Prediction for motion events

The class MotionPredictor will be used to call into native code to
execute prediction algorithm.

The feature can be enabled by setting the appropriate config on the
device.

To enable the feature:
adb shell setprop persist.input.enable_motion_prediction true

Bug: 210158587
Test: m MotionPrediction && adb install $ANDROID_PRODUCT_OUT/system/app/MotionPrediction/MotionPrediction.apk
Change-Id: Iaee80d99b18da2f788fa8eacf2e14a6b5c6a7088

core/java/android/view/MotionPredictor.java

@@ -0,0 +1,116 @@
+/*
+ * Copyright (C) 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 android.view;
+
+import android.annotation.NonNull;
+import android.content.Context;
+
+import libcore.util.NativeAllocationRegistry;
+
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * Calculates motion predictions.
+ *
+ * Add motions here to get predicted events!
+ * @hide
+ */
+// Acts as a pass-through to the native MotionPredictor object.
+// Do not store any state in this Java layer, or add any business logic here. All of the
+// implementation details should go into the native MotionPredictor.
+// The context / resource access must be here rather than in native layer due to the lack of the
+// corresponding native API surface.
+public final class MotionPredictor {
+
+    private static class RegistryHolder {
+        public static final NativeAllocationRegistry REGISTRY =
+                NativeAllocationRegistry.createMalloced(
+                        MotionPredictor.class.getClassLoader(),
+                        nativeGetNativeMotionPredictorFinalizer());
+    }
+
+    // Pointer to the native object.
+    private final long mPtr;
+    private final Context mContext;
+
+    /**
+     * Create a new MotionPredictor for the provided {@link Context}.
+     * @param context The context for the predictions
+     */
+    public MotionPredictor(@NonNull Context context) {
+        mContext = context;
+        final int offsetNanos = mContext.getResources().getInteger(
+                com.android.internal.R.integer.config_motionPredictionOffsetNanos);
+        mPtr = nativeInitialize(offsetNanos);
+        RegistryHolder.REGISTRY.registerNativeAllocation(this, mPtr);
+    }
+
+    /**
+     * Record a movement so that in the future, a prediction for the current gesture can be
+     * generated. Ensure to add all motions from the gesture of interest to generate the correct
+     * prediction.
+     * @param event The received event
+     */
+    public void record(@NonNull MotionEvent event) {
+        nativeRecord(mPtr, event);
+    }
+
+    /**
+     * Get predicted events for all gestures that have been provided to the 'record' function.
+     * If events from multiple devices were sent to 'record', this will produce a separate
+     * {@link MotionEvent} for each device id. The returned list may be empty if no predictions for
+     * any of the added events are available.
+     * Predictions may not reach the requested timestamp if the confidence in the prediction results
+     * is low.
+     *
+     * @param predictionTimeNanos The time that the prediction should target, in the
+     * {@link android.os.SystemClock#uptimeMillis} time base, but in nanoseconds.
+     *
+     * @return the list of predicted motion events, for each device id. Ensure to check the
+     * historical data in addition to the latest ({@link MotionEvent#getX getX()},
+     * {@link MotionEvent#getY getY()}) coordinates for smoothest prediction curves. Empty list is
+     * returned if predictions are not supported, or not possible for the current set of gestures.
+     */
+    @NonNull
+    public List<MotionEvent> predict(long predictionTimeNanos) {
+        return Arrays.asList(nativePredict(mPtr, predictionTimeNanos));
+    }
+
+    /**
+     * Check whether this device supports motion predictions for the given source type.
+     *
+     * @param deviceId The input device id
+     * @param source The source of input events
+     * @return True if the current device supports predictions, false otherwise.
+     */
+    public boolean isPredictionAvailable(int deviceId, int source) {
+        // Device-specific override
+        if (!mContext.getResources().getBoolean(
+                com.android.internal.R.bool.config_enableMotionPrediction)) {
+            return false;
+        }
+        return nativeIsPredictionAvailable(mPtr, deviceId, source);
+    }
+
+    private static native long nativeInitialize(int offsetNanos);
+    private static native void nativeRecord(long nativePtr, MotionEvent event);
+    private static native MotionEvent[] nativePredict(long nativePtr, long predictionTimeNanos);
+    private static native boolean nativeIsPredictionAvailable(long nativePtr, int deviceId,
+            int source);
+    private static native long nativeGetNativeMotionPredictorFinalizer();
+}

core/jni/Android.bp

@@ -129,6 +129,7 @@ cc_library_shared {
                 "android_view_KeyCharacterMap.cpp",
                 "android_view_KeyEvent.cpp",
                 "android_view_MotionEvent.cpp",
+                "android_view_MotionPredictor.cpp",
                 "android_view_PointerIcon.cpp",
                 "android_view_Surface.cpp",
                 "android_view_SurfaceControl.cpp",
@@ -283,6 +284,7 @@ cc_library_shared {
                 "libhwui",
                 "libmediandk",
                 "libpermission",
+                "libPlatformProperties",
                 "libsensor",
                 "libinput",
                 "libcamera_client",

core/jni/AndroidRuntime.cpp

@@ -187,6 +187,7 @@ extern int register_android_view_InputQueue(JNIEnv* env);
 extern int register_android_view_KeyCharacterMap(JNIEnv *env);
 extern int register_android_view_KeyEvent(JNIEnv* env);
 extern int register_android_view_MotionEvent(JNIEnv* env);
+extern int register_android_view_MotionPredictor(JNIEnv* env);
 extern int register_android_view_PointerIcon(JNIEnv* env);
 extern int register_android_view_VelocityTracker(JNIEnv* env);
 extern int register_android_view_VerifiedKeyEvent(JNIEnv* env);
@@ -1643,6 +1644,7 @@ static const RegJNIRec gRegJNI[] = {
         REG_JNI(register_android_view_InputQueue),
         REG_JNI(register_android_view_KeyEvent),
         REG_JNI(register_android_view_MotionEvent),
+        REG_JNI(register_android_view_MotionPredictor),
         REG_JNI(register_android_view_PointerIcon),
         REG_JNI(register_android_view_VelocityTracker),
         REG_JNI(register_android_view_VerifiedKeyEvent),

core/jni/android_view_InputDevice.cpp

@@ -97,7 +97,6 @@ jobject android_view_InputDevice_create(JNIEnv* env, const InputDeviceInfo& devi
     return env->NewLocalRef(inputDeviceObj.get());
 }
 
-
 int register_android_view_InputDevice(JNIEnv* env)
 {
     gInputDeviceClassInfo.clazz = FindClassOrDie(env, "android/view/InputDevice");
@@ -108,9 +107,8 @@ int register_android_view_InputDevice(JNIEnv* env)
                                                   "String;ZIILandroid/view/KeyCharacterMap;Ljava/"
                                                   "lang/String;Ljava/lang/String;ZZZZZZ)V");
 
-    gInputDeviceClassInfo.addMotionRange = GetMethodIDOrDie(env, gInputDeviceClassInfo.clazz,
-            "addMotionRange", "(IIFFFFF)V");
-
+    gInputDeviceClassInfo.addMotionRange =
+            GetMethodIDOrDie(env, gInputDeviceClassInfo.clazz, "addMotionRange", "(IIFFFFF)V");
     return 0;
 }
 

core/jni/android_view_MotionEvent.cpp

@@ -102,6 +102,20 @@ jobject android_view_MotionEvent_obtainAsCopy(JNIEnv* env, const MotionEvent& ev
     return eventObj;
 }
 
+jobject android_view_MotionEvent_obtainFromNative(JNIEnv* env, std::unique_ptr<MotionEvent> event) {
+    if (event == nullptr) {
+        return nullptr;
+    }
+    jobject eventObj =
+            env->CallStaticObjectMethod(gMotionEventClassInfo.clazz, gMotionEventClassInfo.obtain);
+    if (env->ExceptionCheck() || !eventObj) {
+        LOGE_EX(env);
+        LOG_ALWAYS_FATAL("An exception occurred while obtaining a Java motion event.");
+    }
+    android_view_MotionEvent_setNativePtr(env, eventObj, event.release());
+    return eventObj;
+}
+
 status_t android_view_MotionEvent_recycle(JNIEnv* env, jobject eventObj) {
     env->CallVoidMethod(eventObj, gMotionEventClassInfo.recycle);
     if (env->ExceptionCheck()) {

core/jni/android_view_MotionEvent.h

@@ -28,6 +28,11 @@ class MotionEvent;
  * Returns NULL on error. */
 extern jobject android_view_MotionEvent_obtainAsCopy(JNIEnv* env, const MotionEvent& event);
 
+/* Obtains an instance of a Java MotionEvent object, taking over the ownership of the provided
+ * native MotionEvent instance. Crashes on error. */
+extern jobject android_view_MotionEvent_obtainFromNative(JNIEnv* env,
+                                                         std::unique_ptr<MotionEvent> event);
+
 /* Gets the underlying native MotionEvent instance within a DVM MotionEvent object.
  * Returns NULL if the event is NULL or if it is uninitialized. */
 extern MotionEvent* android_view_MotionEvent_getNativePtr(JNIEnv* env, jobject eventObj);

core/jni/android_view_MotionPredictor.cpp

@@ -0,0 +1,100 @@
+/*
+ * Copyright (C) 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.
+ */
+
+#define LOG_TAG "MotionPredictor-JNI"
+
+#include <input/Input.h>
+#include <input/MotionPredictor.h>
+
+#include "android_view_MotionEvent.h"
+#include "core_jni_converters.h"
+#include "core_jni_helpers.h"
+
+/**
+ * This file is a bridge from Java to native for MotionPredictor class.
+ * It should be pass-through only. Do not store any state or put any business logic into this file.
+ */
+
+namespace android {
+
+// ----------------------------------------------------------------------------
+
+static struct {
+    jclass clazz;
+} gMotionEventClassInfo;
+
+// ----------------------------------------------------------------------------
+
+static void release(void* ptr) {
+    delete reinterpret_cast<MotionPredictor*>(ptr);
+}
+
+static jlong android_view_MotionPredictor_nativeGetNativeMotionPredictorFinalizer(JNIEnv* env,
+                                                                                  jclass clazz) {
+    return reinterpret_cast<jlong>(release);
+}
+
+static jlong android_view_MotionPredictor_nativeInitialize(JNIEnv* env, jclass clazz,
+                                                           jint offsetNanos) {
+    const nsecs_t offset = static_cast<nsecs_t>(offsetNanos);
+    return reinterpret_cast<jlong>(new MotionPredictor(offset));
+}
+
+static void android_view_MotionPredictor_nativeRecord(JNIEnv* env, jclass clazz, jlong ptr,
+                                                      jobject event) {
+    MotionPredictor* predictor = reinterpret_cast<MotionPredictor*>(ptr);
+    MotionEvent* motionEvent = android_view_MotionEvent_getNativePtr(env, event);
+    predictor->record(*motionEvent);
+}
+
+static jobject android_view_MotionPredictor_nativePredict(JNIEnv* env, jclass clazz, jlong ptr,
+                                                          jlong predictionTimeNanos) {
+    MotionPredictor* predictor = reinterpret_cast<MotionPredictor*>(ptr);
+    return toJavaArray(env, predictor->predict(static_cast<nsecs_t>(predictionTimeNanos)),
+                       gMotionEventClassInfo.clazz, &android_view_MotionEvent_obtainFromNative);
+}
+
+static jboolean android_view_MotionPredictor_nativeIsPredictionAvailable(JNIEnv* env, jclass clazz,
+                                                                         jlong ptr, jint deviceId,
+                                                                         jint source) {
+    MotionPredictor* predictor = reinterpret_cast<MotionPredictor*>(ptr);
+    return predictor->isPredictionAvailable(static_cast<int32_t>(deviceId),
+                                            static_cast<int32_t>(source));
+}
+
+// ----------------------------------------------------------------------------
+
+static const std::array<JNINativeMethod, 5> gMotionPredictorMethods{{
+        /* name, signature, funcPtr */
+        {"nativeInitialize", "(I)J", (void*)android_view_MotionPredictor_nativeInitialize},
+        {"nativeGetNativeMotionPredictorFinalizer", "()J",
+         (void*)android_view_MotionPredictor_nativeGetNativeMotionPredictorFinalizer},
+        {"nativeRecord", "(JLandroid/view/MotionEvent;)V",
+         (void*)android_view_MotionPredictor_nativeRecord},
+        {"nativePredict", "(JJ)[Landroid/view/MotionEvent;",
+         (void*)android_view_MotionPredictor_nativePredict},
+        {"nativeIsPredictionAvailable", "(JII)Z",
+         (void*)android_view_MotionPredictor_nativeIsPredictionAvailable},
+}};
+
+int register_android_view_MotionPredictor(JNIEnv* env) {
+    jclass motionEventClazz = FindClassOrDie(env, "android/view/MotionEvent");
+    gMotionEventClassInfo.clazz = MakeGlobalRefOrDie(env, motionEventClazz);
+    return RegisterMethodsOrDie(env, "android/view/MotionPredictor", gMotionPredictorMethods.data(),
+                                gMotionPredictorMethods.size());
+}
+
+} // namespace android

core/jni/core_jni_converters.h

@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 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.
+ */
+
+#pragma once
+
+#include <nativehelper/scoped_local_ref.h>
+
+template <class T>
+static jobject toJavaArray(JNIEnv* env, std::vector<T>&& list, jclass clazz,
+                           jobject (*convert)(JNIEnv* env, T)) {
+    jobjectArray arr = env->NewObjectArray(list.size(), clazz, nullptr);
+    LOG_ALWAYS_FATAL_IF(arr == nullptr);
+    for (size_t i = 0; i < list.size(); i++) {
+        T& t = list[i];
+        ScopedLocalRef<jobject> javaObj(env, convert(env, std::move(t)));
+        env->SetObjectArrayElement(arr, i, javaObj.get());
+    }
+    return arr;
+}

core/res/res/values/config.xml

@@ -2344,6 +2344,24 @@
          display, this value should be true. -->
     <bool name="config_perDisplayFocusEnabled">false</bool>
 
+    <!-- Whether the system enables motion prediction. Only enable this after confirming that the
+         model works well on your device. To enable system-based prediction, set this value to true.
+          -->
+    <bool name="config_enableMotionPrediction">true</bool>
+
+    <!-- Additional offset to use for motion prediction, in nanoseconds. A positive number indicates
+         that the prediction will take place further in the future. For example, suppose a
+         MotionEvent arrives with timestamp t=1, and the current expected presentation time is t=2.
+         Typically, the prediction will target the presentation time, t=2. If you'd like to make
+         prediction more aggressive, you could set the offset to a positive number.
+         Setting the offset to 1 here would mean that the prediction will be done for time t=3.
+         A negative number may also be provided, to make the prediction less aggressive. In general,
+         the offset here should represent some built-in hardware delays that may not be accounted
+         for by the "expected present time". See also:
+         https://developer.android.com/reference/android/view/
+                  Choreographer.FrameTimeline#getExpectedPresentationTimeNanos() -->
+    <integer name="config_motionPredictionOffsetNanos">0</integer>
+
     <!-- Whether a software navigation bar should be shown. NOTE: in the future this may be
          autodetected from the Configuration. -->
     <bool name="config_showNavigationBar">false</bool>

core/res/res/values/symbols.xml

@@ -1684,6 +1684,8 @@
   <java-symbol type="bool" name="config_lockUiMode" />
   <java-symbol type="bool" name="config_reverseDefaultRotation" />
   <java-symbol type="bool" name="config_perDisplayFocusEnabled" />
+  <java-symbol type="bool" name="config_enableMotionPrediction" />
+  <java-symbol type="integer" name="config_motionPredictionOffsetNanos" />
   <java-symbol type="bool" name="config_showNavigationBar" />
   <java-symbol type="bool" name="config_supportAutoRotation" />
   <java-symbol type="bool" name="config_dockedStackDividerFreeSnapMode" />

tests/Input/Android.bp

@@ -18,6 +18,7 @@ android_test {
     static_libs: [
         "androidx.test.ext.junit",
         "androidx.test.rules",
+        "mockito-target-minus-junit4",
         "services.core.unboosted",
         "testables",
         "truth-prebuilt",

tests/Input/src/com/android/test/input/MotionPredictorTest.kt

@@ -0,0 +1,138 @@
+/*
+ * Copyright (C) 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 com.android.test.input
+
+import android.content.Context
+import android.content.res.Resources
+import android.os.SystemProperties
+import android.view.InputDevice
+import android.view.MotionEvent
+import android.view.MotionEvent.ACTION_DOWN
+import android.view.MotionEvent.ACTION_MOVE
+import android.view.MotionEvent.PointerCoords
+import android.view.MotionEvent.PointerProperties
+import android.view.MotionPredictor
+
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import androidx.test.filters.SmallTest
+import androidx.test.platform.app.InstrumentationRegistry
+
+import org.mockito.Mockito.mock
+import org.mockito.Mockito.`when`
+
+import org.junit.After
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+
+import java.time.Duration
+
+private fun getStylusMotionEvent(
+        eventTime: Duration,
+        action: Int,
+        x: Float,
+        y: Float,
+        ): MotionEvent{
+    // One-time: send a DOWN event
+    val pointerCount = 1
+    val properties = arrayOfNulls<MotionEvent.PointerProperties>(pointerCount)
+    val coords = arrayOfNulls<MotionEvent.PointerCoords>(pointerCount)
+
+    for (i in 0 until pointerCount) {
+        properties[i] = PointerProperties()
+        properties[i]!!.id = i
+        properties[i]!!.toolType = MotionEvent.TOOL_TYPE_STYLUS
+        coords[i] = PointerCoords()
+        coords[i]!!.x = x
+        coords[i]!!.y = y
+    }
+
+    return MotionEvent.obtain(/*downTime=*/0, eventTime.toMillis(), action, properties.size,
+                properties, coords, /*metaState=*/0, /*buttonState=*/0,
+                /*xPrecision=*/0f, /*yPrecision=*/0f, /*deviceId=*/0, /*edgeFlags=*/0,
+                InputDevice.SOURCE_STYLUS, /*flags=*/0)
+}
+
+private fun getPredictionContext(offset: Duration, enablePrediction: Boolean): Context {
+    val context = mock(Context::class.java)
+    val resources: Resources = mock(Resources::class.java)
+    `when`(context.getResources()).thenReturn(resources)
+    `when`(resources.getInteger(
+            com.android.internal.R.integer.config_motionPredictionOffsetNanos)).thenReturn(
+                offset.toNanos().toInt())
+    `when`(resources.getBoolean(
+            com.android.internal.R.bool.config_enableMotionPrediction)).thenReturn(enablePrediction)
+    return context
+}
+
+@RunWith(AndroidJUnit4::class)
+@SmallTest
+class MotionPredictorTest {
+    private val instrumentation = InstrumentationRegistry.getInstrumentation()
+    val initialPropertyValue = SystemProperties.get("persist.input.enable_motion_prediction")
+
+    @Before
+    fun setUp() {
+        instrumentation.uiAutomation.executeShellCommand(
+            "setprop persist.input.enable_motion_prediction true")
+    }
+
+    @After
+    fun tearDown() {
+        instrumentation.uiAutomation.executeShellCommand(
+            "setprop persist.input.enable_motion_prediction $initialPropertyValue")
+    }
+
+    /**
+     * In a typical usage, app will send the event to the predictor and then call .predict to draw
+     * a prediction. Here, we send 2 events to the predictor and check the returned event.
+     * Input:
+     * t = 0 x = 0 y = 0
+     * t = 1 x = 1 y = 2
+     * Output (expected):
+     * t = 3 x = 3 y = 6
+     *
+     * Historical data is ignored for simplicity.
+     */
+    @Test
+    fun testPredictedCoordinatesAndTime() {
+        val context = getPredictionContext(
+            /*offset=*/Duration.ofMillis(1), /*enablePrediction=*/true)
+        val predictor = MotionPredictor(context)
+        var eventTime = Duration.ofMillis(0)
+        val downEvent = getStylusMotionEvent(eventTime, ACTION_DOWN, /*x=*/0f, /*y=*/0f)
+        // ACTION_DOWN t=0 x=0 y=0
+        predictor.record(downEvent)
+
+        eventTime += Duration.ofMillis(1)
+        val moveEvent = getStylusMotionEvent(eventTime, ACTION_MOVE, /*x=*/1f, /*y=*/2f)
+        // ACTION_MOVE t=1 x=1 y=2
+        predictor.record(moveEvent)
+
+        val predicted = predictor.predict(Duration.ofMillis(2).toNanos())
+        assertEquals(1, predicted.size)
+        val event = predicted[0]
+        assertNotNull(event)
+
+        // Prediction will happen for t=3 (2 + 1, since offset is 1 and present time is 2)
+        assertEquals(3, event.eventTime)
+        assertEquals(3f, event.x, /*delta=*/0.001f)
+        assertEquals(6f, event.y, /*delta=*/0.001f)
+    }
+}

tests/MotionPrediction/Android.bp

@@ -0,0 +1,31 @@
+//
+// Copyright (C) 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: "MotionPrediction",
+    srcs: ["**/*.kt"],
+    platform_apis: true,
+    certificate: "platform",
+}

tests/MotionPrediction/AndroidManifest.xml

@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 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.motionprediction">
+
+    <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>

tests/MotionPrediction/OWNERS

@@ -0,0 +1 @@
+include platform/frameworks/base:/INPUT_OWNERS

tests/MotionPrediction/res/layout/activity_main.xml

@@ -0,0 +1,32 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 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.motionprediction.MainActivity">
+
+    <test.motionprediction.DrawingView
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:id="@+id/output" />
+
+</LinearLayout>

tests/MotionPrediction/res/values-w820dp/dimens.xml

@@ -0,0 +1,20 @@
+<!-- Copyright (C) 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>

tests/MotionPrediction/res/values/colors.xml

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 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>

tests/MotionPrediction/res/values/dimens.xml

@@ -0,0 +1,19 @@
+<!-- Copyright (C) 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>

tests/MotionPrediction/res/values/strings.xml

@@ -0,0 +1,17 @@
+<!-- Copyright (C) 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">Motion Prediction</string>
+</resources>

tests/MotionPrediction/res/values/styles.xml

@@ -0,0 +1,23 @@
+<!-- Copyright (C) 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>

tests/MotionPrediction/src/test/motionprediction/DrawingView.kt

@@ -0,0 +1,106 @@
+/*
+ * Copyright (C) 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.motionprediction
+
+import android.content.Context
+import android.graphics.Canvas
+import android.graphics.Color
+import android.graphics.Paint
+import android.util.AttributeSet
+import android.view.MotionEvent
+import android.view.MotionEvent.ACTION_DOWN
+import android.view.MotionPredictor
+import android.view.View
+
+import java.util.Vector
+
+private fun drawLine(canvas: Canvas, from: MotionEvent, to: MotionEvent, paint: Paint) {
+    canvas.apply {
+        val x0 = from.getX()
+        val y0 = from.getY()
+        val x1 = to.getX()
+        val y1 = to.getY()
+        // TODO: handle historical data
+        drawLine(x0, y0, x1, y1, paint)
+    }
+}
+
+/**
+ * Draw the current stroke and predicted values
+ */
+class DrawingView(context: Context, attrs: AttributeSet) : View(context, attrs) {
+    private val TAG = "DrawingView"
+
+    val events: MutableMap<Int, Vector<MotionEvent>> = mutableMapOf<Int, Vector<MotionEvent>>()
+
+    var isPredictionAvailable = false
+    private val predictor = MotionPredictor(getContext())
+
+    private var predictionPaint = Paint()
+    private var realPaint = Paint()
+
+    init {
+        setBackgroundColor(Color.WHITE)
+        predictionPaint.color = Color.BLACK
+        predictionPaint.setStrokeWidth(5f)
+        realPaint.color = Color.RED
+        realPaint.setStrokeWidth(5f)
+    }
+
+    private fun addEvent(event: MotionEvent) {
+        if (event.getActionMasked() == ACTION_DOWN) {
+            events.remove(event.deviceId)
+        }
+        var vec = events.getOrPut(event.deviceId) { Vector<MotionEvent>() }
+        vec.add(MotionEvent.obtain(event))
+        predictor.record(event)
+        invalidate()
+    }
+
+    public override fun onTouchEvent(event: MotionEvent): Boolean {
+        isPredictionAvailable = predictor.isPredictionAvailable(event.getDeviceId(),
+                                                                event.getSource())
+        addEvent(event)
+        return true
+    }
+
+    public override fun onDraw(canvas: Canvas) {
+        super.onDraw(canvas)
+        if (!isPredictionAvailable) {
+            canvas.apply {
+                drawRect(0f, 0f, 200f, 200f, realPaint)
+            }
+        }
+
+        var eventTime = 0L
+
+        // Draw real events
+        for ((_, vec) in events ) {
+            for (i in 1 until vec.size) {
+                drawLine(canvas, vec[i - 1], vec[i], realPaint)
+            }
+            eventTime = vec.lastElement().eventTime
+        }
+
+        // Draw predictions. Convert to nanos and hardcode to +20ms into the future
+        val predictionList = predictor.predict(eventTime * 1000000 + 20000000)
+        for (prediction in predictionList) {
+            val realEvents = events.get(prediction.deviceId)!!
+            drawLine(canvas, realEvents[realEvents.size - 1], prediction, predictionPaint)
+        }
+    }
+}

tests/MotionPrediction/src/test/motionprediction/MainActivity.kt

@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) 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.motionprediction
+
+import android.app.Activity
+import android.os.Bundle
+
+class MainActivity : Activity() {
+    val TAG = "MotionPrediction"
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContentView(R.layout.activity_main)
+    }
+}