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>

2 files changed, 73 insertions, 2 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
diff --git a/ui/style_dark.qss b/ui/style_dark.qss
index 3a20cba..ce43d74 100644
--- a/ui/style_dark.qss
+++ b/ui/style_dark.qss
@@ -348,6 +348,11 @@ QComboBox#channelPickerCb { font-family: "IBM Plex Mono", monospace; font-size:
 QComboBox#channelPickerCb:focus { border-color: #3b82f6; }
 
 /* ── Tabs ────────────────────────────────────────────────────────── */
+/* The bare QTabWidget/QTabBar containers (not ::pane or ::tab) have no
+   background of their own otherwise, so the strip beside/above the tab
+   buttons falls back to the default light palette. */
+QTabWidget { background-color: transparent; }
+QTabBar    { background-color: transparent; }
 QTabWidget::pane { background-color: #111620; border: 1px solid #2a3558; border-radius: 4px; }
 QTabBar::tab {
     background-color: #0b0e13; color: #8b9dc3;
@@ -385,10 +390,18 @@ QScrollBar::handle:horizontal { background: #2a3558; border-radius: 4px; min-wid
 QScrollBar::handle:horizontal:hover { background: #3b82f6; }
 QScrollBar::add-line:horizontal, QScrollBar::sub-line:horizontal { width: 0; }
 
-/* ── Splitter ─────────────────────────────────────────────────────── */
+/* ── Splitter / dock separator ───────────────────────────────────────
+   Qt draws the little grip-dot decoration on a splitter/dock separator
+   from the app's QPalette (Light/Midlight roles), not from QSS
+   background-color — see MainWindow._apply_palette() in ui/main_window.py,
+   which sets those roles dark too. background-color here still matters
+   for the flat part of the handle. */
 QSplitter::handle       { background-color: #2a3558; }
 QSplitter::handle:hover { background-color: #3b82f6; }
 
+QMainWindow::separator       { background-color: #2a3558; width: 4px; height: 4px; }
+QMainWindow::separator:hover { background-color: #3b82f6; }
+
 /* ── Status bar ───────────────────────────────────────────────────── */
 QStatusBar {
     background-color: #0b0e13; border-top: 1px solid #2a3558;
@@ -554,6 +567,33 @@ QFileDialog QComboBox {
     color: #e2e8f0;
 }
 
+/* ── Menus (generic — covers the View menu and any other unnamed QMenu,
+   not just the named ones below) ───────────────────────────────────── */
+QMenu {
+    background-color: #111620;
+    border: 1px solid #2a3558;
+    border-radius: 4px;
+    padding: 4px 0;
+    color: #e2e8f0;
+    font-size: 13px;
+}
+QMenu::item { padding: 7px 20px 7px 28px; color: #c7d2fe; }
+QMenu::item:selected  { background-color: #1e3a5f; color: #e0f2fe; }
+QMenu::item:disabled  { color: #475569; }
+QMenu::separator      { height: 1px; background: #2a3558; margin: 3px 8px; }
+/* Checkable QAction indicator — drawn as a small filled/outline square
+   rather than relying on the native tick glyph, so it's guaranteed
+   visible regardless of palette. */
+QMenu::indicator {
+    width: 13px; height: 13px; margin-left: 6px;
+}
+QMenu::indicator:checked {
+    background-color: #3b82f6; border: 1px solid #3b82f6; border-radius: 3px;
+}
+QMenu::indicator:unchecked {
+    background-color: transparent; border: 1px solid #2a3558; border-radius: 3px;
+}
+
 /* ── Profile / File menu ─────────────────────────────────────────── */
 QMenu#profileMenu {
     background-color: #111620;