allow user override system theme

Task-number: #216

include/FramelessHelper/Core/framelessmanager.h

@@ -36,7 +36,7 @@ class FRAMELESSHELPER_CORE_API FramelessManager : public QObject
     Q_OBJECT
     Q_DECLARE_PRIVATE(FramelessManager)
     Q_DISABLE_COPY_MOVE(FramelessManager)
-    Q_PROPERTY(Global::SystemTheme systemTheme READ systemTheme NOTIFY systemThemeChanged FINAL)
+    Q_PROPERTY(Global::SystemTheme systemTheme READ systemTheme WRITE setOverrideTheme NOTIFY systemThemeChanged FINAL)
     Q_PROPERTY(QColor systemAccentColor READ systemAccentColor NOTIFY systemThemeChanged FINAL)
     Q_PROPERTY(QString wallpaper READ wallpaper NOTIFY wallpaperChanged FINAL)
     Q_PROPERTY(Global::WallpaperAspectStyle wallpaperAspectStyle READ wallpaperAspectStyle NOTIFY wallpaperChanged FINAL)
@@ -55,6 +55,7 @@ public:
 public Q_SLOTS:
     void addWindow(const SystemParameters *params);
     void removeWindow(const WId windowId);
+    void setOverrideTheme(const Global::SystemTheme theme);
 
 Q_SIGNALS:
     void systemThemeChanged();

include/FramelessHelper/Core/private/framelessmanager_p.h

@@ -60,12 +60,16 @@ public:
 
     Q_NODISCARD static bool usePureQtImplementation();
 
+    void setOverrideTheme(const Global::SystemTheme theme);
+    Q_NODISCARD bool isThemeOverrided() const;
+
 private:
     void initialize();
 
 private:
     FramelessManager *q_ptr = nullptr;
     Global::SystemTheme m_systemTheme = Global::SystemTheme::Unknown;
+    std::optional<Global::SystemTheme> m_overrideTheme = std::nullopt;
     QColor m_accentColor = {};
 #ifdef Q_OS_WINDOWS
     Global::DwmColorizationArea m_colorizationArea = Global::DwmColorizationArea::None;

src/core/framelessmanager.cpp

@@ -168,6 +168,11 @@ QFont FramelessManagerPrivate::getIconFont()
 
 SystemTheme FramelessManagerPrivate::systemTheme() const
 {
+    // The user's choice has top priority.
+    if (isThemeOverrided()) {
+        const QMutexLocker locker(&g_helper()->mutex);
+        return m_overrideTheme.value();
+    }
     const QMutexLocker locker(&g_helper()->mutex);
     return m_systemTheme;
 }
@@ -270,7 +275,8 @@ void FramelessManagerPrivate::notifySystemThemeHasChangedOrNot()
         notify = true;
     }
 #endif
-    if (notify) {
+    // Don't emit the signal if the user has overrided the global theme.
+    if (notify && (m_overrideTheme.value_or(SystemTheme::Unknown) == SystemTheme::Unknown)) {
         Q_Q(FramelessManager);
         Q_EMIT q->systemThemeChanged();
         DEBUG.nospace() << "System theme changed. Current theme: " << m_systemTheme
@@ -316,6 +322,24 @@ bool FramelessManagerPrivate::usePureQtImplementation()
     return result;
 }
 
+void FramelessManagerPrivate::setOverrideTheme(const SystemTheme theme)
+{
+    const QMutexLocker locker(&g_helper()->mutex);
+    if (theme == SystemTheme::Unknown) {
+        m_overrideTheme = std::nullopt;
+    } else {
+        m_overrideTheme = theme;
+    }
+    Q_Q(FramelessManager);
+    Q_EMIT q->systemThemeChanged();
+}
+
+bool FramelessManagerPrivate::isThemeOverrided() const
+{
+    const QMutexLocker locker(&g_helper()->mutex);
+    return (m_overrideTheme.value_or(SystemTheme::Unknown) != SystemTheme::Unknown);
+}
+
 void FramelessManagerPrivate::initialize()
 {
     const QMutexLocker locker(&g_helper()->mutex);
@@ -409,4 +433,10 @@ void FramelessManager::removeWindow(const WId windowId)
     d->removeWindow(windowId);
 }
 
+void FramelessManager::setOverrideTheme(const SystemTheme theme)
+{
+    Q_D(FramelessManager);
+    d->setOverrideTheme(theme);
+}
+
 FRAMELESSHELPER_END_NAMESPACE