[idd] audio: add the mediated device connector

Open the optional audio broker from a passive worker and move bounded
playback and capture packets through a transport-neutral audio hub.

Attach audio sources after transport initialization without making audio
driver availability part of display transport readiness.

idd/LGIdd/audio/CLGAudioDevice.h

@@ -0,0 +1,94 @@
+/**
+ * Looking Glass
+ * Copyright © 2017-2026 The Looking Glass Authors
+ * https://looking-glass.io
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc., 59
+ * Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#pragma once
+
+#include "transport/IAudioSource.h"
+
+#include <memory>
+
+struct LGAudioDeviceSnapshot
+{
+  AudioEndpointStatus status;
+  bool     open            = false;
+  bool     bound           = false;
+  bool     activeRequested = false;
+  bool     deactivating    = false;
+  uint64_t renderPackets   = 0;
+  uint64_t renderBytes     = 0;
+  uint64_t capturePackets  = 0;
+  uint64_t captureBytes    = 0;
+  uint64_t reconnects      = 0;
+  uint32_t lastError       = 0;
+};
+
+class ILGAudioDeviceEvents
+{
+public:
+  virtual ~ILGAudioDeviceEvents() = default;
+
+  virtual void LGAudioState(const AudioEndpointStatus& state) = 0;
+  virtual AudioResult LGAudioPlayback(const AudioPacket& packet,
+    const uint8_t * data, size_t size) = 0;
+  virtual void LGAudioCaptureReady() = 0;
+};
+
+class ILGAudioDevice
+{
+public:
+  virtual ~ILGAudioDevice() = default;
+
+  // Methods are thread-safe and nonblocking except Stop. Stop is a callback-
+  // quiescence barrier; after it returns no event callback can still run.
+  virtual bool Start(ILGAudioDeviceEvents& events) = 0;
+  virtual void Stop() = 0;
+  virtual LGAudioDeviceSnapshot Snapshot() const = 0;
+  virtual AudioResult SetActive(bool active) = 0;
+  virtual AudioResult SendCapture(const AudioPacket& packet,
+    const uint8_t * data, size_t size) = 0;
+  virtual AudioResult SetClockFeedback(
+    const AudioClockFeedback& feedback) = 0;
+  virtual void PlaybackReceiveReady() = 0;
+};
+
+class CLGAudioDevice final : public ILGAudioDevice
+{
+private:
+  class CState;
+  std::unique_ptr<CState> m_state;
+
+public:
+  CLGAudioDevice();
+  ~CLGAudioDevice();
+
+  CLGAudioDevice(const CLGAudioDevice&) = delete;
+  CLGAudioDevice& operator=(const CLGAudioDevice&) = delete;
+
+  bool Start(ILGAudioDeviceEvents& events) override;
+  void Stop() override;
+
+  LGAudioDeviceSnapshot Snapshot() const override;
+  AudioResult SetActive(bool active) override;
+  AudioResult SendCapture(const AudioPacket& packet,
+    const uint8_t * data, size_t size) override;
+  AudioResult SetClockFeedback(
+    const AudioClockFeedback& feedback) override;
+  void PlaybackReceiveReady() override;
+};