Handle audio device changes on Windows.

media/audio/win/audio_device_listener_win.cc

Index: media/audio/win/audio_device_listener_win.cc
diff --git a/media/audio/win/audio_device_listener_win.cc b/media/audio/win/audio_device_listener_win.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d3e9933edeed9310cc67f43d9fe841d96aec8b39
--- /dev/null
+++ b/media/audio/win/audio_device_listener_win.cc
@@ -0,0 +1,143 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "media/audio/win/audio_device_listener_win.h"
+
+#include "base/logging.h"
+#include "base/utf_string_conversions.h"
+#include "base/win/scoped_co_mem.h"
+#include "base/win/windows_version.h"
+
+#include <Audioclient.h>
+
+using base::win::ScopedCoMem;
+
+namespace media {
+
+// TODO(henrika): Move to CoreAudioUtil class.
+static ScopedComPtr<IMMDeviceEnumerator> CreateDeviceEnumerator() {
+  ScopedComPtr<IMMDeviceEnumerator> device_enumerator;
+  HRESULT hr = CoCreateInstance(__uuidof(MMDeviceEnumerator),
+                                NULL,
+                                CLSCTX_INPROC_SERVER,
+                                __uuidof(IMMDeviceEnumerator),
+                                device_enumerator.ReceiveVoid());
+  DLOG_IF(ERROR, FAILED(hr)) << "CoCreateInstance(IMMDeviceEnumerator): "
+                             << std::hex << hr;
+  return device_enumerator;
+}
+
+AudioDeviceListenerWin::AudioDeviceListenerWin(
+    AudioManager::AudioDeviceListener* listener)
+    : listener_(listener) {
+  // Windows Core Audio is only supported on Vista or higher.
+  if (base::win::GetVersion() < base::win::VERSION_VISTA)

[scherkus (not reviewing), 2012/10/24 04:27:09]

FYI this is equivalent to calling !IsWASAPISupported()

[DaleCurtis, 2012/10/24 19:27:29]

Hah! Really?! I thought we were actually querying to see if WASAPI was supported
as I thought it could be disabled under certain circumstances... 

[henrika (OOO until Aug 14), 2012/10/24 19:49:22]

I have not been able to come up with a better method than this. It is simple and
it works well.

+    return;
+
+  device_enumerator_ = CreateDeviceEnumerator();
+  if (!device_enumerator_)
+    return;
+
+  HRESULT hr = device_enumerator_->RegisterEndpointNotificationCallback(this);
+  if (FAILED(hr)) {
+    DLOG(ERROR)  << "RegisterEndpointNotificationCallback failed: "
+                 << std::hex << hr;
+    return;
+  }
+
+  ScopedComPtr<IMMDevice> endpoint_render_device;
+  hr = device_enumerator_->GetDefaultAudioEndpoint(
+      eRender, eConsole, endpoint_render_device.Receive());
+  // This will fail if there are no audio devices currently plugged in, so we
+  // still want to keep our endpoint registered.
+  if (FAILED(hr)) {
+    DLOG(ERROR) << "GetDefaultAudioEndpoint() failed.  No devices?  Error: "
+                << std::hex << hr;
+    return;
+  }
+
+  ScopedCoMem<WCHAR> render_device_id;
+  hr = endpoint_render_device->GetId(&render_device_id);
+  if (FAILED(hr)) {
+    DLOG(ERROR) << "GetId() failed: " << std::hex << hr;
+    return;
+  }
+
+  default_render_device_id_ = WideToUTF8(static_cast<WCHAR*>(render_device_id));
+  DVLOG(1) << "Default render device: " << default_render_device_id_;
+}
+
+AudioDeviceListenerWin::~AudioDeviceListenerWin() {
+  if (device_enumerator_)
+    device_enumerator_->UnregisterEndpointNotificationCallback(this);
+}
+
+STDMETHODIMP_(ULONG) AudioDeviceListenerWin::AddRef() {
+  return 1;
+}
+
+STDMETHODIMP_(ULONG) AudioDeviceListenerWin::Release() {
+  return 1;
+}
+
+STDMETHODIMP AudioDeviceListenerWin::QueryInterface(REFIID iid, void** object) {
+  if (iid == IID_IUnknown || iid == __uuidof(IMMNotificationClient)) {

[scherkus (not reviewing), 2012/10/24 04:27:09]

I ain't a COM pro... but does this say if it's IUnknown we cast to
IMMNotificationClient? Does that work?

[DaleCurtis, 2012/10/24 19:27:29]

This looks correct (minus a fix I just added) from the literature I've found:
http://blogs.msdn.com/b/oldnewthing/archive/2004/03/26/96777.aspx
http://msdn.microsoft.com/en-us/library/windows/desktop/ms686590(v=vs.85).aspx

Essentially if we receive an IUnknown query we have to return our current
pointer  for identity checks or something.

[henrika (OOO until Aug 14), 2012/10/24 19:49:22]

Working with COM usually result in that you must turn to MSDN examples for
guidance. Here is an example which is inline with our current implementation:
http://msdn.microsoft.com/en-us/library/windows/desktop/dd370810(v=vs.85).aspx

+    *object = static_cast < IMMNotificationClient*>(this);

[scherkus (not reviewing), 2012/10/24 04:27:09]

remove extra spaces

[DaleCurtis, 2012/10/24 19:27:29]

Done.

+  } else {
+    return E_NOINTERFACE;
+  }
+  return S_OK;
+}
+
+STDMETHODIMP AudioDeviceListenerWin::OnPropertyValueChanged(
+    LPCWSTR device_id, const PROPERTYKEY key) {
+  // TODO(dalecurtis): We need to handle changes for the current default device
+  // here.  It's tricky because this method may be called many (20+) times for
+  // a single change like sample rate.  http://crbug.com/153056
+  return S_OK;
+}
+
+STDMETHODIMP AudioDeviceListenerWin::OnDeviceAdded(LPCWSTR device_id) {
+  // We don't care when devices are added.
+  return S_OK;
+}
+
+STDMETHODIMP AudioDeviceListenerWin::OnDeviceRemoved(LPCWSTR device_id) {
+  // We don't care when devices are removed.
+  return S_OK;
+}
+
+STDMETHODIMP AudioDeviceListenerWin::OnDeviceStateChanged(LPCWSTR device_id,
+                                                          DWORD new_state) {
+  return S_OK;
+}
+
+STDMETHODIMP AudioDeviceListenerWin::OnDefaultDeviceChanged(
+    EDataFlow flow, ERole role, LPCWSTR new_default_device_id) {
+  // Only listen for output device changes right now...
+  if (flow != eConsole && role != eRender)
+    return S_OK;
+
+  // If no device is now available, |new_default_device_id| will be NULL.
+  std::string new_device_id = "";
+  if (new_default_device_id) {
+    new_device_id = WideToUTF8(static_cast<const WCHAR*>(
+        new_default_device_id));
+  }
+
+  // Only fire a state change event if the device has actually changed.
+  if (new_device_id.compare(default_render_device_id_) == 0)
+    return S_OK;
+
+  default_render_device_id_ = new_device_id;
+
+  // TODO(dalecurtis): This still seems to fire an extra event on my machine for
+  // an unplug event (probably others too); e.g., we get two transitions to a
+  // new default device id.
+  listener_->OnDeviceChange();
+
+  return S_OK;
+}
+
+}  // namespace media