fix(notification_banner): connect to light/dark mode change

bec_widgets/widgets/containers/main_window/addons/notification_center/notification_banner.py

@@ -62,6 +62,21 @@ LIGHT_PALETTE = {
 }
 
 
+def _connect_theme_change(slot) -> None:
+    """Connect *slot* to the available application theme-change signals."""
+    qapp = QApplication.instance()
+    if qapp is None:
+        return
+
+    theme = getattr(qapp, "theme", None)
+    if hasattr(theme, "theme_changed"):
+        theme.theme_changed.connect(slot)
+
+    legacy_signal = getattr(qapp, "theme_signal", None)
+    if hasattr(legacy_signal, "theme_updated"):
+        legacy_signal.theme_updated.connect(slot)
+
+
 class NotificationToast(QFrame):
     """
     Notification toast widget with title, body, optional traceback,
@@ -257,9 +272,7 @@ class NotificationToast(QFrame):
     # ------------------------------------------------------------------
     def _connect_to_theme_change(self):
         """Connect this toast to the global theme‑updated signal."""
-        qapp = QApplication.instance()
-        if hasattr(qapp, "theme_signal"):
-            qapp.theme_signal.theme_updated.connect(self.apply_theme)
+        _connect_theme_change(self.apply_theme)
 
     # helper methods -----------------------------------------------------
     def _current_inner_width(self) -> int:
@@ -403,11 +416,18 @@ class NotificationToast(QFrame):
             #NotificationToast QPushButton:hover {{ color: {btn_hover}; }}
             """)
         # traceback panel colours
-        trace_bg = "#1e1e1e" if theme == "dark" else "#f0f0f0"
+        if theme == "dark":
+            trace_bg = "#1e1e1e"
+            trace_fg = palette["body"]
+            trace_border = "rgba(255,255,255,48)"
+        else:
+            trace_bg = "#ffffff"
+            trace_fg = palette["body"]
+            trace_border = "rgba(15,23,42,54)"
         self.trace_view.setStyleSheet(f"""
             background:{trace_bg};
-            color:{palette['body']};
-            border:none;
+            color:{trace_fg};
+            border: 1px solid {trace_border};
             border-radius:8px;
             """)
 
@@ -438,7 +458,7 @@ class NotificationToast(QFrame):
             }}
             """)
 
-        self._accent_alpha = 28 if theme == "light" else 60
+        self._accent_alpha = 6 if theme == "light" else 60
         self._gradient_width_factor = 1.0 if theme == "light" else 0.70
         self.update()
 
@@ -674,9 +694,7 @@ class NotificationCentre(QScrollArea):
 
     def _connect_to_theme_change(self):
         """Connect to the theme change signal."""
-        qapp = QApplication.instance()
-        if hasattr(qapp, "theme_signal"):
-            qapp.theme_signal.theme_updated.connect(self.apply_theme)
+        _connect_theme_change(self.apply_theme)
 
     #  public API
     def add_notification(

tests/unit_tests/test_notifications.py

@@ -40,8 +40,10 @@ def test_apply_theme_updates_colours(qtbot, toast):
     """apply_theme("light") should inject LIGHT palette colours into stylesheets."""
     toast.apply_theme("light")
     assert LIGHT_PALETTE["title"] in toast._title_lbl.styleSheet()
-    assert toast._accent_alpha == 28
+    assert toast._accent_alpha == 6
     assert toast._gradient_width_factor == 1.0
+    assert "border: 1px solid" in toast.trace_view.styleSheet()
+    assert "border:none" not in toast.trace_view.styleSheet()
 
     toast.apply_theme("dark")
     assert DARK_PALETTE["title"] in toast._title_lbl.styleSheet()
@@ -49,6 +51,16 @@ def test_apply_theme_updates_colours(qtbot, toast):
     assert toast._gradient_width_factor == 0.70
 
 
+def test_toast_updates_from_qapp_theme_changed_signal(qtbot, toast):
+    app = QtWidgets.QApplication.instance()
+    assert hasattr(app, "theme")
+
+    app.theme.theme_changed.emit("light")
+    qtbot.wait(10)
+
+    assert LIGHT_PALETTE["title"] in toast._title_lbl.styleSheet()
+
+
 def test_expired_signal(qtbot, toast):
     """Toast must emit expired once its lifetime finishes."""
     with qtbot.waitSignal(toast.expired, timeout=1000):
@@ -255,6 +267,20 @@ def test_theme_propagation(qtbot, centre):
     assert LIGHT_PALETTE["title"] in toast._title_lbl.styleSheet()
 
 
+def test_centre_updates_from_qapp_theme_changed_signal(qtbot, centre):
+    toast = _post(centre, SeverityKind.INFO)
+    centre.apply_theme("dark")
+
+    app = QtWidgets.QApplication.instance()
+    assert hasattr(app, "theme")
+
+    app.theme.theme_changed.emit("light")
+    qtbot.wait(10)
+
+    assert centre._theme == "light"
+    assert LIGHT_PALETTE["title"] in toast._title_lbl.styleSheet()
+
+
 # ------------------------------------------------------------------------
 # NotificationIndicator tests
 # ------------------------------------------------------------------------