Add event listening function to openvr device

device/vr/openvr/openvr_device.cc

Index: device/vr/openvr/openvr_device.cc
diff --git a/device/vr/openvr/openvr_device.cc b/device/vr/openvr/openvr_device.cc
index f129d977e0a77510ee14f763cf9f171dcea8b523..68d02db48ff3b3b410dc5a200e8cccdbc762076f 100644
--- a/device/vr/openvr/openvr_device.cc
+++ b/device/vr/openvr/openvr_device.cc
@@ -76,7 +76,7 @@ std::vector<float> HmdMatrix34ToWebVRTransformMatrix(
 
 namespace device {
 
-OpenVRDevice::OpenVRDevice() {}
+OpenVRDevice::OpenVRDevice() : weak_ptr_factory_(this) {}
 OpenVRDevice::~OpenVRDevice() {}
 
 void OpenVRDevice::CreateVRDisplayInfo(
@@ -149,6 +149,9 @@ void OpenVRDevice::CreateVRDisplayInfo(
 
   render_loop_ = std::make_unique<OpenVRRenderLoop>(vr_system);
 
+  render_loop_->RegistPollingEventCallback(base::Bind(
+      &OpenVRDevice::OnPollingEvent, weak_ptr_factory_.GetWeakPtr()));
+
   on_created.Run(std::move(device));
 }
 
@@ -179,6 +182,23 @@ void OpenVRDevice::UpdateLayerBounds(int16_t frame_index,
   // We don't support presentation currently, so don't do anything.
 }
 
+// TODO(shaobo): OnConnect and OnDisconnect need to be added to VrDisplayClient
+// in vr_service.mojom
+void OpenVRDevice::OnPollingEvent(OpenVRDevice::VREvent event) {
+  switch (event) {
+    case OpenVRDevice::VREvent::CONNECTED:
+    case OpenVRDevice::VREvent::DISCONNECTED:
+      break;
+
+    case OpenVRDevice::VREvent::CHANGED:
+      OnChanged();

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

I just find that this will cause vr_system created several times based on
current logic. I'll update it but I questioned that vr_system is reasonable to
be held in either OpenVRRenderLoop or OpenVRDevice(maybe a utility class is
better?) 

+      break;
+
+    default:
+      break;
+  }
+}
+
 void OpenVRDevice::GetVRVSyncProvider(mojom::VRVSyncProviderRequest request) {
   render_loop_->Bind(std::move(request));
 }
@@ -238,11 +258,67 @@ device::mojom::VRPosePtr OpenVRDevice::OpenVRRenderLoop::getPose() {
   return std::move(pose);
 }
 
+// Only deal with event which will cause displayInfo changed now.
+void OpenVRDevice::OpenVRRenderLoop::PollEvent() {
+  if (!vr_system_ || on_polling_event_.is_null())
+    return;
+
+  vr::VREvent_t event;
+  bool is_changed = false;
+  while (vr_system_->PollNextEvent(&event, sizeof(event))) {
+    if (event.trackedDeviceIndex != vr::k_unTrackedDeviceIndex_Hmd &&
+        event.trackedDeviceIndex != vr::k_unTrackedDeviceIndexInvalid) {
+      continue;
+    }
+
+    switch (event.eventType) {
+      case vr::VREvent_TrackedDeviceActivated:
+        on_polling_event_.Run(OpenVRDevice::VREvent::CONNECTED);
+        break;
+
+      case vr::VREvent_TrackedDeviceDeactivated:
+        on_polling_event_.Run(OpenVRDevice::VREvent::DISCONNECTED);
+        break;
+
+      case vr::VREvent_TrackedDeviceUpdated:
+      case vr::VREvent_IpdChanged:
+      case vr::VREvent_ChaperoneDataHasChanged:
+      case vr::VREvent_ChaperoneSettingsHaveChanged:
+      case vr::VREvent_ChaperoneUniverseHasChanged:
+        is_changed = true;

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

If there is the only one place to trigger Changed event, can we call
VRDevice::OnChanged right here?

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

I introduce this bool variable here for the situation that OnChanged may be
called several times in one rAF call. Since each call of OnChanged will cause
vrdisplayInfo updated (fetch new data, transfer data and update on blink side),
I think combine them and call OnChanged only once per rAF is a performance
optimization. Pls correct me if any mistake :)

+        break;
+
+      default:
+        break;
+    }
+  }
+
+  if (is_changed) {
+    on_polling_event_.Run(OpenVRDevice::VREvent::CHANGED);
+  }
+}
+
+// Regist a callback function to deal with system event.
+void OpenVRDevice::OpenVRRenderLoop::RegistPollingEventCallback(
+    const base::Callback<void(OpenVRDevice::VREvent)>& onPollingEvent) {
+  if (onPollingEvent.is_null())
+    return;
+
+  on_polling_event_ = onPollingEvent;
+}
+
+void OpenVRDevice::OpenVRRenderLoop::UnregistPollingEventCallback() {
+  on_polling_event_.Reset();
+}
+
 void OpenVRDevice::OpenVRRenderLoop::GetVSync(
     const mojom::VRVSyncProvider::GetVSyncCallback& callback) {
   static int16_t next_frame = 0;
   int16_t frame = next_frame++;
 
+  // VSync could be used as a signal to poll event.
+  PollEvent();
+
   // TODO(BillOrr): Give real values when VSync loop is hooked up.  This is the
   // presentation time for the frame. Just returning a default value for now
   // since we don't have VSync hooked up.