Allow to choose color scheme on Windows

PR #21615.

src/gui/uithememanager.h

@@ -31,6 +31,7 @@
 #pragma once
 
 #include <QtSystemDetection>
+#include <QtVersionChecks>
 #include <QColor>
 #include <QHash>
 #include <QIcon>
@@ -40,6 +41,15 @@
 
 #include "uithemesource.h"
 
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)) && defined(Q_OS_WIN)
+#define QBT_HAS_COLORSCHEME_OPTION
+#endif
+
+#ifdef QBT_HAS_COLORSCHEME_OPTION
+#include "base/settingvalue.h"
+#include "colorscheme.h"
+#endif
+
 class UIThemeManager final : public QObject
 {
     Q_OBJECT
@@ -50,6 +60,11 @@ public:
     static void freeInstance();
     static UIThemeManager *instance();
 
+#ifdef QBT_HAS_COLORSCHEME_OPTION
+    ColorScheme colorScheme() const;
+    void setColorScheme(ColorScheme value);
+#endif
+
     QIcon getIcon(const QString &iconId, const QString &fallback = {}) const;
     QIcon getFlagIcon(const QString &countryIsoCode) const;
     QPixmap getScaledPixmap(const QString &iconId, int height) const;
@@ -66,8 +81,15 @@ private:
     void applyStyleSheet() const;
     void onColorSchemeChanged();
 
+#ifdef QBT_HAS_COLORSCHEME_OPTION
+    void applyColorScheme() const;
+#endif
+
     static UIThemeManager *m_instance;
     const bool m_useCustomTheme;
+#ifdef QBT_HAS_COLORSCHEME_OPTION
+    SettingValue<ColorScheme> m_colorSchemeSetting;
+#endif
 #if (defined(Q_OS_UNIX) && !defined(Q_OS_MACOS))
     const bool m_useSystemIcons;
 #endif