Add ALSA support to volume keys

chrome/browser/chromeos/audio_mixer_base.h

+// Copyright (c) 2010 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.
+
+#ifndef CHROME_BROWSER_CHROMEOS_AUDIO_MIXER_BASE_H_
+#define CHROME_BROWSER_CHROMEOS_AUDIO_MIXER_BASE_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "base/callback.h"
+
+namespace chromeos {
+
+const double kSilenceDb = -200.0;

[scherkus (not reviewing), 2010/12/22 22:31:58]

this needs a comment + move the actual assignment to the .cc

[davejcool, 2010/12/23 03:09:02]

It seems a const can't be defined elsewhere except at the declaration.  It looks
like making it a static member of the class and defining it there is an accepted
practice.

+
+class AudioMixerBase {

[scherkus (not reviewing), 2010/12/22 22:31:58]

this looks more like an interface rather than a base class

I'd rename this simply AudioMixer

+ public:
+  enum State {
+    UNINITIALIZED = 0,
+    INITIALIZING,
+    READY,
+    SHUTTING_DOWN,
+    IN_ERROR

[scherkus (not reviewing), 2010/12/22 22:31:58]

nit: add trailing ,

+  };
+
+  AudioMixerBase() {}

[scherkus (not reviewing), 2010/12/22 22:31:58]

avoid inlining virtual methods (i.e., put these in a .cc)

+  virtual ~AudioMixerBase() {}
+
+  // Non-blocking, connect to Mixer and find a default device, and call
+  // callback when complete with success code.
+  typedef Callback1<bool>::Type InitDoneCallback;
+  virtual bool Init(InitDoneCallback* callback) = 0;
+
+  // Blocking init call guarantees Mixer is connected before returning.
+  virtual bool InitSync() = 0;
+
+  // Blocking call. Returns a default of kSilenceDb on error.
+  virtual double GetVolumeDb() const = 0;
+
+  virtual void GetVolumeLimits(double* vol_min, double* vol_max) = 0;

[scherkus (not reviewing), 2010/12/22 22:31:58]

needs a comment

is it blocking?  etc..

+
+  // Non-blocking call.

[scherkus (not reviewing), 2010/12/22 22:31:58]

do all these blocking comments apply to both pulse and alsa?

or is it a contract of the interface that this not be a blocking call?

+  virtual void SetVolumeDb(double vol_db) = 0;
+
+  // Gets the mute state of the default device (true == mute). Blocking call.
+  // Returns a default of false on error.
+  virtual bool IsMute() const = 0;
+
+  // Non-Blocking call.
+  virtual void SetMute(bool mute) = 0;
+
+  // Returns READY if we have a valid working connection to the Mixer.
+  // This can return IN_ERROR if we lose the connection, even after an original
+  // successful init.  Non-blocking call.
+  virtual State CheckState() const = 0;
+
+ protected:

[scherkus (not reviewing), 2010/12/22 22:31:58]

believe this should be private (no need to have subclasses have access to copy
constructor, etc...)

+

[scherkus (not reviewing), 2010/12/22 22:31:58]

nit: no blank line

+  DISALLOW_COPY_AND_ASSIGN(AudioMixerBase);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_AUDIO_MIXER_BASE_H_
+