diff --git a/tests/MotionPrediction/Android.bp b/tests/MotionPrediction/Android.bp
index 6cda8f0..b4a4359 100644
--- a/tests/MotionPrediction/Android.bp
+++ b/tests/MotionPrediction/Android.bp
@@ -26,5 +26,8 @@
 android_app {
     name: "MotionPrediction",
     srcs: ["**/*.kt"],
+    kotlincflags: [
+        "-Werror",
+    ],
     sdk_version: "current",
 }
diff --git a/tests/MultiDeviceInput/Android.bp b/tests/MultiDeviceInput/Android.bp
new file mode 100644
index 0000000..3c80873
--- /dev/null
+++ b/tests/MultiDeviceInput/Android.bp
@@ -0,0 +1,33 @@
+//
+// Copyright 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package {
+    // See: http://go/android-license-faq
+    // A large-scale-change added 'default_applicable_licenses' to import
+    // all of the 'license_kinds' from "frameworks_base_license"
+    // to get the below license kinds:
+    //   SPDX-license-identifier-Apache-2.0
+    default_applicable_licenses: ["frameworks_base_license"],
+}
+
+android_app {
+    name: "MultiDeviceInput",
+    srcs: ["**/*.kt"],
+    kotlincflags: [
+        "-Werror",
+    ],
+    sdk_version: "current",
+}
diff --git a/tests/MultiDeviceInput/AndroidManifest.xml b/tests/MultiDeviceInput/AndroidManifest.xml
new file mode 100644
index 0000000..ed8cadb
--- /dev/null
+++ b/tests/MultiDeviceInput/AndroidManifest.xml
@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright 2023 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+     package="test.multideviceinput">
+
+    <application android:allowBackup="false"
+         android:icon="@mipmap/ic_launcher"
+         android:label="@string/app_name"
+         android:supportsRtl="true"
+         android:theme="@style/AppTheme">
+        <activity android:name=".MainActivity"
+             android:exported="true">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN"/>
+                <category android:name="android.intent.category.LAUNCHER"/>
+            </intent-filter>
+        </activity>
+    </application>
+
+</manifest>
diff --git a/tests/MultiDeviceInput/OWNERS b/tests/MultiDeviceInput/OWNERS
new file mode 100644
index 0000000..c88bfe9
--- /dev/null
+++ b/tests/MultiDeviceInput/OWNERS
@@ -0,0 +1 @@
+include platform/frameworks/base:/INPUT_OWNERS
diff --git a/tests/MultiDeviceInput/README.md b/tests/MultiDeviceInput/README.md
new file mode 100644
index 0000000..5fcdeda
--- /dev/null
+++ b/tests/MultiDeviceInput/README.md
@@ -0,0 +1,19 @@
+# MultiDeviceInput test app #
+
+This demo app is for manual testing of the multi-device input feature.
+It creates two windows - one on the left and one on the right. You can use different input devices
+in these windows.
+
+## Installation ##
+Install this using:
+```
+APP=MultiDeviceInput; m $APP && adb install $ANDROID_PRODUCT_OUT/system/app/$APP/$APP.apk
+```
+
+## Features ##
+
+* Touch in one window, use stylus in another window, at the same time
+* Visualize hovering stylus
+* Pinch zoom in one window to affect the line thickness in another window
+* Check whether stylus rejects touch in the same window
+* (in the future) Check stylus and touch operation in the same window
diff --git a/tests/MultiDeviceInput/res/layout/activity_main.xml b/tests/MultiDeviceInput/res/layout/activity_main.xml
new file mode 100644
index 0000000..a6a6f891
--- /dev/null
+++ b/tests/MultiDeviceInput/res/layout/activity_main.xml
@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright 2023 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical"
+    android:paddingBottom="@dimen/activity_vertical_margin"
+    android:paddingLeft="@dimen/activity_horizontal_margin"
+    android:paddingRight="@dimen/activity_horizontal_margin"
+    android:paddingTop="@dimen/activity_vertical_margin"
+    tools:context="test.multideviceinput.MainActivity">
+
+</LinearLayout>
diff --git a/tests/MultiDeviceInput/res/mipmap-hdpi/ic_launcher.png b/tests/MultiDeviceInput/res/mipmap-hdpi/ic_launcher.png
new file mode 100644
index 0000000..cde69bc
--- /dev/null
+++ b/tests/MultiDeviceInput/res/mipmap-hdpi/ic_launcher.png
Binary files differ
diff --git a/tests/MultiDeviceInput/res/mipmap-mdpi/ic_launcher.png b/tests/MultiDeviceInput/res/mipmap-mdpi/ic_launcher.png
new file mode 100644
index 0000000..c133a0c
--- /dev/null
+++ b/tests/MultiDeviceInput/res/mipmap-mdpi/ic_launcher.png
Binary files differ
diff --git a/tests/MultiDeviceInput/res/mipmap-xhdpi/ic_launcher.png b/tests/MultiDeviceInput/res/mipmap-xhdpi/ic_launcher.png
new file mode 100644
index 0000000..bfa42f0
--- /dev/null
+++ b/tests/MultiDeviceInput/res/mipmap-xhdpi/ic_launcher.png
Binary files differ
diff --git a/tests/MultiDeviceInput/res/mipmap-xxhdpi/ic_launcher.png b/tests/MultiDeviceInput/res/mipmap-xxhdpi/ic_launcher.png
new file mode 100644
index 0000000..324e72c
--- /dev/null
+++ b/tests/MultiDeviceInput/res/mipmap-xxhdpi/ic_launcher.png
Binary files differ
diff --git a/tests/MultiDeviceInput/res/mipmap-xxxhdpi/ic_launcher.png b/tests/MultiDeviceInput/res/mipmap-xxxhdpi/ic_launcher.png
new file mode 100644
index 0000000..aee44e1
--- /dev/null
+++ b/tests/MultiDeviceInput/res/mipmap-xxxhdpi/ic_launcher.png
Binary files differ
diff --git a/tests/MultiDeviceInput/res/values-w820dp/dimens.xml b/tests/MultiDeviceInput/res/values-w820dp/dimens.xml
new file mode 100644
index 0000000..b14a560
--- /dev/null
+++ b/tests/MultiDeviceInput/res/values-w820dp/dimens.xml
@@ -0,0 +1,20 @@
+<!-- Copyright 2023 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+<resources>
+    <!-- Example customization of dimensions originally defined in res/values/dimens.xml
+         (such as screen margins) for screens with more than 820dp of available width. This
+         would include 7" and 10" devices in landscape (~960dp and ~1280dp respectively). -->
+    <dimen name="activity_horizontal_margin">64dp</dimen>
+</resources>
diff --git a/tests/MultiDeviceInput/res/values/colors.xml b/tests/MultiDeviceInput/res/values/colors.xml
new file mode 100644
index 0000000..c37df9f
--- /dev/null
+++ b/tests/MultiDeviceInput/res/values/colors.xml
@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright 2023 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+<resources>
+    <color name="colorPrimary">#3F51B5</color>
+    <color name="colorPrimaryDark">#303F9F</color>
+    <color name="colorAccent">#FF4081</color>
+</resources>
diff --git a/tests/MultiDeviceInput/res/values/dimens.xml b/tests/MultiDeviceInput/res/values/dimens.xml
new file mode 100644
index 0000000..bdb8ede
--- /dev/null
+++ b/tests/MultiDeviceInput/res/values/dimens.xml
@@ -0,0 +1,19 @@
+<!-- Copyright 2023 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+<resources>
+    <!-- Default screen margins, per the Android Design guidelines. -->
+    <dimen name="activity_horizontal_margin">16dp</dimen>
+    <dimen name="activity_vertical_margin">16dp</dimen>
+</resources>
diff --git a/tests/MultiDeviceInput/res/values/strings.xml b/tests/MultiDeviceInput/res/values/strings.xml
new file mode 100644
index 0000000..3827c34
--- /dev/null
+++ b/tests/MultiDeviceInput/res/values/strings.xml
@@ -0,0 +1,17 @@
+<!-- Copyright 2023 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+<resources>
+    <string name="app_name">Simultaneous touch and stylus</string>
+</resources>
diff --git a/tests/MultiDeviceInput/res/values/styles.xml b/tests/MultiDeviceInput/res/values/styles.xml
new file mode 100644
index 0000000..a563e7e
--- /dev/null
+++ b/tests/MultiDeviceInput/res/values/styles.xml
@@ -0,0 +1,23 @@
+<!-- Copyright 2023 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+<resources>
+    <!-- Base application theme. -->
+    <style name="AppTheme" parent="@android:style/Theme.Material.Light.DarkActionBar">
+        <!-- Customize your theme here. -->
+        <item name="android:colorPrimary">@color/colorPrimary</item>
+        <item name="android:colorPrimaryDark">@color/colorPrimaryDark</item>
+        <item name="android:colorAccent">@color/colorAccent</item>
+    </style>
+</resources>
diff --git a/tests/MultiDeviceInput/src/test/multideviceinput/DrawingView.kt b/tests/MultiDeviceInput/src/test/multideviceinput/DrawingView.kt
new file mode 100644
index 0000000..b5bd9ca
--- /dev/null
+++ b/tests/MultiDeviceInput/src/test/multideviceinput/DrawingView.kt
@@ -0,0 +1,183 @@
+/*
+ * Copyright 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package test.multideviceinput
+
+import android.content.Context
+import android.graphics.Canvas
+import android.graphics.Color
+import android.graphics.Paint
+import android.util.AttributeSet
+import android.view.InputDevice.SOURCE_STYLUS
+import android.view.MotionEvent
+import android.view.MotionEvent.ACTION_DOWN
+import android.view.MotionEvent.ACTION_HOVER_EXIT
+import android.view.MotionEvent.ACTION_UP
+import android.view.ScaleGestureDetector
+import android.view.View
+
+import java.util.Vector
+
+private fun drawLine(canvas: Canvas, from: MotionEvent, to: MotionEvent, paint: Paint) {
+    // Correct implementation here would require us to build a set of pointers and then iterate
+    // through them. Instead, we are taking a few shortcuts and ignore some of the events, which
+    // causes occasional gaps in the drawings.
+    if (from.pointerCount != to.pointerCount) {
+        return
+    }
+    // Now, 'from' is guaranteed to have as many pointers as the 'to' event. It doesn't
+    // necessarily mean they are the same pointers, though.
+    for (p in 0..<from.pointerCount) {
+        val x0 = from.getX(p)
+        val y0 = from.getY(p)
+        if (to.getPointerId(p) == from.getPointerId(p)) {
+            // This only works when the i-th pointer in "to" is the same pointer
+            // as the i-th pointer in "from"`. It's not guaranteed by the input APIs,
+            // but it works in practice.
+            val x1 = to.getX(p)
+            val y1 = to.getY(p)
+            // Ignoring historical data here for simplicity
+            canvas.drawLine(x0, y0, x1, y1, paint)
+        }
+    }
+}
+
+private fun drawCircle(canvas: Canvas, event: MotionEvent, paint: Paint, radius: Float) {
+    val x = event.getX()
+    val y = event.getY()
+    canvas.drawCircle(x, y, radius, paint)
+}
+
+/**
+ * Draw the current stroke
+ */
+class DrawingView : View {
+    private val TAG = "DrawingView"
+
+    private var myState: SharedScaledPointerSize? = null
+    private var otherState: SharedScaledPointerSize? = null
+
+    constructor(
+            context: Context,
+            myState: SharedScaledPointerSize,
+            otherState: SharedScaledPointerSize
+            ) : super(context) {
+        this.myState = myState
+        this.otherState = otherState
+        init()
+    }
+
+    constructor(context: Context, attrs: AttributeSet) : super(context, attrs) {
+        init()
+    }
+
+    val touchEvents = mutableMapOf<Int, Vector<Pair<MotionEvent, Paint>>>()
+    val hoverEvents = mutableMapOf<Int, MotionEvent>()
+
+    val scaleGestureListener = object : ScaleGestureDetector.SimpleOnScaleGestureListener() {
+
+        override fun onScaleBegin(scaleGestureDetector: ScaleGestureDetector): Boolean {
+            return true
+        }
+
+        override fun onScale(scaleGestureDetector: ScaleGestureDetector): Boolean {
+            val scaleFactor = scaleGestureDetector.scaleFactor
+            when (otherState?.state) {
+                PointerState.DOWN -> {
+                    otherState?.lineSize = (otherState?.lineSize ?: 5f) * scaleFactor
+                }
+                PointerState.HOVER -> {
+                    otherState?.circleSize = (otherState?.circleSize ?: 20f) * scaleFactor
+                }
+                else -> {}
+            }
+            return true
+        }
+    }
+    private val scaleGestureDetector = ScaleGestureDetector(context, scaleGestureListener, null)
+
+    private var touchPaint = Paint()
+    private var stylusPaint = Paint()
+
+    private fun init() {
+        touchPaint.color = Color.RED
+        touchPaint.setStrokeWidth(5f)
+        stylusPaint.color = Color.YELLOW
+        stylusPaint.setStrokeWidth(5f)
+
+        setOnHoverListener { _, event -> processHoverEvent(event); true }
+    }
+
+    private fun processTouchEvent(event: MotionEvent) {
+        scaleGestureDetector.onTouchEvent(event)
+        if (event.actionMasked == ACTION_DOWN) {
+            touchEvents.remove(event.deviceId)
+            myState?.state = PointerState.DOWN
+        } else if (event.actionMasked == ACTION_UP) {
+            myState?.state = PointerState.NONE
+        }
+        var vec = touchEvents.getOrPut(event.deviceId) { Vector<Pair<MotionEvent, Paint>>() }
+
+        val paint = if (event.isFromSource(SOURCE_STYLUS)) {
+            val size = myState?.lineSize ?: 5f
+            stylusPaint.setStrokeWidth(size)
+            Paint(stylusPaint)
+        } else {
+            val size = myState?.lineSize ?: 5f
+            touchPaint.setStrokeWidth(size)
+            Paint(touchPaint)
+        }
+        vec.add(Pair(MotionEvent.obtain(event), paint))
+        invalidate()
+    }
+
+    private fun processHoverEvent(event: MotionEvent) {
+        hoverEvents.remove(event.deviceId)
+        if (event.getActionMasked() != ACTION_HOVER_EXIT) {
+            hoverEvents.put(event.deviceId, MotionEvent.obtain(event))
+            myState?.state = PointerState.HOVER
+        } else {
+            myState?.state = PointerState.NONE
+        }
+        invalidate()
+    }
+
+    public override fun onTouchEvent(event: MotionEvent): Boolean {
+        processTouchEvent(event)
+        return true
+    }
+
+    public override fun onDraw(canvas: Canvas) {
+        super.onDraw(canvas)
+
+        // Draw touch and stylus MotionEvents
+        for ((_, vec) in touchEvents ) {
+            for (i in 1 until vec.size) {
+                drawLine(canvas, vec[i - 1].first, vec[i].first, vec[i].second)
+            }
+        }
+        // Draw hovers
+        for ((_, event) in hoverEvents ) {
+            if (event.isFromSource(SOURCE_STYLUS)) {
+                val size = myState?.circleSize ?: 20f
+                drawCircle(canvas, event, stylusPaint, size)
+            } else {
+                val size = myState?.circleSize ?: 20f
+                drawCircle(canvas, event, touchPaint, size)
+            }
+        }
+    }
+}
diff --git a/tests/MultiDeviceInput/src/test/multideviceinput/MainActivity.kt b/tests/MultiDeviceInput/src/test/multideviceinput/MainActivity.kt
new file mode 100644
index 0000000..9112085
--- /dev/null
+++ b/tests/MultiDeviceInput/src/test/multideviceinput/MainActivity.kt
@@ -0,0 +1,83 @@
+/*
+ * Copyright 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package test.multideviceinput
+
+import android.app.Activity
+import android.graphics.Color
+import android.view.Gravity
+import android.view.View
+import android.view.ViewGroup
+import android.view.WindowInsets.Type
+import android.view.WindowManager
+
+
+enum class PointerState {
+    DOWN, // One or more pointer(s) down, lines are being drawn
+    HOVER, // Pointer is hovering
+    NONE, // Nothing is touching or hovering
+}
+
+data class SharedScaledPointerSize(
+        var lineSize: Float,
+        var circleSize: Float,
+        var state: PointerState
+)
+
+class MainActivity : Activity() {
+    val TAG = "MultiDeviceInput"
+    private val leftState = SharedScaledPointerSize(5f, 20f, PointerState.NONE)
+    private val rightState = SharedScaledPointerSize(5f, 20f, PointerState.NONE)
+    private lateinit var left: View
+    private lateinit var right: View
+
+    override fun onResume() {
+        super.onResume()
+
+        val wm = getSystemService(WindowManager::class.java)
+        val wmlp = WindowManager.LayoutParams(WindowManager.LayoutParams.TYPE_APPLICATION)
+        wmlp.flags = (wmlp.flags or
+                      WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL or
+                      WindowManager.LayoutParams.FLAG_SPLIT_TOUCH)
+
+        val windowMetrics = windowManager.currentWindowMetrics
+        val insets = windowMetrics.windowInsets.getInsetsIgnoringVisibility(Type.systemBars())
+        val width = windowMetrics.bounds.width() - insets.left - insets.right
+        val height = windowMetrics.bounds.height() - insets.top - insets.bottom
+
+        wmlp.width = width * 24 / 50
+        wmlp.height = height * 35 / 50
+
+        val vglp = ViewGroup.LayoutParams(
+                ViewGroup.LayoutParams.WRAP_CONTENT,
+                ViewGroup.LayoutParams.WRAP_CONTENT
+        )
+
+        wmlp.setTitle("Left -- " + getPackageName())
+        wmlp.gravity = Gravity.CENTER_VERTICAL or Gravity.START
+        left = DrawingView(this, leftState, rightState)
+        left.setBackgroundColor(Color.LTGRAY)
+        left.setLayoutParams(vglp)
+        wm.addView(left, wmlp)
+
+        wmlp.setTitle("Right -- " + getPackageName())
+        wmlp.gravity = Gravity.CENTER_VERTICAL or Gravity.END
+        right = DrawingView(this, rightState, leftState)
+        right.setBackgroundColor(Color.LTGRAY)
+        right.setLayoutParams(vglp)
+        wm.addView(right, wmlp)
+    }
+}