From 584b3fea95e06809ab677d73ba36a3194eb17c6b Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Wed, 30 Mar 2011 13:53:56 +0000
Subject: add an API for listening to AU properties

git-svn-id: svn://localhost/ardour2/branches/2.0-ongoing@9246 d708f5d6-7413-0410-9779-e7cbd77b26cf
---
 libs/appleutility/CAAudioUnit.cpp | 82 ++++++++++++++++++++++++++++++++++++++-
 libs/appleutility/CAAudioUnit.h   | 24 +++++++++++-
 2 files changed, 102 insertions(+), 4 deletions(-)

diff --git a/libs/appleutility/CAAudioUnit.cpp b/libs/appleutility/CAAudioUnit.cpp
index aaf57f233d..0e2cdbfe49 100644
--- a/libs/appleutility/CAAudioUnit.cpp
+++ b/libs/appleutility/CAAudioUnit.cpp
@@ -223,24 +223,102 @@ CAAudioUnit::CAAudioUnit (const AudioUnit& inUnit)
 }
 
 CAAudioUnit::CAAudioUnit (const CAComponent& inComp)
-	: mComp (inComp), mDataPtr (0)
+	: mComp (inComp), mDataPtr (0), mPropertyCallback (0)
 {
 	mDataPtr = new AUState (mComp.Comp());
 }
 
 CAAudioUnit::CAAudioUnit (const AUNode &inNode, const AudioUnit& inUnit)
-	: mComp (inUnit), mDataPtr(new AUState (inNode, inUnit)) 
+	: mComp (inUnit), mDataPtr(new AUState (inNode, inUnit)), mPropertyCallback (0)
 {
 }
 
 CAAudioUnit::~CAAudioUnit ()
 {
+	dropPropertyListens ();
+
 	if (mDataPtr) {
 		mDataPtr->release();
 		mDataPtr = NULL;
 	}
 }
 
+void
+CAAudioUnit::addPropertyListen (AudioUnitPropertyID id)
+{
+	if (mPropertyCallback == 0) {
+		return;
+	}
+
+	if (mWatching.find (id) != mWatching.end()) {
+		return;
+	}
+
+	if (AudioUnitAddPropertyListener (AU(), id, PropertyCallback, this) == noErr) {
+		mWatching.insert (id);
+	}
+}
+
+void
+CAAudioUnit::removePropertyListen (AudioUnitPropertyID id)
+{
+	if (!mPropertyCallback) {
+		return;
+	}
+	std::set<AudioUnitPropertyID>::iterator i = mWatching.find (id);
+	if (i != mWatching.end()) {
+		mWatching.erase (i);
+	}
+	/* this is for 10.6 and above ...
+	   AudioUnitRemovePropertyListenerWithUserData (AU(), id, PropertyCallback, this);
+	*/
+	AudioUnitRemovePropertyListener (AU(), id, PropertyCallback);
+}
+
+void
+CAAudioUnit::dropPropertyListens ()
+{
+	for (std::set<AudioUnitPropertyID>::iterator i = mWatching.begin(); i != mWatching.end(); ++i) {
+		/* this is for 10.6 and above ...
+		AudioUnitRemovePropertyListenerWithUserData (AU(), *i, PropertyCallback, this);
+		*/
+		AudioUnitRemovePropertyListener (AU(), *i, PropertyCallback);
+	}
+	mWatching.clear ();
+}
+
+void
+CAAudioUnit::SetPropertyCallback (void (*prop_callback)(void*, int32_t, float, void*), void* arg)
+{
+	dropPropertyListens ();
+	mPropertyCallback = prop_callback;
+	mPropertyCallbackArg = arg;
+}
+
+void
+CAAudioUnit::PropertyCallback (void                *inRefCon,
+			       AudioUnit            inUnit,
+			       AudioUnitPropertyID  inID,
+			       AudioUnitScope       inScope,
+			       AudioUnitElement     inElement)
+{
+	static_cast<CAAudioUnit*>(inRefCon)->
+		DoPropertyCallback (inUnit, inID, inScope, inElement);
+}
+
+void
+CAAudioUnit::DoPropertyCallback (AudioUnit            inUnit,
+				 AudioUnitPropertyID  inID,
+				 AudioUnitScope       inScope,
+				 AudioUnitElement     inElement)
+{
+	if (mPropertyCallback) {
+		float value;
+		AudioUnitGetParameter (inUnit, inID, inScope, inElement, &value);
+		mPropertyCallback (this, inID, value, mPropertyCallbackArg);
+	}
+}
+
 CAAudioUnit&	CAAudioUnit::operator= (const CAAudioUnit &a)
 {
 	if (mDataPtr != a.mDataPtr) {
diff --git a/libs/appleutility/CAAudioUnit.h b/libs/appleutility/CAAudioUnit.h
index 810b81be2f..9f6f5905e1 100644
--- a/libs/appleutility/CAAudioUnit.h
+++ b/libs/appleutility/CAAudioUnit.h
@@ -57,6 +57,7 @@
 #endif
 
 #include <vector>
+#include <set>
 #include "CAStreamBasicDescription.h"
 #include "CAComponent.h"
 #include "CAAudioChannelLayout.h"
@@ -328,14 +329,33 @@ public:
 #pragma mark __Print	
 	void					Print () const { Print (stdout); }
 	void					Print (FILE* file) const;
+
+	void SetPropertyCallback (void (*param_callback)(void*, int32_t, float, void*), void* arg);
+	void addPropertyListen (AudioUnitPropertyID);
+	void removePropertyListen (AudioUnitPropertyID);
 	
 private:
 	CAComponent				mComp;
 	
 	class AUState;
 	AUState*		mDataPtr;
-		
-		// this can throw - so wrap this up in a static that returns a result code...
+	
+	void (*mPropertyCallback)(void* Unit, int32_t which, float val, void*);
+	void* mPropertyCallbackArg;
+	std::set<AudioUnitPropertyID> mWatching;
+	void dropPropertyListens ();
+	static void             PropertyCallback (
+		void                 *inRefCon,
+		AudioUnit            inUnit,
+		AudioUnitPropertyID  inID,
+		AudioUnitScope       inScope,
+		AudioUnitElement     inElement);
+	void DoPropertyCallback (AudioUnit            inUnit,
+				 AudioUnitPropertyID  inID,
+				 AudioUnitScope       inScope,
+				 AudioUnitElement     inElement);
+
+	// this can throw - so wrap this up in a static that returns a result code...
 	CAAudioUnit (const CAComponent& inComp);
 
 	bool				HasDynamicScope (AudioUnitScope inScope, SInt32 &outTotalNumChannels) const;
-- 
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