Add support for a base gain level to be applied to all sound effects.

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@4124 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/openal/Sound.java

@@ -94,6 +94,9 @@ public class Sound
      * corresponding to +6db amplification. This will not affect an
      * already playing sound but will take effect the next time it is
      * played.
+     *
+     * <p><em>Note:</em> this value is multiplied by the base gain configured
+     * in the sound manager.
      */
     public void setGain (float gain)
     {
@@ -224,7 +227,7 @@ public class Sound
 
         // configure the source with our ephemera
         AL10.alSourcef(_sourceId, AL10.AL_PITCH, _pitch);
-        AL10.alSourcef(_sourceId, AL10.AL_GAIN, _gain);
+        AL10.alSourcef(_sourceId, AL10.AL_GAIN, _gain * _group.getBaseGain());
         if (_position != null) {
             AL10.alSource(_sourceId, AL10.AL_POSITION, _position);
         }

src/java/com/threerings/openal/SoundGroup.java

@@ -122,6 +122,14 @@ public class SoundGroup
         return -1;
     }
 
+    /**
+     * Used to pass the base gain through to sound effects.
+     */
+    protected float getBaseGain ()
+    {
+        return _manager.getBaseGain();
+    }
+
     /** Used to track which sources are in use. */
     protected static class Source
     {

src/java/com/threerings/openal/SoundManager.java

@@ -88,6 +88,24 @@ public class SoundManager
         _clips.setMaxSize(bytes);
     }
 
+    /**
+     * Configures the base gain (which must be a value between 0 and 1.0) which
+     * is multiplied to the individual gain assigned to sound effects (but not
+     * music).
+     */
+    public void setBaseGain (float gain)
+    {
+        _baseGain = gain;
+    }
+
+    /**
+     * Returns the base gain used for sound effects (not music).
+     */
+    public float getBaseGain ()
+    {
+        return _baseGain;
+    }
+
     /**
      * Creates an object that can be used to manage and play a group of
      * sounds. <em>Note:</em> the sound group <em>must</em> be disposed
@@ -126,7 +144,7 @@ public class SoundManager
             _streams.get(ii).update(time);
         }
     }
-    
+
     /**
      * Creates a sound manager and initializes the OpenAL sound subsystem.
      */
@@ -285,6 +303,10 @@ public class SoundManager
     /** Used to get back from the background thread to our "main" thread. */
     protected RunQueue _rqueue;
 
+    /** A base gain that is multiplied by the individual gain assigned to
+     * sounds. */
+    protected float _baseGain = 1;
+
     /** Contains a mapping of all currently-loading clips. */
     protected HashMap<Comparable,ClipBuffer> _loading =
         new HashMap<Comparable,ClipBuffer>();