@ -22,7 +22,8 @@ from __future__ import annotations
 from typing import Any, Dict, List, Optional
 
 from PyQt6.QtWidgets import (
-    QDoubleSpinBox, QFormLayout, QLabel, QSpinBox, QWidget,
+    QComboBox, QDoubleSpinBox, QFormLayout, QHBoxLayout,
+    QLabel, QPushButton, QWidget,
 )
 
 from plugins.base_plugin import LabPlugin, PluginAction, PluginContext
@@ -90,17 +91,26 @@ class MotionCapturePlugin(LabPlugin):
         ]
 
     def get_settings_widget(self) -> Optional[QWidget]:
+        from tracker import list_cameras
         w = QWidget()
         lay = QFormLayout(w)
         lay.setContentsMargins(0, 4, 0, 4)
 
-        self._s_cam = QSpinBox()
-        self._s_cam.setRange(0, 9)
-        self._s_cam.setValue(
-            self._win.get_camera_index() if self._win else 0)
-        self._s_cam.setObjectName("traceWidthSpin")
-        self._s_cam.valueChanged.connect(self._sync_cam_to_window)
-        lay.addRow("Camera index:", self._s_cam)
+        cam_row = QHBoxLayout()
+        self._s_cam = QComboBox()
+        self._s_cam.setObjectName("channelPickerCb")
+        self._s_cameras: list = []
+        self._s_refresh_btn = QPushButton("⟳")
+        self._s_refresh_btn.setObjectName("configButton")
+        self._s_refresh_btn.setFixedWidth(28)
+        self._s_refresh_btn.setToolTip("Rescan cameras")
+        self._s_refresh_btn.clicked.connect(lambda: self._populate_settings_cam(list_cameras))
+        cam_row.addWidget(self._s_cam, 1)
+        cam_row.addWidget(self._s_refresh_btn)
+        lay.addRow("Camera:", cam_row)
+
+        self._populate_settings_cam(list_cameras)
+        self._s_cam.currentIndexChanged.connect(self._sync_cam_to_window)
 
         self._s_pxmm = QDoubleSpinBox()
         self._s_pxmm.setRange(0.01, 100_000)
@@ -168,9 +178,25 @@ class MotionCapturePlugin(LabPlugin):
         if self._toolbar_btn is not None:
             self._toolbar_btn.setChecked(False)
 
-    def _sync_cam_to_window(self, v: int) -> None:
+    def _populate_settings_cam(self, list_cameras_fn) -> None:
+        current = self._win.get_camera_index() if self._win else 0
+        self._s_cam.blockSignals(True)
+        self._s_cam.clear()
+        self._s_cameras = list_cameras_fn()
+        for _, label in self._s_cameras:
+            self._s_cam.addItem(label)
+        for i, (idx, _) in enumerate(self._s_cameras):
+            if idx == current:
+                self._s_cam.setCurrentIndex(i)
+                break
+        self._s_cam.blockSignals(False)
+
+    def _sync_cam_to_window(self, combo_i: int) -> None:
+        if not self._s_cameras:
+            return
+        idx = self._s_cameras[combo_i][0]
         if self._win:
-            self._win.set_camera_index(v)
+            self._win.set_camera_index(idx)
 
     def _sync_pxmm_to_window(self, v: float) -> None:
         if self._win:
diff --git a/plugins/motion_capture/tracker.py b/plugins/motion_capture/tracker.py
index 847a170..d65aca1 100644
--- a/plugins/motion_capture/tracker.py
+++ b/plugins/motion_capture/tracker.py
@@ -99,6 +99,13 @@ class CameraTracker:
         self.stop()
         self._running = True
 
+        if camera_index == -1:
+            with self._lock:
+                self._simulated = True
+            self._thread = threading.Thread(target=self._run_sim, daemon=True)
+            self._thread.start()
+            return True
+
         try:
             import cv2
             cap = cv2.VideoCapture(camera_index)
@@ -287,6 +294,50 @@ class CameraTracker:
             time.sleep(1 / 30)
 
 
+# ── Camera enumeration ────────────────────────────────────────────────────────
+
+def list_cameras():
+    """
+    Return list of (index, label) for all detected camera devices.
+
+    On Linux: reads /dev/video* and pulls human-readable names from sysfs.
+    Falls back to probing cv2.VideoCapture indices 0-7 on other platforms.
+    Always appends a Simulation entry.
+    """
+    cameras = []
+
+    import os, glob
+
+    video_nodes = sorted(glob.glob("/dev/video*"))
+    if video_nodes:
+        for path in video_nodes:
+            try:
+                idx = int(path.replace("/dev/video", ""))
+            except ValueError:
+                continue
+            name_path = f"/sys/class/video4linux/video{idx}/name"
+            try:
+                with open(name_path) as f:
+                    name = f.read().strip()
+            except OSError:
+                name = path
+            cameras.append((idx, f"{name}  [/dev/video{idx}]"))
+    else:
+        # Non-Linux fallback: probe indices
+        try:
+            import cv2
+            for idx in range(8):
+                cap = cv2.VideoCapture(idx)
+                if cap.isOpened():
+                    cameras.append((idx, f"Camera {idx}"))
+                    cap.release()
+        except ImportError:
+            pass
+
+    cameras.append((-1, "Simulation (no camera)"))
+    return cameras
+
+
 # ── Helper ────────────────────────────────────────────────────────────────────
 
 def _make_cv_tracker():
diff --git a/plugins/motion_capture/window.py b/plugins/motion_capture/window.py
index 082a8f6..40b436f 100644
--- a/plugins/motion_capture/window.py
+++ b/plugins/motion_capture/window.py
@@ -15,8 +15,8 @@ from __future__ import annotations
 from PyQt6.QtCore import Qt, QTimer, pyqtSignal
 from PyQt6.QtGui import QCloseEvent, QImage, QMouseEvent, QPixmap
 from PyQt6.QtWidgets import (
-    QDoubleSpinBox, QFrame, QHBoxLayout, QLabel, QPushButton,
-    QSizePolicy, QSpinBox, QVBoxLayout, QWidget,
+    QComboBox, QDoubleSpinBox, QFrame, QHBoxLayout, QLabel, QPushButton,
+    QSizePolicy, QVBoxLayout, QWidget,
 )
 
 import numpy as np
@@ -92,11 +92,19 @@ class MotionCaptureWindow(QWidget):
         ctrl.setContentsMargins(10, 6, 10, 6); ctrl.setSpacing(6)
 
         ctrl.addWidget(QLabel("Camera:"))
-        self._cam_spin = QSpinBox()
-        self._cam_spin.setRange(0, 9); self._cam_spin.setValue(0)
-        self._cam_spin.setObjectName("traceWidthSpin")
-        self._cam_spin.setFixedWidth(52)
-        ctrl.addWidget(self._cam_spin)
+        self._cam_combo = QComboBox()
+        self._cam_combo.setObjectName("channelPickerCb")
+        self._cam_combo.setMinimumWidth(200)
+        ctrl.addWidget(self._cam_combo)
+
+        self._refresh_btn = QPushButton("⟳")
+        self._refresh_btn.setObjectName("configButton")
+        self._refresh_btn.setFixedWidth(28)
+        self._refresh_btn.setToolTip("Rescan cameras")
+        self._refresh_btn.clicked.connect(self._scan_cameras)
+        ctrl.addWidget(self._refresh_btn)
+
+        self._scan_cameras()   # populate on open
 
         self._conn_btn = QPushButton("Connect")
         self._conn_btn.setObjectName("applyButton")
@@ -136,6 +144,21 @@ class MotionCaptureWindow(QWidget):
 
     # ── Actions ───────────────────────────────────────────────────────────
 
+    def _scan_cameras(self):
+        from tracker import list_cameras
+        current_idx = self.get_camera_index()
+        self._cam_combo.blockSignals(True)
+        self._cam_combo.clear()
+        self._cameras = list_cameras()   # [(index, label), ...]
+        for _, label in self._cameras:
+            self._cam_combo.addItem(label)
+        # Restore selection by index if still present
+        for i, (idx, _) in enumerate(self._cameras):
+            if idx == current_idx:
+                self._cam_combo.setCurrentIndex(i)
+                break
+        self._cam_combo.blockSignals(False)
+
     def _toggle_connect(self):
         if self._connected:
             self._tracker.stop()
@@ -150,7 +173,7 @@ class MotionCaptureWindow(QWidget):
             self._sim_badge.setVisible(False)
             self._status.setText("Disconnected")
         else:
-            ok = self._tracker.start(self._cam_spin.value())
+            ok = self._tracker.start(self.get_camera_index())
             if ok:
                 self._connected = True
                 self._conn_btn.setText("Disconnect")
@@ -243,10 +266,18 @@ class MotionCaptureWindow(QWidget):
     # ── State accessors (used by plugin for save/restore) ─────────────────
 
     def get_camera_index(self) -> int:
-        return self._cam_spin.value()
+        i = self._cam_combo.currentIndex()
+        cameras = getattr(self, "_cameras", [])
+        if 0 <= i < len(cameras):
+            return cameras[i][0]
+        return 0
 
     def set_camera_index(self, v: int):
-        self._cam_spin.setValue(v)
+        cameras = getattr(self, "_cameras", [])
+        for i, (idx, _) in enumerate(cameras):
+            if idx == v:
+                self._cam_combo.setCurrentIndex(i)
+                return
 
     def get_px_per_mm(self) -> float:
         return self._pxmm_spin.value()