Audio|Refactor: Allow loading multiple audio plugins

Refactored the audio plugin loader to allow loading more than one
plugin at a time. The loading and initialization of the audio
plugins was moved to the new AudioDriver module.

The loading was also made platform-independent through the use
of the Library class (which presently lacks a Windows implementation).

The AudioDriver module chooses which SFX, Music, and CD interface
to use from which loaded plugin.

doomsday/engine/api/sys_audiod.h

@@ -20,8 +20,8 @@
  * 02110-1301 USA</small>
  */
 
-#ifndef LIBDENG_AUDIO_DRIVER_H
-#define LIBDENG_AUDIO_DRIVER_H
+#ifndef LIBDENG_AUDIO_DRIVER_INTERFACE_H
+#define LIBDENG_AUDIO_DRIVER_INTERFACE_H
 
 /**
  * @defgroup audio Audio
@@ -52,6 +52,10 @@ typedef struct audiodriver_s {
     int (*Set) (int prop, const void* ptr);
 } audiodriver_t;
 
+typedef struct audiointerface_base_s {
+    int (*Init) (void);
+} audiointerface_base_t;
+
 ///@}
 
-#endif /* LIBDENG_AUDIO_DRIVER_H */
+#endif /* LIBDENG_AUDIO_DRIVER_INTERFACE_H */

doomsday/engine/engine.pro

@@ -112,6 +112,7 @@ DENG_API_HEADERS = \
 DENG_HEADERS = \
     portable/include/abstractfile.h \
     portable/include/abstractresource.h \
+    portable/include/audiodriver.h \
     portable/include/bitmapfont.h \
     portable/include/blockset.h \
     portable/include/bsp_edge.h \
@@ -284,7 +285,6 @@ DENG_HEADERS = \
     portable/include/svg.h \
     portable/include/sys_audio.h \
     portable/include/sys_audiod_dummy.h \
-    portable/include/sys_audiod_loader.h \
     portable/include/sys_console.h \
     portable/include/sys_direc.h \
     portable/include/sys_findfile.h \
@@ -360,22 +360,21 @@ HEADERS += \
 DENG_UNIX_SOURCES += \
     portable/src/sys_sdl_window.c \
     unix/src/dd_uinit.c \
-    unix/src/sys_audiod_loader.c \
     unix/src/sys_console.c \
     unix/src/sys_findfile.c \
     unix/src/sys_input.c \
     unix/src/sys_path.c
 
 DENG_WIN32_SOURCES += \
     win32/src/dd_winit.c \
-    win32/src/sys_audiod_loader.c \
     win32/src/sys_console.c \
     win32/src/sys_findfile.c \
     win32/src/sys_input.c \
     win32/src/sys_window.c
 
 SOURCES += \
     portable/src/abstractfile.c \
+    portable/src/audiodriver.c \
     portable/src/animator.c \
     portable/src/bitmapfont.c \
     portable/src/blockset.c \

doomsday/engine/portable/include/audiodriver.h

@@ -0,0 +1,56 @@
+/**
+ * @file audiodriver.h
+ * Audio driver loading and interface management. @ingroup audio
+ *
+ * @authors Copyright © 2012 Jaakko Keränen <jaakko.keranen@iki.fi>
+ * @authors Copyright © 2012 Daniel Swanson <danij@dengine.net>
+ *
+ * @par License
+ * GPL: http://www.gnu.org/licenses/gpl.html
+ *
+ * <small>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 St, Fifth Floor, Boston, MA
+ * 02110-1301 USA</small>
+ */
+
+#ifndef LIBDENG_AUDIO_DRIVER_H
+#define LIBDENG_AUDIO_DRIVER_H
+
+#include "sys_audiod.h"
+#include "sys_audiod_sfx.h"
+#include "sys_audiod_mus.h"
+
+boolean AudioDriver_Init(void);
+void AudioDriver_Shutdown(void);
+
+/**
+ * Retrieves the main interface of the audio driver to which @a sfxMusicOrCd belongs to.
+ */
+audiodriver_t* AudioDriver_Interface(void* sfxMusicOrCd);
+
+/**
+ * Returns the current active SFX interface. @c NULL is returned is no SFX
+ * playback is available.
+ */
+audiointerface_sfx_generic_t* AudioDriver_SFX(void);
+
+/**
+ * Returns the currently active Music interface. @c NULL is returned if no music
+ * playback is available.
+ */
+audiointerface_music_t* AudioDriver_Music(void);
+
+/**
+ * Returns the currently active CD playback interface. @c NULL is returned if
+ * CD playback is not available.
+ */
+audiointerface_cd_t* AudioDriver_CD(void);
+
+#endif // LIBDENG_AUDIO_DRIVER_H

doomsday/engine/portable/include/de_audio.h

@@ -29,6 +29,7 @@
 #ifndef __DOOMSDAY_AUDIO__
 #define __DOOMSDAY_AUDIO__
 
+#include "audiodriver.h"
 #include "s_main.h"
 #include "s_environ.h"
 #include "s_sfx.h"

doomsday/engine/portable/include/s_main.h

@@ -44,8 +44,6 @@ extern int      showSoundInfo;
 extern int      soundMinDist, soundMaxDist;
 extern int      sfxVolume, musVolume;
 
-extern audiodriver_t* audioDriver;
-
 void            S_Register(void);
 boolean         S_Init(void);
 void            S_Shutdown(void);

doomsday/engine/portable/include/sys_audio.h

@@ -36,8 +36,6 @@
 #include "sys_audiod.h"
 #include "sys_audiod_sfx.h"
 #include "sys_audiod_mus.h"
-
-#include "sys_audiod_loader.h"
 #include "sys_audiod_dummy.h"
 
 #ifndef DENG_DISABLE_SDLMIXER