[Event Handler] Fix observers for reused classes

Fix class handling so it cleans up observers if the InputNode is reused.

Signed-off-by: Christopher Snowhill <kode54@gmail.com>

Audio/Chain/InputNode.m

@@ -33,6 +33,8 @@ static void *kInputNodeContext = &kInputNodeContext;
 }
 
 - (BOOL)openWithSource:(id<CogSource>)source {
+	[self removeObservers];
+
 	decoder = [AudioDecoder audioDecoderForSource:source];
 
 	if(decoder == nil)
@@ -63,6 +65,8 @@ static void *kInputNodeContext = &kInputNodeContext;
 }
 
 - (BOOL)openWithDecoder:(id<CogDecoder>)d {
+	[self removeObservers];
+
 	DLog(@"Opening with old decoder: %@", d);
 	decoder = d;
 

Audio/CogPluginMulti.h

@@ -12,6 +12,7 @@
 @interface CogDecoderMulti : NSObject <CogDecoder> {
 	NSArray *theDecoders;
 	id<CogDecoder> theDecoder;
+	BOOL observersAdded;
 }
 
 - (id)initWithDecoders:(NSArray *)decoders;

Audio/CogPluginMulti.m

@@ -113,20 +113,26 @@ static void *kCogDecoderMultiContext = &kCogDecoderMultiContext;
 }
 
 - (void)registerObservers {
-	[theDecoder addObserver:self
-	             forKeyPath:@"properties"
-	                options:(NSKeyValueObservingOptionNew)
-	                context:kCogDecoderMultiContext];
+	if(!observersAdded) {
+		[theDecoder addObserver:self
+		             forKeyPath:@"properties"
+		                options:(NSKeyValueObservingOptionNew)
+		                context:kCogDecoderMultiContext];
 
-	[theDecoder addObserver:self
-	             forKeyPath:@"metadata"
-	                options:(NSKeyValueObservingOptionNew)
-	                context:kCogDecoderMultiContext];
+		[theDecoder addObserver:self
+		             forKeyPath:@"metadata"
+		                options:(NSKeyValueObservingOptionNew)
+		                context:kCogDecoderMultiContext];
+		observersAdded = YES;
+	}
 }
 
 - (void)removeObservers {
-	[theDecoder removeObserver:self forKeyPath:@"properties" context:kCogDecoderMultiContext];
-	[theDecoder removeObserver:self forKeyPath:@"metadata" context:kCogDecoderMultiContext];
+	if(observersAdded) {
+		observersAdded = NO;
+		[theDecoder removeObserver:self forKeyPath:@"properties" context:kCogDecoderMultiContext];
+		[theDecoder removeObserver:self forKeyPath:@"metadata" context:kCogDecoderMultiContext];
+	}
 }
 
 - (BOOL)setTrack:(NSURL *)track {