Audio extension API.

chrome/common/extensions/api/audio.idl

+// Copyright (c) 2013 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.
+
+namespace audio {
+
+  dictionary OutputDeviceInfo {
+    // The unique identifier of the audio output device.
+    DOMString id;
+    // The user-friendly name (e.g. "Bose Amplifier").
+    DOMString name;
+    // True if this is the current active device.
+    boolean isActive;
+    // True if this is muted.
+    boolean isMuted;
+    // The output volume ranging from 0.0 to 1.0.
+    double volume;
+  };
+
+  dictionary InputDeviceInfo {
+    // The unique identifier of the audio input device.
+    DOMString id;
+    // The user-friendly name (e.g. "USB Microphone").
+    DOMString name;
+    // True if this is the current active device.
+    boolean isActive;
+    // True if this is muted.
+    boolean isMuted;
+    // The input gain ranging from 0.0 to 1.0.
+    double gain;
+  };
+
+  dictionary DeviceProperties {
+    // True if this is muted.
+    boolean isMuted;
+    // If this is an output device then this field indicates the output volume.
+    // If this is an input device then this field is ignored.
+    double? volume;
+    // If this is an input device then this field indicates the input gain.
+    // If this is an output device then this field is ignored.
+    double? gain;
+  };
+
+  callback GetInfoCallback = void(OutputDeviceInfo[] outputInfo,
+                                  InputDeviceInfo[] inputInfo);
+  callback SetActiveDevicesCallback = void();
+  callback SetPropertiesCallback = void();
+
+  interface Functions {
+    // Get the information of all audio output and input devices.
+    static void getInfo(GetInfoCallback callback);
+
+    // Select a subset of audio devices as active.
+    static void setActiveDevices(DOMString[] ids,
+                                 SetActiveDevicesCallback callback);
+
+    // Sets the properties for the input or output device.
+    static void setProperties(DOMString id,
+                              DeviceProperties properties,
+                              SetPropertiesCallback callback);
+  };
+
+  interface Events {
+    // Fired when anything changes to the audio device configuration.
+    static void onDeviceChanged();

[Matt Perry, 2013/04/22 23:57:26]

This should pass down the same data as the getInfo callback. The app/extension
will likely need the new device data anyway.

[hshi1, 2013/04/23 00:07:34]

This event is defined this way because it is not trivial (takes two extra async
calls through dbus::CrasAudioClient) to collect the list of audio device nodes
as well as the volume state. I would like to keep this simple so that we do not
duplicate too much code in the C++ layer.

[Matt Perry, 2013/04/23 00:12:54]

Maybe I don't understand how onDeviceChanged will be used. But it seems likely
to me that extensions will almost always need to just call audio.getInfo() to
query what has changed. If that's the case, I'd rather complicate things at the
C++ layer to make the API easier to use for developers.

+  };
+};