Fix white native-chrome artifacts on dark thememain

QSS alone doesn't reach everything Qt draws — splitter/dock separator
grip-dot decorations and a checkable QMenu item's tick come from the
app's QPalette, which was never set (stylesheet-only theming), so they
stayed Qt's default light palette under the dark stylesheet:

- MainWindow._apply_theme() now also sets a matching dark QPalette
  (restored to the style's standard palette for light theme).
- QMainWindow::separator and a generic QMenu rule (only #profileMenu was
  styled before — the toolbar's View menu had no objectName and so no
  styling at all) added to style_dark.qss, with QMenu::indicator styled
  as a filled/outline square so checkmarks are visible regardless of
  palette.
- QTabWidget/QTabBar (the bare containers, not ::pane/::tab) had no
  background set, so the strip beside the tab buttons fell back to the
  light palette — fixed globally, covers both the Devices/Channels/Plot
  config tabs and the Settings window since both share the same
  QTabWidget styling.

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

1 files changed, 32 insertions, 1 deletions

diff --git a/ui/main_window.py b/ui/main_window.py
index 07ab0b2..d7c297f 100644
--- a/ui/main_window.py
+++ b/ui/main_window.py
@@ -13,7 +13,7 @@ from PyQt6.QtWidgets import (
     QAbstractSpinBox, QComboBox, QMenu,
 )
 from PyQt6.QtCore import Qt, QTimer, QObject, QEvent, QRect, QByteArray, pyqtSignal, pyqtSlot
-from PyQt6.QtGui import QPainter, QColor, QFont, QAction
+from PyQt6.QtGui import QPainter, QColor, QFont, QAction, QPalette
 import logging
 import base64
 import os
@@ -822,8 +822,39 @@ class MainWindow(QMainWindow):
         if os.path.exists(qss_file):
             with open(qss_file) as f:
                 QApplication.instance().setStyleSheet(f.read())
+        self._apply_palette(theme)
         self._chart.set_theme(theme)
 
+    def _apply_palette(self, theme: str):
+        """QSS alone doesn't reach every Qt-drawn pixel — a splitter/dock
+        separator's grip-dot decoration, a QMenu's checkmark tick, etc. are
+        drawn from the app's QPalette, not stylesheet background-color.
+        Without ever setting one, those stay Qt's default light palette
+        regardless of the dark stylesheet, showing up as stray white dots/
+        slivers on top of otherwise-correctly-dark widgets."""
+        app = QApplication.instance()
+        if theme == "dark":
+            pal = QPalette()
+            pal.setColor(QPalette.ColorRole.Window,         QColor("#0b0e13"))
+            pal.setColor(QPalette.ColorRole.WindowText,     QColor("#c7d2fe"))
+            pal.setColor(QPalette.ColorRole.Base,            QColor("#111620"))
+            pal.setColor(QPalette.ColorRole.AlternateBase,   QColor("#161d2e"))
+            pal.setColor(QPalette.ColorRole.Text,            QColor("#c7d2fe"))
+            pal.setColor(QPalette.ColorRole.Button,          QColor("#161d2e"))
+            pal.setColor(QPalette.ColorRole.ButtonText,      QColor("#c7d2fe"))
+            pal.setColor(QPalette.ColorRole.Highlight,       QColor("#3b82f6"))
+            pal.setColor(QPalette.ColorRole.HighlightedText, QColor("#0b0e13"))
+            pal.setColor(QPalette.ColorRole.ToolTipBase,     QColor("#161d2e"))
+            pal.setColor(QPalette.ColorRole.ToolTipText,     QColor("#c7d2fe"))
+            pal.setColor(QPalette.ColorRole.Light,           QColor("#2a3558"))
+            pal.setColor(QPalette.ColorRole.Midlight,        QColor("#2a3558"))
+            pal.setColor(QPalette.ColorRole.Dark,            QColor("#060810"))
+            pal.setColor(QPalette.ColorRole.Mid,             QColor("#1c2540"))
+            pal.setColor(QPalette.ColorRole.Shadow,          QColor("#000000"))
+            app.setPalette(pal)
+        else:
+            app.setPalette(app.style().standardPalette())
+
     def _apply_settings_on_startup(self):
         self._apply_theme(self._settings.get("theme", "dark"))
         self.engine._interval = self._settings.get("poll_ms", 100) / 1000.0