Mixer: add class MixerListener

Use a listener interface instead of GlobalEvents.

24 files changed, 144 insertions, 74 deletions

diff --git a/Makefile.am b/Makefile.am
index 6a985e76f..8e70ff290 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1033,6 +1033,7 @@ MIXER_LIBS = \
 	$(PULSE_LIBS)
 
 MIXER_API_SRC = \
+	src/mixer/Listener.hxx \
 	src/mixer/MixerPlugin.hxx \
 	src/mixer/MixerList.hxx \
 	src/mixer/MixerControl.cxx src/mixer/MixerControl.hxx \
diff --git a/src/GlobalEvents.hxx b/src/GlobalEvents.hxx
index 9b678a4f6..a9df03724 100644
--- a/src/GlobalEvents.hxx
+++ b/src/GlobalEvents.hxx
@@ -42,9 +42,6 @@ namespace GlobalEvents {
 		/** the current song's tag has changed */
 		TAG,
 
-		/** a hardware mixer plugin has detected a change */
-		MIXER,
-
 #ifdef WIN32
 		/** shutdown requested */
 		SHUTDOWN,
diff --git a/src/Main.cxx b/src/Main.cxx
index de74925e5..e52b40d58 100644
--- a/src/Main.cxx
+++ b/src/Main.cxx
@@ -33,7 +33,6 @@
 #include "client/ClientList.hxx"
 #include "command/AllCommands.hxx"
 #include "Partition.hxx"
-#include "mixer/Volume.hxx"
 #include "tag/TagConfig.hxx"
 #include "ReplayGainConfig.hxx"
 #include "Idle.hxx"
@@ -469,7 +468,6 @@ int mpd_main(int argc, char *argv[])
 
 	command_init();
 	initialize_decoder_and_player();
-	volume_init();
 	initAudioConfig();
 	instance->partition->outputs.Configure(*instance->event_loop,
 					       instance->partition->pc);
diff --git a/src/Partition.cxx b/src/Partition.cxx
index 4d4504338..512912f96 100644
--- a/src/Partition.cxx
+++ b/src/Partition.cxx
@@ -21,6 +21,8 @@
 #include "Partition.hxx"
 #include "DetachedSong.hxx"
 #include "output/MultipleOutputs.hxx"
+#include "mixer/Volume.hxx"
+#include "Idle.hxx"
 
 #ifdef ENABLE_DATABASE
 
@@ -47,3 +49,12 @@ Partition::SyncWithPlayer()
 {
 	playlist.SyncWithPlayer(pc);
 }
+
+void
+Partition::OnMixerVolumeChanged(gcc_unused Mixer &mixer, gcc_unused int volume)
+{
+	InvalidateHardwareVolume();
+
+	/* notify clients */
+	idle_add(IDLE_MIXER);
+}
diff --git a/src/Partition.hxx b/src/Partition.hxx
index 57dc9a5f4..cbdce2e86 100644
--- a/src/Partition.hxx
+++ b/src/Partition.hxx
@@ -22,6 +22,7 @@
 
 #include "Playlist.hxx"
 #include "output/MultipleOutputs.hxx"
+#include "mixer/Listener.hxx"
 #include "PlayerControl.hxx"
 
 struct Instance;
@@ -32,7 +33,7 @@ class SongLoader;
  * A partition of the Music Player Daemon.  It is a separate unit with
  * a playlist, a player, outputs etc.
  */
-struct Partition {
+struct Partition final : private MixerListener {
 	Instance &instance;
 
 	struct playlist playlist;
@@ -46,6 +47,7 @@ struct Partition {
 		  unsigned buffer_chunks,
 		  unsigned buffered_before_play)
 		:instance(_instance), playlist(max_length),
+		 outputs(*this),
 		 pc(outputs, buffer_chunks, buffered_before_play) {}
 
 	void ClearQueue() {
@@ -188,6 +190,10 @@ struct Partition {
 	 * Synchronize the player with the play queue.
 	 */
 	void SyncWithPlayer();
+
+private:
+	/* virtual methods from class MixerListener */
+	virtual void OnMixerVolumeChanged(Mixer &mixer, int volume) override;
 };
 
 #endif
diff --git a/src/mixer/Listener.hxx b/src/mixer/Listener.hxx
new file mode 100644
index 000000000..6f48fbd4d
--- /dev/null
+++ b/src/mixer/Listener.hxx
@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_MIXER_LISTENER_HXX
+#define MPD_MIXER_LISTENER_HXX
+
+class Mixer;
+
+/**
+ * An interface that listens on events from mixer plugins.  The
+ * methods must be thread-safe and non-blocking.
+ */
+class MixerListener {
+public:
+	virtual void OnMixerVolumeChanged(Mixer &mixer, int volume) = 0;
+};
+
+#endif
diff --git a/src/mixer/MixerControl.cxx b/src/mixer/MixerControl.cxx
index 568fad058..6d08140db 100644
--- a/src/mixer/MixerControl.cxx
+++ b/src/mixer/MixerControl.cxx
@@ -27,10 +27,11 @@
 Mixer *
 mixer_new(EventLoop &event_loop,
 	  const MixerPlugin &plugin, AudioOutput &ao,
+	  MixerListener &listener,
 	  const config_param &param,
 	  Error &error)
 {
-	Mixer *mixer = plugin.init(event_loop, ao, param, error);
+	Mixer *mixer = plugin.init(event_loop, ao, listener, param, error);
 
 	assert(mixer == nullptr || mixer->IsPlugin(plugin));
 
diff --git a/src/mixer/MixerControl.hxx b/src/mixer/MixerControl.hxx
index 46a9138e6..75255d98c 100644
--- a/src/mixer/MixerControl.hxx
+++ b/src/mixer/MixerControl.hxx
@@ -30,10 +30,12 @@ class Mixer;
 class EventLoop;
 struct AudioOutput;
 struct MixerPlugin;
+class MixerListener;
 struct config_param;
 
 Mixer *
 mixer_new(EventLoop &event_loop, const MixerPlugin &plugin, AudioOutput &ao,
+	  MixerListener &listener,
 	  const config_param &param,
 	  Error &error);
 
diff --git a/src/mixer/MixerInternal.hxx b/src/mixer/MixerInternal.hxx
index 2c6282ebb..7b2cf2b32 100644
--- a/src/mixer/MixerInternal.hxx
+++ b/src/mixer/MixerInternal.hxx
@@ -25,10 +25,14 @@
 #include "thread/Mutex.hxx"
 #include "Compiler.h"
 
+class MixerListener;
+
 class Mixer {
 public:
 	const MixerPlugin &plugin;
 
+	MixerListener &listener;
+
 	/**
 	 * This mutex protects all of the mixer struct, including its
 	 * implementation, so plugins don't have to deal with that.
@@ -47,8 +51,8 @@ public:
 	bool failed;
 
 public:
-	explicit Mixer(const MixerPlugin &_plugin)
-		:plugin(_plugin),
+	explicit Mixer(const MixerPlugin &_plugin, MixerListener &_listener)
+		:plugin(_plugin), listener(_listener),
 		 open(false),
 		 failed(false) {}
 
diff --git a/src/mixer/MixerPlugin.hxx b/src/mixer/MixerPlugin.hxx
index bf9af14e3..02bae844e 100644
--- a/src/mixer/MixerPlugin.hxx
+++ b/src/mixer/MixerPlugin.hxx
@@ -30,6 +30,7 @@
 struct config_param;
 struct AudioOutput;
 class Mixer;
+class MixerListener;
 class EventLoop;
 class Error;
 
@@ -44,6 +45,7 @@ struct MixerPlugin {
 	 * @return a mixer object, or nullptr on error
 	 */
 	Mixer *(*init)(EventLoop &event_loop, AudioOutput &ao,
+		       MixerListener &listener,
 		       const config_param &param,
 		       Error &error);
 
diff --git a/src/mixer/Volume.cxx b/src/mixer/Volume.cxx
index aaae5d9ee..596b3c12a 100644
--- a/src/mixer/Volume.cxx
+++ b/src/mixer/Volume.cxx
@@ -21,7 +21,6 @@
 #include "Volume.hxx"
 #include "output/MultipleOutputs.hxx"
 #include "Idle.hxx"
-#include "GlobalEvents.hxx"
 #include "util/StringUtil.hxx"
 #include "util/Domain.hxx"
 #include "system/PeriodClock.hxx"
@@ -41,22 +40,11 @@ static int last_hardware_volume = -1;
 /** the age of #last_hardware_volume */
 static PeriodClock hardware_volume_clock;
 
-/**
- * Handler for #GlobalEvents::MIXER.
- */
-static void
-mixer_event_callback(void)
+void
+InvalidateHardwareVolume()
 {
 	/* flush the hardware volume cache */
 	last_hardware_volume = -1;
-
-	/* notify clients */
-	idle_add(IDLE_MIXER);
-}
-
-void volume_init(void)
-{
-	GlobalEvents::Register(GlobalEvents::MIXER, mixer_event_callback);
 }
 
 int
diff --git a/src/mixer/Volume.hxx b/src/mixer/Volume.hxx
index b86328d88..a02c21a21 100644
--- a/src/mixer/Volume.hxx
+++ b/src/mixer/Volume.hxx
@@ -26,7 +26,8 @@
 
 class MultipleOutputs;
 
-void volume_init(void);
+void
+InvalidateHardwareVolume();
 
 gcc_pure
 int
diff --git a/src/mixer/plugins/AlsaMixerPlugin.cxx b/src/mixer/plugins/AlsaMixerPlugin.cxx
index 26007fef3..cd787182a 100644
--- a/src/mixer/plugins/AlsaMixerPlugin.cxx
+++ b/src/mixer/plugins/AlsaMixerPlugin.cxx
@@ -19,8 +19,8 @@
 
 #include "config.h"
 #include "mixer/MixerInternal.hxx"
+#include "mixer/Listener.hxx"
 #include "output/OutputAPI.hxx"
-#include "GlobalEvents.hxx"
 #include "event/MultiSocketMonitor.hxx"
 #include "event/DeferredMonitor.hxx"
 #include "event/Loop.hxx"
@@ -76,8 +76,9 @@ class AlsaMixer final : public Mixer {
 	AlsaMixerMonitor *monitor;
 
 public:
-	AlsaMixer(EventLoop &_event_loop)
-		:Mixer(alsa_mixer_plugin), event_loop(_event_loop) {}
+	AlsaMixer(EventLoop &_event_loop, MixerListener &_listener)
+		:Mixer(alsa_mixer_plugin, _listener),
+		 event_loop(_event_loop) {}
 
 	virtual ~AlsaMixer();
 
@@ -142,10 +143,15 @@ AlsaMixerMonitor::DispatchSockets()
  */
 
 static int
-alsa_mixer_elem_callback(gcc_unused snd_mixer_elem_t *elem, unsigned mask)
+alsa_mixer_elem_callback(snd_mixer_elem_t *elem, unsigned mask)
 {
-	if (mask & SND_CTL_EVENT_MASK_VALUE)
-		GlobalEvents::Emit(GlobalEvents::MIXER);
+	AlsaMixer &mixer = *(AlsaMixer *)
+		snd_mixer_elem_get_callback_private(elem);
+
+	if (mask & SND_CTL_EVENT_MASK_VALUE) {
+		int volume = mixer.GetVolume(IgnoreError());
+		mixer.listener.OnMixerVolumeChanged(mixer, volume);
+	}
 
 	return 0;
 }
@@ -168,10 +174,11 @@ AlsaMixer::Configure(const config_param &param)
 
 static Mixer *
 alsa_mixer_init(EventLoop &event_loop, gcc_unused AudioOutput &ao,
+		MixerListener &listener,
 		const config_param &param,
 		gcc_unused Error &error)
 {
-	AlsaMixer *am = new AlsaMixer(event_loop);
+	AlsaMixer *am = new AlsaMixer(event_loop, listener);
 	am->Configure(param);
 
 	return am;
@@ -236,6 +243,7 @@ AlsaMixer::Setup(Error &error)
 	snd_mixer_selem_get_playback_volume_range(elem, &volume_min,
 						  &volume_max);
 
+	snd_mixer_elem_set_callback_private(elem, this);
 	snd_mixer_elem_set_callback(elem, alsa_mixer_elem_callback);
 
 	monitor = new AlsaMixerMonitor(event_loop, handle);
diff --git a/src/mixer/plugins/OssMixerPlugin.cxx b/src/mixer/plugins/OssMixerPlugin.cxx
index 939fe0824..6615c7022 100644
--- a/src/mixer/plugins/OssMixerPlugin.cxx
+++ b/src/mixer/plugins/OssMixerPlugin.cxx
@@ -49,7 +49,8 @@ class OssMixer final : public Mixer {
 	int volume_control;
 
 public:
-	OssMixer():Mixer(oss_mixer_plugin) {}
+	OssMixer(MixerListener &_listener)
+		:Mixer(oss_mixer_plugin, _listener) {}
 
 	bool Configure(const config_param &param, Error &error);
 
@@ -98,10 +99,11 @@ OssMixer::Configure(const config_param &param, Error &error)
 
 static Mixer *
 oss_mixer_init(gcc_unused EventLoop &event_loop, gcc_unused AudioOutput &ao,
+	       MixerListener &listener,
 	       const config_param &param,
 	       Error &error)
 {
-	OssMixer *om = new OssMixer();
+	OssMixer *om = new OssMixer(listener);
 
 	if (!om->Configure(param, error)) {
 		delete om;
diff --git a/src/mixer/plugins/PulseMixerPlugin.cxx b/src/mixer/plugins/PulseMixerPlugin.cxx
index b838de689..0a765bf68 100644
--- a/src/mixer/plugins/PulseMixerPlugin.cxx
+++ b/src/mixer/plugins/PulseMixerPlugin.cxx
@@ -20,8 +20,8 @@
 #include "config.h"
 #include "PulseMixerPlugin.hxx"
 #include "mixer/MixerInternal.hxx"
+#include "mixer/Listener.hxx"
 #include "output/plugins/PulseOutputPlugin.hxx"
-#include "GlobalEvents.hxx"
 #include "util/Error.hxx"
 #include "util/Domain.hxx"
 #include "Log.hxx"
@@ -41,9 +41,9 @@ class PulseMixer final : public Mixer {
 	struct pa_cvolume volume;
 
 public:
-	PulseMixer(PulseOutput &_output)
-		:Mixer(pulse_mixer_plugin),
-		output(_output), online(false)
+	PulseMixer(PulseOutput &_output, MixerListener &_listener)
+		:Mixer(pulse_mixer_plugin, _listener),
+		 output(_output), online(false)
 	{
 	}
 
@@ -75,7 +75,7 @@ PulseMixer::Offline()
 
 	online = false;
 
-	GlobalEvents::Emit(GlobalEvents::MIXER);
+	listener.OnMixerVolumeChanged(*this, -1);
 }
 
 inline void
@@ -92,7 +92,7 @@ PulseMixer::VolumeCallback(const pa_sink_input_info *i, int eol)
 	online = true;
 	volume = i->volume;
 
-	GlobalEvents::Emit(GlobalEvents::MIXER);
+	listener.OnMixerVolumeChanged(*this, GetVolume(IgnoreError()));
 }
 
 /**
@@ -165,11 +165,12 @@ pulse_mixer_on_change(PulseMixer &pm,
 
 static Mixer *
 pulse_mixer_init(gcc_unused EventLoop &event_loop, AudioOutput &ao,
+		 MixerListener &listener,
 		 gcc_unused const config_param &param,
 		 gcc_unused Error &error)
 {
 	PulseOutput &po = (PulseOutput &)ao;
-	PulseMixer *pm = new PulseMixer(po);
+	PulseMixer *pm = new PulseMixer(po, listener);
 
 	pulse_output_set_mixer(po, *pm);
 
diff --git a/src/mixer/plugins/RoarMixerPlugin.cxx b/src/mixer/plugins/RoarMixerPlugin.cxx
index 7c2a25dfb..8e198478d 100644
--- a/src/mixer/plugins/RoarMixerPlugin.cxx
+++ b/src/mixer/plugins/RoarMixerPlugin.cxx
@@ -29,9 +29,9 @@ class RoarMixer final : public Mixer {
 	RoarOutput &self;
 
 public:
-	RoarMixer(RoarOutput &_output)
-		:Mixer(roar_mixer_plugin),
-		self(_output) {}
+	RoarMixer(RoarOutput &_output, MixerListener &_listener)
+		:Mixer(roar_mixer_plugin, _listener),
+		 self(_output) {}
 
 	/* virtual methods from class Mixer */
 	virtual bool Open(gcc_unused Error &error) override {
@@ -47,10 +47,11 @@ public:
 
 static Mixer *
 roar_mixer_init(gcc_unused EventLoop &event_loop, AudioOutput &ao,
+		MixerListener &listener,
 		gcc_unused const config_param &param,
 		gcc_unused Error &error)
 {
-	return new RoarMixer((RoarOutput &)ao);
+	return new RoarMixer((RoarOutput &)ao, listener);
 }
 
 int
diff --git a/src/mixer/plugins/SoftwareMixerPlugin.cxx b/src/mixer/plugins/SoftwareMixerPlugin.cxx
index 78f0769ab..0cde682f6 100644
--- a/src/mixer/plugins/SoftwareMixerPlugin.cxx
+++ b/src/mixer/plugins/SoftwareMixerPlugin.cxx
@@ -52,8 +52,8 @@ class SoftwareMixer final : public Mixer {
 	unsigned volume;
 
 public:
-	SoftwareMixer()
-		:Mixer(software_mixer_plugin),
+	SoftwareMixer(MixerListener &_listener)
+		:Mixer(software_mixer_plugin, _listener),
 		 filter(CreateVolumeFilter()),
 		 owns_filter(true),
 		 volume(100)
@@ -86,10 +86,11 @@ public:
 static Mixer *
 software_mixer_init(gcc_unused EventLoop &event_loop,
 		    gcc_unused AudioOutput &ao,
+		    MixerListener &listener,
 		    gcc_unused const config_param &param,
 		    gcc_unused Error &error)
 {
-	return new SoftwareMixer();
+	return new SoftwareMixer(listener);
 }
 
 bool
diff --git a/src/mixer/plugins/WinmmMixerPlugin.cxx b/src/mixer/plugins/WinmmMixerPlugin.cxx
index 6b81fa095..e0436011a 100644
--- a/src/mixer/plugins/WinmmMixerPlugin.cxx
+++ b/src/mixer/plugins/WinmmMixerPlugin.cxx
@@ -34,8 +34,8 @@ class WinmmMixer final : public Mixer {
 	WinmmOutput &output;
 
 public:
-	WinmmMixer(WinmmOutput &_output)
-		:Mixer(winmm_mixer_plugin),
+	WinmmMixer(WinmmOutput &_output, MixerListener &_listener)
+		:Mixer(winmm_mixer_plugin, _listener),
 		output(_output) {
 	}
 
@@ -68,10 +68,11 @@ winmm_volume_encode(int volume)
 
 static Mixer *
 winmm_mixer_init(gcc_unused EventLoop &event_loop, AudioOutput &ao,
+		 MixerListener &listener,
 		 gcc_unused const config_param &param,
 		 gcc_unused Error &error)
 {
-	return new WinmmMixer((WinmmOutput &)ao);
+	return new WinmmMixer((WinmmOutput &)ao, listener);
 }
 
 int
diff --git a/src/output/Init.cxx b/src/output/Init.cxx
index 69ee12b35..eafcec432 100644
--- a/src/output/Init.cxx
+++ b/src/output/Init.cxx
@@ -116,6 +116,7 @@ audio_output_load_mixer(EventLoop &event_loop, AudioOutput &ao,
 			const config_param &param,
 			const MixerPlugin *plugin,
 			Filter &filter_chain,
+			MixerListener &listener,
 			Error &error)
 {
 	Mixer *mixer;
@@ -129,10 +130,12 @@ audio_output_load_mixer(EventLoop &event_loop, AudioOutput &ao,
 		if (plugin == nullptr)
 			return nullptr;
 
-		return mixer_new(event_loop, *plugin, ao, param, error);
+		return mixer_new(event_loop, *plugin, ao, listener,
+				 param, error);
 
 	case MIXER_TYPE_SOFTWARE:
 		mixer = mixer_new(event_loop, software_mixer_plugin, ao,
+				  listener,
 				  config_param(),
 				  IgnoreError());
 		assert(mixer != nullptr);
@@ -212,6 +215,7 @@ AudioOutput::Configure(const config_param &param, Error &error)
 
 static bool
 audio_output_setup(EventLoop &event_loop, AudioOutput &ao,
+		   MixerListener &mixer_listener,
 		   const config_param &param,
 		   Error &error)
 {
@@ -244,7 +248,9 @@ audio_output_setup(EventLoop &event_loop, AudioOutput &ao,
 	Error mixer_error;
 	ao.mixer = audio_output_load_mixer(event_loop, ao, param,
 					   ao.plugin.mixer_plugin,
-					   *ao.filter, mixer_error);
+					   *ao.filter,
+					   mixer_listener,
+					   mixer_error);
 	if (ao.mixer == nullptr && mixer_error.IsDefined())
 		FormatError(mixer_error,
 			    "Failed to initialize hardware mixer for '%s'",
@@ -279,6 +285,7 @@ audio_output_setup(EventLoop &event_loop, AudioOutput &ao,
 
 AudioOutput *
 audio_output_new(EventLoop &event_loop, const config_param &param,
+		 MixerListener &mixer_listener,
 		 PlayerControl &pc,
 		 Error &error)
 {
@@ -317,7 +324,8 @@ audio_output_new(EventLoop &event_loop, const config_param &param,
 	if (ao == nullptr)
 		return nullptr;
 
-	if (!audio_output_setup(event_loop, *ao, param, error)) {
+	if (!audio_output_setup(event_loop, *ao, mixer_listener,
+				param, error)) {
 		ao_plugin_finish(ao);
 		return nullptr;
 	}
diff --git a/src/output/Internal.hxx b/src/output/Internal.hxx
index 9b08a9228..266930448 100644
--- a/src/output/Internal.hxx
+++ b/src/output/Internal.hxx
@@ -33,6 +33,8 @@ class Error;
 class Filter;
 class MusicPipe;
 class EventLoop;
+class Mixer;
+class MixerListener;
 struct music_chunk;
 struct config_param;
 struct PlayerControl;
@@ -79,7 +81,7 @@ struct AudioOutput {
 	 * May be nullptr if none is available, or if software volume is
 	 * configured.
 	 */
-	class Mixer *mixer;
+	Mixer *mixer;
 
 	/**
 	 * Will this output receive tags from the decoder?  The
@@ -424,6 +426,7 @@ extern struct notify audio_output_client_notify;
 
 AudioOutput *
 audio_output_new(EventLoop &event_loop, const config_param &param,
+		 MixerListener &mixer_listener,
 		 PlayerControl &pc,
 		 Error &error);
 
diff --git a/src/output/MultipleOutputs.cxx b/src/output/MultipleOutputs.cxx
index a65fb73c0..10e3e3bd5 100644
--- a/src/output/MultipleOutputs.cxx
+++ b/src/output/MultipleOutputs.cxx
@@ -35,8 +35,9 @@
 #include <assert.h>
 #include <string.h>
 
-MultipleOutputs::MultipleOutputs()
-	:buffer(nullptr), pipe(nullptr),
+MultipleOutputs::MultipleOutputs(MixerListener &_mixer_listener)
+	:mixer_listener(_mixer_listener),
+	 buffer(nullptr), pipe(nullptr),
 	 elapsed_time(-1)
 {
 }
@@ -50,10 +51,13 @@ MultipleOutputs::~MultipleOutputs()
 }
 
 static AudioOutput *
-LoadOutput(EventLoop &event_loop, PlayerControl &pc, const config_param &param)
+LoadOutput(EventLoop &event_loop, MixerListener &mixer_listener,
+	   PlayerControl &pc, const config_param &param)
 {
 	Error error;
-	AudioOutput *output = audio_output_new(event_loop, param, pc, error);
+	AudioOutput *output = audio_output_new(event_loop, param,
+					       mixer_listener,
+					       pc, error);
 	if (output == nullptr) {
 		if (param.line > 0)
 			FormatFatalError("line %i: %s",
@@ -72,7 +76,8 @@ MultipleOutputs::Configure(EventLoop &event_loop, PlayerControl &pc)
 	const config_param *param = nullptr;
 	while ((param = config_get_next_param(CONF_AUDIO_OUTPUT,
 					      param)) != nullptr) {
-		auto output = LoadOutput(event_loop, pc, *param);
+		auto output = LoadOutput(event_loop, mixer_listener,
+					 pc, *param);
 		if (FindByName(output->name) != nullptr)
 			FormatFatalError("output devices with identical "
 					 "names: %s", output->name);
@@ -83,7 +88,8 @@ MultipleOutputs::Configure(EventLoop &event_loop, PlayerControl &pc)
 	if (outputs.empty()) {
 		/* auto-detect device */
 		const config_param empty;
-		auto output = LoadOutput(event_loop, pc, empty);
+		auto output = LoadOutput(event_loop, mixer_listener,
+					 pc, empty);
 		outputs.push_back(output);
 	}
 }
diff --git a/src/output/MultipleOutputs.hxx b/src/output/MultipleOutputs.hxx
index 4fe1aa4f1..296b9815e 100644
--- a/src/output/MultipleOutputs.hxx
+++ b/src/output/MultipleOutputs.hxx
@@ -38,12 +38,15 @@ struct AudioFormat;
 class MusicBuffer;
 class MusicPipe;
 class EventLoop;
+class MixerListener;
 struct music_chunk;
 struct PlayerControl;
 struct AudioOutput;
 class Error;
 
 class MultipleOutputs {
+	MixerListener &mixer_listener;
+
 	std::vector<AudioOutput *> outputs;
 
 	AudioFormat input_audio_format;
@@ -70,7 +73,7 @@ public:
 	 * Load audio outputs from the configuration file and
 	 * initialize them.
 	 */
-	MultipleOutputs();
+	MultipleOutputs(MixerListener &_mixer_listener);
 	~MultipleOutputs();
 
 	void Configure(EventLoop &event_loop, PlayerControl &pc);
diff --git a/test/read_mixer.cxx b/test/read_mixer.cxx
index 881f517c7..97529057f 100644
--- a/test/read_mixer.cxx
+++ b/test/read_mixer.cxx
@@ -22,7 +22,6 @@
 #include "mixer/MixerList.hxx"
 #include "filter/FilterRegistry.hxx"
 #include "pcm/Volume.hxx"
-#include "GlobalEvents.hxx"
 #include "Main.hxx"
 #include "event/Loop.hxx"
 #include "config/ConfigData.hxx"
@@ -35,11 +34,6 @@
 #include <string.h>
 #include <unistd.h>
 
-void
-GlobalEvents::Emit(gcc_unused Event event)
-{
-}
-
 const struct filter_plugin *
 filter_plugin_by_name(gcc_unused const char *name)
 {
@@ -65,6 +59,7 @@ int main(int argc, gcc_unused char **argv)
 	Error error;
 	Mixer *mixer = mixer_new(event_loop, alsa_mixer_plugin,
 				 *(AudioOutput *)nullptr,
+				 *(MixerListener *)nullptr,
 				 config_param(), error);
 	if (mixer == NULL) {
 		LogError(error, "mixer_new() failed");
diff --git a/test/run_output.cxx b/test/run_output.cxx
index 374a0ceca..8aac5e555 100644
--- a/test/run_output.cxx
+++ b/test/run_output.cxx
@@ -26,7 +26,6 @@
 #include "Idle.hxx"
 #include "Main.hxx"
 #include "event/Loop.hxx"
-#include "GlobalEvents.hxx"
 #include "IOThread.hxx"
 #include "fs/Path.hxx"
 #include "AudioParser.hxx"
@@ -47,11 +46,6 @@
 #include <stdlib.h>
 #include <stdio.h>
 
-void
-GlobalEvents::Emit(gcc_unused Event event)
-{
-}
-
 const struct filter_plugin *
 filter_plugin_by_name(gcc_unused const char *name)
 {
@@ -95,7 +89,9 @@ load_audio_output(EventLoop &event_loop, const char *name)
 
 	Error error;
 	AudioOutput *ao =
-		audio_output_new(event_loop, *param, dummy_player_control,
+		audio_output_new(event_loop, *param,
+				 *(MixerListener *)nullptr,
+				 dummy_player_control,
 				 error);
 	if (ao == nullptr)
 		LogError(error);