Add event listening function to openvr device

device/vr/openvr/openvr_device.h

 // Copyright 2017 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 DEVICE_VR_OPENVR_DEVICE_H
 #define DEVICE_VR_OPENVR_DEVICE_H
 
 #include "base/macros.h"
 #include "base/threading/simple_thread.h"
 #include "device/vr/vr_device.h"
 #include "mojo/public/cpp/bindings/binding.h"
 
 namespace vr {
 class IVRSystem;
 }  // namespace vr
 
 namespace device {
 
 class OpenVRDevice : public VRDevice {
  public:
+  enum VREvent { CONNECTED = 0, DISCONNECTED = 1, CHANGED = 2 };

[nhu, 2017/04/24 01:47:06]

No need to define general vr events in OpenVRDevice implementation, define them
or re-use exiting ones in VRDevice.

+
   OpenVRDevice();
   ~OpenVRDevice() override;
 
   // VRDevice
   void CreateVRDisplayInfo(
       const base::Callback<void(mojom::VRDisplayInfoPtr)>& on_created) override;
 
   void RequestPresent(mojom::VRSubmitFrameClientPtr submit_client,
                       const base::Callback<void(bool)>& callback) override;
   void SetSecureOrigin(bool secure_origin) override;
   void ExitPresent() override;
 
   void SubmitFrame(int16_t frame_index,
                    const gpu::MailboxHolder& mailbox) override;
   void UpdateLayerBounds(int16_t frame_index,
                          mojom::VRLayerBoundsPtr left_bounds,
                          mojom::VRLayerBoundsPtr right_bounds,
                          int16_t source_width,
                          int16_t source_height) override;
   void GetVRVSyncProvider(mojom::VRVSyncProviderRequest request) override;
 
+  void OnPollingEvent(OpenVRDevice::VREvent event);

[nhu, 2017/04/24 01:47:06]

VRDevice already defines OnXXX functions for event handling (See
https://cs.chromium.org/chromium/src/device/vr/vr_device.h?type=cs&l=53). 

Can we use them instead of introducing this new "OnPollingEvent"?

[shaobo.yan, 2017/04/24 02:27:27]

Due to the current class relationship, I think OpenVRRenderLoop cannot access
OpenVRDevice non-static function directly(Am I right?). So if I re-use these
functions I need to either transfer an OpenVRDeivce instance(which I think will
break the access control) or register a set of callbacks. Pls correct me if I'm
wrong :) 

+
  private:
   class OpenVRRenderLoop : public base::SimpleThread,
                            device::mojom::VRVSyncProvider {
    public:
     OpenVRRenderLoop(vr::IVRSystem* vr);
 
+    void RegistPollingEventCallback(
+        const base::Callback<void(OpenVRDevice::VREvent)>& onPollingVREvent);

[nhu, 2017/04/24 01:47:06]

Can we use a VRDevice reference to OpenVRDevice instance? Then OpenVRRenderLoop
is able to call OnXXX event handlers of VRDevice to notify.

[shaobo.yan, 2017/04/24 02:27:27]

Yes, I think this is the base question need to discsussion. All of the patch
design is based on avoiding OpenVRRenderLoop instance and OpenVRDevice holding
each other. If they hold each other the life-cycle management is a little bit
complex(maybe :) ).
And If OpenVRRenderLoop need VRDevice to do more jobs I think it indeed could
hold VRDevice reference. but if only need event handling I prefer a callback :)

+
+    void UnregistPollingEventCallback();
+
     void Bind(mojom::VRVSyncProviderRequest request);
 
     mojom::VRPosePtr getPose();
 
+    // OpenVR need invoke pollNextEvent to query system event.
+    void PollEvent();

[nhu, 2017/04/24 01:47:06]

naming: PollEvent -> PollEvents?

[shaobo.yan, 2017/04/24 02:27:28]

That's a better name !

+
    private:
     void Run() override;
 
     void GetVSync(const device::mojom::VRVSyncProvider::GetVSyncCallback&
                       callback) override;
 
     scoped_refptr<base::SingleThreadTaskRunner> main_thread_task_runner_;
+    base::Callback<void(OpenVRDevice::VREvent)> on_polling_event_;
     vr::IVRSystem* vr_system_;
     mojo::Binding<device::mojom::VRVSyncProvider> binding_;
   };
 
   std::unique_ptr<OpenVRRenderLoop>
       render_loop_;  // TODO (BillOrr): This should not be a unique_ptr because
                      // the render_loop_ binds to VRVSyncProvider requests,
                      // so its lifetime should be tied to the lifetime of that
                      // binding.
 
   mojom::VRSubmitFrameClientPtr submit_client_;
 
+  base::WeakPtrFactory<OpenVRDevice> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(OpenVRDevice);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_VR_OPENVR_DEVICE_H