update tracking state according to device changes

Author: ritamerkl

Packages/com.unity.inputsystem/InputSystem/Plugins/XR/TrackedPoseDriver.cs

@@ -432,6 +432,7 @@ protected virtual void Awake()
         protected void OnEnable()
         {
             InputSystem.onAfterUpdate += UpdateCallback;
+            InputSystem.onDeviceChange += OnDeviceChanged;
             BindActions();
 
             // Read current input values when becoming enabled,
@@ -446,6 +447,7 @@ protected void OnDisable()
         {
             UnbindActions();
             InputSystem.onAfterUpdate -= UpdateCallback;
+            InputSystem.onDeviceChange -= OnDeviceChanged;
         }
 
         /// <summary>
@@ -484,7 +486,7 @@ protected void UpdateCallback()
                 else
                     m_CurrentRotation = transform.localRotation;
 
-                ReadTrackingState(hasResolvedPositionInputControl, hasResolvedRotationInputControl);
+                ReadTrackingState();
 
                 m_IsFirstUpdate = false;
             }
@@ -495,7 +497,38 @@ protected void UpdateCallback()
                 OnUpdate();
         }
 
-        void ReadTrackingState(bool hasResolvedPositionInputControl, bool hasResolvedRotationInputControl)
+        void OnDeviceChanged(InputDevice inputDevice, InputDeviceChange inputDeviceChange)
+        {
+            ReadTrackingStateWithoutTrackingAction();
+        }
+
+        /// <summary>
+        /// React to changes of devices to stop the tracking of position / rotation or both if a device is removed, starts the tracking if
+        /// a device is added.
+        /// </summary>
+        void ReadTrackingStateWithoutTrackingAction()
+        {
+            var trackingStateAction = m_TrackingStateInput.action;
+            if (trackingStateAction != null && trackingStateAction.m_BindingsCount != 0)
+                return;
+
+            var hasResolvedPositionInputControl = HasResolvedControl(m_PositionInput.action);
+            var hasResolvedRotationInputControl = HasResolvedControl(m_RotationInput.action);
+
+            // Treat an Input Action Reference with no reference the same as
+            // an enabled Input Action with no authored bindings, and allow driving the Transform pose.
+            // Check if we have transform and rotation controls to drive the pose.
+            if (hasResolvedPositionInputControl && hasResolvedRotationInputControl)
+                m_CurrentTrackingState = TrackingStates.Position | TrackingStates.Rotation;
+            else if (hasResolvedPositionInputControl)
+                m_CurrentTrackingState = TrackingStates.Position;
+            else if (hasResolvedRotationInputControl)
+                m_CurrentTrackingState = TrackingStates.Rotation;
+            else
+                m_CurrentTrackingState = TrackingStates.None;
+        }
+
+        void ReadTrackingState()
         {
             var trackingStateAction = m_TrackingStateInput.action;
             if (trackingStateAction != null && !trackingStateAction.enabled)
@@ -504,29 +537,16 @@ void ReadTrackingState(bool hasResolvedPositionInputControl, bool hasResolvedRot
                 m_CurrentTrackingState = TrackingStates.None;
                 return;
             }
-
-            if (trackingStateAction == null || trackingStateAction.m_BindingsCount == 0)
-            {
-                // Treat an Input Action Reference with no reference the same as
-                // an enabled Input Action with no authored bindings, and allow driving the Transform pose.
-                // Check if we have transform and rotation controls to drive the pose.
-                if (hasResolvedPositionInputControl && hasResolvedRotationInputControl)
-                    m_CurrentTrackingState = TrackingStates.Position | TrackingStates.Rotation;
-                else if (hasResolvedPositionInputControl)
-                    m_CurrentTrackingState = TrackingStates.Position;
-                else if (hasResolvedRotationInputControl)
-                    m_CurrentTrackingState = TrackingStates.Rotation;
-                else
-                    m_CurrentTrackingState = TrackingStates.None;
-            }
-            else if (HasResolvedControl(trackingStateAction))
+            if (HasResolvedControl(trackingStateAction))
             {
                 // Retain the current value if there is no resolved binding.
                 // Since the field initializes to allowing position and rotation,
                 // this allows for driving the Transform pose always when the device
                 // doesn't support reporting the tracking state.
                 m_CurrentTrackingState = (TrackingStates)trackingStateAction.ReadValue<int>();
+                return;
             }
+            ReadTrackingStateWithoutTrackingAction();
         }
 
         /// <summary>