Migrate back animation to shell transition

When back animation finished, it will invoke the real back callback and
cause a new transition started.

In this CL, we introduce the back transition handler to consume the
incoming transition request and takeover the whole transition if the
transition info contians same departing window token.

This also seperated the behaviors of enabled/disabled shell
transition.

Bug: 238475694
Test: Enabled shell transition, atest BackNavigationControllerTests
      BackAnimationControllerTest
Change-Id: I57e7c89ce6cb7a99ab3af403704b9dd948f26151

core/java/android/window/BackNavigationInfo.java

@@ -89,6 +89,8 @@ public final class BackNavigationInfo implements Parcelable {
     @Nullable
     private final IOnBackInvokedCallback mOnBackInvokedCallback;
     private final boolean mPrepareRemoteAnimation;
+    @Nullable
+    private WindowContainerToken mDepartingWindowContainerToken;
 
     /**
      * Create a new {@link BackNavigationInfo} instance.
@@ -97,6 +99,7 @@ public final class BackNavigationInfo implements Parcelable {
      * @param onBackNavigationDone    The callback to be called once the client is done with the
      *                                back preview.
      * @param onBackInvokedCallback   The back callback registered by the current top level window.
+     * @param departingWindowContainerToken The {@link WindowContainerToken} of departing window.
      * @param isPrepareRemoteAnimation  Return whether the core is preparing a back gesture
      *                                  animation, if true, the caller of startBackNavigation should
      *                                  be expected to receive an animation start callback.
@@ -104,11 +107,13 @@ public final class BackNavigationInfo implements Parcelable {
     private BackNavigationInfo(@BackTargetType int type,
             @Nullable RemoteCallback onBackNavigationDone,
             @Nullable IOnBackInvokedCallback onBackInvokedCallback,
-            boolean isPrepareRemoteAnimation) {
+            boolean isPrepareRemoteAnimation,
+            @Nullable WindowContainerToken departingWindowContainerToken) {
         mType = type;
         mOnBackNavigationDone = onBackNavigationDone;
         mOnBackInvokedCallback = onBackInvokedCallback;
         mPrepareRemoteAnimation = isPrepareRemoteAnimation;
+        mDepartingWindowContainerToken = departingWindowContainerToken;
     }
 
     private BackNavigationInfo(@NonNull Parcel in) {
@@ -116,6 +121,7 @@ public final class BackNavigationInfo implements Parcelable {
         mOnBackNavigationDone = in.readTypedObject(RemoteCallback.CREATOR);
         mOnBackInvokedCallback = IOnBackInvokedCallback.Stub.asInterface(in.readStrongBinder());
         mPrepareRemoteAnimation = in.readBoolean();
+        mDepartingWindowContainerToken = in.readTypedObject(WindowContainerToken.CREATOR);
     }
 
     @Override
@@ -124,6 +130,7 @@ public final class BackNavigationInfo implements Parcelable {
         dest.writeTypedObject(mOnBackNavigationDone, flags);
         dest.writeStrongInterface(mOnBackInvokedCallback);
         dest.writeBoolean(mPrepareRemoteAnimation);
+        dest.writeTypedObject(mDepartingWindowContainerToken, flags);
     }
 
     /**
@@ -156,6 +163,18 @@ public final class BackNavigationInfo implements Parcelable {
         return mPrepareRemoteAnimation;
     }
 
+    /**
+     * Returns the {@link WindowContainerToken} of the highest container in the hierarchy being
+     * removed.
+     * <p>
+     * For example, if an Activity is the last one of its Task, the Task's token will be given.
+     * Otherwise, it will be the Activity's token.
+     */
+    @Nullable
+    public WindowContainerToken getDepartingWindowContainerToken() {
+        return mDepartingWindowContainerToken;
+    }
+
     /**
      * Callback to be called when the back preview is finished in order to notify the server that
      * it can clean up the resources created for the animation.
@@ -193,6 +212,7 @@ public final class BackNavigationInfo implements Parcelable {
                 + "mType=" + typeToString(mType) + " (" + mType + ")"
                 + ", mOnBackNavigationDone=" + mOnBackNavigationDone
                 + ", mOnBackInvokedCallback=" + mOnBackInvokedCallback
+                + ", mWindowContainerToken=" + mDepartingWindowContainerToken
                 + '}';
     }
 
@@ -228,6 +248,9 @@ public final class BackNavigationInfo implements Parcelable {
         @Nullable
         private IOnBackInvokedCallback mOnBackInvokedCallback = null;
         private boolean mPrepareRemoteAnimation;
+        @Nullable
+        private WindowContainerToken mDepartingWindowContainerToken = null;
+
         /**
          * @see BackNavigationInfo#getType()
          */
@@ -261,12 +284,21 @@ public final class BackNavigationInfo implements Parcelable {
             return this;
         }
 
+        /**
+         * @see BackNavigationInfo#getDepartingWindowContainerToken()
+         */
+        public void setDepartingWCT(@NonNull WindowContainerToken windowContainerToken) {
+            mDepartingWindowContainerToken = windowContainerToken;
+        }
+
         /**
          * Builds and returns an instance of {@link BackNavigationInfo}
          */
         public BackNavigationInfo build() {
             return new BackNavigationInfo(mType, mOnBackNavigationDone,
-                    mOnBackInvokedCallback, mPrepareRemoteAnimation);
+                    mOnBackInvokedCallback,
+                    mPrepareRemoteAnimation,
+                    mDepartingWindowContainerToken);
         }
     }
 }

libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimationController.java

@@ -58,6 +58,7 @@ import com.android.wm.shell.common.ShellExecutor;
 import com.android.wm.shell.common.annotations.ShellBackgroundThread;
 import com.android.wm.shell.common.annotations.ShellMainThread;
 import com.android.wm.shell.sysui.ShellInit;
+import com.android.wm.shell.transition.Transitions;
 
 import java.util.concurrent.atomic.AtomicBoolean;
 
@@ -75,6 +76,9 @@ public class BackAnimationController implements RemoteCallable<BackAnimationCont
                     SETTING_VALUE_ON) != SETTING_VALUE_OFF;
     private static final int PROGRESS_THRESHOLD = SystemProperties
             .getInt(PREDICTIVE_BACK_PROGRESS_THRESHOLD_PROP, -1);
+
+    // TODO (b/241808055) Find a appropriate time to remove during refactor
+    private static final boolean ENABLE_SHELL_TRANSITIONS = Transitions.ENABLE_SHELL_TRANSITIONS;
     /**
      * Max duration to wait for a transition to finish before accepting another gesture start
      * request.
@@ -113,6 +117,8 @@ public class BackAnimationController implements RemoteCallable<BackAnimationCont
     private final TouchTracker mTouchTracker = new TouchTracker();
 
     private final SparseArray<BackAnimationRunner> mAnimationDefinition = new SparseArray<>();
+    private final Transitions mTransitions;
+    private BackTransitionHandler mBackTransitionHandler;
 
     @VisibleForTesting
     final IWindowFocusObserver mFocusObserver = new IWindowFocusObserver.Stub() {
@@ -184,9 +190,11 @@ public class BackAnimationController implements RemoteCallable<BackAnimationCont
             @NonNull ShellInit shellInit,
             @NonNull @ShellMainThread ShellExecutor shellExecutor,
             @NonNull @ShellBackgroundThread Handler backgroundHandler,
-            Context context) {
+            Context context,
+            Transitions transitions) {
         this(shellInit, shellExecutor, backgroundHandler,
-                ActivityTaskManager.getService(), context, context.getContentResolver());
+                ActivityTaskManager.getService(), context, context.getContentResolver(),
+                transitions);
     }
 
     @VisibleForTesting
@@ -195,18 +203,24 @@ public class BackAnimationController implements RemoteCallable<BackAnimationCont
             @NonNull @ShellMainThread ShellExecutor shellExecutor,
             @NonNull @ShellBackgroundThread Handler bgHandler,
             @NonNull IActivityTaskManager activityTaskManager,
-            Context context, ContentResolver contentResolver) {
+            Context context, ContentResolver contentResolver,
+            Transitions transitions) {
         mShellExecutor = shellExecutor;
         mActivityTaskManager = activityTaskManager;
         mContext = context;
         mContentResolver = contentResolver;
         mBgHandler = bgHandler;
         shellInit.addInitCallback(this::onInit, this);
+        mTransitions = transitions;
     }
 
     private void onInit() {
         setupAnimationDeveloperSettingsObserver(mContentResolver, mBgHandler);
         createAdapter();
+        if (ENABLE_SHELL_TRANSITIONS) {
+            mBackTransitionHandler = new BackTransitionHandler(this);
+            mTransitions.addHandler(mBackTransitionHandler);
+        }
     }
 
     private void setupAnimationDeveloperSettingsObserver(
@@ -333,7 +347,18 @@ public class BackAnimationController implements RemoteCallable<BackAnimationCont
                 dispatchOnBackCancelled(callback);
             }
         }
-        finishAnimation();
+
+        // In legacy transition, it would use `Task.mBackGestureStarted` in core to handle the
+        // following transition when back callback is invoked.
+        // If the back callback is not invoked, we should reset the token and finish the whole back
+        // navigation without waiting the transition.
+        if (!ENABLE_SHELL_TRANSITIONS) {
+            finishBackNavigation();
+        } else if (!mTriggerBack) {
+            // reset the token to prevent it consume next transition.
+            mBackTransitionHandler.setDepartingWindowContainerToken(null);
+            finishBackNavigation();
+        }
     }
 
     /**
@@ -373,7 +398,7 @@ public class BackAnimationController implements RemoteCallable<BackAnimationCont
         ProtoLog.d(WM_SHELL_BACK_PREVIEW, "initAnimation mMotionStarted=%b", mBackGestureStarted);
         if (mBackGestureStarted || mBackNavigationInfo != null) {
             Log.e(TAG, "Animation is being initialized but is already started.");
-            finishAnimation();
+            finishBackNavigation();
         }
 
         mTouchTracker.setGestureStartLocation(touchX, touchY);
@@ -385,7 +410,7 @@ public class BackAnimationController implements RemoteCallable<BackAnimationCont
             onBackNavigationInfoReceived(mBackNavigationInfo);
         } catch (RemoteException remoteException) {
             Log.e(TAG, "Failed to initAnimation", remoteException);
-            finishAnimation();
+            finishBackNavigation();
         }
     }
 
@@ -448,7 +473,7 @@ public class BackAnimationController implements RemoteCallable<BackAnimationCont
     private void onGestureFinished(boolean fromTouch) {
         ProtoLog.d(WM_SHELL_BACK_PREVIEW, "onGestureFinished() mTriggerBack == %s", mTriggerBack);
         if (!mBackGestureStarted) {
-            finishAnimation();
+            finishBackNavigation();
             return;
         }
 
@@ -468,7 +493,7 @@ public class BackAnimationController implements RemoteCallable<BackAnimationCont
             if (mTriggerBack) {
                 injectBackKey();
             }
-            finishAnimation();
+            finishBackNavigation();
             return;
         }
 
@@ -492,7 +517,7 @@ public class BackAnimationController implements RemoteCallable<BackAnimationCont
         }
         if (!shouldDispatchToAnimator) {
             // Animation callback missing. Simply finish animation.
-            finishAnimation();
+            finishBackNavigation();
         }
     }
 
@@ -562,8 +587,9 @@ public class BackAnimationController implements RemoteCallable<BackAnimationCont
         mTouchTracker.setProgressThreshold(progressThreshold);
     }
 
-    private void finishAnimation() {
-        ProtoLog.d(WM_SHELL_BACK_PREVIEW, "BackAnimationController: finishAnimation()");
+    @VisibleForTesting
+    void finishBackNavigation() {
+        ProtoLog.d(WM_SHELL_BACK_PREVIEW, "BackAnimationController: finishBackNavigation()");
         BackNavigationInfo backNavigationInfo = mBackNavigationInfo;
         boolean triggerBack = mTriggerBack;
         mBackNavigationInfo = null;
@@ -590,17 +616,31 @@ public class BackAnimationController implements RemoteCallable<BackAnimationCont
             return;
         }
         mTransitionInProgress = true;
+        if (ENABLE_SHELL_TRANSITIONS) {
+            mBackTransitionHandler.setDepartingWindowContainerToken(
+                    mBackNavigationInfo.getDepartingWindowContainerToken());
+        }
         mShellExecutor.executeDelayed(mResetTransitionRunnable, MAX_TRANSITION_DURATION);
     }
 
-    private void stopTransition() {
-        if (!mTransitionInProgress) {
-            return;
-        }
+    void stopTransition() {
         mShellExecutor.removeCallbacks(mResetTransitionRunnable);
         mTransitionInProgress = false;
     }
 
+    /**
+     * This should be called from {@link BackTransitionHandler#startAnimation} when the following
+     * transition is triggered by the real back callback in {@link #onBackAnimationFinished}.
+     * Will consume the default transition and finish current back navigation.
+     */
+    void finishTransition(Transitions.TransitionFinishCallback finishCallback) {
+        ProtoLog.d(WM_SHELL_BACK_PREVIEW, "BackAnimationController: finishTransition()");
+        mShellExecutor.execute(() -> {
+            finishBackNavigation();
+            finishCallback.onTransitionFinished(null, null);
+        });
+    }
+
     private void createAdapter() {
         IBackAnimationRunner runner = new IBackAnimationRunner.Stub() {
             @Override

libs/WindowManager/Shell/src/com/android/wm/shell/back/BackTransitionHandler.java

@@ -0,0 +1,78 @@
+/*
+ * 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.wm.shell.back;
+
+import android.os.IBinder;
+import android.view.SurfaceControl;
+import android.window.TransitionInfo;
+import android.window.TransitionRequestInfo;
+import android.window.WindowContainerToken;
+import android.window.WindowContainerTransaction;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+import com.android.wm.shell.transition.Transitions;
+
+class BackTransitionHandler implements Transitions.TransitionHandler {
+    private BackAnimationController mBackAnimationController;
+    private WindowContainerToken mDepartingWindowContainerToken;
+
+    BackTransitionHandler(@NonNull BackAnimationController backAnimationController) {
+        mBackAnimationController = backAnimationController;
+    }
+
+    @Override
+    public boolean startAnimation(@NonNull IBinder transition, @NonNull TransitionInfo info,
+            @NonNull SurfaceControl.Transaction startTransaction,
+            @NonNull SurfaceControl.Transaction finishTransaction,
+            @NonNull Transitions.TransitionFinishCallback finishCallback) {
+        if (mDepartingWindowContainerToken != null) {
+            final TransitionInfo.Change change = info.getChange(mDepartingWindowContainerToken);
+            if (change == null) {
+                return false;
+            }
+
+            startTransaction.hide(change.getLeash());
+            startTransaction.apply();
+            mDepartingWindowContainerToken = null;
+            mBackAnimationController.finishTransition(finishCallback);
+            return true;
+        }
+
+        return false;
+    }
+
+    @Nullable
+    @Override
+    public WindowContainerTransaction handleRequest(@NonNull IBinder transition,
+            @NonNull TransitionRequestInfo request) {
+        return null;
+    }
+
+    @Override
+    public void mergeAnimation(@NonNull IBinder transition, @NonNull TransitionInfo info,
+            @NonNull SurfaceControl.Transaction t, @NonNull IBinder mergeTarget,
+            @NonNull Transitions.TransitionFinishCallback finishCallback) {
+    }
+
+    void setDepartingWindowContainerToken(
+            @Nullable WindowContainerToken departingWindowContainerToken) {
+        mDepartingWindowContainerToken = departingWindowContainerToken;
+    }
+}
+

libs/WindowManager/Shell/src/com/android/wm/shell/dagger/WMShellBaseModule.java

@@ -273,12 +273,13 @@ public abstract class WMShellBaseModule {
             Context context,
             ShellInit shellInit,
             @ShellMainThread ShellExecutor shellExecutor,
-            @ShellBackgroundThread Handler backgroundHandler
+            @ShellBackgroundThread Handler backgroundHandler,
+            Transitions transitions
     ) {
         if (BackAnimationController.IS_ENABLED) {
             return Optional.of(
                     new BackAnimationController(shellInit, shellExecutor, backgroundHandler,
-                            context));
+                            context, transitions));
         }
         return Optional.empty();
     }

libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/back/BackAnimationControllerTest.java

@@ -61,6 +61,7 @@ import com.android.internal.util.test.FakeSettingsProvider;
 import com.android.wm.shell.ShellTestCase;
 import com.android.wm.shell.TestShellExecutor;
 import com.android.wm.shell.sysui.ShellInit;
+import com.android.wm.shell.transition.Transitions;
 
 import org.junit.Before;
 import org.junit.Rule;
@@ -98,6 +99,9 @@ public class BackAnimationControllerTest extends ShellTestCase {
     @Mock
     private IRemoteAnimationRunner mBackAnimationRunner;
 
+    @Mock
+    private Transitions mTransitions;
+
     private BackAnimationController mController;
 
     private int mEventTime = 0;
@@ -117,7 +121,7 @@ public class BackAnimationControllerTest extends ShellTestCase {
         mController = new BackAnimationController(mShellInit,
                 mShellExecutor, new Handler(mTestableLooper.getLooper()),
                 mActivityTaskManager, mContext,
-                mContentResolver);
+                mContentResolver, mTransitions);
         mShellInit.init();
         mEventTime = 0;
         mShellExecutor.flushAll();
@@ -209,7 +213,7 @@ public class BackAnimationControllerTest extends ShellTestCase {
         mController = new BackAnimationController(shellInit,
                 mShellExecutor, new Handler(mTestableLooper.getLooper()),
                 mActivityTaskManager, mContext,
-                mContentResolver);
+                mContentResolver, mTransitions);
         shellInit.init();
         mController.setBackToLauncherCallback(mIOnBackInvokedCallback, mBackAnimationRunner);
 
@@ -250,6 +254,8 @@ public class BackAnimationControllerTest extends ShellTestCase {
         doMotionEvent(MotionEvent.ACTION_DOWN, 0);
         verifyNoMoreInteractions(mIOnBackInvokedCallback);
         mController.onBackAnimationFinished();
+        // Pretend the transition handler called finishAnimation.
+        mController.finishBackNavigation();
 
         // Verify that more events from a rejected swipe cannot start animation.
         doMotionEvent(MotionEvent.ACTION_MOVE, 100);
@@ -278,6 +284,8 @@ public class BackAnimationControllerTest extends ShellTestCase {
         // Simulate transition timeout.
         mShellExecutor.flushAll();
         mController.onBackAnimationFinished();
+        // Pretend the transition handler called finishAnimation.
+        mController.finishBackNavigation();
 
         doMotionEvent(MotionEvent.ACTION_DOWN, 0);
         doMotionEvent(MotionEvent.ACTION_MOVE, 100);

services/core/java/com/android/server/wm/BackNavigationController.java

@@ -43,6 +43,7 @@ import android.window.IBackAnimationFinishedCallback;
 import android.window.OnBackInvokedCallbackInfo;
 import android.window.ScreenCapture;
 import android.window.TaskSnapshot;
+import android.window.WindowContainerToken;
 
 import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.protolog.common.ProtoLog;
@@ -61,6 +62,9 @@ class BackNavigationController {
     private boolean mShowWallpaper;
     private Runnable mPendingAnimation;
 
+    // TODO (b/241808055) Find a appropriate time to remove during refactor
+    // Execute back animation with legacy transition system. Temporary flag for easier debugging.
+    static final boolean ENABLE_SHELL_TRANSITIONS = WindowManagerService.sEnableShellTransitions;
     /**
      * Returns true if the back predictability feature is enabled
      */
@@ -263,12 +267,14 @@ class BackNavigationController {
             // Only prepare animation if no leash has been created (no animation is running).
             // TODO(b/241808055): Cancel animation when preparing back animation.
             if (prepareAnimation
-                    && removedWindowContainer.hasCommittedReparentToAnimationLeash()) {
+                    && (removedWindowContainer.hasCommittedReparentToAnimationLeash()
+                            || removedWindowContainer.mTransitionController.inTransition())) {
                 Slog.w(TAG, "Can't prepare back animation due to another animation is running.");
                 prepareAnimation = false;
             }
 
             if (prepareAnimation) {
+                infoBuilder.setDepartingWCT(toWindowContainerToken(currentTask));
                 prepareAnimationIfNeeded(currentTask, prevTask, prevActivity,
                         removedWindowContainer, backType, adapter);
             }
@@ -287,6 +293,13 @@ class BackNavigationController {
         return infoBuilder.build();
     }
 
+    private static WindowContainerToken toWindowContainerToken(WindowContainer<?> windowContainer) {
+        if (windowContainer == null || windowContainer.mRemoteToken == null) {
+            return null;
+        }
+        return windowContainer.mRemoteToken.toWindowContainerToken();
+    }
+
     private void prepareAnimationIfNeeded(Task currentTask,
             Task prevTask, ActivityRecord prevActivity, WindowContainer<?> removedWindowContainer,
             int backType, BackAnimationAdapter adapter) {
@@ -352,8 +365,10 @@ class BackNavigationController {
                 leashes.add(screenshotSurface);
             }
         } else if (prevTask != null) {
-            // Special handling for preventing next transition.
-            currentTask.mBackGestureStarted = true;
+            if (!ENABLE_SHELL_TRANSITIONS) {
+                // Special handling for preventing next transition.
+                currentTask.mBackGestureStarted = true;
+            }
             prevActivity = prevTask.getTopNonFinishingActivity();
             if (prevActivity != null) {
                 // Make previous task show from behind by marking its top activity as visible
@@ -396,16 +411,27 @@ class BackNavigationController {
                         }
 
                         synchronized (mWindowManagerService.mGlobalLock) {
-                            if (triggerBack) {
-                                final SurfaceControl surfaceControl =
-                                        removedWindowContainer.getSurfaceControl();
-                                if (surfaceControl != null && surfaceControl.isValid()) {
-                                    // When going back to home, hide the task surface before it is
-                                    // re-parented to avoid flicker.
-                                    finishedTransaction.hide(surfaceControl);
+                            if (ENABLE_SHELL_TRANSITIONS) {
+                                if (!triggerBack) {
+                                    if (!needsScreenshot(backType)) {
+                                        restoreLaunchBehind(finalPrevActivity);
+                                    }
+                                }
+                            } else {
+                                if (triggerBack) {
+                                    final SurfaceControl surfaceControl =
+                                            removedWindowContainer.getSurfaceControl();
+                                    if (surfaceControl != null && surfaceControl.isValid()) {
+                                        // When going back to home, hide the task surface before it
+                                        // re-parented to avoid flicker.
+                                        finishedTransaction.hide(surfaceControl);
+                                    }
+                                } else {
+                                    currentTask.mBackGestureStarted = false;
+                                    if (!needsScreenshot(backType)) {
+                                        restoreLaunchBehind(finalPrevActivity);
+                                    }
                                 }
-                            } else if (!needsScreenshot(backType)) {
-                                restoreLaunchBehind(finalPrevActivity);
                             }
                         }
                         finishedTransaction.apply();