Provide a means of overriding the base gain at the group level.

git-svn-id: svn+ssh://src.earth.threerings.net/nenya/trunk@981 ed5b42cb-e716-0410-a449-f6a68f950b19

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

@@ -393,7 +393,7 @@ public class Sound
     protected void updateSourceGain ()
     {
         if (_source != null) {
-            _source.setGain(_gain * _group.getBaseGain());
+            _source.setGain(_gain * _group.getInheritedBaseGain());
         }
     }
 

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

@@ -35,6 +35,25 @@ import static com.threerings.openal.Log.log;
  */
 public class SoundGroup
 {
+    /**
+     * Sets the base gain for this group, or -1 to inherit from the manager (the default).
+     */
+    public void setBaseGain (float gain)
+    {
+        if (_baseGain != gain) {
+            _baseGain = gain;
+            baseGainChanged();
+        }
+    }
+
+    /**
+     * Returns the base gain for this group, or -1 if inherited from the manager.
+     */
+    public float getBaseGain ()
+    {
+        return _baseGain;
+    }
+
     /**
      * Queues up the specified sound clip for pre-loading into the cache.
      */
@@ -140,15 +159,15 @@ public class SoundGroup
     /**
      * Used to pass the base gain through to sound effects.
      */
-    protected float getBaseGain ()
+    protected float getInheritedBaseGain ()
     {
-        return _manager.getBaseGain();
+        return (_baseGain < 0f) ? _manager.getBaseGain() : _baseGain;
     }
 
     /**
      * Called by the manager when the base gain has changed.
      */
-    protected void baseGainChanged (float gain)
+    protected void baseGainChanged ()
     {
         // notify any sound currently holding a source
         for (int ii = 0, nn = _sources.size(); ii < nn; ii++) {
@@ -170,4 +189,7 @@ public class SoundGroup
     protected ClipProvider _provider;
 
     protected ArrayList<PooledSource> _sources = Lists.newArrayList();
+
+    /** The base gain, or -1 to inherit from the manager. */
+    protected float _baseGain = -1f;
 }

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

@@ -120,9 +120,12 @@ public class SoundManager
         }
         _baseGain = gain;
 
-        // alert the groups
+        // alert the groups that inherite the gain
         for (int ii = 0, nn = _groups.size(); ii < nn; ii++) {
-            _groups.get(ii).baseGainChanged(gain);
+            SoundGroup group = _groups.get(ii);
+            if (group.getBaseGain() < 0f) {
+                group.baseGainChanged();
+            }
         }
     }