lib/avahi/Client: add method IsConnected()

Publish only if the client is really connected.

src/lib/avahi/Client.cxx

@@ -30,11 +30,15 @@ void
 Client::Close() noexcept
 {
 	if (client != nullptr) {
+		connected = false;
+
 		for (auto *l : listeners)
 			l->OnAvahiDisconnect();
 
 		avahi_client_free(client);
 		client = nullptr;
+	} else {
+		assert(!connected);
 	}
 
 	reconnect_timer.Cancel();
@@ -45,6 +49,8 @@ Client::ClientCallback(AvahiClient *c, AvahiClientState state) noexcept
 {
 	switch (state) {
 	case AVAHI_CLIENT_S_RUNNING:
+		connected = true;
+
 		for (auto *l : listeners)
 			l->OnAvahiConnect(c);
 
@@ -73,12 +79,15 @@ Client::ClientCallback(AvahiClient *c, AvahiClientState state) noexcept
 
 	case AVAHI_CLIENT_S_COLLISION:
 	case AVAHI_CLIENT_S_REGISTERING:
+		assert(!connected);
+
 		for (auto *l : listeners)
 			l->OnAvahiChanged();
 
 		break;
 
 	case AVAHI_CLIENT_CONNECTING:
+		assert(!connected);
 		break;
 	}
 }
@@ -95,6 +104,7 @@ void
 Client::OnReconnectTimer() noexcept
 {
 	assert(client == nullptr);
+	assert(!connected);
 
 	int error;
 	client = avahi_client_new(&poll, AVAHI_CLIENT_NO_FAIL,

src/lib/avahi/Client.hxx

@@ -29,6 +29,8 @@ class Client final {
 
 	std::forward_list<ConnectionListener *> listeners;
 
+	bool connected = false;
+
 public:
 	Client(EventLoop &event_loop, ErrorHandler &_error_handler) noexcept;
 	~Client() noexcept;
@@ -42,6 +44,10 @@ public:
 
 	void Close() noexcept;
 
+	bool IsConnected() const noexcept {
+		return connected;
+	}
+
 	AvahiClient *GetClient() noexcept {
 		return client;
 	}

src/lib/avahi/Publisher.cxx

@@ -48,9 +48,8 @@ Publisher::Publisher(Client &_client, const char *_name,
 
 	client.AddListener(*this);
 
-	auto *c = client.GetClient();
+	if (client.IsConnected())
-	if (c != nullptr)
+		RegisterServices(client.GetClient());
-		RegisterServices(c);
 }
 
 Publisher::~Publisher() noexcept
@@ -168,9 +167,8 @@ Publisher::ShowServices() noexcept
 
 	visible = true;
 
-	auto *c = client.GetClient();
+	if (client.IsConnected())
-	if (c != nullptr)
+		RegisterServices(client.GetClient());
-		RegisterServices(c);
 }
 
 void