Partition: add a local idle_monitor

Make idle events per-partition, but leave Instance::EmitIdle() and its
underlying idle_monitor which broadcasts idle events to all
partitions.

src/Instance.cxx

@@ -180,10 +180,7 @@ Instance::OnRemoteTag(const char *uri, const Tag &tag) noexcept
 void
 Instance::OnIdle(unsigned flags) noexcept
 {
-	/* send "idle" notifications to all subscribed
-	   clients */
-	client_list->IdleAdd(flags);
-
-	if (flags & (IDLE_PLAYLIST|IDLE_PLAYER|IDLE_MIXER|IDLE_OUTPUT))
-		OnStateModified();
+	/* broadcast to all partitions */
+	for (auto &partition : partitions)
+		partition.EmitIdle(flags);
 }

src/Instance.hxx

@@ -101,6 +101,10 @@ struct Instance final
 
 	std::unique_ptr<InputCacheManager> input_cache;
 
+	/**
+	 * Monitor for global idle events to be broadcasted to all
+	 * partitions.
+	 */
 	MaskMonitor idle_monitor;
 
 #ifdef ENABLE_NEIGHBOR_PLUGINS

src/Partition.cxx

@@ -40,6 +40,7 @@ Partition::Partition(Instance &_instance,
 	:instance(_instance),
 	 name(_name),
 	 listener(new ClientListener(instance.event_loop, *this)),
+	 idle_monitor(instance.event_loop, BIND_THIS_METHOD(OnIdleMonitor)),
 	 global_events(instance.event_loop, BIND_THIS_METHOD(OnGlobalEvent)),
 	 playlist(max_length, *this),
 	 outputs(*this),
@@ -60,12 +61,6 @@ Partition::BeginShutdown() noexcept
 	listener.reset();
 }
 
-void
-Partition::EmitIdle(unsigned mask) noexcept
-{
-	instance.EmitIdle(mask);
-}
-
 static void
 PrefetchSong(InputCacheManager &cache, const char *uri) noexcept
 {
@@ -215,6 +210,18 @@ Partition::OnMixerVolumeChanged(Mixer &, int) noexcept
 	EmitIdle(IDLE_MIXER);
 }
 
+void
+Partition::OnIdleMonitor(unsigned mask) noexcept
+{
+	/* send "idle" notifications to all subscribed
+	   clients */
+	for (auto &client : clients)
+		client.IdleAdd(mask);
+
+	if (mask & (IDLE_PLAYLIST|IDLE_PLAYER|IDLE_MIXER|IDLE_OUTPUT))
+		instance.OnStateModified();
+}
+
 void
 Partition::OnGlobalEvent(unsigned mask) noexcept
 {

src/Partition.hxx

@@ -63,6 +63,11 @@ struct Partition final : QueueListener, PlayerListener, MixerListener {
 											    boost::intrusive::link_mode<boost::intrusive::normal_link>>>,
 			       boost::intrusive::constant_time_size<false>> clients;
 
+	/**
+	 * Monitor for idle events local to this partition.
+	 */
+	MaskMonitor idle_monitor;
+
 	MaskMonitor global_events;
 
 	struct playlist playlist;
@@ -91,10 +96,11 @@ struct Partition final : QueueListener, PlayerListener, MixerListener {
 	/**
 	 * Emit an "idle" event to all clients of this partition.
 	 *
-	 * This method is not thread-safe and may only be called from
-	 * the main thread.
+	 * This method can be called from any thread.
 	 */
-	void EmitIdle(unsigned mask) noexcept;
+	void EmitIdle(unsigned mask) noexcept {
+		idle_monitor.OrMask(mask);
+	}
 
 	/**
 	 * Populate the #InputCacheManager with soon-to-be-played song
@@ -282,6 +288,9 @@ private:
 	/* virtual methods from class MixerListener */
 	void OnMixerVolumeChanged(Mixer &mixer, int volume) noexcept override;
 
+	/* callback for #idle_monitor */
+	void OnIdleMonitor(unsigned mask) noexcept;
+
 	/* callback for #global_events */
 	void OnGlobalEvent(unsigned mask) noexcept;
 };

src/client/List.cxx

@@ -34,12 +34,3 @@ ClientList::Remove(Client &client) noexcept
 
 	list.erase(list.iterator_to(client));
 }
-
-void
-ClientList::IdleAdd(unsigned flags) noexcept
-{
-	assert(flags != 0);
-
-	for (auto &client : list)
-		client.IdleAdd(flags);
-}

src/client/List.hxx

@@ -56,8 +56,6 @@ public:
 	}
 
 	void Remove(Client &client) noexcept;
-
-	void IdleAdd(unsigned flags) noexcept;
 };
 
 #endif