Fix new input system touches on android.

Author: timbotimbo

android/src/main/kotlin/com/xraph/plugin/flutter_unity_widget/CustomUnityPlayer.kt

@@ -46,7 +46,19 @@ class CustomUnityPlayer(context: Activity, upl: IUnityPlayerLifecycleEvents?) :
         if (event == null) return false
 
         event.source = InputDevice.SOURCE_TOUCHSCREEN
-        return super.onTouchEvent(event)
+        
+        // true for Flutter Virtual Display, false for Hybrid composition.
+        if (event.deviceId == 0) {        
+            /* 
+              Flutter creates a touchscreen motion event with deviceId 0. (https://github.com/flutter/flutter/blob/34b454f42dd6f8721dfe43fc7de5d215705b5e52/packages/flutter/lib/src/services/platform_views.dart#L639)
+              Unity's new Input System package does not detect these touches, copy the motion event to change the immutable deviceId.
+            */
+            val modifiedEvent = event.copy(deviceId = -1)
+            event.recycle()
+            return super.onTouchEvent(modifiedEvent)
+        } else {
+            return super.onTouchEvent(event)
+        }
     }
 
 }

android/src/main/kotlin/com/xraph/plugin/flutter_unity_widget/utils/CopyMotionEvent.kt

@@ -0,0 +1,56 @@
+// source https://gist.github.com/sebschaef/b803da53217c88e8c691aeed08602193
+
+package com.xraph.plugin.flutter_unity_widget
+
+import android.view.MotionEvent
+
+/*
+  Copies a MotionEvent. Use the named parameters to modify immutable properties.
+  Don't forget to recycle the original event if it is not used anymore.
+*/
+fun MotionEvent.copy(
+    downTime: Long = getDownTime(),
+    eventTime: Long = getEventTime(),
+    action: Int = getAction(),
+    pointerCount: Int = getPointerCount(),
+    pointerProperties: Array<MotionEvent.PointerProperties>? =
+        (0 until getPointerCount())
+            .map { index ->
+                MotionEvent.PointerProperties().also { pointerProperties ->
+                    getPointerProperties(index, pointerProperties)
+                }
+            }
+            .toTypedArray(),
+    pointerCoords: Array<MotionEvent.PointerCoords>? =
+        (0 until getPointerCount())
+            .map { index ->
+                MotionEvent.PointerCoords().also { pointerCoords ->
+                    getPointerCoords(index, pointerCoords)
+                }
+            }
+            .toTypedArray(),
+    metaState: Int = getMetaState(),
+    buttonState: Int = getButtonState(),
+    xPrecision: Float = getXPrecision(),
+    yPrecision: Float = getYPrecision(),
+    deviceId: Int = getDeviceId(),
+    edgeFlags: Int = getEdgeFlags(),
+    source: Int = getSource(),
+    flags: Int = getFlags()
+): MotionEvent =
+    MotionEvent.obtain(
+        downTime,
+        eventTime,
+        action,
+        pointerCount,
+        pointerProperties,
+        pointerCoords,
+        metaState,
+        buttonState,
+        xPrecision,
+        yPrecision,
+        deviceId,
+        edgeFlags,
+        source,
+        flags
+    )