CoreAudio: subscribe to device-alive property

This notifies the user about device disconnect and properly
shuts down the backend.

libs/backends/coreaudio/coreaudio_backend.cc

@@ -60,6 +60,12 @@ static void error_callback_ptr (void *arg)
 	d->error_callback();
 }
 
+static void halted_callback_ptr (void *arg)
+{
+	CoreAudioBackend *d = static_cast<CoreAudioBackend*> (arg);
+	d->halted_callback();
+}
+
 static void xrun_callback_ptr (void *arg)
 {
 	CoreAudioBackend *d = static_cast<CoreAudioBackend*> (arg);
@@ -544,6 +550,7 @@ CoreAudioBackend::_start (bool for_latency_measurement)
 	_last_process_start = 0;
 
 	_pcmio->set_error_callback (error_callback_ptr, this);
+	_pcmio->set_halted_callback (halted_callback_ptr, this);
 	_pcmio->set_buffer_size_callback (buffer_size_callback_ptr, this);
 	_pcmio->set_sample_rate_callback (sample_rate_callback_ptr, this);
 
@@ -1521,16 +1528,31 @@ CoreAudioBackend::process_callback (const uint32_t n_samples, const uint64_t hos
 }
 
 void
-CoreAudioBackend::error_callback ()
+CoreAudioBackend::unset_callbacks ()
 {
 	_pcmio->set_error_callback (NULL, NULL);
+	_pcmio->set_halted_callback (NULL, NULL);
 	_pcmio->set_sample_rate_callback (NULL, NULL);
 	_pcmio->set_xrun_callback (NULL, NULL);
 	_midiio->set_port_changed_callback(NULL, NULL);
+}
+
+void
+CoreAudioBackend::error_callback ()
+{
+	unset_callbacks ();
 	engine.halted_callback("CoreAudio Process aborted.");
 	_active_ca = false;
 }
 
+void
+CoreAudioBackend::halted_callback ()
+{
+	unset_callbacks ();
+	engine.halted_callback("Audio device was disconnected or shut down.");
+	stop ();
+}
+
 void
 CoreAudioBackend::xrun_callback ()
 {
@@ -1558,10 +1580,7 @@ CoreAudioBackend::sample_rate_callback ()
 #endif
 		return;
 	}
-	_pcmio->set_error_callback (NULL, NULL);
+	unset_callbacks ();
-	_pcmio->set_sample_rate_callback (NULL, NULL);
-	_pcmio->set_xrun_callback (NULL, NULL);
-	_midiio->set_port_changed_callback(NULL, NULL);
 	engine.halted_callback("Sample Rate Changed.");
 	stop();
 }

libs/backends/coreaudio/coreaudio_backend.h

@@ -234,6 +234,7 @@ class CoreAudioBackend : public AudioBackend, public PortEngineSharedImpl {
 	// really private, but needing static access:
 	int process_callback(uint32_t, uint64_t);
 	void error_callback();
+	void halted_callback();
 	void xrun_callback();
 	void buffer_size_callback();
 	void sample_rate_callback();
@@ -371,6 +372,8 @@ class CoreAudioBackend : public AudioBackend, public PortEngineSharedImpl {
 	enum DeviceFilter { All, Input, Output, Duplex };
 	uint32_t name_to_id(std::string, DeviceFilter filter = All) const;
 
+	void unset_callbacks ();
+
 	/* processing */
 	float  _dsp_load;
 	ARDOUR::DSPLoadCalculator  _dsp_load_calc;

libs/backends/coreaudio/coreaudio_pcmio.cc

@@ -139,6 +139,9 @@ static OSStatus property_callback_ptr (AudioObjectID inObjectID, UInt32 inNumber
 			case kAudioDevicePropertyNominalSampleRate:
 				self->sample_rate_callback();
 				break;
+			case kAudioDevicePropertyDeviceIsAlive:
+				self->halted_callback();
+				break;
 			default:
 				break;
 		}
@@ -222,6 +225,7 @@ CoreAudioPCM::CoreAudioPCM ()
 	, _n_devices (0)
 	, _process_callback (0)
 	, _error_callback (0)
+	, _halted_callback (0)
 	, _hw_changed_callback (0)
 	, _xrun_callback (0)
 	, _buffer_size_callback (0)
@@ -266,7 +270,6 @@ CoreAudioPCM::~CoreAudioPCM ()
 	pthread_mutex_destroy (&_discovery_lock);
 }
 
-
 void
 CoreAudioPCM::hw_changed_callback() {
 #ifndef NDEBUG
@@ -278,6 +281,15 @@ CoreAudioPCM::hw_changed_callback() {
 	}
 }
 
+void
+CoreAudioPCM::halted_callback() {
+#ifndef NDEBUG
+	printf("CoreAudio halted callback..\n");
+#endif
+	if (_halted_callback) {
+		_halted_callback(_halted_arg);
+	}
+}
 
 int
 CoreAudioPCM::available_sample_rates(uint32_t device_id, std::vector<float>& sampleRates)
@@ -711,12 +723,15 @@ CoreAudioPCM::pcm_stop ()
 			AudioObjectRemovePropertyListener(_active_device_id, &prop, &property_callback_ptr, this);
 			prop.mSelector = kAudioDevicePropertyNominalSampleRate;
 			AudioObjectRemovePropertyListener(_active_device_id, &prop, &property_callback_ptr, this);
+			prop.mSelector = kAudioDevicePropertyDeviceIsAlive;
+			AudioObjectRemovePropertyListener(_active_device_id, &prop, &property_callback_ptr, this);
 		}
 #else
 		if (_active_device_id > 0) {
 			AudioDeviceRemovePropertyListener(_active_device_id, 0, true, kAudioDeviceProcessorOverload, property_callback_ptr);
 			AudioDeviceRemovePropertyListener(_active_device_id, 0, true, kAudioDevicePropertyBufferFrameSize, property_callback_ptr);
 			AudioDeviceRemovePropertyListener(_active_device_id, 0, true, kAudioDevicePropertyNominalSampleRate, property_callback_ptr);
+			AudioDeviceRemovePropertyListener(_active_device_id, 0, true, kAudioDevicePropertyDeviceIsAlive, property_callback_ptr);
 		}
 #endif
 	}
@@ -746,6 +761,7 @@ CoreAudioPCM::pcm_stop ()
 	_output_names.clear();
 
 	_error_callback = 0;
+	_halted_callback = 0;
 	_process_callback = 0;
 	_xrun_callback = 0;
 }
@@ -973,6 +989,10 @@ CoreAudioPCM::pcm_start (
 	err = add_listener (_active_device_id, kAudioDevicePropertyNominalSampleRate, this);
 	if (err != noErr) { errorMsg="kAudioDevicePropertyNominalSampleRate, Listen"; _state = -9; goto error; }
 
+	err = add_listener (_active_device_id, kAudioDevicePropertyDeviceIsAlive, this);
+	if (err != noErr) { errorMsg="kAudioDevicePropertyNominalSampleRate, Listen"; _state = -9; goto error; }
+
+
 	_samples_per_period = current_buffer_size_id(_active_device_id);
 
 	// Setup callback

libs/backends/coreaudio/coreaudio_pcmio.h

@@ -101,6 +101,14 @@ public:
 		_error_arg = error_arg;
 	}
 
+	void set_halted_callback (
+			void ( halted_callback (void*)),
+			void * halted_arg
+			) {
+		_halted_callback = halted_callback;
+		_halted_arg = halted_arg;
+	}
+
 	void     set_hw_changed_callback (
 			void ( callback (void*)),
 			void * arg
@@ -148,6 +156,7 @@ public:
 	void buffer_size_callback ();
 	void sample_rate_callback ();
 	void hw_changed_callback ();
+	void halted_callback ();
 
 private:
 	float    current_sample_rate_id (AudioDeviceID id, bool input);
@@ -192,6 +201,9 @@ private:
 	void (* _error_callback) (void*);
 	void  * _error_arg;
 
+	void (* _halted_callback) (void*);
+	void  * _halted_arg;
+
 	void (* _hw_changed_callback) (void*);
 	void  * _hw_changed_arg;