feat: float alert banners over content as anchored toasts

Banners in the root layout shifted the whole UI on every message; now
they float over the content root (repositioned on resize) and the baton
toast anchors as a compact pill under the camera view, auto-clearing in
4s instead of 10s.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/aare/gui/main_window.py

@@ -153,6 +153,17 @@ class ClickableCursorFilter(QObject):
         return False
 
 
+class _AlertBannerHost(QWidget):
+    """Content root that repositions the floating alert banners on resize.
+    A plain resizeEvent override instead of event filters: filters firing
+    during widget teardown corrupted PySide in the test suite."""
+
+    def resizeEvent(self, event):
+        super().resizeEvent(event)
+        for banner in self.findChildren(AlertBanner):
+            banner.reposition()
+
+
 class MainWindow(QMainWindow):
     sample_geometry = Signal(SampleGeometryModel)
 
@@ -277,17 +288,19 @@ class MainWindow(QMainWindow):
         self._separator_hint_timer.setInterval(SEPARATOR_HINT_DELAY_MS)
         self._separator_hint_timer.timeout.connect(lambda: self._set_separator_hint(True))
 
-        root_widget = QWidget(parent=self)
+        root_widget = _AlertBannerHost(parent=self)
         root_widget.setObjectName("mainContentRoot")
         root_layout = QVBoxLayout(root_widget)
         root_layout.setContentsMargins(0, 0, 0, 0)
         root_layout.setSpacing(0)
 
+        # Banners float over the content instead of sitting in root_layout, so
+        # messages (e.g. "Baton acquired!") no longer shift the whole UI.
         self.alert_banner = AlertBanner(parent=root_widget)
-        root_layout.addWidget(self.alert_banner)
+        self.alert_banner.float_over(root_widget)
 
         self.alert_banner_secondary = AlertBanner(parent=root_widget)
-        root_layout.addWidget(self.alert_banner_secondary)
+        self.alert_banner_secondary.float_over(root_widget)
 
         self.content_stack = QStackedWidget(parent=root_widget)
         root_layout.addWidget(self.content_stack, 1)
@@ -424,6 +437,9 @@ class MainWindow(QMainWindow):
         self.sample_camera = SampleCameraImageLabel(
             geom=geom, raster=self.raster, parent=top_widget, default_image=default_image
         )
+        # Baton toasts sit as a compact pill under the camera view instead of
+        # a full-width bar at the top of the window.
+        self.alert_banner.anchor_to(self.sample_camera)
 
         self.beamline_view = VideoGraphicsView()
         self.beamline_view_panel = AxisVideoPanel(
@@ -2635,10 +2651,10 @@ class MainWindow(QMainWindow):
             self._close_baton_pending_dialog()
 
             if status.you_are_holder:
-                self.alert_banner.show_message("Baton acquired!", False, auto_clear_ms=10000)
+                self.alert_banner.show_message("Baton acquired!", False, auto_clear_ms=4000)
             else:
                 self.alert_banner.show_message(
-                    "Request declined or cancelled", False, auto_clear_ms=10000
+                    "Request declined or cancelled", False, auto_clear_ms=4000
                 )
 
         # Manage incoming request dialog (when someone requests from us)
@@ -2656,7 +2672,7 @@ class MainWindow(QMainWindow):
         """
         if result.get("granted"):
             self._waiting_for_baton_response = False
-            self.alert_banner.show_message("Baton acquired!", False, auto_clear_ms=10000)
+            self.alert_banner.show_message("Baton acquired!", False, auto_clear_ms=4000)
             logger.info("Baton acquired")
             # Close pending dialog; StatusBar will trigger p-group selection via SSE
             self._close_baton_pending_dialog()
@@ -2717,12 +2733,12 @@ class MainWindow(QMainWindow):
         logger.debug(f"Baton response result: {result}")
         if result.get("accepted"):
             self._waiting_for_baton_response = False
-            self.alert_banner.show_message("Control transferred", False, auto_clear_ms=10000)
+            self.alert_banner.show_message("Control transferred", False, auto_clear_ms=4000)
             self._close_baton_dialog()
             self.status_bar.update_baton_status(self.status_bar._baton_status)
         elif result.get("refused"):
             self._waiting_for_baton_response = False
-            self.alert_banner.show_message("Request declined", False, auto_clear_ms=10000)
+            self.alert_banner.show_message("Request declined", False, auto_clear_ms=4000)
             self._close_baton_dialog()
             self.status_bar.update_baton_status(self.status_bar._baton_status)
         else:
@@ -2741,7 +2757,7 @@ class MainWindow(QMainWindow):
 
         elif result.get("granted"):
             self._waiting_for_baton_response = False
-            self.alert_banner.show_message("Baton acquired!", False, auto_clear_ms=10000)
+            self.alert_banner.show_message("Baton acquired!", False, auto_clear_ms=4000)
             self._close_baton_pending_dialog()
 
         elif result.get("queued"):
@@ -2760,7 +2776,7 @@ class MainWindow(QMainWindow):
 
         elif result.get("refused"):
             self._waiting_for_baton_response = False
-            self.alert_banner.show_message("Request declined", False, auto_clear_ms=10000)
+            self.alert_banner.show_message("Request declined", False, auto_clear_ms=4000)
             self._close_baton_pending_dialog()
 
         else:

src/aare/gui/widgets/alert_banner.py

@@ -1,5 +1,5 @@
 from aarecommon.config.logger import setup_logger
-from PySide6.QtCore import Qt, QTimer, Slot
+from PySide6.QtCore import QPoint, Qt, QTimer, Slot
 from PySide6.QtWidgets import QFrame, QGraphicsDropShadowEffect, QHBoxLayout, QLabel, QSizePolicy
 
 from aare.gui.constants import LOGGER_NAME
@@ -45,6 +45,53 @@ class AlertBanner(QFrame):
         self.setVisible(False)
         self.setSizePolicy(QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Fixed)
 
+        self._float_host = None
+        self._float_anchor = None
+
+    def float_over(self, host) -> None:
+        """Overlay this banner at the top of `host` instead of occupying layout
+        space — added because showing/hiding the baton banner was shifting the
+        whole content stack up and down. No event filters on purpose: filters
+        firing during widget teardown corrupted PySide (tests crashed with
+        "QPushButton returned NULL"); the host repositions us on resize instead
+        (see _AlertBannerHost in main_window)."""
+        self.setParent(host)
+        self._float_host = host
+        # Click-through: the banner covers live UI now, so it must not eat
+        # mouse events meant for the widgets underneath.
+        self.setAttribute(Qt.WidgetAttribute.WA_TransparentForMouseEvents, True)
+
+    def anchor_to(self, widget) -> None:
+        """Render as a compact toast under `widget`'s bottom edge (must be a
+        descendant of the float host) instead of a full-width top bar — the
+        baton messages sit below the sample camera view this way. Falls back
+        to the top bar while the anchor is hidden (e.g. portrait mode).
+        ponytail: position goes stale if a splitter drag moves the anchor while
+        the toast is up; it self-corrects on the next show."""
+        self._float_anchor = widget
+
+    def showEvent(self, event):
+        super().showEvent(event)
+        self.reposition()
+
+    def reposition(self) -> None:
+        host = self._float_host
+        if host is None or not self.isVisible():
+            return
+        anchor = self._float_anchor
+        if anchor is not None and anchor.isVisible():
+            top_left = anchor.mapTo(host, QPoint(0, 0))
+            w = min(self.sizeHint().width(), anchor.width())
+            h = self.heightForWidth(w) if self.hasHeightForWidth() else self.sizeHint().height()
+            x = top_left.x() + (anchor.width() - w) // 2
+            y = min(top_left.y() + anchor.height() + 4, host.height() - h)
+            self.setGeometry(x, y, w, h)
+        else:
+            w = host.width()
+            h = self.heightForWidth(w) if self.hasHeightForWidth() else self.sizeHint().height()
+            self.setGeometry(0, 0, w, h)
+        self.raise_()
+
     def _set_alert_kind(self, kind: str) -> None:
         self.setProperty("alertKind", kind)
         self.style().unpolish(self)
@@ -79,6 +126,8 @@ class AlertBanner(QFrame):
         self._current_is_error = is_error
         self._label.setText(decorated)
         self.setVisible(True)
+        # Resize to the new text even when already visible (no showEvent then).
+        self.reposition()
 
     @Slot(str, int)
     def show_waiting(self, msg: str, countdown_seconds: int = 0):
@@ -106,6 +155,7 @@ class AlertBanner(QFrame):
             self._countdown_timer.start()
 
         self.setVisible(True)
+        self.reposition()
 
     def _apply_waiting_style(self):
         """Apply yellow/waiting style."""