mixer_api: moved mixer_plugin imports to mixer_list.h

This patch allows the output plugins to import only mixer_list.h,
instead of the full mixer_api.h (which would expose internal
structures).

Makefile.am

@@ -82,6 +82,7 @@ mpd_headers = \
 	src/mixer_all.h \
 	src/mixer_api.h \
 	src/mixer_control.h \
+	src/mixer_list.h \
 	src/event_pipe.h \
 	src/mixer_plugin.h \
 	src/daemon.h \

src/mixer_api.h

@@ -21,14 +21,7 @@
 #define MPD_MIXER_H
 
 #include "mixer_plugin.h"
-
-/*
- * list of currently implemented mixers
- */
-
-extern const struct mixer_plugin alsa_mixer;
-extern const struct mixer_plugin oss_mixer;
-extern const struct mixer_plugin pulse_mixer;
+#include "mixer_list.h"
 
 struct mixer {
 	const struct mixer_plugin *plugin;

src/mixer_list.h

@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2003-2009 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.
+ */
+
+/** \file
+ *
+ * This header provides "extern" declarations for all mixer plugins.
+ */
+
+#ifndef MPD_MIXER_LIST_H
+#define MPD_MIXER_LIST_H
+
+extern const struct mixer_plugin alsa_mixer;
+extern const struct mixer_plugin oss_mixer;
+extern const struct mixer_plugin pulse_mixer;
+
+#endif

src/output/alsa_plugin.c

@@ -18,7 +18,7 @@
  */
 
 #include "../output_api.h"
-#include "../mixer_api.h"
+#include "mixer_list.h"
 #include "mixer_control.h"
 
 #include <glib.h>

src/output/oss_plugin.c

@@ -18,7 +18,7 @@
  */
 
 #include "../output_api.h"
-#include "../mixer_api.h"
+#include "mixer_list.h"
 #include "mixer_control.h"
 
 #include <glib.h>

src/output/pulse_plugin.c

@@ -18,7 +18,7 @@
  */
 
 #include "../output_api.h"
-#include "../mixer_api.h"
+#include "mixer_list.h"
 #include "mixer_control.h"
 
 #include <glib.h>