From cdb02e2b460833db327103e43886e94e1c116c88 Mon Sep 17 00:00:00 2001
From: Andrew Kelley <superjoe30@gmail.com>
Date: Fri, 7 Aug 2015 13:11:34 -0700
Subject: [PATCH] CoreAudio: underflow test passes

---
 README.md         |  1 -
 src/coreaudio.cpp | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 8cd16f9..9060eff 100644
--- a/README.md
+++ b/README.md
@@ -251,7 +251,6 @@ view `coverage/index.html` in a browser.
 
  0. implement CoreAudio (OSX) backend, get examples working
     - microphone example
-    - underflow example
  0. ALSA backend for microphone example is broken
  0. Add some builtin channel layouts from
     https://developer.apple.com/library/mac/documentation/MusicAudio/Reference/CoreAudioDataTypesRef/#//apple_ref/doc/constant_group/Audio_Channel_Layout_Tags
diff --git a/src/coreaudio.cpp b/src/coreaudio.cpp
index fa14cc5..824ab9d 100644
--- a/src/coreaudio.cpp
+++ b/src/coreaudio.cpp
@@ -839,8 +839,29 @@ static void device_thread_run(void *arg) {
     }
 }
 
+static OSStatus on_device_overload(AudioObjectID in_object_id, UInt32 in_number_addresses,
+    const AudioObjectPropertyAddress in_addresses[], void *in_client_data)
+{
+    SoundIoOutStreamPrivate *os = (SoundIoOutStreamPrivate *)in_client_data;
+    SoundIoOutStream *outstream = &os->pub;
+    outstream->underflow_callback(outstream);
+    return noErr;
+}
+
 static void outstream_destroy_ca(struct SoundIoPrivate *si, struct SoundIoOutStreamPrivate *os) {
     SoundIoOutStreamCoreAudio *osca = &os->backend_data.coreaudio;
+    SoundIoOutStream *outstream = &os->pub;
+    SoundIoDevice *device = outstream->device;
+    SoundIoDevicePrivate *dev = (SoundIoDevicePrivate *)device;
+    SoundIoDeviceCoreAudio *dca = &dev->backend_data.coreaudio;
+
+    AudioObjectPropertyAddress prop_address = {
+        kAudioDeviceProcessorOverload,
+        kAudioObjectPropertyScopeGlobal,
+        kAudioObjectPropertyElementMaster
+    };
+    AudioObjectRemovePropertyListener(dca->device_id, &prop_address, on_device_overload, os);
+
     if (osca->output_instance) {
         AudioOutputUnitStop(osca->output_instance);
         AudioComponentInstanceDispose(osca->output_instance);
@@ -928,6 +949,19 @@ static int outstream_open_ca(struct SoundIoPrivate *si, struct SoundIoOutStreamP
         return SoundIoErrorOpeningDevice;
     }
 
+
+    AudioObjectPropertyAddress prop_address = {
+        kAudioDeviceProcessorOverload,
+        kAudioObjectPropertyScopeGlobal,
+        kAudioObjectPropertyElementMaster
+    };
+    if ((os_err = AudioObjectAddPropertyListener(dca->device_id, &prop_address,
+        on_device_overload, os)))
+    {
+        outstream_destroy_ca(si, os);
+        return SoundIoErrorOpeningDevice;
+    }
+
     return 0;
 }