Improved CoreAudio handling of USB audio devices being unplugged

modules/juce_audio_devices/native/juce_mac_CoreAudio.cpp

@@ -388,65 +388,84 @@ public:
         return 0;
     }
 
-    void updateDetailsFromDevice()
+    int getFrameSizeFromDevice() const
     {
-        stopTimer();
+        AudioObjectPropertyAddress pa;
+        pa.mScope = kAudioObjectPropertyScopeWildcard;
+        pa.mElement = kAudioObjectPropertyElementMaster;
+        pa.mSelector = kAudioDevicePropertyBufferFrameSize;
 
-        if (deviceID == 0)
-            return;
+        UInt32 framesPerBuf = (UInt32) bufferSize;
+        UInt32 size = sizeof (framesPerBuf);
+        AudioObjectGetPropertyData (deviceID, &pa, 0, nullptr, &size, &framesPerBuf);
+        return (int) framesPerBuf;
+    }
 
-        // this collects all the new details from the device without any locking, then
-        // locks + swaps them afterwards.
+    bool isDeviceAlive() const
+    {
         AudioObjectPropertyAddress pa;
         pa.mScope = kAudioObjectPropertyScopeWildcard;
         pa.mElement = kAudioObjectPropertyElementMaster;
+        pa.mSelector = kAudioDevicePropertyDeviceIsAlive;
 
-        UInt32 isAlive;
+        UInt32 isAlive = 0;
         UInt32 size = sizeof (isAlive);
-        pa.mSelector = kAudioDevicePropertyDeviceIsAlive;
-        if (OK (AudioObjectGetPropertyData (deviceID, &pa, 0, nullptr, &size, &isAlive)) && isAlive == 0)
-            return;
+        return deviceID != 0
+                && OK (AudioObjectGetPropertyData (deviceID, &pa, 0, nullptr, &size, &isAlive))
+                && isAlive != 0;
+    }
+
+    bool updateDetailsFromDevice()
+    {
+        stopTimer();
 
-        const double currentRate = getNominalSampleRate();
-        if (currentRate > 0)
-            sampleRate = currentRate;
+        if (! isDeviceAlive())
+            return false;
 
-        UInt32 framesPerBuf = (UInt32) bufferSize;
-        size = sizeof (framesPerBuf);
-        pa.mSelector = kAudioDevicePropertyBufferFrameSize;
-        AudioObjectGetPropertyData (deviceID, &pa, 0, nullptr, &size, &framesPerBuf);
+        // this collects all the new details from the device without any locking, then
+        // locks + swaps them afterwards.
 
-        Array<int> newBufferSizes (getBufferSizesFromDevice());
-        Array<double> newSampleRates (getSampleRatesFromDevice());
+        const double newSampleRate = getNominalSampleRate();
+        const int newBufferSize = getFrameSizeFromDevice();
 
-        inputLatency  = getLatencyFromDevice (kAudioDevicePropertyScopeInput);
-        outputLatency = getLatencyFromDevice (kAudioDevicePropertyScopeOutput);
+        Array<int>    newBufferSizes = getBufferSizesFromDevice();
+        Array<double> newSampleRates = getSampleRatesFromDevice();
+
+        const int newInputLatency  = getLatencyFromDevice (kAudioDevicePropertyScopeInput);
+        const int newOutputLatency = getLatencyFromDevice (kAudioDevicePropertyScopeOutput);
 
         Array<CallbackDetailsForChannel> newInChans, newOutChans;
         StringArray newInNames  (getChannelInfo (true,  newInChans));
         StringArray newOutNames (getChannelInfo (false, newOutChans));
 
-        const int inputBitDepth = getBitDepthFromDevice (kAudioDevicePropertyScopeInput);
-        const int outputBitDepth = getBitDepthFromDevice (kAudioDevicePropertyScopeOutput);
+        const int newBitDepth  = jmax (getBitDepthFromDevice (kAudioDevicePropertyScopeInput),
+                                       getBitDepthFromDevice (kAudioDevicePropertyScopeOutput));
+
+        {
+            const ScopedLock sl (callbackLock);
 
-        bitDepth = jmax (inputBitDepth, outputBitDepth);
-        if (bitDepth <= 0)
-            bitDepth = 32;
+            bitDepth = newBitDepth > 0 ? newBitDepth : 32;
 
-        // after getting the new values, lock + apply them
-        const ScopedLock sl (callbackLock);
+            if (newSampleRate > 0)
+                sampleRate = newSampleRate;
 
-        bufferSize = (int) framesPerBuf;
-        allocateTempBuffers();
+            inputLatency  = newInputLatency;
+            outputLatency = newOutputLatency;
+            bufferSize = newBufferSize;
 
-        sampleRates.swapWith (newSampleRates);
-        bufferSizes.swapWith (newBufferSizes);
+            sampleRates.swapWith (newSampleRates);
+            bufferSizes.swapWith (newBufferSizes);
 
-        inChanNames.swapWith (newInNames);
-        outChanNames.swapWith (newOutNames);
+            inChanNames.swapWith (newInNames);
+            outChanNames.swapWith (newOutNames);
 
-        inputChannelInfo.swapWith (newInChans);
-        outputChannelInfo.swapWith (newOutChans);
+            inputChannelInfo.swapWith (newInChans);
+            outputChannelInfo.swapWith (newOutChans);
+
+            allocateTempBuffers();
+        }
+
+        return true;
     }
 
     //==============================================================================
@@ -769,9 +788,10 @@ public:
         stopTimer();
         const double oldSampleRate = sampleRate;
         const int oldBufferSize = bufferSize;
-        updateDetailsFromDevice();
 
-        if (oldBufferSize != bufferSize || oldSampleRate != sampleRate)
+        if (! updateDetailsFromDevice())
+            owner.stop();
+        else if (oldBufferSize != bufferSize || oldSampleRate != sampleRate)
             owner.restart();
     }