service/tray: mostly complete StatusNotifierItem implementation

Notably missing dbusmenu which makes it actually useful.

src/services/status_notifier/watcher.hpp

@@ -0,0 +1,54 @@
+#pragma once
+
+#include <qdbusinterface.h>
+#include <qdbusservicewatcher.h>
+#include <qlist.h>
+#include <qloggingcategory.h>
+#include <qobject.h>
+#include <qtmetamacros.h>
+#include <qtypes.h>
+
+Q_DECLARE_LOGGING_CATEGORY(logStatusNotifierWatcher);
+
+namespace qs::service::sni {
+
+class StatusNotifierWatcher: public QObject {
+	Q_OBJECT;
+	Q_PROPERTY(qint32 ProtocolVersion READ protocolVersion);
+	Q_PROPERTY(bool IsStatusNotifierHostRegistered READ isHostRegistered);
+	Q_PROPERTY(QList<QString> RegisteredStatusNotifierItems READ registeredItems);
+
+public:
+	explicit StatusNotifierWatcher(QObject* parent = nullptr);
+
+	void tryRegister();
+
+	[[nodiscard]] qint32 protocolVersion() const { return 0; } // NOLINT
+	[[nodiscard]] bool isHostRegistered() const;
+	[[nodiscard]] QList<QString> registeredItems() const;
+
+	// NOLINTBEGIN
+	void RegisterStatusNotifierHost(const QString& host);
+	void RegisterStatusNotifierItem(const QString& item);
+	// NOLINTEND
+
+	static StatusNotifierWatcher* instance();
+
+signals:
+	// NOLINTBEGIN
+	void StatusNotifierHostRegistered();
+	void StatusNotifierHostUnregistered();
+	void StatusNotifierItemRegistered(const QString& service);
+	void StatusNotifierItemUnregistered(const QString& service);
+	// NOLINTEND
+
+private slots:
+	void onServiceUnregistered(const QString& service);
+
+private:
+	QDBusServiceWatcher serviceWatcher;
+	QList<QString> hosts;
+	QList<QString> items;
+};
+
+} // namespace qs::service::sni