FEAT(client): Automatically sync theme with OS color scheme

This update introduces an automatic theme switch that changes based on the OS color scheme at startup and during runtime. This feature is implemented for Qt 6.2 and includes compatibility for Qt 6.5 once Mumble upgrades.

Implements mumble-voip#6515

src/mumble/MainWindow.cpp

@@ -86,6 +86,16 @@
 #	include <dbt.h>
 #endif
 
+
+#include <QFile>
+#include <QGuiApplication>
+#include <QPalette>
+#include <QSettings>
+#include <QStyleHints>
+#include <QTextStream>
+
+
+
 #include <algorithm>
 
 MessageBoxEvent::MessageBoxEvent(QString m) : QEvent(static_cast< QEvent::Type >(MB_QEVENT)) {
@@ -117,7 +127,9 @@ MainWindow::MainWindow(QWidget *p)
 	else
 		SvgIcon::addSvgPixmapsToIcon(qiIcon, QLatin1String("skin:mumble.svg"));
 #else
-	{ SvgIcon::addSvgPixmapsToIcon(qiIcon, QLatin1String("skin:mumble.svg")); }
+	{
+		SvgIcon::addSvgPixmapsToIcon(qiIcon, QLatin1String("skin:mumble.svg"));
+	}
 
 	// Set application icon except on MacOSX, where the window-icon
 	// shown in the title-bar usually serves as a draggable version of the
@@ -198,8 +210,81 @@ MainWindow::MainWindow(QWidget *p)
 					 &PluginManager::on_serverSynchronized);
 
 	QAccessible::installFactory(AccessibleSlider::semanticSliderFactory);
+
+	// Theme application
+	applyTheme(); // Apply the light or dark theme during initialization
 }
 
+void MainWindow::applyTheme() {
+	boost::optional< ThemeInfo::StyleInfo > configuredStyle = Themes::getConfiguredStyle(Global::get().s);
+
+	QString lightThemePath = ":/themes/Default/Lite.qss"; // Default light theme path
+	QString darkThemePath  = ":/themes/Default/Dark.qss"; // Default dark theme path
+
+	if (configuredStyle) {
+		if (configuredStyle->name == "Auto") {
+#if QT_VERSION >= QT_VERSION_CHECK(6, 5, 0)
+			auto colorScheme = QGuiApplication::styleHints()->colorScheme();
+			if (colorScheme == Qt::ColorScheme::Dark) {
+				setStyleSheet(loadStyleSheet(darkThemePath)); // Apply dark theme
+			} else {
+				setStyleSheet(loadStyleSheet(lightThemePath)); // Apply light theme
+			}
+#else
+			bool isDarkTheme = detectSystemTheme();
+			if (isDarkTheme) {
+				setStyleSheet(loadStyleSheet(darkThemePath)); // Apply dark theme
+			} else {
+				setStyleSheet(loadStyleSheet(lightThemePath)); // Apply light theme
+			}
+#endif
+		} else if (configuredStyle->themeName == "none") {
+			setStyleSheet(""); // Clear the stylesheet if "None" is selected
+		} else {
+			QString themePath =
+				QString(":/themes/%1/%2.qss").arg(configuredStyle->themeName).arg(configuredStyle->name);
+			setStyleSheet(loadStyleSheet(themePath)); // Apply the selected theme and style
+		}
+	} else {
+		// Handle the case where no theme is configured (fallback to default behavior)
+		setStyleSheet(loadStyleSheet(lightThemePath)); // Default to light theme
+	}
+}
+
+bool MainWindow::detectSystemTheme() {
+#if QT_VERSION >= QT_VERSION_CHECK(6, 5, 0)
+	return false; // This should not be called for Qt 6.5 and above
+#else
+// Custom method to detect dark theme for Qt 6.2 and below
+#	ifdef Q_OS_WIN
+	QSettings settings("HKEY_CURRENT_USER\\Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize",
+					   QSettings::NativeFormat);
+	return settings.value("AppsUseLightTheme", 1).toInt() == 0; // 0 means dark mode
+#	else
+	// Fallback for other OSes
+	QByteArray platform = qgetenv("QT_QPA_PLATFORM");
+	if (platform.contains("darkmode=2")) {
+		return true;
+	} else if (platform.contains("darkmode=1")) {
+		QPalette defaultPalette;
+		return defaultPalette.color(QPalette::WindowText).lightness()
+			   > defaultPalette.color(QPalette::Window).lightness();
+	}
+	return false;
+#	endif
+#endif
+}
+
+QString MainWindow::loadStyleSheet(const QString &path) {
+	QFile file(path);
+	if (file.open(QFile::ReadOnly | QFile::Text)) {
+		QTextStream stream(&file);
+		return stream.readAll(); // Return the stylesheet content
+	}
+	return QString(); // Return empty if the file cannot be loaded
+}
+
+
 void MainWindow::createActions() {
 	gsPushTalk = new GlobalShortcut(this, GlobalShortcutType::PushToTalk, tr("Push-to-Talk", "Global Shortcut"));
 	gsPushTalk->setObjectName(QLatin1String("PushToTalk"));
@@ -756,6 +841,10 @@ void MainWindow::changeEvent(QEvent *e) {
 		QTimer::singleShot(0, this, SLOT(hide()));
 	}
 #endif
+
+	if (e->type() == QEvent::ThemeChange) {
+		applyTheme();
+	}
 }
 
 void MainWindow::keyPressEvent(QKeyEvent *e) {

src/mumble/MainWindow.h

@@ -221,6 +221,10 @@ class MainWindow : public QMainWindow, public Ui::MainWindow {
 
 	void autocompleteUsername();
 
+	void applyTheme();
+	bool detectSystemTheme();
+	QString loadStyleSheet(const QString &path);
+
 public slots:
 	void on_qmServer_aboutToShow();
 	void on_qaServerConnect_triggered(bool autoconnect = false);

themes/Default/theme.ini

@@ -1,6 +1,6 @@
 [theme]
 name=Mumble
-styles=dark,lite
+styles=dark,lite,auto
 [dark]
 name=Dark
 qss=Dark.qss
@@ -9,3 +9,7 @@ qss_MAC=OSX Dark.qss
 name=Lite
 qss=Lite.qss
 qss_MAC=OSX Lite.qss
+[auto]
+name=Auto
+qss=Lite.qss
+qss_MAC=OSX Lite.qss