fix(gui): fire mount auto-centering on the first idle status tick

The "apply after mounting" checkbox clicked Auto Centering as soon as the
status poll showed a new sample id. /sample/mount still holds the hw lock
at that point, /alc/center_loop takes the same lock non-blocking, and the
resulting BeamlineBusyException is a quiet error the GUI swallows. So the
automatic click never did anything; only a later manual click worked.

Arm on the sample-id change and click on the first status tick with
busy=False, which is exactly what the user did by hand. Skip arming while
queue automation runs: it mounts and centers on its own and frees the lock
between /scan/auto calls, so a GUI centering in that gap would steal the
lock from the next scan. Pause during a scan's mount phase can still arm
that one sample, but Pause ends in an unmount, so the window is a ms-wide
lock gap sampled at 2 Hz; accepted, noted in the code.

Supersedes the three-commit approach on
fix/auto-center-after-mount-wait-idle (PR 243).

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/aare/gui/main_window.py

@@ -745,6 +745,9 @@ class MainWindow(QMainWindow):
             self.automation_progress_panel.set_running
         )
         self.job_list_panel.automation_running_changed.connect(self._on_automation_running_changed)
+        self.job_list_panel.automation_running_changed.connect(
+            self.data_collection.set_automation_running
+        )
 
         self.automation_progress_panel.set_samples_in_queue(
             len(self.job_list_panel.table_model.samples)

src/aare/gui/panels/data_collection_settings.py

@@ -195,6 +195,9 @@ class DataCollectionSettings(QFrame):
         # startup must not trigger an auto-centering (hardware would move
         # uninvited on every restart).
         self._status_seen = False
+        # Armed on mount, fired on the first idle status tick (see _track_sample).
+        self._center_after_mount_pending = False
+        self._automation_running = False
 
         self._tab_bar.currentChanged.connect(self._stack.setCurrentIndex)
         self._tab_bar.currentChanged.connect(self._on_tab_changed)
@@ -242,23 +245,47 @@ class DataCollectionSettings(QFrame):
         self.raster.update_daq_status(s)
         self.screening.update_daq_status(s)
         self.simple.update_daq_status(s)
-        self._track_sample(None if s.sample is None else s.sample.db_id)
+        self._track_sample(None if s.sample is None else s.sample.db_id, s.busy)
 
-    def _track_sample(self, db_id: int | None):
+    def _track_sample(self, db_id: int | None, busy: bool = False):
         # Separate from update_daq_status so tests can drive mount detection
         # without building a full DAQStatusModel.
         if db_id is None:
             # Forget on unmount so remounting the same sample counts as a
             # fresh mount below.
             self._sample_id = None
+            self._center_after_mount_pending = False
         elif db_id != self._sample_id:
             self._sample_id = db_id
             self._tab_bar.setCurrentIndex(0)
-            if self._status_seen and self.auto_center_after_mount.isChecked():
-                # Reuse the button wiring (clicked -> daq.center_loop in
-                # main_window) instead of a second signal path.
-                self.find_tip.click()
+            self._center_after_mount_pending = (
+                self._status_seen
+                and self.auto_center_after_mount.isChecked()
+                and not self._automation_running
+            )
         self._status_seen = True
+        # The server publishes the new sample while /sample/mount still holds
+        # the hw lock, and /alc/center_loop takes that lock non-blocking, so a
+        # click on the id change alone was rejected as busy (a quiet error the
+        # GUI swallows). Wait for the first idle tick instead: same as the
+        # user waiting a bit and clicking.
+        if self._center_after_mount_pending and not busy:
+            self._center_after_mount_pending = False
+            # Reuse the button wiring (clicked -> daq.center_loop in
+            # main_window) instead of a second signal path.
+            self.find_tip.click()
+
+    @Slot(bool)
+    def set_automation_running(self, running: bool):
+        # Queue automation mounts and centers each sample itself and frees the
+        # hw lock between /scan/auto calls; a GUI centering in that gap would
+        # steal the lock from the next scan and stop the queue.
+        # ponytail: Pause drops the flag while the current scan may still be
+        # in its mount phase -> at most one extra centering on that sample.
+        # Track in-flight /scan/auto instead if that ever matters.
+        self._automation_running = running
+        if running:
+            self._center_after_mount_pending = False
 
     @Slot(int)
     def _on_tab_changed(self, idx: int):

tests/unit/gui/test_data_collection_settings.py

@@ -353,6 +353,39 @@ def test_auto_center_fires_on_mount_only_when_armed(settings_panel):
     assert len(clicks) == 3
 
 
+def test_auto_center_waits_for_hw_lock_after_mount(settings_panel):
+    clicks = []
+    settings_panel.find_tip.clicked.connect(lambda: clicks.append(1))
+    settings_panel.auto_center_after_mount.setChecked(True)
+    settings_panel._track_sample(None)
+
+    # The mount still holds the hw lock when the sample id first shows up:
+    # /alc/center_loop would be refused, so no click yet.
+    settings_panel._track_sample(1, busy=True)
+    settings_panel._track_sample(1, busy=True)
+    assert not clicks
+    # First idle tick fires it, exactly once.
+    settings_panel._track_sample(1, busy=False)
+    settings_panel._track_sample(1, busy=False)
+    assert len(clicks) == 1
+
+    # Unmount while still pending drops the request.
+    settings_panel._track_sample(None)
+    settings_panel._track_sample(2, busy=True)
+    settings_panel._track_sample(None, busy=False)
+    assert len(clicks) == 1
+
+    # Queue automation mounts and centers on its own: never fire in its gaps.
+    settings_panel.set_automation_running(True)
+    settings_panel._track_sample(3, busy=True)
+    settings_panel._track_sample(3, busy=False)
+    assert len(clicks) == 1
+    settings_panel.set_automation_running(False)
+    settings_panel._track_sample(None)
+    settings_panel._track_sample(4, busy=False)
+    assert len(clicks) == 2
+
+
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