feat(UI): Better integration with system dark modes.

If the OS/desktop environment have dark mode set, then qTox will select
the default dark color scheme as well.

Also, if the user sets light mode, this sets Qt to light mode as well.
This avoids conflicting style hints resulting in invisible text (dark
grey on black).

.clang-tidy

@@ -1,5 +1,6 @@
-Checks: '
-	-*,
-	readability-named-parameter,
-	readability-inconsistent-declaration-parameter-name'
+Checks: "-*
+, modernize-use-emplace
+, readability-named-parameter
+, readability-inconsistent-declaration-parameter-name
+"
 WarningsAsErrors: "*"

src/persistence/settings.cpp

@@ -6,20 +6,17 @@
 
 #include "settings.h"
 #include "src/core/core.h"
-#include "src/core/corefile.h"
 #include "src/nexus.h"
 #include "src/persistence/globalsettingsupgrader.h"
 #include "src/persistence/personalsettingsupgrader.h"
 #include "src/persistence/profile.h"
 #include "src/persistence/profilelocker.h"
 #include "src/persistence/settingsserializer.h"
-#include "src/persistence/smileypack.h"
-#include "src/widget/style.h"
-#include "src/widget/tool/imessageboxmanager.h"
 #ifdef QTOX_PLATFORM_EXT
 #include "src/platform/autorun.h"
 #endif
-#include "src/ipc.h"
+#include "src/widget/style.h"
+#include "src/widget/tool/imessageboxmanager.h"
 
 #include <QApplication>
 #include <QCryptographicHash>
@@ -33,6 +30,7 @@
 #include <QNetworkProxy>
 #include <QStandardPaths>
 #include <QStyleFactory>
+#include <QStyleHints>
 #include <QThread>
 #include <QtCore/QCommandLineParser>
 
@@ -185,19 +183,29 @@ void Settings::loadGlobal()
             smileyPack = DEFAULT_SMILEYS;
         }
 
+        const Style::MainTheme systemTheme =
+#if QT_VERSION >= QT_VERSION_CHECK(6, 5, 0)
+            QGuiApplication::styleHints()->colorScheme() == Qt::ColorScheme::Dark
+#else
+            QGuiApplication::palette().color(QPalette::Window).value() < 128
+#endif
+                ? Style::MainTheme::Dark
+                : Style::MainTheme::Light;
+        qDebug() << "System theme:" << systemTheme;
+
         emojiFontPointSize = s.value("emojiFontPointSize", 24).toInt();
         firstColumnHandlePos = s.value("firstColumnHandlePos", 50).toInt();
         secondColumnHandlePosFromRight = s.value("secondColumnHandlePosFromRight", 50).toInt();
         timestampFormat = s.value("timestampFormat", "hh:mm:ss").toString();
         dateFormat = s.value("dateFormat", "yyyy-MM-dd").toString();
         minimizeOnClose = s.value("minimizeOnClose", false).toBool();
         minimizeToTray = s.value("minimizeToTray", false).toBool();
-        lightTrayIcon = s.value("lightTrayIcon", false).toBool();
+        lightTrayIcon = s.value("lightTrayIcon", systemTheme == Style::MainTheme::Dark).toBool();
         useEmoticons = s.value("useEmoticons", true).toBool();
         statusChangeNotificationEnabled = s.value("statusChangeNotificationEnabled", false).toBool();
         showConferenceJoinLeaveMessages = s.value("showConferenceJoinLeaveMessages", false).toBool();
         spellCheckingEnabled = s.value("spellCheckingEnabled", true).toBool();
-        themeColor = s.value("themeColor", 0).toInt();
+        themeColor = s.value("themeColor", Style::defaultThemeColor(systemTheme)).toInt();
         style = s.value("style", "").toString();
         if (style == "") // Default to Fusion if available, otherwise no style
         {

src/widget/style.cpp

@@ -10,13 +10,15 @@
 #include <QDir>
 #include <QFile>
 #include <QFontInfo>
+#include <QGuiApplication>
 #include <QMap>
 #include <QPainter>
 #include <QRegularExpression>
 #include <QSettings>
 #include <QStandardPaths>
 #include <QStringBuilder>
 #include <QStyle>
+#include <QStyleHints>
 #include <QSvgRenderer>
 #include <QWidget>
 
@@ -111,6 +113,16 @@ const QMap<ColorPalette, QString> aliasColors = {
 };
 } // namespace
 
+int Style::defaultThemeColor(MainTheme theme)
+{
+    for (int i = 0; i < themeNameColors.size(); ++i) {
+        if (themeNameColors[i].type == theme) {
+            return i;
+        }
+    }
+    return 0;
+}
+
 QStringList Style::getThemeColorNames()
 {
     QStringList l;
@@ -279,7 +291,7 @@ const QString Style::resolve(const QString& filename, int themeColor, const QFon
         qss.replace(QRegularExpression(key % QLatin1String{"\\b"}), dictTheme[key]);
     }
 
-    // @getImagePath() function
+    // "@getImagePath()" function
     const QRegularExpression re{QStringLiteral(R"(@getImagePath\([^)\s]*\))")};
     QRegularExpressionMatchIterator i = re.globalMatch(qss);
 
@@ -329,10 +341,24 @@ void Style::setThemeColor(int themeColor, int color)
     dictColor.clear();
     initPalette(themeColor);
     initDictColor();
-    if (color < 0 || color >= themeNameColors.size())
+    if (color < 0 || color >= themeNameColors.size()) {
         setThemeColor(QColor());
-    else
-        setThemeColor(themeNameColors[color].color);
+    } else {
+        const auto& themeName = themeNameColors[color];
+
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+        switch (themeName.type) {
+        case MainTheme::Light:
+            QGuiApplication::styleHints()->setColorScheme(Qt::ColorScheme::Light);
+            break;
+        case MainTheme::Dark:
+            QGuiApplication::styleHints()->setColorScheme(Qt::ColorScheme::Dark);
+            break;
+        }
+#endif
+
+        setThemeColor(themeName.color);
+    }
 }
 
 /**

src/widget/style.h

@@ -57,6 +57,9 @@ class Style : public QObject
         Light,
         Dark
     };
+    Q_ENUM(MainTheme)
+
+    static int defaultThemeColor(MainTheme theme);
 
     static QStringList getThemeColorNames();
     static QString getThemeFolder(int themeColor);