Merge "Add a DefaultMixedHandler handler combined transitions" into tm-qpr-dev

libs/WindowManager/Shell/src/com/android/wm/shell/ShellInitImpl.java

@@ -34,6 +34,7 @@ import com.android.wm.shell.pip.phone.PipTouchHandler;
 import com.android.wm.shell.recents.RecentTasksController;
 import com.android.wm.shell.splitscreen.SplitScreenController;
 import com.android.wm.shell.startingsurface.StartingWindowController;
+import com.android.wm.shell.transition.DefaultMixedHandler;
 import com.android.wm.shell.transition.Transitions;
 import com.android.wm.shell.unfold.UnfoldTransitionHandler;
 
@@ -131,6 +132,13 @@ public class ShellInitImpl {
         if (Transitions.ENABLE_SHELL_TRANSITIONS) {
             mTransitions.register(mShellTaskOrganizer);
             mUnfoldTransitionHandler.ifPresent(UnfoldTransitionHandler::init);
+            if (mSplitScreenOptional.isPresent() && mPipTouchHandlerOptional.isPresent()) {
+                final DefaultMixedHandler mixedHandler = new DefaultMixedHandler(mTransitions,
+                        mPipTouchHandlerOptional.get().getTransitionHandler(),
+                        mSplitScreenOptional.get().getTransitionHandler());
+                // Added at end so that it has highest priority.
+                mTransitions.addHandler(mixedHandler);
+            }
         }
 
         // TODO(b/181599115): This should really be the pip controller, but until we can provide the

libs/WindowManager/Shell/src/com/android/wm/shell/pip/PipTaskOrganizer.java

@@ -295,6 +295,10 @@ public class PipTaskOrganizer implements ShellTaskOrganizer.TaskListener,
         displayController.addDisplayWindowListener(this);
     }
 
+    public PipTransitionController getTransitionController() {
+        return mPipTransitionController;
+    }
+
     public Rect getCurrentOrAnimatingBounds() {
         PipAnimationController.PipTransitionAnimator animator =
                 mPipAnimationController.getCurrentAnimator();

libs/WindowManager/Shell/src/com/android/wm/shell/pip/PipTransition.java

@@ -28,7 +28,6 @@ import static android.view.WindowManager.TRANSIT_OPEN;
 import static android.view.WindowManager.TRANSIT_PIP;
 import static android.view.WindowManager.transitTypeToString;
 import static android.window.TransitionInfo.FLAG_IS_DISPLAY;
-import static android.window.TransitionInfo.FLAG_IS_WALLPAPER;
 
 import static com.android.wm.shell.pip.PipAnimationController.ANIM_TYPE_ALPHA;
 import static com.android.wm.shell.pip.PipAnimationController.ANIM_TYPE_BOUNDS;
@@ -52,6 +51,7 @@ import android.graphics.Rect;
 import android.os.IBinder;
 import android.view.Surface;
 import android.view.SurfaceControl;
+import android.view.WindowManager;
 import android.window.TransitionInfo;
 import android.window.TransitionRequestInfo;
 import android.window.WindowContainerToken;
@@ -217,8 +217,9 @@ public class PipTransition extends PipTransitionController {
         }
 
         // Entering PIP.
-        if (isEnteringPip(info, mCurrentPipTaskToken)) {
+        if (isEnteringPip(info)) {
-            return startEnterAnimation(info, startTransaction, finishTransaction, finishCallback);
+            startEnterAnimation(info, startTransaction, finishTransaction, finishCallback);
+            return true;
         }
 
         // For transition that we don't animate, but contains the PIP leash, we need to update the
@@ -245,22 +246,31 @@ public class PipTransition extends PipTransitionController {
     @Override
     public WindowContainerTransaction handleRequest(@NonNull IBinder transition,
             @NonNull TransitionRequestInfo request) {
-        if (request.getType() == TRANSIT_PIP) {
+        if (requestHasPipEnter(request)) {
             WindowContainerTransaction wct = new WindowContainerTransaction();
-            if (mOneShotAnimationType == ANIM_TYPE_ALPHA) {
+            augmentRequest(transition, request, wct);
-                mRequestedEnterTransition = transition;
-                mRequestedEnterTask = request.getTriggerTask().token;
-                wct.setActivityWindowingMode(request.getTriggerTask().token,
-                        WINDOWING_MODE_UNDEFINED);
-                final Rect destinationBounds = mPipBoundsAlgorithm.getEntryDestinationBounds();
-                wct.setBounds(request.getTriggerTask().token, destinationBounds);
-            }
             return wct;
         } else {
             return null;
         }
     }
 
+    @Override
+    public void augmentRequest(@NonNull IBinder transition,
+            @NonNull TransitionRequestInfo request, @NonNull WindowContainerTransaction outWCT) {
+        if (!requestHasPipEnter(request)) {
+            throw new IllegalStateException("Called PiP augmentRequest when request has no PiP");
+        }
+        if (mOneShotAnimationType == ANIM_TYPE_ALPHA) {
+            mRequestedEnterTransition = transition;
+            mRequestedEnterTask = request.getTriggerTask().token;
+            outWCT.setActivityWindowingMode(request.getTriggerTask().token,
+                    WINDOWING_MODE_UNDEFINED);
+            final Rect destinationBounds = mPipBoundsAlgorithm.getEntryDestinationBounds();
+            outWCT.setBounds(request.getTriggerTask().token, destinationBounds);
+        }
+    }
+
     @Override
     public boolean handleRotateDisplay(int startRotation, int endRotation,
             WindowContainerTransaction wct) {
@@ -559,92 +569,94 @@ public class PipTransition extends PipTransitionController {
     }
 
     /** Whether we should handle the given {@link TransitionInfo} animation as entering PIP. */
-    private static boolean isEnteringPip(@NonNull TransitionInfo info,
+    private boolean isEnteringPip(@NonNull TransitionInfo info) {
-            @Nullable WindowContainerToken currentPipTaskToken) {
         for (int i = info.getChanges().size() - 1; i >= 0; --i) {
             final TransitionInfo.Change change = info.getChanges().get(i);
-            if (change.getTaskInfo() != null
+            if (isEnteringPip(change, info.getType())) return true;
-                    && change.getTaskInfo().getWindowingMode() == WINDOWING_MODE_PINNED
-                    && !change.getContainer().equals(currentPipTaskToken)) {
-                // We support TRANSIT_PIP type (from RootWindowContainer) or TRANSIT_OPEN (from apps
-                // that enter PiP instantly on opening, mostly from CTS/Flicker tests)
-                if (info.getType() == TRANSIT_PIP || info.getType() == TRANSIT_OPEN) {
-                    return true;
-                }
-                // This can happen if the request to enter PIP happens when we are collecting for
-                // another transition, such as TRANSIT_CHANGE (display rotation).
-                if (info.getType() == TRANSIT_CHANGE) {
-                    return true;
-                }
-
-                // Please file a bug to handle the unexpected transition type.
-                throw new IllegalStateException("Entering PIP with unexpected transition type="
-                        + transitTypeToString(info.getType()));
-            }
         }
         return false;
     }
 
-    private boolean startEnterAnimation(@NonNull TransitionInfo info,
+    /** Whether a particular change is a window that is entering pip. */
+    @Override
+    public boolean isEnteringPip(@NonNull TransitionInfo.Change change,
+            @WindowManager.TransitionType int transitType) {
+        if (change.getTaskInfo() != null
+                && change.getTaskInfo().getWindowingMode() == WINDOWING_MODE_PINNED
+                && !change.getContainer().equals(mCurrentPipTaskToken)) {
+            // We support TRANSIT_PIP type (from RootWindowContainer) or TRANSIT_OPEN (from apps
+            // that enter PiP instantly on opening, mostly from CTS/Flicker tests)
+            if (transitType == TRANSIT_PIP || transitType == TRANSIT_OPEN) {
+                return true;
+            }
+            // This can happen if the request to enter PIP happens when we are collecting for
+            // another transition, such as TRANSIT_CHANGE (display rotation).
+            if (transitType == TRANSIT_CHANGE) {
+                return true;
+            }
+
+            // Please file a bug to handle the unexpected transition type.
+            throw new IllegalStateException("Entering PIP with unexpected transition type="
+                    + transitTypeToString(transitType));
+        }
+        return false;
+    }
+
+    private void startEnterAnimation(@NonNull TransitionInfo info,
             @NonNull SurfaceControl.Transaction startTransaction,
             @NonNull SurfaceControl.Transaction finishTransaction,
             @NonNull Transitions.TransitionFinishCallback finishCallback) {
-        // Search for an Enter PiP transition (along with a show wallpaper one)
+        // Search for an Enter PiP transition
         TransitionInfo.Change enterPip = null;
-        TransitionInfo.Change wallpaper = null;
         for (int i = info.getChanges().size() - 1; i >= 0; --i) {
             final TransitionInfo.Change change = info.getChanges().get(i);
             if (change.getTaskInfo() != null
                     && change.getTaskInfo().getWindowingMode() == WINDOWING_MODE_PINNED) {
                 enterPip = change;
-            } else if ((change.getFlags() & FLAG_IS_WALLPAPER) != 0) {
-                wallpaper = change;
             }
         }
         if (enterPip == null) {
-            return false;
+            throw new IllegalStateException("Trying to start PiP animation without a pip"
-        }
+                    + "participant");
-        // Keep track of the PIP task.
-        mCurrentPipTaskToken = enterPip.getContainer();
-        mHasFadeOut = false;
-
-        if (mFinishCallback != null) {
-            callFinishCallback(null /* wct */);
-            mFinishTransaction = null;
-            throw new RuntimeException("Previous callback not called, aborting entering PIP.");
         }
 
-        // Show the wallpaper if there is a wallpaper change.
-        if (wallpaper != null) {
-            startTransaction.show(wallpaper.getLeash());
-            startTransaction.setAlpha(wallpaper.getLeash(), 1.f);
-        }
         // Make sure other open changes are visible as entering PIP. Some may be hidden in
         // Transitions#setupStartState because the transition type is OPEN (such as auto-enter).
         for (int i = info.getChanges().size() - 1; i >= 0; --i) {
             final TransitionInfo.Change change = info.getChanges().get(i);
-            if (change == enterPip || change == wallpaper) {
+            if (change == enterPip) continue;
-                continue;
-            }
             if (isOpeningType(change.getMode())) {
                 final SurfaceControl leash = change.getLeash();
                 startTransaction.show(leash).setAlpha(leash, 1.f);
             }
         }
 
+        startEnterAnimation(enterPip, startTransaction, finishTransaction, finishCallback);
+    }
+
+    @Override
+    public void startEnterAnimation(@NonNull final TransitionInfo.Change pipChange,
+            @NonNull final SurfaceControl.Transaction startTransaction,
+            @NonNull final SurfaceControl.Transaction finishTransaction,
+            @NonNull final Transitions.TransitionFinishCallback finishCallback) {
+        if (mFinishCallback != null) {
+            callFinishCallback(null /* wct */);
+            mFinishTransaction = null;
+            throw new RuntimeException("Previous callback not called, aborting entering PIP.");
+        }
+
+        // Keep track of the PIP task and animation.
+        mCurrentPipTaskToken = pipChange.getContainer();
+        mHasFadeOut = false;
         mPipTransitionState.setTransitionState(PipTransitionState.ENTERING_PIP);
         mFinishCallback = finishCallback;
         mFinishTransaction = finishTransaction;
-        final int endRotation = mInFixedRotation ? mEndFixedRotation : enterPip.getEndRotation();
-        return startEnterAnimation(enterPip.getTaskInfo(), enterPip.getLeash(),
-                startTransaction, finishTransaction, enterPip.getStartRotation(),
-                endRotation);
-    }
 
-    private boolean startEnterAnimation(final TaskInfo taskInfo, final SurfaceControl leash,
+        final ActivityManager.RunningTaskInfo taskInfo = pipChange.getTaskInfo();
-            final SurfaceControl.Transaction startTransaction,
+        final SurfaceControl leash = pipChange.getLeash();
-            final SurfaceControl.Transaction finishTransaction,
+        final int startRotation = pipChange.getStartRotation();
-            final int startRotation, final int endRotation) {
+        final int endRotation = mInFixedRotation ? mEndFixedRotation : pipChange.getEndRotation();
+
         setBoundsStateForEntry(taskInfo.topActivity, taskInfo.pictureInPictureParams,
                 taskInfo.topActivityInfo);
         final Rect destinationBounds = mPipBoundsAlgorithm.getEntryDestinationBounds();
@@ -657,7 +669,6 @@ public class PipTransition extends PipTransitionController {
             computeEnterPipRotatedBounds(rotationDelta, startRotation, endRotation, taskInfo,
                     destinationBounds, sourceHintRect);
         }
-        PipAnimationController.PipTransitionAnimator animator;
         // Set corner radius for entering pip.
         mSurfaceTransactionHelper
                 .crop(finishTransaction, leash, destinationBounds)
@@ -694,7 +705,7 @@ public class PipTransition extends PipTransitionController {
                         null /* callback */, false /* withStartDelay */);
             }
             mPipTransitionState.setInSwipePipToHomeTransition(false);
-            return true;
+            return;
         }
 
         if (rotationDelta != Surface.ROTATION_0) {
@@ -702,6 +713,12 @@ public class PipTransition extends PipTransitionController {
             tmpTransform.postRotate(rotationDelta);
             startTransaction.setMatrix(leash, tmpTransform, new float[9]);
         }
+        if (mOneShotAnimationType == ANIM_TYPE_ALPHA) {
+            startTransaction.setAlpha(leash, 0f);
+        }
+        startTransaction.apply();
+
+        PipAnimationController.PipTransitionAnimator animator;
         if (mOneShotAnimationType == ANIM_TYPE_BOUNDS) {
             animator = mPipAnimationController.getAnimator(taskInfo, leash, currentBounds,
                     currentBounds, destinationBounds, sourceHintRect, TRANSITION_DIRECTION_TO_PIP,
@@ -712,7 +729,6 @@ public class PipTransition extends PipTransitionController {
                 animator.setUseContentOverlay(mContext);
             }
         } else if (mOneShotAnimationType == ANIM_TYPE_ALPHA) {
-            startTransaction.setAlpha(leash, 0f);
             animator = mPipAnimationController.getAnimator(taskInfo, leash, destinationBounds,
                     0f, 1f);
             mOneShotAnimationType = ANIM_TYPE_BOUNDS;
@@ -720,7 +736,6 @@ public class PipTransition extends PipTransitionController {
             throw new RuntimeException("Unrecognized animation type: "
                     + mOneShotAnimationType);
         }
-        startTransaction.apply();
         animator.setTransitionDirection(TRANSITION_DIRECTION_TO_PIP)
                 .setPipAnimationCallback(mPipAnimationCallback)
                 .setDuration(mEnterExitAnimationDuration);
@@ -731,8 +746,6 @@ public class PipTransition extends PipTransitionController {
             animator.setDestinationBounds(mPipBoundsAlgorithm.getEntryDestinationBounds());
         }
         animator.start();
-
-        return true;
     }
 
     /** Computes destination bounds in old rotation and updates source hint rect if available. */

libs/WindowManager/Shell/src/com/android/wm/shell/pip/PipTransitionController.java

@@ -17,6 +17,7 @@
 package com.android.wm.shell.pip;
 
 import static android.app.WindowConfiguration.WINDOWING_MODE_UNDEFINED;
+import static android.view.WindowManager.TRANSIT_PIP;
 
 import static com.android.wm.shell.pip.PipAnimationController.TRANSITION_DIRECTION_REMOVE_STACK;
 import static com.android.wm.shell.pip.PipAnimationController.isInPipDirection;
@@ -28,10 +29,16 @@ import android.content.ComponentName;
 import android.content.pm.ActivityInfo;
 import android.graphics.Rect;
 import android.os.Handler;
+import android.os.IBinder;
 import android.os.Looper;
 import android.view.SurfaceControl;
+import android.view.WindowManager;
+import android.window.TransitionInfo;
+import android.window.TransitionRequestInfo;
 import android.window.WindowContainerTransaction;
 
+import androidx.annotation.NonNull;
+
 import com.android.wm.shell.ShellTaskOrganizer;
 import com.android.wm.shell.transition.Transitions;
 
@@ -206,6 +213,30 @@ public abstract class PipTransitionController implements Transitions.TransitionH
         return false;
     }
 
+    /** @return whether the transition-request represents a pip-entry. */
+    public boolean requestHasPipEnter(@NonNull TransitionRequestInfo request) {
+        return request.getType() == TRANSIT_PIP;
+    }
+
+    /** Whether a particular change is a window that is entering pip. */
+    public boolean isEnteringPip(@NonNull TransitionInfo.Change change,
+            @WindowManager.TransitionType int transitType) {
+        return false;
+    }
+
+    /** Add PiP-related changes to `outWCT` for the given request. */
+    public void augmentRequest(@NonNull IBinder transition,
+            @NonNull TransitionRequestInfo request, @NonNull WindowContainerTransaction outWCT) {
+        throw new IllegalStateException("Request isn't entering PiP");
+    }
+
+    /** Play a transition animation for entering PiP on a specific PiP change. */
+    public void startEnterAnimation(@NonNull final TransitionInfo.Change pipChange,
+            @NonNull final SurfaceControl.Transaction startTransaction,
+            @NonNull final SurfaceControl.Transaction finishTransaction,
+            @NonNull final Transitions.TransitionFinishCallback finishCallback) {
+    }
+
     /**
      * Callback interface for PiP transitions (both from and to PiP mode)
      */

libs/WindowManager/Shell/src/com/android/wm/shell/pip/phone/PipTouchHandler.java

@@ -53,6 +53,7 @@ import com.android.wm.shell.pip.PipAnimationController;
 import com.android.wm.shell.pip.PipBoundsAlgorithm;
 import com.android.wm.shell.pip.PipBoundsState;
 import com.android.wm.shell.pip.PipTaskOrganizer;
+import com.android.wm.shell.pip.PipTransitionController;
 import com.android.wm.shell.pip.PipUiEventLogger;
 import com.android.wm.shell.protolog.ShellProtoLogGroup;
 
@@ -249,6 +250,10 @@ public class PipTouchHandler {
                 });
     }
 
+    public PipTransitionController getTransitionHandler() {
+        return mPipTaskOrganizer.getTransitionController();
+    }
+
     private void reloadResources() {
         final Resources res = mContext.getResources();
         mBottomOffsetBufferPx = res.getDimensionPixelSize(R.dimen.pip_bottom_offset_buffer);

libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/SplitScreenController.java

@@ -108,7 +108,7 @@ public class SplitScreenController implements DragAndDropPolicy.Starter,
     static final int EXIT_REASON_ROOT_TASK_VANISHED = 6;
     static final int EXIT_REASON_SCREEN_LOCKED = 7;
     static final int EXIT_REASON_SCREEN_LOCKED_SHOW_ON_TOP = 8;
-    static final int EXIT_REASON_CHILD_TASK_ENTER_PIP = 9;
+    public static final int EXIT_REASON_CHILD_TASK_ENTER_PIP = 9;
     @IntDef(value = {
             EXIT_REASON_UNKNOWN,
             EXIT_REASON_APP_DOES_NOT_SUPPORT_MULTIWINDOW,
@@ -198,6 +198,10 @@ public class SplitScreenController implements DragAndDropPolicy.Starter,
         return mStageCoordinator.isSplitScreenVisible();
     }
 
+    public StageCoordinator getTransitionHandler() {
+        return mStageCoordinator;
+    }
+
     @Nullable
     public ActivityManager.RunningTaskInfo getTaskInfo(@SplitPosition int splitPosition) {
         if (!isSplitScreenVisible() || splitPosition == SPLIT_POSITION_UNDEFINED) {

libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/SplitScreenTransitions.java

@@ -21,7 +21,6 @@ import static android.view.WindowManager.TRANSIT_CLOSE;
 import static android.view.WindowManager.TRANSIT_OPEN;
 import static android.view.WindowManager.TRANSIT_TO_BACK;
 import static android.view.WindowManager.TRANSIT_TO_FRONT;
-import static android.window.TransitionInfo.FLAG_FIRST_CUSTOM;
 
 import static com.android.wm.shell.splitscreen.SplitScreen.stageTypeToString;
 import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_DRAG_DIVIDER;
@@ -58,9 +57,6 @@ import java.util.ArrayList;
 class SplitScreenTransitions {
     private static final String TAG = "SplitScreenTransitions";
 
-    /** Flag applied to a transition change to identify it as a divider bar for animation. */
-    public static final int FLAG_IS_DIVIDER_BAR = FLAG_FIRST_CUSTOM;
-
     private final TransactionPool mTransactionPool;
     private final Transitions mTransitions;
     private final Runnable mOnFinish;
@@ -187,27 +183,28 @@ class SplitScreenTransitions {
     }
 
     /** Starts a transition to dismiss split. */
-    IBinder startDismissTransition(@Nullable IBinder transition, WindowContainerTransaction wct,
+    IBinder startDismissTransition(WindowContainerTransaction wct,
             Transitions.TransitionHandler handler, @SplitScreen.StageType int dismissTop,
             @SplitScreenController.ExitReason int reason) {
         final int type = reason == EXIT_REASON_DRAG_DIVIDER
                 ? TRANSIT_SPLIT_DISMISS_SNAP : TRANSIT_SPLIT_DISMISS;
-        if (transition == null) {
+        IBinder transition = mTransitions.startTransition(type, wct, handler);
-            transition = mTransitions.startTransition(type, wct, handler);
+        setDismissTransition(transition, dismissTop, reason);
-        }
+        return transition;
+    }
+
+    /** Sets a transition to dismiss split. */
+    void setDismissTransition(@NonNull IBinder transition, @SplitScreen.StageType int dismissTop,
+            @SplitScreenController.ExitReason int reason) {
         mPendingDismiss = new DismissTransition(transition, reason, dismissTop);
 
         ProtoLog.v(ShellProtoLogGroup.WM_SHELL_TRANSITIONS, "  splitTransition "
                         + " deduced Dismiss due to %s. toTop=%s",
                 exitReasonToString(reason), stageTypeToString(dismissTop));
-        return transition;
     }
 
-    IBinder startRecentTransition(@Nullable IBinder transition, WindowContainerTransaction wct,
+    void setRecentTransition(@NonNull IBinder transition,
-            Transitions.TransitionHandler handler, @Nullable RemoteTransition remoteTransition) {
+            @Nullable RemoteTransition remoteTransition) {
-        if (transition == null) {
-            transition = mTransitions.startTransition(TRANSIT_OPEN, wct, handler);
-        }
         mPendingRecent = transition;
 
         if (remoteTransition != null) {
@@ -219,7 +216,6 @@ class SplitScreenTransitions {
 
         ProtoLog.v(ShellProtoLogGroup.WM_SHELL_TRANSITIONS, "  splitTransition "
                         + " deduced Enter recent panel");
-        return transition;
     }
 
     void mergeAnimation(IBinder transition, TransitionInfo info, SurfaceControl.Transaction t,

libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/StageCoordinator.java

@@ -28,6 +28,7 @@ import static android.view.WindowManager.TRANSIT_CHANGE;
 import static android.view.WindowManager.TRANSIT_TO_BACK;
 import static android.view.WindowManager.TRANSIT_TO_FRONT;
 import static android.view.WindowManager.transitTypeToString;
+import static android.window.TransitionInfo.FLAG_FIRST_CUSTOM;
 import static android.window.TransitionInfo.FLAG_IS_DISPLAY;
 
 import static com.android.wm.shell.common.split.SplitLayout.PARALLAX_ALIGN_CENTER;
@@ -47,7 +48,6 @@ import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON
 import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_SCREEN_LOCKED_SHOW_ON_TOP;
 import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_UNKNOWN;
 import static com.android.wm.shell.splitscreen.SplitScreenController.exitReasonToString;
-import static com.android.wm.shell.splitscreen.SplitScreenTransitions.FLAG_IS_DIVIDER_BAR;
 import static com.android.wm.shell.transition.Transitions.ENABLE_SHELL_TRANSITIONS;
 import static com.android.wm.shell.transition.Transitions.TRANSIT_SPLIT_SCREEN_OPEN_TO_SIDE;
 import static com.android.wm.shell.transition.Transitions.TRANSIT_SPLIT_SCREEN_PAIR_OPEN;
@@ -126,12 +126,15 @@ import javax.inject.Provider;
  * This rules are mostly implemented in {@link #onStageVisibilityChanged(StageListenerImpl)} and
  * {@link #onStageHasChildrenChanged(StageListenerImpl).}
  */
-class StageCoordinator implements SplitLayout.SplitLayoutHandler,
+public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         DisplayController.OnDisplaysChangedListener, Transitions.TransitionHandler,
         ShellTaskOrganizer.TaskListener {
 
     private static final String TAG = StageCoordinator.class.getSimpleName();
 
+    /** Flag applied to a transition change to identify it as a divider bar for animation. */
+    public static final int FLAG_IS_DIVIDER_BAR = FLAG_FIRST_CUSTOM;
+
     private final SurfaceSession mSurfaceSession = new SurfaceSession();
 
     private final MainStage mMainStage;
@@ -619,7 +622,7 @@ class StageCoordinator implements SplitLayout.SplitLayoutHandler,
             if (ENABLE_SHELL_TRANSITIONS) {
                 final WindowContainerTransaction wct = new WindowContainerTransaction();
                 prepareExitSplitScreen(mTopStageAfterFoldDismiss, wct);
-                mSplitTransitions.startDismissTransition(null /* transition */, wct, this,
+                mSplitTransitions.startDismissTransition(wct, this,
                         mTopStageAfterFoldDismiss, EXIT_REASON_DEVICE_FOLDED);
             } else {
                 exitSplitScreen(
@@ -649,8 +652,8 @@ class StageCoordinator implements SplitLayout.SplitLayoutHandler,
                 final int dismissTop = mainStageVisible ? STAGE_TYPE_MAIN : STAGE_TYPE_SIDE;
                 final WindowContainerTransaction wct = new WindowContainerTransaction();
                 prepareExitSplitScreen(dismissTop, wct);
-                mSplitTransitions.startDismissTransition(null /* transition */, wct, this,
+                mSplitTransitions.startDismissTransition(wct, this, dismissTop,
-                        dismissTop, EXIT_REASON_SCREEN_LOCKED_SHOW_ON_TOP);
+                        EXIT_REASON_SCREEN_LOCKED_SHOW_ON_TOP);
             }
         }
     }
@@ -712,10 +715,7 @@ class StageCoordinator implements SplitLayout.SplitLayoutHandler,
                     .setWindowCrop(mSideStage.mRootLeash, null);
         });
 
-        // Hide divider and reset its position.
+        onTransitionAnimationComplete();
-        mSplitLayout.resetDividerPosition();
-        mSplitLayout.release();
-        mTopStageAfterFoldDismiss = STAGE_TYPE_UNDEFINED;
         Slog.i(TAG, "applyExitSplitScreen, reason = " + exitReasonToString(exitReason));
         // Log the exit
         if (childrenToTop != null) {
@@ -1111,8 +1111,7 @@ class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         final int dismissTop = mainStageToTop ? STAGE_TYPE_MAIN : STAGE_TYPE_SIDE;
         final WindowContainerTransaction wct = new WindowContainerTransaction();
         prepareExitSplitScreen(dismissTop, wct);
-        mSplitTransitions.startDismissTransition(
+        mSplitTransitions.startDismissTransition(wct, this, dismissTop, EXIT_REASON_DRAG_DIVIDER);
-                null /* transition */, wct, this, dismissTop, EXIT_REASON_DRAG_DIVIDER);
     }
 
     @Override
@@ -1301,7 +1300,8 @@ class StageCoordinator implements SplitLayout.SplitLayoutHandler,
             @Nullable TransitionRequestInfo request) {
         final ActivityManager.RunningTaskInfo triggerTask = request.getTriggerTask();
         if (triggerTask == null) {
-            if (mMainStage.isActive()) {
+            if (isSplitActive()) {
+                // Check if the display is rotating.
                 final TransitionRequestInfo.DisplayChange displayChange =
                         request.getDisplayChange();
                 if (request.getType() == TRANSIT_CHANGE && displayChange != null
@@ -1328,7 +1328,7 @@ class StageCoordinator implements SplitLayout.SplitLayoutHandler,
             mRecentTasks.ifPresent(recentTasks -> recentTasks.removeSplitPair(triggerTask.taskId));
         }
 
-        if (mMainStage.isActive()) {
+        if (isSplitActive()) {
             // Try to handle everything while in split-screen, so return a WCT even if it's empty.
             ProtoLog.v(ShellProtoLogGroup.WM_SHELL_TRANSITIONS, "  split is active so using split"
                             + "Transition to handle request. triggerTask=%d type=%s mainChildren=%d"
@@ -1343,7 +1343,7 @@ class StageCoordinator implements SplitLayout.SplitLayoutHandler,
                     int dismissTop = getStageType(stage) == STAGE_TYPE_MAIN ? STAGE_TYPE_SIDE
                             : STAGE_TYPE_MAIN;
                     prepareExitSplitScreen(dismissTop, out);
-                    mSplitTransitions.startDismissTransition(transition, out, this, dismissTop,
+                    mSplitTransitions.setDismissTransition(transition, dismissTop,
                             EXIT_REASON_APP_FINISHED);
                 }
             } else if (isOpening && inFullscreen) {
@@ -1353,12 +1353,12 @@ class StageCoordinator implements SplitLayout.SplitLayoutHandler,
                 } else if (activityType == ACTIVITY_TYPE_HOME
                         || activityType == ACTIVITY_TYPE_RECENTS) {
                     // Enter overview panel, so start recent transition.
-                    mSplitTransitions.startRecentTransition(transition, out, this,
+                    mSplitTransitions.setRecentTransition(transition,
                             request.getRemoteTransition());
                 } else {
                     // Occluded by the other fullscreen task, so dismiss both.
                     prepareExitSplitScreen(STAGE_TYPE_UNDEFINED, out);
-                    mSplitTransitions.startDismissTransition(transition, out, this,
+                    mSplitTransitions.setDismissTransition(transition,
                             STAGE_TYPE_UNDEFINED, EXIT_REASON_UNKNOWN);
                 }
             }
@@ -1373,6 +1373,33 @@ class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         return out;
     }
 
+    /**
+     * This is used for mixed scenarios. For such scenarios, just make sure to include exiting
+     * split or entering split when appropriate.
+     */
+    public void addEnterOrExitIfNeeded(@Nullable TransitionRequestInfo request,
+            @NonNull WindowContainerTransaction outWCT) {
+        final ActivityManager.RunningTaskInfo triggerTask = request.getTriggerTask();
+        if (triggerTask != null && triggerTask.displayId != mDisplayId) {
+            // Skip handling task on the other display.
+            return;
+        }
+        final @WindowManager.TransitionType int type = request.getType();
+        if (isSplitActive() && !isOpeningType(type)
+                    && (mMainStage.getChildCount() == 0 || mSideStage.getChildCount() == 0)) {
+            ProtoLog.v(ShellProtoLogGroup.WM_SHELL_TRANSITIONS, "  One of the splits became "
+                            + "empty during a mixed transition (one not handled by split),"
+                            + " so make sure split-screen state is cleaned-up. "
+                            + "mainStageCount=%d sideStageCount=%d", mMainStage.getChildCount(),
+                    mSideStage.getChildCount());
+            prepareExitSplitScreen(STAGE_TYPE_UNDEFINED, outWCT);
+        }
+    }
+
+    public boolean isSplitActive() {
+        return mMainStage.isActive();
+    }
+
     @Override
     public void mergeAnimation(IBinder transition, TransitionInfo info,
             SurfaceControl.Transaction t, IBinder mergeTarget,
@@ -1465,7 +1492,8 @@ class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         return true;
     }
 
-    void onTransitionAnimationComplete() {
+    /** Called to clean-up state and do house-keeping after the animation is done. */
+    public void onTransitionAnimationComplete() {
         // If still playing, let it finish.
         if (!mMainStage.isActive()) {
             // Update divider state after animation so that it is still around and positioned
@@ -1529,8 +1557,8 @@ class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         return true;
     }
 
-    private boolean startPendingDismissAnimation(
+    /** Synchronize split-screen state with transition and make appropriate preparations. */
-            @NonNull SplitScreenTransitions.DismissTransition dismissTransition,
+    public void prepareDismissAnimation(@StageType int toStage, @ExitReason int dismissReason,
             @NonNull TransitionInfo info, @NonNull SurfaceControl.Transaction t,
             @NonNull SurfaceControl.Transaction finishT) {
         // Make some noise if things aren't totally expected. These states shouldn't effect
@@ -1563,7 +1591,7 @@ class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         mRecentTasks.ifPresent(recentTasks -> {
             // Notify recents if we are exiting in a way that breaks the pair, and disable further
             // updates to splits in the recents until we enter split again
-            if (shouldBreakPairedTaskInRecents(dismissTransition.mReason) && mShouldUpdateRecents) {
+            if (shouldBreakPairedTaskInRecents(dismissReason) && mShouldUpdateRecents) {
                 for (TransitionInfo.Change change : info.getChanges()) {
                     final ActivityManager.RunningTaskInfo taskInfo = change.getTaskInfo();
                     if (taskInfo != null
@@ -1580,30 +1608,38 @@ class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         // Wait until after animation to update divider
 
         // Reset crops so they don't interfere with subsequent launches
-        t.setWindowCrop(mMainStage.mRootLeash, null);
+        t.setCrop(mMainStage.mRootLeash, null);
-        t.setWindowCrop(mSideStage.mRootLeash, null);
+        t.setCrop(mSideStage.mRootLeash, null);
 
-        if (dismissTransition.mDismissTop == STAGE_TYPE_UNDEFINED) {
+        if (toStage == STAGE_TYPE_UNDEFINED) {
-            logExit(dismissTransition.mReason);
+            logExit(dismissReason);
-            // TODO: Have a proper remote for this. Until then, though, reset state and use the
-            //       normal animation stuff (which falls back to the normal launcher remote).
-            mSplitLayout.release(t);
-            mSplitTransitions.mPendingDismiss = null;
-            return false;
         } else {
-            logExitToStage(dismissTransition.mReason,
+            logExitToStage(dismissReason, toStage == STAGE_TYPE_MAIN);
-                    dismissTransition.mDismissTop == STAGE_TYPE_MAIN);
         }
 
         addDividerBarToTransition(info, t, false /* show */);
-        // We're dismissing split by moving the other one to fullscreen.
-        // Since we don't have any animations for this yet, just use the internal example
-        // animations.
 
         // Hide divider and dim layer on transition finished.
         setDividerVisibility(false, finishT);
         finishT.hide(mMainStage.mDimLayer);
         finishT.hide(mSideStage.mDimLayer);
+    }
+
+    private boolean startPendingDismissAnimation(
+            @NonNull SplitScreenTransitions.DismissTransition dismissTransition,
+            @NonNull TransitionInfo info, @NonNull SurfaceControl.Transaction t,
+            @NonNull SurfaceControl.Transaction finishT) {
+        prepareDismissAnimation(dismissTransition.mDismissTop, dismissTransition.mReason, info,
+                t, finishT);
+        if (dismissTransition.mDismissTop == STAGE_TYPE_UNDEFINED) {
+            // TODO: Have a proper remote for this. Until then, though, reset state and use the
+            //       normal animation stuff (which falls back to the normal launcher remote).
+            t.hide(mSplitLayout.getDividerLeash());
+            mSplitLayout.release(t);
+            mSplitTransitions.mPendingDismiss = null;
+            return false;
+        }
+
         return true;
     }
 
@@ -1776,7 +1812,7 @@ class StageCoordinator implements SplitLayout.SplitLayoutHandler,
 
                 final WindowContainerTransaction wct = new WindowContainerTransaction();
                 prepareExitSplitScreen(STAGE_TYPE_UNDEFINED, wct);
-                mSplitTransitions.startDismissTransition(null /* transition */, wct,
+                mSplitTransitions.startDismissTransition(wct,
                         StageCoordinator.this, STAGE_TYPE_UNDEFINED,
                         EXIT_REASON_APP_DOES_NOT_SUPPORT_MULTIWINDOW);
             }

libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/StageTaskListener.java

@@ -268,13 +268,13 @@ class StageTaskListener implements ShellTaskOrganizer.TaskListener {
             mChildrenTaskInfo.remove(taskId);
             mChildrenLeashes.remove(taskId);
             mCallbacks.onChildTaskStatusChanged(taskId, false /* present */, taskInfo.isVisible);
-            if (taskInfo.getWindowingMode() == WINDOWING_MODE_PINNED) {
-                mCallbacks.onChildTaskEnterPip(taskId);
-            }
             if (ENABLE_SHELL_TRANSITIONS) {
                 // Status is managed/synchronized by the transition lifecycle.
                 return;
             }
+            if (taskInfo.getWindowingMode() == WINDOWING_MODE_PINNED) {
+                mCallbacks.onChildTaskEnterPip(taskId);
+            }
             sendStatusChanged();
         } else {
             throw new IllegalArgumentException(this + "\n Unknown task: " + taskInfo

libs/WindowManager/Shell/src/com/android/wm/shell/transition/DefaultMixedHandler.java

@@ -0,0 +1,253 @@
+/*
+ * 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.transition;
+
+import static android.app.WindowConfiguration.ACTIVITY_TYPE_HOME;
+import static android.view.WindowManager.TRANSIT_TO_BACK;
+import static android.window.TransitionInfo.FLAG_IS_WALLPAPER;
+
+import static com.android.wm.shell.splitscreen.SplitScreen.STAGE_TYPE_UNDEFINED;
+import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_CHILD_TASK_ENTER_PIP;
+import static com.android.wm.shell.splitscreen.StageCoordinator.FLAG_IS_DIVIDER_BAR;
+
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.os.IBinder;
+import android.view.SurfaceControl;
+import android.view.WindowManager;
+import android.window.TransitionInfo;
+import android.window.TransitionRequestInfo;
+import android.window.WindowContainerTransaction;
+
+import com.android.internal.protolog.common.ProtoLog;
+import com.android.wm.shell.pip.PipTransitionController;
+import com.android.wm.shell.protolog.ShellProtoLogGroup;
+import com.android.wm.shell.splitscreen.StageCoordinator;
+
+import java.util.ArrayList;
+
+/**
+ * A handler for dealing with transitions involving multiple other handlers. For example: an
+ * activity in split-screen going into PiP.
+ */
+public class DefaultMixedHandler implements Transitions.TransitionHandler {
+
+    private final Transitions mPlayer;
+    private final PipTransitionController mPipHandler;
+    private final StageCoordinator mSplitHandler;
+
+    private static class MixedTransition {
+        static final int TYPE_ENTER_PIP_FROM_SPLIT = 1;
+
+        final int mType;
+        final IBinder mTransition;
+
+        Transitions.TransitionFinishCallback mFinishCallback = null;
+
+        /**
+         * Mixed transitions are made up of multiple "parts". This keeps track of how many
+         * parts are currently animating.
+         */
+        int mInFlightSubAnimations = 0;
+
+        MixedTransition(int type, IBinder transition) {
+            mType = type;
+            mTransition = transition;
+        }
+    }
+    private final ArrayList<MixedTransition> mActiveTransitions = new ArrayList<>();
+
+    public DefaultMixedHandler(@NonNull Transitions player,
+            @NonNull PipTransitionController pipHandler, @NonNull StageCoordinator splitHandler) {
+        mPlayer = player;
+        mPipHandler = pipHandler;
+        mSplitHandler = splitHandler;
+    }
+
+    @Nullable
+    @Override
+    public WindowContainerTransaction handleRequest(@NonNull IBinder transition,
+            @NonNull TransitionRequestInfo request) {
+        if (mPipHandler.requestHasPipEnter(request) && mSplitHandler.isSplitActive()) {
+            ProtoLog.v(ShellProtoLogGroup.WM_SHELL_TRANSITIONS, " Got a PiP-enter request while "
+                    + "Split-Screen is active, so treat it as Mixed.");
+            if (request.getRemoteTransition() != null) {
+                throw new IllegalStateException("Unexpected remote transition in"
+                        + "pip-enter-from-split request");
+            }
+            mActiveTransitions.add(new MixedTransition(MixedTransition.TYPE_ENTER_PIP_FROM_SPLIT,
+                    transition));
+
+            WindowContainerTransaction out = new WindowContainerTransaction();
+            mPipHandler.augmentRequest(transition, request, out);
+            mSplitHandler.addEnterOrExitIfNeeded(request, out);
+            return out;
+        }
+        return null;
+    }
+
+    private TransitionInfo subCopy(@NonNull TransitionInfo info,
+            @WindowManager.TransitionType int newType) {
+        final TransitionInfo out = new TransitionInfo(newType, info.getFlags());
+        for (int i = 0; i < info.getChanges().size(); ++i) {
+            out.getChanges().add(info.getChanges().get(i));
+        }
+        out.setRootLeash(info.getRootLeash(), info.getRootOffset().x, info.getRootOffset().y);
+        out.setAnimationOptions(info.getAnimationOptions());
+        return out;
+    }
+
+    private boolean isHomeOpening(@NonNull TransitionInfo.Change change) {
+        return change.getTaskInfo() != null
+                && change.getTaskInfo().getActivityType() != ACTIVITY_TYPE_HOME;
+    }
+
+    private boolean isWallpaper(@NonNull TransitionInfo.Change change) {
+        return (change.getFlags() & FLAG_IS_WALLPAPER) != 0;
+    }
+
+    @Override
+    public boolean startAnimation(@NonNull IBinder transition, @NonNull TransitionInfo info,
+            @NonNull SurfaceControl.Transaction startTransaction,
+            @NonNull SurfaceControl.Transaction finishTransaction,
+            @NonNull Transitions.TransitionFinishCallback finishCallback) {
+        MixedTransition mixed = null;
+        for (int i = mActiveTransitions.size() - 1; i >= 0; --i) {
+            if (mActiveTransitions.get(i).mTransition != transition) continue;
+            mixed = mActiveTransitions.remove(i);
+            break;
+        }
+        if (mixed == null) return false;
+
+        if (mixed.mType == MixedTransition.TYPE_ENTER_PIP_FROM_SPLIT) {
+            return animateEnterPipFromSplit(mixed, info, startTransaction, finishTransaction,
+                    finishCallback);
+        } else {
+            throw new IllegalStateException("Starting mixed animation without a known mixed type? "
+                    + mixed.mType);
+        }
+    }
+
+    private boolean animateEnterPipFromSplit(@NonNull final MixedTransition mixed,
+            @NonNull TransitionInfo info,
+            @NonNull SurfaceControl.Transaction startTransaction,
+            @NonNull SurfaceControl.Transaction finishTransaction,
+            @NonNull Transitions.TransitionFinishCallback finishCallback) {
+        ProtoLog.v(ShellProtoLogGroup.WM_SHELL_TRANSITIONS, " Animating a mixed transition for "
+                + "entering PIP while Split-Screen is active.");
+        TransitionInfo.Change pipChange = null;
+        TransitionInfo.Change wallpaper = null;
+        final TransitionInfo everythingElse = subCopy(info, TRANSIT_TO_BACK);
+        boolean homeIsOpening = false;
+        for (int i = info.getChanges().size() - 1; i >= 0; --i) {
+            TransitionInfo.Change change = info.getChanges().get(i);
+            if (mPipHandler.isEnteringPip(change, info.getType())) {
+                if (pipChange != null) {
+                    throw new IllegalStateException("More than 1 pip-entering changes in one"
+                            + " transition? " + info);
+                }
+                pipChange = change;
+                // going backwards, so remove-by-index is fine.
+                everythingElse.getChanges().remove(i);
+            } else if (isHomeOpening(change)) {
+                homeIsOpening = true;
+            } else if (isWallpaper(change)) {
+                wallpaper = change;
+            }
+        }
+        if (pipChange == null) {
+            // um, something probably went wrong.
+            return false;
+        }
+        final boolean isGoingHome = homeIsOpening;
+        mixed.mFinishCallback = finishCallback;
+        Transitions.TransitionFinishCallback finishCB = (wct, wctCB) -> {
+            --mixed.mInFlightSubAnimations;
+            if (mixed.mInFlightSubAnimations > 0) return;
+            if (isGoingHome) {
+                mSplitHandler.onTransitionAnimationComplete();
+            }
+            mixed.mFinishCallback.onTransitionFinished(wct, wctCB);
+        };
+        if (isGoingHome) {
+            ProtoLog.v(ShellProtoLogGroup.WM_SHELL_TRANSITIONS, " Animation is actually mixed "
+                    + "since entering-PiP caused us to leave split and return home.");
+            // We need to split the transition into 2 parts: the pip part (animated by pip)
+            // and the dismiss-part (animated by launcher).
+            mixed.mInFlightSubAnimations = 2;
+            // immediately make the wallpaper visible (so that we don't see it pop-in during
+            // the time it takes to start recents animation (which is remote).
+            if (wallpaper != null) {
+                startTransaction.show(wallpaper.getLeash()).setAlpha(wallpaper.getLeash(), 1.f);
+            }
+            // make a new startTransaction because pip's startEnterAnimation "consumes" it so
+            // we need a separate one to send over to launcher.
+            SurfaceControl.Transaction otherStartT = new SurfaceControl.Transaction();
+            // Let split update internal state for dismiss.
+            mSplitHandler.prepareDismissAnimation(STAGE_TYPE_UNDEFINED,
+                    EXIT_REASON_CHILD_TASK_ENTER_PIP, everythingElse, otherStartT,
+                    finishTransaction);
+
+            // We are trying to accommodate launcher's close animation which can't handle the
+            // divider-bar, so if split-handler is closing the divider-bar, just hide it and remove
+            // from transition info.
+            for (int i = everythingElse.getChanges().size() - 1; i >= 0; --i) {
+                if ((everythingElse.getChanges().get(i).getFlags() & FLAG_IS_DIVIDER_BAR) != 0) {
+                    everythingElse.getChanges().remove(i);
+                    break;
+                }
+            }
+
+            mPipHandler.startEnterAnimation(pipChange, startTransaction, finishTransaction,
+                    finishCB);
+            // Dispatch the rest of the transition normally. This will most-likely be taken by
+            // recents or default handler.
+            mPlayer.dispatchTransition(mixed.mTransition, everythingElse, otherStartT,
+                    finishTransaction, finishCB, this);
+        } else {
+            ProtoLog.v(ShellProtoLogGroup.WM_SHELL_TRANSITIONS, "  Not leaving split, so just "
+                    + "forward animation to Pip-Handler.");
+            // This happens if the pip-ing activity is in a multi-activity task (and thus a
+            // new pip task is spawned). In this case, we don't actually exit split so we can
+            // just let pip transition handle the animation verbatim.
+            mixed.mInFlightSubAnimations = 1;
+            mPipHandler.startAnimation(mixed.mTransition, info, startTransaction, finishTransaction,
+                    finishCB);
+        }
+        return true;
+    }
+
+    @Override
+    public void mergeAnimation(@NonNull IBinder transition, @NonNull TransitionInfo info,
+            @NonNull SurfaceControl.Transaction t, @NonNull IBinder mergeTarget,
+            @NonNull Transitions.TransitionFinishCallback finishCallback) {
+    }
+
+    @Override
+    public void onTransitionMerged(@NonNull IBinder transition) {
+        MixedTransition mixed = null;
+        for (int i = mActiveTransitions.size() - 1; i >= 0; --i) {
+            if (mActiveTransitions.get(i).mTransition != transition) continue;
+            mixed = mActiveTransitions.remove(i);
+            break;
+        }
+        if (mixed == null) return;
+        if (mixed.mType == MixedTransition.TYPE_ENTER_PIP_FROM_SPLIT) {
+            mPipHandler.onTransitionMerged(transition);
+        }
+    }
+}

libs/WindowManager/Shell/src/com/android/wm/shell/transition/Transitions.java

@@ -435,33 +435,42 @@ public class Transitions implements RemoteCallable<Transitions> {
                 playing.mToken, (wct, cb) -> onFinish(merging.mToken, wct, cb));
     }
 
-    boolean startAnimation(@NonNull ActiveTransition active, TransitionHandler handler) {
+    private void playTransition(@NonNull ActiveTransition active) {
-        return handler.startAnimation(active.mToken, active.mInfo, active.mStartT, active.mFinishT,
-                (wct, cb) -> onFinish(active.mToken, wct, cb));
-    }
-
-    void playTransition(@NonNull ActiveTransition active) {
         setupAnimHierarchy(active.mInfo, active.mStartT, active.mFinishT);
 
         // If a handler already chose to run this animation, try delegating to it first.
         if (active.mHandler != null) {
             ProtoLog.v(ShellProtoLogGroup.WM_SHELL_TRANSITIONS, " try firstHandler %s",
                     active.mHandler);
-            if (startAnimation(active, active.mHandler)) {
+            boolean consumed = active.mHandler.startAnimation(active.mToken, active.mInfo,
+                    active.mStartT, active.mFinishT, (wct, cb) -> onFinish(active.mToken, wct, cb));
+            if (consumed) {
                 ProtoLog.v(ShellProtoLogGroup.WM_SHELL_TRANSITIONS, " animated by firstHandler");
                 return;
             }
         }
-        // Otherwise give every other handler a chance (in order)
+        // Otherwise give every other handler a chance
+        active.mHandler = dispatchTransition(active.mToken, active.mInfo, active.mStartT,
+                active.mFinishT, (wct, cb) -> onFinish(active.mToken, wct, cb), active.mHandler);
+    }
+
+    /**
+     * Gives every handler (in order) a chance to animate until one consumes the transition.
+     * @return the handler which consumed the transition.
+     */
+    TransitionHandler dispatchTransition(@NonNull IBinder transition, @NonNull TransitionInfo info,
+            @NonNull SurfaceControl.Transaction startT, @NonNull SurfaceControl.Transaction finishT,
+            @NonNull TransitionFinishCallback finishCB, @Nullable TransitionHandler skip) {
         for (int i = mHandlers.size() - 1; i >= 0; --i) {
-            if (mHandlers.get(i) == active.mHandler) continue;
+            if (mHandlers.get(i) == skip) continue;
             ProtoLog.v(ShellProtoLogGroup.WM_SHELL_TRANSITIONS, " try handler %s",
                     mHandlers.get(i));
-            if (startAnimation(active, mHandlers.get(i))) {
+            boolean consumed = mHandlers.get(i).startAnimation(transition, info, startT, finishT,
+                    finishCB);
+            if (consumed) {
                 ProtoLog.v(ShellProtoLogGroup.WM_SHELL_TRANSITIONS, " animated by %s",
                         mHandlers.get(i));
-                active.mHandler = mHandlers.get(i);
+                return mHandlers.get(i);
-                return;
             }
         }
         throw new IllegalStateException(

libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/splitscreen/SplitTransitionTests.java

@@ -333,7 +333,7 @@ public class SplitTransitionTests extends ShellTestCase {
         TransitionInfo info = new TransitionInfo(TRANSIT_TO_BACK, 0);
         info.addChange(mainChange);
         info.addChange(sideChange);
-        IBinder transition = mSplitScreenTransitions.startDismissTransition(null,
+        IBinder transition = mSplitScreenTransitions.startDismissTransition(
                 new WindowContainerTransaction(), mStageCoordinator,
                 EXIT_REASON_APP_DOES_NOT_SUPPORT_MULTIWINDOW, STAGE_TYPE_SIDE);
         boolean accepted = mStageCoordinator.startAnimation(transition, info,
@@ -355,7 +355,7 @@ public class SplitTransitionTests extends ShellTestCase {
         TransitionInfo info = new TransitionInfo(TRANSIT_TO_BACK, 0);
         info.addChange(mainChange);
         info.addChange(sideChange);
-        IBinder transition = mSplitScreenTransitions.startDismissTransition(null,
+        IBinder transition = mSplitScreenTransitions.startDismissTransition(
                 new WindowContainerTransaction(), mStageCoordinator, EXIT_REASON_DRAG_DIVIDER,
                 STAGE_TYPE_SIDE);
         mMainStage.onTaskVanished(mMainChild);