app_shell: Do simple audio initialization.

extensions/shell/browser/shell_audio_controller_chromeos.cc

+// Copyright 2014 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 "extensions/shell/browser/shell_audio_controller_chromeos.h"
+
+#include <algorithm>
+
+#include "chromeos/audio/audio_device.h"
+
+namespace extensions {
+
+namespace {
+
+// Default output and input volume.
+const double kOutputVolumePercent = 100.0;
+const double kInputGainPercent = 100.0;
+
+// Returns a pointer to the device in |devices| with ID |node_id|, or NULL if it
+// isn't present.
+const chromeos::AudioDevice* GetDevice(const chromeos::AudioDeviceList& devices,
+                                       uint64 node_id) {
+  for (chromeos::AudioDeviceList::const_iterator it = devices.begin();
+       it != devices.end(); ++it) {
+    if (it->id == node_id)
+      return &(*it);
+  }
+  return NULL;
+}
+
+}  // namespace
+
+ShellAudioController::PrefHandler::PrefHandler() {}
+
+double ShellAudioController::PrefHandler::GetOutputVolumeValue(
+    const chromeos::AudioDevice* device) {
+  return kOutputVolumePercent;
+}
+
+double ShellAudioController::PrefHandler::GetInputGainValue(
+    const chromeos::AudioDevice* device) {
+  return kInputGainPercent;
+}
+
+void ShellAudioController::PrefHandler::SetVolumeGainValue(
+    const chromeos::AudioDevice& device,
+    double value) {
+  // TODO(derat): Shove volume and mute prefs into a map so we can at least
+  // honor changes that are made at runtime.

[jennyz, 2014/08/28 17:42:49]

Do we have a plan to persist the volume/gain and mute preference set by the app
in the future? 

[Daniel Erat, 2014/08/28 23:27:57]

you mean across app_shell runs? we'll probably want to do that at some point,
but i figured i'd just punt on it for now.

+}
+
+bool ShellAudioController::PrefHandler::GetMuteValue(
+    const chromeos::AudioDevice& device) {
+  return false;
+}
+void ShellAudioController::PrefHandler::SetMuteValue(

[James Cook, 2014/08/28 18:48:37]

nit: blank line above

[Daniel Erat, 2014/08/28 23:27:57]

whoops, done

+    const chromeos::AudioDevice& device,
+    bool mute_on) {}
+
+bool ShellAudioController::PrefHandler::GetAudioCaptureAllowedValue() {
+  return true;
+}
+
+bool ShellAudioController::PrefHandler::GetAudioOutputAllowedValue() {
+  return true;
+}
+
+void ShellAudioController::PrefHandler::AddAudioPrefObserver(
+    chromeos::AudioPrefObserver* observer) {}
+
+void ShellAudioController::PrefHandler::RemoveAudioPrefObserver(
+    chromeos::AudioPrefObserver* observer) {}
+
+ShellAudioController::PrefHandler::~PrefHandler() {}
+
+ShellAudioController::ShellAudioController() {
+  chromeos::CrasAudioHandler::Get()->AddAudioObserver(this);
+  ActivateDevices();
+}
+
+ShellAudioController::~ShellAudioController() {
+  chromeos::CrasAudioHandler::Get()->RemoveAudioObserver(this);
+}
+
+void ShellAudioController::OnOutputVolumeChanged() {}
+
+void ShellAudioController::OnOutputMuteChanged() {}
+
+void ShellAudioController::OnInputGainChanged() {}
+
+void ShellAudioController::OnInputMuteChanged() {}
+
+void ShellAudioController::OnAudioNodesChanged() {
+  VLOG(1) << "Audio nodes changed";
+  ActivateDevices();
+}
+
+void ShellAudioController::OnActiveOutputNodeChanged() {}
+
+void ShellAudioController::OnActiveInputNodeChanged() {}
+
+void ShellAudioController::ActivateDevices() {
+  chromeos::CrasAudioHandler* handler = chromeos::CrasAudioHandler::Get();
+  chromeos::AudioDeviceList devices;
+  handler->GetAudioDevices(&devices);
+  sort(devices.begin(), devices.end(), chromeos::AudioDeviceCompare());
+
+  uint64 best_input = 0, best_output = 0;
+  for (chromeos::AudioDeviceList::const_reverse_iterator it = devices.rbegin();
+       it != devices.rend() && (!best_input || !best_output); ++it) {

[James Cook, 2014/08/28 18:48:37]

optional: this loop might be clearer if the best_input / best_output condition
was moved to the end as a specific break:

for (rbegin; rend; ++it) {
  if (is_input)
    best_input = id
  if (is_output)
    best_output = id
  if (best_input && best_output)
    // we're done
    break
}

[Daniel Erat, 2014/08/28 23:27:57]

i considered that, but it felt weird to me since it means we'll look at the
first device unconditionally. duplicating the check outside of the loop and
putting it at the beginning of the loop also seemed gross.

+    // TODO(derat): Need to check |plugged_time|?

[Daniel Erat, 2014/08/28 04:00:29]

jenny, let me know if there's a danger of e.g. unplugged headphone jacks showing
up here.

[jennyz, 2014/08/28 17:42:49]

If the headphone jack is unplugged, it should not be returned in the
GetAudioDevices, and plug time is already counted in AudioDeviceCompare, no need
to check again.

+    if (it->is_input && !best_input)
+      best_input = it->id;
+    else if (!it->is_input && !best_output)
+      best_output = it->id;
+  }
+
+  if (best_input && best_input != handler->GetActiveInputNode()) {
+    const chromeos::AudioDevice* device = GetDevice(devices, best_input);
+    DCHECK(device);
+    VLOG(1) << "Activating input device: " << device->ToString();
+    handler->SwitchToDevice(*device);
+  }
+  if (best_output && best_output != handler->GetActiveOutputNode()) {
+    const chromeos::AudioDevice* device = GetDevice(devices, best_output);
+    DCHECK(device);
+    VLOG(1) << "Activating output device: " << device->ToString();
+    handler->SwitchToDevice(*device);
+  }
+}
+
+}  // namespace extensions