FIX: The button is not clickable when using Windows touch simulation inputs (ISXB-483) (#2012)

* Pair simulated touchscreen with PlayerInput user

* Add period to end of sentence

* Fix formatting

* Refactored initial fix to queue state events instead

Based on review and code comments, this seems like a better solution that fixes the main problem and also better simulates a touchscreen when used together with PlayerInput.
Automatic pairing and control scheme occurs now since we're using input events a real device would also use.

* Change logic to be based on state events

The previous logic was based on changing state and didn't apply if we queued events.

Also, this commit avoids processing the queued events for the simulated Touchscreen.

* Remove unnecessary left over code

* Fix setting wrong touchIDs when moving multiple touches

Author: jfreire-unity

Packages/com.unity.inputsystem/CHANGELOG.md

@@ -30,6 +30,7 @@ however, it has to be formatted properly to pass verification tests.
 - Fixed "MissingReferenceException" errors when closing an in-game dropdown field [ISXB-1081](https://issuetracker.unity3d.com/product/unity/issues/guid/ISXB-1081).
 - Fixed potential crash on Mac when using stale references to deleted InputDevice objects [ISXB-606](https://issuetracker.unity3d.com/product/unity/issues/guid/ISXB-606).
 - Fixed conditional compilation for non-editor analytics on platforms not enabling analytics.
+- Fixed simulated touch input not working with PlayerInput component [ISXB-483](https://issuetracker.unity3d.com/product/unity/issues/guid/ISXB-483).
 
 ### Changed
 - Renamed editor Resources directories to PackageResources to fix package validation warnings.

Packages/com.unity.inputsystem/InputSystem/Plugins/EnhancedTouch/TouchSimulation.cs

@@ -121,6 +121,12 @@ protected void RemovePointer(Pointer pointer)
 
         private unsafe void OnEvent(InputEventPtr eventPtr, InputDevice device)
         {
+            if (device == simulatedTouchscreen)
+            {
+                // Avoid processing events queued by this simulation device
+                return;
+            }
+
             var pointerIndex = m_Pointers.IndexOfReference(device, m_NumPointers);
             if (pointerIndex < 0)
                 return;
@@ -129,9 +135,6 @@ private unsafe void OnEvent(InputEventPtr eventPtr, InputDevice device)
             if (eventType != StateEvent.Type && eventType != DeltaStateEvent.Type)
                 return;
 
-            ////TODO: this can be simplified if we use events instead of InputState.Change() but doing so requires work on buffering events while processing; also
-            ////       needs extra handling to not lag into the next frame
-
             ////REVIEW: should we have specialized paths for MouseState and PenState here? (probably can only use for StateEvents)
 
             Pointer pointer = m_Pointers[pointerIndex];
@@ -254,6 +257,9 @@ protected void OnEnable()
             if (m_Touches == null)
                 m_Touches = new ButtonControl[simulatedTouchscreen.touches.Count];
 
+            if (m_TouchIds == null)
+                m_TouchIds = new int[simulatedTouchscreen.touches.Count];
+
             foreach (var device in InputSystem.devices)
                 OnDeviceChange(device, InputDeviceChange.Added);
 
@@ -280,7 +286,6 @@ protected void OnDisable()
 
             m_NumPointers = 0;
             m_LastTouchId = 0;
-            m_PrimaryTouchIndex = -1;
 
             InputSystem.onDeviceChange -= m_OnDeviceChange;
             InputSystem.onEvent -= m_OnEvent;
@@ -292,55 +297,34 @@ private unsafe void UpdateTouch(int touchIndex, int pointerIndex, TouchPhase pha
             Debug.Assert(m_CurrentDisplayIndices[pointerIndex] <= byte.MaxValue, "Display index was larger than expected");
             byte displayIndex = (byte)m_CurrentDisplayIndices[pointerIndex];
 
+            // We need to partially set TouchState in a similar way that the Native side would do, but deriving that
+            // data from the Pointer events.
+            // The handling of the remaining fields is done by the Touchscreen.OnStateEvent() callback.
             var touch = new TouchState
             {
                 phase = phase,
                 position = position,
                 displayIndex = displayIndex
             };
-            var time = eventPtr.valid ? eventPtr.time : InputState.currentTime;
-
-            var oldTouchState = (TouchState*)((byte*)simulatedTouchscreen.currentStatePtr +
-                simulatedTouchscreen.touches[touchIndex].stateBlock.byteOffset);
 
             if (phase == TouchPhase.Began)
             {
-                touch.isPrimaryTouch = m_PrimaryTouchIndex < 0;
-                touch.startTime = time;
+                touch.startTime = eventPtr.valid ? eventPtr.time : InputState.currentTime;
                 touch.startPosition = position;
                 touch.touchId = ++m_LastTouchId;
-                touch.tapCount = oldTouchState->tapCount; // Get reset automatically by Touchscreen.
-
-                if (touch.isPrimaryTouch)
-                    m_PrimaryTouchIndex = touchIndex;
+                m_TouchIds[touchIndex] = m_LastTouchId;
             }
             else
             {
-                touch.touchId = oldTouchState->touchId;
-                touch.isPrimaryTouch = m_PrimaryTouchIndex == touchIndex;
-                touch.delta = position - oldTouchState->position;
-                touch.startPosition = oldTouchState->startPosition;
-                touch.startTime = oldTouchState->startTime;
-                touch.tapCount = oldTouchState->tapCount;
-
-                if (phase == TouchPhase.Ended)
-                {
-                    touch.isTap = time - oldTouchState->startTime <= Touchscreen.s_TapTime &&
-                        (position - oldTouchState->startPosition).sqrMagnitude <= Touchscreen.s_TapRadiusSquared;
-                    if (touch.isTap)
-                        ++touch.tapCount;
-                }
+                touch.touchId = m_TouchIds[touchIndex];
             }
 
-            if (touch.isPrimaryTouch)
-                InputState.Change(simulatedTouchscreen.primaryTouch, touch, eventPtr: eventPtr);
-            InputState.Change(simulatedTouchscreen.touches[touchIndex], touch, eventPtr: eventPtr);
+            //NOTE: Processing these events still happen in the current frame.
+            InputSystem.QueueStateEvent(simulatedTouchscreen, touch);
 
             if (phase.IsEndedOrCanceled())
             {
                 m_Touches[touchIndex] = null;
-                if (m_PrimaryTouchIndex == touchIndex)
-                    m_PrimaryTouchIndex = -1;
             }
         }
 
@@ -349,9 +333,9 @@ private unsafe void UpdateTouch(int touchIndex, int pointerIndex, TouchPhase pha
         [NonSerialized] private Vector2[] m_CurrentPositions;
         [NonSerialized] private int[] m_CurrentDisplayIndices;
         [NonSerialized] private ButtonControl[] m_Touches;
+        [NonSerialized] private int[] m_TouchIds;
 
         [NonSerialized] private int m_LastTouchId;
-        [NonSerialized] private int m_PrimaryTouchIndex = -1;
         [NonSerialized] private Action<InputDevice, InputDeviceChange> m_OnDeviceChange;
         [NonSerialized] private Action<InputEventPtr, InputDevice> m_OnEvent;