output: add native Haiku audio output and mixer support

Also uses the notification system to display tags.

src/mixer/MixerList.hxx

@@ -30,6 +30,7 @@ struct MixerPlugin;
 extern const MixerPlugin null_mixer_plugin;
 extern const MixerPlugin software_mixer_plugin;
 extern const MixerPlugin alsa_mixer_plugin;
+extern const MixerPlugin haiku_mixer_plugin;
 extern const MixerPlugin oss_mixer_plugin;
 extern const MixerPlugin roar_mixer_plugin;
 extern const MixerPlugin pulse_mixer_plugin;

src/mixer/plugins/HaikuMixerPlugin.cxx

@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2003-2015 The Music Player Daemon Project
+ * Copyright (C) 2010-2011 Philipp 'ph3-der-loewe' Schafft
+ * Copyright (C) 2010-2011 Hans-Kristian 'maister' Arntzen
+ * Copyright (C) 2014-2015 François 'mmu_man' Revol
+ *
+ * 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.
+ */
+
+
+#include "config.h"
+#include "mixer/MixerInternal.hxx"
+#include "output/plugins/HaikuOutputPlugin.hxx"
+#include "Compiler.h"
+
+class HaikuMixer final : public Mixer {
+	/** the base mixer class */
+	HaikuOutput &self;
+
+public:
+	HaikuMixer(HaikuOutput &_output, MixerListener &_listener)
+		:Mixer(haiku_mixer_plugin, _listener),
+		 self(_output) {}
+
+	/* virtual methods from class Mixer */
+	virtual bool Open(gcc_unused Error &error) override {
+		return true;
+	}
+
+	virtual void Close() override {
+	}
+
+	virtual int GetVolume(Error &error) override;
+	virtual bool SetVolume(unsigned volume, Error &error) override;
+};
+
+static Mixer *
+haiku_mixer_init(gcc_unused EventLoop &event_loop, AudioOutput &ao,
+		MixerListener &listener,
+		gcc_unused const ConfigBlock &block,
+		gcc_unused Error &error)
+{
+	return new HaikuMixer((HaikuOutput &)ao, listener);
+}
+
+int
+HaikuMixer::GetVolume(gcc_unused Error &error)
+{
+	return haiku_output_get_volume(self);
+}
+
+bool
+HaikuMixer::SetVolume(unsigned volume, gcc_unused Error &error)
+{
+	return haiku_output_set_volume(self, volume);
+}
+
+const MixerPlugin haiku_mixer_plugin = {
+	haiku_mixer_init,
+	false,
+};