Update DreamService -> DreamOverlayService connection to handle crashes

This change implements PersistentServiceConnection and
ObservableServiceConnection helper classes in framework for better
handling of crashes.

Fixes: 247103878
Test: manually by crashing systemui using adb while dreaming and
verifying that the overlay is visible
Test: atest com.android.internal.util.PersistentServiceConnectionTest
Test: atest com.android.internal.util.ObservableServiceConnectionTest

Change-Id: Ib9a7e8675e408c1724567335a3c186fe5c9f5f59
Merged-In: Ib9a7e8675e408c1724567335a3c186fe5c9f5f59

core/java/android/service/dreams/DreamService.java

@@ -31,9 +31,9 @@ import android.compat.annotation.UnsupportedAppUsage;
 import android.content.ComponentName;
 import android.content.Context;
 import android.content.Intent;
-import android.content.ServiceConnection;
 import android.content.pm.PackageManager;
 import android.content.pm.ServiceInfo;
+import android.content.res.Resources;
 import android.content.res.TypedArray;
 import android.content.res.XmlResourceParser;
 import android.graphics.drawable.Drawable;
@@ -68,6 +68,8 @@ import android.view.accessibility.AccessibilityEvent;
 
 import com.android.internal.R;
 import com.android.internal.util.DumpUtils;
+import com.android.internal.util.ObservableServiceConnection;
+import com.android.internal.util.PersistentServiceConnection;
 
 import org.xmlpull.v1.XmlPullParser;
 import org.xmlpull.v1.XmlPullParserException;
@@ -75,7 +77,8 @@ import org.xmlpull.v1.XmlPullParserException;
 import java.io.FileDescriptor;
 import java.io.IOException;
 import java.io.PrintWriter;
-import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.concurrent.Executor;
 import java.util.function.Consumer;
 
 /**
@@ -225,6 +228,7 @@ public class DreamService extends Service implements Window.Callback {
 
     /**
      * The default value for whether to show complications on the overlay.
+     *
      * @hide
      */
     public static final boolean DEFAULT_SHOW_COMPLICATIONS = false;
@@ -251,77 +255,66 @@ public class DreamService extends Service implements Window.Callback {
     private DreamServiceWrapper mDreamServiceWrapper;
     private Runnable mDispatchAfterOnAttachedToWindow;
 
-    private final OverlayConnection mOverlayConnection;
+    private OverlayConnection mOverlayConnection;
 
-    private static class OverlayConnection implements ServiceConnection {
+    private static class OverlayConnection extends PersistentServiceConnection<IDreamOverlay> {
         // Overlay set during onBind.
         private IDreamOverlay mOverlay;
-        // A Queue of pending requests to execute on the overlay.
-        private final ArrayDeque<Consumer<IDreamOverlay>> mRequests;
+        // A list of pending requests to execute on the overlay.
+        private final ArrayList<Consumer<IDreamOverlay>> mConsumers = new ArrayList<>();
 
-        private boolean mBound;
-
-        OverlayConnection() {
-            mRequests = new ArrayDeque<>();
-        }
-
-        public void bind(Context context, @Nullable ComponentName overlayService,
-                ComponentName dreamService) {
-            if (overlayService == null) {
-                return;
+        private final Callback<IDreamOverlay> mCallback = new Callback<IDreamOverlay>() {
+            @Override
+            public void onConnected(ObservableServiceConnection<IDreamOverlay> connection,
+                    IDreamOverlay service) {
+                mOverlay = service;
+                for (Consumer<IDreamOverlay> consumer : mConsumers) {
+                    consumer.accept(mOverlay);
+                }
             }
 
-            final ServiceInfo serviceInfo = fetchServiceInfo(context, dreamService);
-
-            final Intent overlayIntent = new Intent();
-            overlayIntent.setComponent(overlayService);
-            overlayIntent.putExtra(EXTRA_SHOW_COMPLICATIONS,
-                    fetchShouldShowComplications(context, serviceInfo));
-            overlayIntent.putExtra(EXTRA_DREAM_COMPONENT, dreamService);
-
-            context.bindService(overlayIntent,
-                    this, Context.BIND_AUTO_CREATE | Context.BIND_FOREGROUND_SERVICE);
-            mBound = true;
-        }
-
-        public void unbind(Context context) {
-            if (!mBound) {
-                return;
+            @Override
+            public void onDisconnected(ObservableServiceConnection<IDreamOverlay> connection,
+                    int reason) {
+                mOverlay = null;
             }
+        };
 
-            context.unbindService(this);
-            mBound = false;
-        }
-
-        public void request(Consumer<IDreamOverlay> request) {
-            mRequests.push(request);
-            evaluate();
-        }
-
-        private void evaluate() {
-            if (mOverlay == null) {
-                return;
-            }
-
-            // Any new requests that arrive during this loop will be processed synchronously after
-            // the loop exits.
-            while (!mRequests.isEmpty()) {
-                final Consumer<IDreamOverlay> request = mRequests.pop();
-                request.accept(mOverlay);
-            }
+        OverlayConnection(Context context,
+                Executor executor,
+                Handler handler,
+                ServiceTransformer<IDreamOverlay> transformer,
+                Intent serviceIntent,
+                int flags,
+                int minConnectionDurationMs,
+                int maxReconnectAttempts,
+                int baseReconnectDelayMs) {
+            super(context, executor, handler, transformer, serviceIntent, flags,
+                    minConnectionDurationMs,
+                    maxReconnectAttempts, baseReconnectDelayMs);
         }
 
         @Override
-        public void onServiceConnected(ComponentName name, IBinder service) {
-            // Store Overlay and execute pending requests.
-            mOverlay = IDreamOverlay.Stub.asInterface(service);
-            evaluate();
+        public boolean bind() {
+            addCallback(mCallback);
+            return super.bind();
         }
 
         @Override
-        public void onServiceDisconnected(ComponentName name) {
-            // Clear Overlay binder to prevent further request processing.
-            mOverlay = null;
+        public void unbind() {
+            removeCallback(mCallback);
+            super.unbind();
+        }
+
+        public void addConsumer(Consumer<IDreamOverlay> consumer) {
+            mConsumers.add(consumer);
+            if (mOverlay != null) {
+                consumer.accept(mOverlay);
+            }
+        }
+
+        public void removeConsumer(Consumer<IDreamOverlay> consumer) {
+            mConsumers.remove(consumer);
         }
     }
 
@@ -336,7 +329,6 @@ public class DreamService extends Service implements Window.Callback {
 
     public DreamService() {
         mDreamManager = IDreamManager.Stub.asInterface(ServiceManager.getService(DREAM_SERVICE));
-        mOverlayConnection = new OverlayConnection();
     }
 
     /**
@@ -532,7 +524,7 @@ public class DreamService extends Service implements Window.Callback {
         return mWindow;
     }
 
-   /**
+    /**
      * Inflates a layout resource and set it to be the content view for this Dream.
      * Behaves similarly to {@link android.app.Activity#setContentView(int)}.
      *
@@ -996,13 +988,33 @@ public class DreamService extends Service implements Window.Callback {
     public final IBinder onBind(Intent intent) {
         if (mDebug) Slog.v(mTag, "onBind() intent = " + intent);
         mDreamServiceWrapper = new DreamServiceWrapper();
+        final ComponentName overlayComponent = intent.getParcelableExtra(
+                EXTRA_DREAM_OVERLAY_COMPONENT, ComponentName.class);
 
         // Connect to the overlay service if present.
-        if (!mWindowless) {
-            mOverlayConnection.bind(
+        if (!mWindowless && overlayComponent != null) {
+            final Resources resources = getResources();
+            final ComponentName dreamService = new ComponentName(this, getClass());
+
+            final ServiceInfo serviceInfo = fetchServiceInfo(this, dreamService);
+            final Intent overlayIntent = new Intent()
+                    .setComponent(overlayComponent)
+                    .putExtra(EXTRA_SHOW_COMPLICATIONS,
+                            fetchShouldShowComplications(this, serviceInfo))
+                    .putExtra(EXTRA_DREAM_COMPONENT, dreamService);
+
+            mOverlayConnection = new OverlayConnection(
                     /* context= */ this,
-                    intent.getParcelableExtra(EXTRA_DREAM_OVERLAY_COMPONENT),
-                    new ComponentName(this, getClass()));
+                    getMainExecutor(),
+                    mHandler,
+                    IDreamOverlay.Stub::asInterface,
+                    overlayIntent,
+                    /* flags= */ Context.BIND_AUTO_CREATE | Context.BIND_FOREGROUND_SERVICE,
+                    resources.getInteger(R.integer.config_minDreamOverlayDurationMs),
+                    resources.getInteger(R.integer.config_dreamOverlayMaxReconnectAttempts),
+                    resources.getInteger(R.integer.config_dreamOverlayReconnectTimeoutMs));
+
+            mOverlayConnection.bind();
         }
 
         return mDreamServiceWrapper;
@@ -1011,7 +1023,9 @@ public class DreamService extends Service implements Window.Callback {
     @Override
     public boolean onUnbind(Intent intent) {
         // We must unbind from any overlay connection if we are unbound before finishing.
-        mOverlayConnection.unbind(this);
+        if (mOverlayConnection != null) {
+            mOverlayConnection.unbind();
+        }
 
         return super.onUnbind(intent);
     }
@@ -1040,7 +1054,9 @@ public class DreamService extends Service implements Window.Callback {
         }
         mFinished = true;
 
-        mOverlayConnection.unbind(this);
+        if (mOverlayConnection != null) {
+            mOverlayConnection.unbind();
+        }
 
         if (mDreamToken == null) {
             Slog.w(mTag, "Finish was called before the dream was attached.");
@@ -1337,19 +1353,24 @@ public class DreamService extends Service implements Window.Callback {
 
         mWindow.getDecorView().addOnAttachStateChangeListener(
                 new View.OnAttachStateChangeListener() {
+                    private Consumer<IDreamOverlay> mDreamStartOverlayConsumer;
+
                     @Override
                     public void onViewAttachedToWindow(View v) {
                         mDispatchAfterOnAttachedToWindow.run();
 
-                        // Request the DreamOverlay be told to dream with dream's window parameters
-                        // once the window has been attached.
-                        mOverlayConnection.request(overlay -> {
-                            try {
-                                overlay.startDream(mWindow.getAttributes(), mOverlayCallback);
-                            } catch (RemoteException e) {
-                                Log.e(mTag, "could not send window attributes:" + e);
-                            }
-                        });
+                        if (mOverlayConnection != null) {
+                            // Request the DreamOverlay be told to dream with dream's window
+                            // parameters once the window has been attached.
+                            mDreamStartOverlayConsumer = overlay -> {
+                                try {
+                                    overlay.startDream(mWindow.getAttributes(), mOverlayCallback);
+                                } catch (RemoteException e) {
+                                    Log.e(mTag, "could not send window attributes:" + e);
+                                }
+                            };
+                            mOverlayConnection.addConsumer(mDreamStartOverlayConsumer);
+                        }
                     }
 
                     @Override
@@ -1362,6 +1383,9 @@ public class DreamService extends Service implements Window.Callback {
                             mActivity = null;
                             finish();
                         }
+                        if (mOverlayConnection != null && mDreamStartOverlayConsumer != null) {
+                            mOverlayConnection.removeConsumer(mDreamStartOverlayConsumer);
+                        }
                     }
                 });
     }

core/java/com/android/internal/util/ObservableServiceConnection.java

@@ -0,0 +1,258 @@
+/*
+ * Copyright (C) 2022 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.internal.util;
+
+import android.annotation.CallbackExecutor;
+import android.annotation.IntDef;
+import android.annotation.NonNull;
+import android.content.ComponentName;
+import android.content.Context;
+import android.content.Intent;
+import android.content.ServiceConnection;
+import android.os.IBinder;
+
+import com.android.internal.annotations.GuardedBy;
+import com.android.internal.util.CallbackRegistry.NotifierCallback;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.util.concurrent.Executor;
+
+/**
+ * {@link ObservableServiceConnection} is a concrete implementation of {@link ServiceConnection}
+ * that enables monitoring the status of a binder connection. It also aides in automatically
+ * converting a proxy into an internal wrapper type.
+ *
+ * @param <T> The type of the wrapper over the resulting service.
+ */
+public class ObservableServiceConnection<T> implements ServiceConnection {
+    /**
+     * An interface for converting the service proxy into a given internal wrapper type.
+     *
+     * @param <T> The type of the wrapper over the resulting service.
+     */
+    public interface ServiceTransformer<T> {
+        /**
+         * Called to convert the service proxy to the wrapper type.
+         *
+         * @param service The service proxy to create the wrapper type from.
+         * @return The wrapper type.
+         */
+        T convert(IBinder service);
+    }
+
+    /**
+     * An interface for listening to the connection status.
+     *
+     * @param <T> The wrapper type.
+     */
+    public interface Callback<T> {
+        /**
+         * Invoked when the service has been successfully connected to.
+         *
+         * @param connection The {@link ObservableServiceConnection} instance that is now connected
+         * @param service    The service proxy converted into the typed wrapper.
+         */
+        void onConnected(ObservableServiceConnection<T> connection, T service);
+
+        /**
+         * Invoked when the service has been disconnected.
+         *
+         * @param connection The {@link ObservableServiceConnection} that is now disconnected.
+         * @param reason     The reason for the disconnection.
+         */
+        void onDisconnected(ObservableServiceConnection<T> connection,
+                @DisconnectReason int reason);
+    }
+
+    /**
+     * Default state, service has not yet disconnected.
+     */
+    public static final int DISCONNECT_REASON_NONE = 0;
+    /**
+     * Disconnection was due to the resulting binding being {@code null}.
+     */
+    public static final int DISCONNECT_REASON_NULL_BINDING = 1;
+    /**
+     * Disconnection was due to the remote end disconnecting.
+     */
+    public static final int DISCONNECT_REASON_DISCONNECTED = 2;
+    /**
+     * Disconnection due to the binder dying.
+     */
+    public static final int DISCONNECT_REASON_BINDING_DIED = 3;
+    /**
+     * Disconnection from an explicit unbinding.
+     */
+    public static final int DISCONNECT_REASON_UNBIND = 4;
+
+    @Retention(RetentionPolicy.SOURCE)
+    @IntDef({
+            DISCONNECT_REASON_NONE,
+            DISCONNECT_REASON_NULL_BINDING,
+            DISCONNECT_REASON_DISCONNECTED,
+            DISCONNECT_REASON_BINDING_DIED,
+            DISCONNECT_REASON_UNBIND
+    })
+    public @interface DisconnectReason {
+    }
+
+    private final Object mLock = new Object();
+    private final Context mContext;
+    private final Executor mExecutor;
+    private final ServiceTransformer<T> mTransformer;
+    private final Intent mServiceIntent;
+    private final int mFlags;
+
+    @GuardedBy("mLock")
+    private T mService;
+    @GuardedBy("mLock")
+    private boolean mBoundCalled = false;
+    @GuardedBy("mLock")
+    private int mLastDisconnectReason = DISCONNECT_REASON_NONE;
+
+    private final CallbackRegistry<Callback<T>, ObservableServiceConnection<T>, T>
+            mCallbackRegistry = new CallbackRegistry<>(
+            new NotifierCallback<Callback<T>, ObservableServiceConnection<T>, T>() {
+                    @Override
+                    public void onNotifyCallback(Callback<T> callback,
+                            ObservableServiceConnection<T> sender,
+                            int disconnectReason, T service) {
+                        mExecutor.execute(() -> {
+                            synchronized (mLock) {
+                                if (service != null) {
+                                    callback.onConnected(sender, service);
+                                } else if (mLastDisconnectReason != DISCONNECT_REASON_NONE) {
+                                    callback.onDisconnected(sender, disconnectReason);
+                                }
+                            }
+                        });
+                    }
+                });
+
+    /**
+     * Default constructor for {@link ObservableServiceConnection}.
+     *
+     * @param context     The context from which the service will be bound with.
+     * @param executor    The executor for connection callbacks to be delivered on
+     * @param transformer A {@link ObservableServiceConnection.ServiceTransformer} for transforming
+     *                    the resulting service into a desired type.
+     */
+    public ObservableServiceConnection(@NonNull Context context,
+            @NonNull @CallbackExecutor Executor executor,
+            @NonNull ServiceTransformer<T> transformer,
+            Intent serviceIntent,
+            int flags) {
+        mContext = context;
+        mExecutor = executor;
+        mTransformer = transformer;
+        mServiceIntent = serviceIntent;
+        mFlags = flags;
+    }
+
+    /**
+     * Initiate binding to the service.
+     *
+     * @return {@code true} if initiating binding succeed, {@code false} if the binding failed or
+     * if this service is already bound. Regardless of the return value, you should later call
+     * {@link #unbind()} to release the connection.
+     */
+    public boolean bind() {
+        synchronized (mLock) {
+            if (mBoundCalled) {
+                return false;
+            }
+            final boolean bindResult =
+                    mContext.bindService(mServiceIntent, mFlags, mExecutor, this);
+            mBoundCalled = true;
+            return bindResult;
+        }
+    }
+
+    /**
+     * Disconnect from the service if bound.
+     */
+    public void unbind() {
+        onDisconnected(DISCONNECT_REASON_UNBIND);
+    }
+
+    /**
+     * Adds a callback for receiving connection updates.
+     *
+     * @param callback The {@link Callback} to receive future updates.
+     */
+    public void addCallback(Callback<T> callback) {
+        mCallbackRegistry.add(callback);
+        mExecutor.execute(() -> {
+            synchronized (mLock) {
+                if (mService != null) {
+                    callback.onConnected(this, mService);
+                } else if (mLastDisconnectReason != DISCONNECT_REASON_NONE) {
+                    callback.onDisconnected(this, mLastDisconnectReason);
+                }
+            }
+        });
+    }
+
+    /**
+     * Removes previously added callback from receiving future connection updates.
+     *
+     * @param callback The {@link Callback} to be removed.
+     */
+    public void removeCallback(Callback<T> callback) {
+        synchronized (mLock) {
+            mCallbackRegistry.remove(callback);
+        }
+    }
+
+    private void onDisconnected(@DisconnectReason int reason) {
+        synchronized (mLock) {
+            if (!mBoundCalled) {
+                return;
+            }
+            mBoundCalled = false;
+            mLastDisconnectReason = reason;
+            mContext.unbindService(this);
+            mService = null;
+            mCallbackRegistry.notifyCallbacks(this, reason, null);
+        }
+    }
+
+    @Override
+    public final void onServiceConnected(ComponentName name, IBinder service) {
+        synchronized (mLock) {
+            mService = mTransformer.convert(service);
+            mLastDisconnectReason = DISCONNECT_REASON_NONE;
+            mCallbackRegistry.notifyCallbacks(this, mLastDisconnectReason, mService);
+        }
+    }
+
+    @Override
+    public final void onServiceDisconnected(ComponentName name) {
+        onDisconnected(DISCONNECT_REASON_DISCONNECTED);
+    }
+
+    @Override
+    public final void onBindingDied(ComponentName name) {
+        onDisconnected(DISCONNECT_REASON_BINDING_DIED);
+    }
+
+    @Override
+    public final void onNullBinding(ComponentName name) {
+        onDisconnected(DISCONNECT_REASON_NULL_BINDING);
+    }
+}

core/java/com/android/internal/util/PersistentServiceConnection.java

@@ -0,0 +1,200 @@
+/*
+ * Copyright (C) 2022 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.internal.util;
+
+import android.content.Context;
+import android.content.Intent;
+import android.content.ServiceConnection;
+import android.os.Handler;
+import android.os.SystemClock;
+
+import com.android.internal.annotations.GuardedBy;
+import com.android.internal.annotations.VisibleForTesting;
+
+import java.util.concurrent.Executor;
+
+/**
+ * {@link PersistentServiceConnection} is a concrete implementation of {@link ServiceConnection}
+ * that maintains the binder connection by handling reconnection when a failure occurs.
+ *
+ * @param <T> The transformed connection type handled by the service.
+ *
+ * When the target process is killed (by OOM-killer, force-stopped, crash, etc..) then this class
+ * will trigger a reconnection to the target. This should be used carefully.
+ *
+ * NOTE: This class does *not* handle package-updates -- i.e. even if the binding dies due to
+ * the target package being updated, this class won't reconnect.  This is because this class doesn't
+ * know what to do when the service component has gone missing, for example.  If the user of this
+ * class wants to restore the connection, then it should call {@link #unbind()} and {@link #bind}
+ * explicitly.
+ */
+public class PersistentServiceConnection<T> extends ObservableServiceConnection<T> {
+    private final Callback<T> mConnectionCallback = new Callback<T>() {
+        private long mConnectedTime;
+
+        @Override
+        public void onConnected(ObservableServiceConnection<T> connection, T service) {
+            mConnectedTime = mInjector.uptimeMillis();
+        }
+
+        @Override
+        public void onDisconnected(ObservableServiceConnection<T> connection,
+                @DisconnectReason int reason) {
+            if (reason == DISCONNECT_REASON_UNBIND) return;
+            synchronized (mLock) {
+                if ((mInjector.uptimeMillis() - mConnectedTime) > mMinConnectionDurationMs) {
+                    mReconnectAttempts = 0;
+                    bindInternalLocked();
+                } else {
+                    scheduleConnectionAttemptLocked();
+                }
+            }
+        }
+    };
+
+    private final Object mLock = new Object();
+    private final Injector mInjector;
+    private final Handler mHandler;
+    private final int mMinConnectionDurationMs;
+    private final int mMaxReconnectAttempts;
+    private final int mBaseReconnectDelayMs;
+    @GuardedBy("mLock")
+    private int mReconnectAttempts;
+    @GuardedBy("mLock")
+    private Object mCancelToken;
+
+    private final Runnable mConnectRunnable = new Runnable() {
+        @Override
+        public void run() {
+            synchronized (mLock) {
+                mCancelToken = null;
+                bindInternalLocked();
+            }
+        }
+    };
+
+    /**
+     * Default constructor for {@link PersistentServiceConnection}.
+     *
+     * @param context     The context from which the service will be bound with.
+     * @param executor    The executor for connection callbacks to be delivered on
+     * @param transformer A {@link ServiceTransformer} for transforming
+     */
+    public PersistentServiceConnection(Context context,
+            Executor executor,
+            Handler handler,
+            ServiceTransformer<T> transformer,
+            Intent serviceIntent,
+            int flags,
+            int minConnectionDurationMs,
+            int maxReconnectAttempts,
+            int baseReconnectDelayMs) {
+        this(context,
+                executor,
+                handler,
+                transformer,
+                serviceIntent,
+                flags,
+                minConnectionDurationMs,
+                maxReconnectAttempts,
+                baseReconnectDelayMs,
+                new Injector());
+    }
+
+    @VisibleForTesting
+    public PersistentServiceConnection(
+            Context context,
+            Executor executor,
+            Handler handler,
+            ServiceTransformer<T> transformer,
+            Intent serviceIntent,
+            int flags,
+            int minConnectionDurationMs,
+            int maxReconnectAttempts,
+            int baseReconnectDelayMs,
+            Injector injector) {
+        super(context, executor, transformer, serviceIntent, flags);
+        mHandler = handler;
+        mMinConnectionDurationMs = minConnectionDurationMs;
+        mMaxReconnectAttempts = maxReconnectAttempts;
+        mBaseReconnectDelayMs = baseReconnectDelayMs;
+        mInjector = injector;
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public boolean bind() {
+        synchronized (mLock) {
+            addCallback(mConnectionCallback);
+            mReconnectAttempts = 0;
+            return bindInternalLocked();
+        }
+    }
+
+    @GuardedBy("mLock")
+    private boolean bindInternalLocked() {
+        return super.bind();
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public void unbind() {
+        synchronized (mLock) {
+            removeCallback(mConnectionCallback);
+            cancelPendingConnectionAttemptLocked();
+            super.unbind();
+        }
+    }
+
+    @GuardedBy("mLock")
+    private void cancelPendingConnectionAttemptLocked() {
+        if (mCancelToken != null) {
+            mHandler.removeCallbacksAndMessages(mCancelToken);
+            mCancelToken = null;
+        }
+    }
+
+    @GuardedBy("mLock")
+    private void scheduleConnectionAttemptLocked() {
+        cancelPendingConnectionAttemptLocked();
+
+        if (mReconnectAttempts >= mMaxReconnectAttempts) {
+            return;
+        }
+
+        final long reconnectDelayMs =
+                (long) Math.scalb(mBaseReconnectDelayMs, mReconnectAttempts);
+
+        mCancelToken = new Object();
+        mHandler.postDelayed(mConnectRunnable, mCancelToken, reconnectDelayMs);
+        mReconnectAttempts++;
+    }
+
+    /**
+     * Injector for testing
+     */
+    @VisibleForTesting
+    public static class Injector {
+        /**
+         * Returns milliseconds since boot, not counting time spent in deep sleep. Can be overridden
+         * in tests with a fake clock.
+         */
+        public long uptimeMillis() {
+            return SystemClock.uptimeMillis();
+        }
+    }
+}

core/res/res/values/config.xml

@@ -553,6 +553,14 @@
     <!-- If this is true, then keep dreaming when undocking. -->
     <bool name="config_keepDreamingWhenUndocking">false</bool>
 
+    <!-- The timeout (in ms) to wait before attempting to reconnect to the dream overlay service if
+         it becomes disconnected -->
+    <integer name="config_dreamOverlayReconnectTimeoutMs">1000</integer> <!-- 1 second -->
+    <!-- The maximum number of times to attempt reconnecting to the dream overlay service -->
+    <integer name="config_dreamOverlayMaxReconnectAttempts">3</integer>
+    <!-- The duration after which the dream overlay connection should be considered stable -->
+    <integer name="config_minDreamOverlayDurationMs">10000</integer> <!-- 10 seconds -->
+
     <!-- Auto-rotation behavior -->
 
     <!-- If true, enables auto-rotation features using the accelerometer.

core/res/res/values/symbols.xml

@@ -2239,6 +2239,9 @@
   <java-symbol type="array" name="config_supportedDreamComplications" />
   <java-symbol type="array" name="config_disabledDreamComponents" />
   <java-symbol type="bool" name="config_dismissDreamOnActivityStart" />
+  <java-symbol type="integer" name="config_dreamOverlayReconnectTimeoutMs" />
+  <java-symbol type="integer" name="config_dreamOverlayMaxReconnectAttempts" />
+  <java-symbol type="integer" name="config_minDreamOverlayDurationMs" />
   <java-symbol type="string" name="config_loggable_dream_prefix" />
   <java-symbol type="string" name="config_dozeComponent" />
   <java-symbol type="string" name="enable_explore_by_touch_warning_title" />

core/tests/utiltests/Android.bp

@@ -34,6 +34,7 @@ android_test {
         "mockito-target-minus-junit4",
         "androidx.test.ext.junit",
         "truth-prebuilt",
+        "servicestests-utils",
     ],
 
     libs: [

core/tests/utiltests/src/com/android/internal/util/ObservableServiceConnectionTest.java

@@ -0,0 +1,226 @@
+/*
+ * Copyright (C) 2022 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.internal.util;
+
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.any;
+import static org.mockito.Mockito.clearInvocations;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import android.content.ComponentName;
+import android.content.Context;
+import android.content.Intent;
+import android.os.IBinder;
+
+import androidx.test.filters.SmallTest;
+
+import com.android.internal.util.ObservableServiceConnection.ServiceTransformer;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import java.util.ArrayDeque;
+import java.util.Objects;
+import java.util.Queue;
+import java.util.concurrent.Executor;
+
+@SmallTest
+public class ObservableServiceConnectionTest {
+    private static final ComponentName COMPONENT_NAME =
+            new ComponentName("test.package", "component");
+
+    public static class Foo {
+        int mValue;
+
+        Foo(int value) {
+            mValue = value;
+        }
+
+        @Override
+        public boolean equals(Object o) {
+            if (this == o) return true;
+            if (!(o instanceof Foo)) return false;
+            Foo foo = (Foo) o;
+            return mValue == foo.mValue;
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hash(mValue);
+        }
+    }
+
+
+    @Mock
+    private Context mContext;
+    @Mock
+    private Intent mIntent;
+    @Mock
+    private Foo mResult;
+    @Mock
+    private IBinder mBinder;
+    @Mock
+    private ServiceTransformer<Foo> mTransformer;
+    @Mock
+    private ObservableServiceConnection.Callback<Foo> mCallback;
+    private final FakeExecutor mExecutor = new FakeExecutor();
+    private ObservableServiceConnection<Foo> mConnection;
+
+    @Before
+    public void setUp() throws Exception {
+        MockitoAnnotations.initMocks(this);
+        mConnection = new ObservableServiceConnection<>(
+                mContext,
+                mExecutor,
+                mTransformer,
+                mIntent,
+                /* flags= */ Context.BIND_AUTO_CREATE);
+    }
+
+    @After
+    public void tearDown() {
+        mExecutor.clearAll();
+    }
+
+    @Test
+    public void testConnect() {
+        // Register twice to ensure only one callback occurs.
+        mConnection.addCallback(mCallback);
+        mConnection.addCallback(mCallback);
+
+        mExecutor.runAll();
+        mConnection.bind();
+
+        // Ensure that no callbacks happen before connection.
+        verify(mCallback, never()).onConnected(any(), any());
+        verify(mCallback, never()).onDisconnected(any(), anyInt());
+
+        when(mTransformer.convert(mBinder)).thenReturn(mResult);
+        mConnection.onServiceConnected(COMPONENT_NAME, mBinder);
+
+        mExecutor.runAll();
+        verify(mCallback, times(1)).onConnected(mConnection, mResult);
+    }
+
+    @Test
+    public void testDisconnectBeforeBind() {
+        mConnection.addCallback(mCallback);
+        mExecutor.runAll();
+        mConnection.onServiceDisconnected(COMPONENT_NAME);
+        mExecutor.runAll();
+        // Disconnects before binds should be ignored.
+        verify(mCallback, never()).onDisconnected(eq(mConnection), anyInt());
+    }
+
+    @Test
+    public void testDisconnect() {
+        mConnection.addCallback(mCallback);
+        mExecutor.runAll();
+        mConnection.bind();
+        mConnection.onServiceDisconnected(COMPONENT_NAME);
+
+        // Ensure the callback doesn't get triggered until the executor runs.
+        verify(mCallback, never()).onDisconnected(eq(mConnection), anyInt());
+        mExecutor.runAll();
+        // Ensure proper disconnect reason reported.
+        verify(mCallback, times(1)).onDisconnected(mConnection,
+                ObservableServiceConnection.DISCONNECT_REASON_DISCONNECTED);
+        // Verify unbound from service.
+        verify(mContext, times(1)).unbindService(mConnection);
+
+        clearInvocations(mContext);
+        // Ensure unbind after disconnect has no effect on the connection
+        mConnection.unbind();
+        verify(mContext, never()).unbindService(mConnection);
+    }
+
+    @Test
+    public void testBindingDied() {
+        mConnection.addCallback(mCallback);
+        mExecutor.runAll();
+        mConnection.bind();
+        mConnection.onBindingDied(COMPONENT_NAME);
+
+        // Ensure the callback doesn't get triggered until the executor runs.
+        verify(mCallback, never()).onDisconnected(eq(mConnection), anyInt());
+        mExecutor.runAll();
+        // Ensure proper disconnect reason reported.
+        verify(mCallback, times(1)).onDisconnected(mConnection,
+                ObservableServiceConnection.DISCONNECT_REASON_BINDING_DIED);
+        // Verify unbound from service.
+        verify(mContext, times(1)).unbindService(mConnection);
+    }
+
+    @Test
+    public void testNullBinding() {
+        mConnection.addCallback(mCallback);
+        mExecutor.runAll();
+        mConnection.bind();
+        mConnection.onNullBinding(COMPONENT_NAME);
+
+        // Ensure the callback doesn't get triggered until the executor runs.
+        verify(mCallback, never()).onDisconnected(eq(mConnection), anyInt());
+        mExecutor.runAll();
+        // Ensure proper disconnect reason reported.
+        verify(mCallback, times(1)).onDisconnected(mConnection,
+                ObservableServiceConnection.DISCONNECT_REASON_NULL_BINDING);
+        // Verify unbound from service.
+        verify(mContext, times(1)).unbindService(mConnection);
+    }
+
+    @Test
+    public void testUnbind() {
+        mConnection.addCallback(mCallback);
+        mExecutor.runAll();
+        mConnection.bind();
+        mConnection.unbind();
+
+        // Ensure the callback doesn't get triggered until the executor runs.
+        verify(mCallback, never()).onDisconnected(eq(mConnection), anyInt());
+        mExecutor.runAll();
+        verify(mCallback).onDisconnected(mConnection,
+                ObservableServiceConnection.DISCONNECT_REASON_UNBIND);
+    }
+
+    static class FakeExecutor implements Executor {
+        private final Queue<Runnable> mQueue = new ArrayDeque<>();
+
+        @Override
+        public void execute(Runnable command) {
+            mQueue.add(command);
+        }
+
+        public void runAll() {
+            while (!mQueue.isEmpty()) {
+                mQueue.remove().run();
+            }
+        }
+
+        public void clearAll() {
+            while (!mQueue.isEmpty()) {
+                mQueue.remove();
+            }
+        }
+    }
+}

core/tests/utiltests/src/com/android/internal/util/PersistentServiceConnectionTest.java

@@ -0,0 +1,215 @@
+/*
+ * Copyright (C) 2022 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.internal.util;
+
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.ArgumentMatchers.anyLong;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.any;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import android.content.ComponentName;
+import android.content.Context;
+import android.content.Intent;
+import android.os.IBinder;
+
+import com.android.internal.util.ObservableServiceConnection.ServiceTransformer;
+import com.android.server.testutils.OffsettableClock;
+import com.android.server.testutils.TestHandler;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import java.util.ArrayDeque;
+import java.util.Queue;
+import java.util.concurrent.Executor;
+
+public class PersistentServiceConnectionTest {
+    private static final ComponentName COMPONENT_NAME =
+            new ComponentName("test.package", "component");
+    private static final int MAX_RETRIES = 2;
+    private static final int RETRY_DELAY_MS = 1000;
+    private static final int CONNECTION_MIN_DURATION_MS = 5000;
+    private PersistentServiceConnection<Proxy> mConnection;
+
+    public static class Proxy {
+    }
+
+    @Mock
+    private Context mContext;
+    @Mock
+    private Intent mIntent;
+    @Mock
+    private Proxy mResult;
+    @Mock
+    private IBinder mBinder;
+    @Mock
+    private ServiceTransformer<Proxy> mTransformer;
+    @Mock
+    private ObservableServiceConnection.Callback<Proxy> mCallback;
+    private TestHandler mHandler;
+    private final FakeExecutor mFakeExecutor = new FakeExecutor();
+    private OffsettableClock mClock;
+
+    @Before
+    public void setup() {
+        MockitoAnnotations.initMocks(this);
+
+        mClock = new OffsettableClock.Stopped();
+        mHandler = spy(new TestHandler(null, mClock));
+
+        mConnection = new PersistentServiceConnection<>(
+                mContext,
+                mFakeExecutor,
+                mHandler,
+                mTransformer,
+                mIntent,
+                /* flags= */ Context.BIND_AUTO_CREATE,
+                CONNECTION_MIN_DURATION_MS,
+                MAX_RETRIES,
+                RETRY_DELAY_MS,
+                new TestInjector(mClock));
+
+        mClock.fastForward(1000);
+        mConnection.addCallback(mCallback);
+        when(mTransformer.convert(mBinder)).thenReturn(mResult);
+    }
+
+    @After
+    public void tearDown() {
+        mFakeExecutor.clearAll();
+    }
+
+    @Test
+    public void testConnect() {
+        mConnection.bind();
+        mConnection.onServiceConnected(COMPONENT_NAME, mBinder);
+        mFakeExecutor.runAll();
+        // Ensure that we did not schedule a retry
+        verify(mHandler, never()).postDelayed(any(), anyLong());
+    }
+
+    @Test
+    public void testRetryOnBindFailure() {
+        mConnection.bind();
+
+        verify(mContext, times(1)).bindService(
+                eq(mIntent),
+                anyInt(),
+                eq(mFakeExecutor),
+                eq(mConnection));
+
+        // After disconnect, a reconnection should be attempted after the RETRY_DELAY_MS
+        mConnection.onServiceDisconnected(COMPONENT_NAME);
+        mFakeExecutor.runAll();
+        advanceTime(RETRY_DELAY_MS);
+        verify(mContext, times(2)).bindService(
+                eq(mIntent),
+                anyInt(),
+                eq(mFakeExecutor),
+                eq(mConnection));
+
+        // Reconnect attempt #2
+        mConnection.onServiceDisconnected(COMPONENT_NAME);
+        mFakeExecutor.runAll();
+        advanceTime(RETRY_DELAY_MS * 2);
+        verify(mContext, times(3)).bindService(
+                eq(mIntent),
+                anyInt(),
+                eq(mFakeExecutor),
+                eq(mConnection));
+
+        // There should be no more reconnect attempts, since the maximum is 2
+        mConnection.onServiceDisconnected(COMPONENT_NAME);
+        mFakeExecutor.runAll();
+        advanceTime(RETRY_DELAY_MS * 4);
+        verify(mContext, times(3)).bindService(
+                eq(mIntent),
+                anyInt(),
+                eq(mFakeExecutor),
+                eq(mConnection));
+    }
+
+    @Test
+    public void testManualUnbindDoesNotReconnect() {
+        mConnection.bind();
+
+        verify(mContext, times(1)).bindService(
+                eq(mIntent),
+                anyInt(),
+                eq(mFakeExecutor),
+                eq(mConnection));
+
+        mConnection.unbind();
+        // Ensure that disconnection after unbind does not reconnect.
+        mConnection.onServiceDisconnected(COMPONENT_NAME);
+        mFakeExecutor.runAll();
+        advanceTime(RETRY_DELAY_MS);
+
+        verify(mContext, times(1)).bindService(
+                eq(mIntent),
+                anyInt(),
+                eq(mFakeExecutor),
+                eq(mConnection));
+    }
+
+    private void advanceTime(long millis) {
+        mClock.fastForward(millis);
+        mHandler.timeAdvance();
+    }
+
+    static class TestInjector extends PersistentServiceConnection.Injector {
+        private final OffsettableClock mClock;
+
+        TestInjector(OffsettableClock clock) {
+            mClock = clock;
+        }
+
+        @Override
+        public long uptimeMillis() {
+            return mClock.now();
+        }
+    }
+
+    static class FakeExecutor implements Executor {
+        private final Queue<Runnable> mQueue = new ArrayDeque<>();
+
+        @Override
+        public void execute(Runnable command) {
+            mQueue.add(command);
+        }
+
+        public void runAll() {
+            while (!mQueue.isEmpty()) {
+                mQueue.remove().run();
+            }
+        }
+
+        public void clearAll() {
+            while (!mQueue.isEmpty()) {
+                mQueue.remove();
+            }
+        }
+    }
+}