Merge changes Id75611af,I1ead6501 into tm-qpr-dev

* changes:
  Support back to split
  Support back gesture to split pair in background

libs/WindowManager/Shell/src/com/android/wm/shell/draganddrop/DragAndDropPolicy.java

@@ -240,7 +240,7 @@ public class DragAndDropPolicy {
             // Update launch options for the split side we are targeting.
             position = leftOrTop ? SPLIT_POSITION_TOP_OR_LEFT : SPLIT_POSITION_BOTTOM_OR_RIGHT;
             // Add some data for logging splitscreen once it is invoked
-            mSplitScreen.logOnDroppedToSplit(position, mLoggerSessionId);
+            mSplitScreen.onDroppedToSplit(position, mLoggerSessionId);
         }
 
         final ClipDescription description = data.getDescription();

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

@@ -16,9 +16,6 @@
 
 package com.android.wm.shell.splitscreen;
 
-import static com.android.wm.shell.common.split.SplitScreenConstants.CONTROLLED_ACTIVITY_TYPES;
-import static com.android.wm.shell.common.split.SplitScreenConstants.CONTROLLED_WINDOWING_MODES;
-
 import android.content.Context;
 import android.view.SurfaceSession;
 import android.window.WindowContainerToken;
@@ -34,8 +31,6 @@ import com.android.wm.shell.common.SyncTransactionQueue;
  * @see StageCoordinator
  */
 class MainStage extends StageTaskListener {
-    private static final String TAG = MainStage.class.getSimpleName();
-
     private boolean mIsActive = false;
 
     MainStage(Context context, ShellTaskOrganizer taskOrganizer, int displayId,
@@ -52,15 +47,8 @@ class MainStage extends StageTaskListener {
     void activate(WindowContainerTransaction wct, boolean includingTopTask) {
         if (mIsActive) return;
 
-        final WindowContainerToken rootToken = mRootTaskInfo.token;
         if (includingTopTask) {
-            wct.reparentTasks(
+            reparentTopTask(wct);
-                    null /* currentParent */,
-                    rootToken,
-                    CONTROLLED_WINDOWING_MODES,
-                    CONTROLLED_ACTIVITY_TYPES,
-                    true /* onTop */,
-                    true /* reparentTopOnly */);
         }
 
         mIsActive = true;

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

@@ -121,7 +121,8 @@ public class SplitScreenController implements DragAndDropPolicy.Starter,
     public static final int EXIT_REASON_SCREEN_LOCKED = 7;
     public static final int EXIT_REASON_SCREEN_LOCKED_SHOW_ON_TOP = 8;
     public static final int EXIT_REASON_CHILD_TASK_ENTER_PIP = 9;
-    public static final int EXIT_REASON_FULLSCREEN_SHORTCUT = 10;
+    public static final int EXIT_REASON_RECREATE_SPLIT = 10;
+    public static final int EXIT_REASON_FULLSCREEN_SHORTCUT = 11;
     @IntDef(value = {
             EXIT_REASON_UNKNOWN,
             EXIT_REASON_APP_DOES_NOT_SUPPORT_MULTIWINDOW,
@@ -133,6 +134,7 @@ public class SplitScreenController implements DragAndDropPolicy.Starter,
             EXIT_REASON_SCREEN_LOCKED,
             EXIT_REASON_SCREEN_LOCKED_SHOW_ON_TOP,
             EXIT_REASON_CHILD_TASK_ENTER_PIP,
+            EXIT_REASON_RECREATE_SPLIT,
             EXIT_REASON_FULLSCREEN_SHORTCUT,
     })
     @Retention(RetentionPolicy.SOURCE)
@@ -470,7 +472,7 @@ public class SplitScreenController implements DragAndDropPolicy.Starter,
      */
     public void startShortcut(String packageName, String shortcutId, @SplitPosition int position,
             @Nullable Bundle options, UserHandle user, @NonNull InstanceId instanceId) {
-        mStageCoordinator.getLogger().enterRequested(instanceId, ENTER_REASON_LAUNCHER);
+        mStageCoordinator.onRequestToSplit(instanceId, ENTER_REASON_LAUNCHER);
         startShortcut(packageName, shortcutId, position, options, user);
     }
 
@@ -518,7 +520,7 @@ public class SplitScreenController implements DragAndDropPolicy.Starter,
      */
     public void startIntent(PendingIntent intent, @Nullable Intent fillInIntent,
             @SplitPosition int position, @Nullable Bundle options, @NonNull InstanceId instanceId) {
-        mStageCoordinator.getLogger().enterRequested(instanceId, ENTER_REASON_LAUNCHER);
+        mStageCoordinator.onRequestToSplit(instanceId, ENTER_REASON_LAUNCHER);
         startIntent(intent, fillInIntent, position, options);
     }
 
@@ -784,10 +786,10 @@ public class SplitScreenController implements DragAndDropPolicy.Starter,
         return splitTasksLayer;
     }
     /**
-     * Sets drag info to be logged when splitscreen is entered.
+     * Drop callback when splitscreen is entered.
      */
-    public void logOnDroppedToSplit(@SplitPosition int position, InstanceId dragSessionId) {
+    public void onDroppedToSplit(@SplitPosition int position, InstanceId dragSessionId) {
-        mStageCoordinator.logOnDroppedToSplit(position, dragSessionId);
+        mStageCoordinator.onDroppedToSplit(position, dragSessionId);
     }
 
     /**
@@ -815,6 +817,8 @@ public class SplitScreenController implements DragAndDropPolicy.Starter,
                 return "APP_DOES_NOT_SUPPORT_MULTIWINDOW";
             case EXIT_REASON_CHILD_TASK_ENTER_PIP:
                 return "CHILD_TASK_ENTER_PIP";
+            case EXIT_REASON_RECREATE_SPLIT:
+                return "RECREATE_SPLIT";
             default:
                 return "unknown reason, reason int = " + exitReason;
         }

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

@@ -21,9 +21,11 @@ import static com.android.internal.util.FrameworkStatsLog.SPLITSCREEN_UICHANGED_
 import static com.android.internal.util.FrameworkStatsLog.SPLITSCREEN_UICHANGED__ENTER_REASON__UNKNOWN_ENTER;
 import static com.android.internal.util.FrameworkStatsLog.SPLITSCREEN_UICHANGED__EXIT_REASON__APP_DOES_NOT_SUPPORT_MULTIWINDOW;
 import static com.android.internal.util.FrameworkStatsLog.SPLITSCREEN_UICHANGED__EXIT_REASON__APP_FINISHED;
+import static com.android.internal.util.FrameworkStatsLog.SPLITSCREEN_UICHANGED__EXIT_REASON__CHILD_TASK_ENTER_PIP;
 import static com.android.internal.util.FrameworkStatsLog.SPLITSCREEN_UICHANGED__EXIT_REASON__DEVICE_FOLDED;
 import static com.android.internal.util.FrameworkStatsLog.SPLITSCREEN_UICHANGED__EXIT_REASON__DRAG_DIVIDER;
 import static com.android.internal.util.FrameworkStatsLog.SPLITSCREEN_UICHANGED__EXIT_REASON__FULLSCREEN_SHORTCUT;
+import static com.android.internal.util.FrameworkStatsLog.SPLITSCREEN_UICHANGED__EXIT_REASON__RECREATE_SPLIT;
 import static com.android.internal.util.FrameworkStatsLog.SPLITSCREEN_UICHANGED__EXIT_REASON__RETURN_HOME;
 import static com.android.internal.util.FrameworkStatsLog.SPLITSCREEN_UICHANGED__EXIT_REASON__ROOT_TASK_VANISHED;
 import static com.android.internal.util.FrameworkStatsLog.SPLITSCREEN_UICHANGED__EXIT_REASON__SCREEN_LOCKED;
@@ -37,9 +39,11 @@ import static com.android.wm.shell.splitscreen.SplitScreenController.ENTER_REASO
 import static com.android.wm.shell.splitscreen.SplitScreenController.ENTER_REASON_UNKNOWN;
 import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_APP_DOES_NOT_SUPPORT_MULTIWINDOW;
 import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_APP_FINISHED;
+import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_CHILD_TASK_ENTER_PIP;
 import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_DEVICE_FOLDED;
 import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_DRAG_DIVIDER;
 import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_FULLSCREEN_SHORTCUT;
+import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_RECREATE_SPLIT;
 import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_RETURN_HOME;
 import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_ROOT_TASK_VANISHED;
 import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_SCREEN_LOCKED;
@@ -182,6 +186,10 @@ public class SplitscreenEventLogger {
                 return SPLITSCREEN_UICHANGED__EXIT_REASON__SCREEN_LOCKED;
             case EXIT_REASON_SCREEN_LOCKED_SHOW_ON_TOP:
                 return SPLITSCREEN_UICHANGED__EXIT_REASON__SCREEN_LOCKED_SHOW_ON_TOP;
+            case EXIT_REASON_CHILD_TASK_ENTER_PIP:
+                return SPLITSCREEN_UICHANGED__EXIT_REASON__CHILD_TASK_ENTER_PIP;
+            case EXIT_REASON_RECREATE_SPLIT:
+                return SPLITSCREEN_UICHANGED__EXIT_REASON__RECREATE_SPLIT;
             case EXIT_REASON_FULLSCREEN_SHORTCUT:
                 return SPLITSCREEN_UICHANGED__EXIT_REASON__FULLSCREEN_SHORTCUT;
             case EXIT_REASON_UNKNOWN:

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

@@ -49,10 +49,11 @@ import static com.android.wm.shell.splitscreen.SplitScreenController.ENTER_REASO
 import static com.android.wm.shell.splitscreen.SplitScreenController.ENTER_REASON_MULTI_INSTANCE;
 import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_APP_DOES_NOT_SUPPORT_MULTIWINDOW;
 import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_APP_FINISHED;
-import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_FULLSCREEN_SHORTCUT;
 import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_CHILD_TASK_ENTER_PIP;
 import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_DEVICE_FOLDED;
 import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_DRAG_DIVIDER;
+import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_FULLSCREEN_SHORTCUT;
+import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_RECREATE_SPLIT;
 import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_RETURN_HOME;
 import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_ROOT_TASK_VANISHED;
 import static com.android.wm.shell.splitscreen.SplitScreenController.EXIT_REASON_SCREEN_LOCKED_SHOW_ON_TOP;
@@ -199,7 +200,8 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
     // and exit, since exit itself can trigger a number of changes that update the stages.
     private boolean mShouldUpdateRecents;
     private boolean mExitSplitScreenOnHide;
-    private boolean mIsDividerRemoteAnimating;
+    private boolean mIsSplitEntering;
+    private boolean mIsDropEntering;
     private boolean mIsExiting;
 
     /** The target stage to dismiss to when unlock after folded. */
@@ -347,10 +349,19 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         return mSplitTransitions;
     }
 
-    boolean isSplitScreenVisible() {
+    public boolean isSplitScreenVisible() {
         return mSideStageListener.mVisible && mMainStageListener.mVisible;
     }
 
+    public boolean isSplitActive() {
+        return mMainStage.isActive();
+    }
+
+    boolean isSplitScreenRunningBackground() {
+        return !isSplitScreenVisible() && mMainStageListener.mHasChildren
+                && mSideStageListener.mHasChildren;
+    }
+
     @StageType
     int getStageOfTask(int taskId) {
         if (mMainStage.containsTask(taskId)) {
@@ -373,11 +384,12 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
             targetStage = mSideStage;
             sideStagePosition = stagePosition;
         } else {
-            if (mMainStage.isActive()) {
+            if (isSplitScreenVisible()) {
                 // If the split screen is activated, retrieves target stage based on position.
                 targetStage = stagePosition == mSideStagePosition ? mSideStage : mMainStage;
                 sideStagePosition = mSideStagePosition;
             } else {
+                exitSplitIfBackground();
                 targetStage = mSideStage;
                 sideStagePosition = stagePosition;
             }
@@ -673,6 +685,7 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
             @Nullable PendingIntent mainPendingIntent, @Nullable Intent mainFillInIntent,
             @Nullable Bundle mainOptions, @SplitPosition int sidePosition, float splitRatio,
             RemoteAnimationAdapter adapter, InstanceId instanceId) {
+        exitSplitIfBackground();
         // Init divider first to make divider leash for remote animation target.
         mSplitLayout.init();
         mSplitLayout.setDivideRatio(splitRatio);
@@ -685,11 +698,13 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
 
         // Set false to avoid record new bounds with old task still on top;
         mShouldUpdateRecents = false;
-        mIsDividerRemoteAnimating = true;
+        mIsSplitEntering = true;
 
         final WindowContainerTransaction evictWct = new WindowContainerTransaction();
-        prepareEvictChildTasks(SPLIT_POSITION_TOP_OR_LEFT, evictWct);
+        if (isSplitScreenVisible()) {
-        prepareEvictChildTasks(SPLIT_POSITION_BOTTOM_OR_RIGHT, evictWct);
+            mMainStage.evictAllChildren(evictWct);
+            mSideStage.evictAllChildren(evictWct);
+        }
 
         IRemoteAnimationRunner wrapper = new IRemoteAnimationRunner.Stub() {
             @Override
@@ -769,7 +784,7 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
 
     private void onRemoteAnimationFinishedOrCancelled(boolean cancel,
             WindowContainerTransaction evictWct) {
-        mIsDividerRemoteAnimating = false;
+        mIsSplitEntering = false;
         mShouldUpdateRecents = true;
         // If any stage has no child after animation finished, it means that split will display
         // nothing, such status will happen if task and intent is same app but not support
@@ -781,6 +796,9 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
             mSplitUnsupportedToast.show();
         } else {
             mSyncQueue.queue(evictWct);
+            mSyncQueue.runInSync(t -> {
+                updateSurfaceBounds(mSplitLayout, t, false /* applyResizingOffset */);
+            });
         }
     }
 
@@ -815,7 +833,7 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         switch (stage) {
             case STAGE_TYPE_UNDEFINED: {
                 if (position != SPLIT_POSITION_UNDEFINED) {
-                    if (mMainStage.isActive()) {
+                    if (isSplitScreenVisible()) {
                         // Use the stage of the specified position
                         options = resolveStartStage(
                                 position == mSideStagePosition ? STAGE_TYPE_SIDE : STAGE_TYPE_MAIN,
@@ -1045,7 +1063,7 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
             }
         });
         mShouldUpdateRecents = false;
-        mIsDividerRemoteAnimating = false;
+        mIsSplitEntering = false;
 
         mSplitLayout.getInvisibleBounds(mTempRect1);
         if (childrenToTop == null || childrenToTop.getTopVisibleChildTaskId() == INVALID_TASK_ID) {
@@ -1064,6 +1082,8 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
             wct.setSmallestScreenWidthDp(childrenToTop.mRootTaskInfo.token,
                     SMALLEST_SCREEN_WIDTH_DP_UNDEFINED);
         }
+        wct.setReparentLeafTaskIfRelaunch(mRootTaskInfo.token,
+                false /* reparentLeafTaskIfRelaunch */);
         mSyncQueue.queue(wct);
         mSyncQueue.runInSync(t -> {
             t.setWindowCrop(mMainStage.mRootLeash, null)
@@ -1102,6 +1122,13 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         }
     }
 
+    /** Exit split screen if it still running background */
+    public void exitSplitIfBackground() {
+        if (!isSplitScreenRunningBackground()) return;
+
+        exitSplitScreen(null /* childrenToTop */, EXIT_REASON_RECREATE_SPLIT);
+    }
+
     /**
      * Overridden by child classes.
      */
@@ -1374,7 +1401,7 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
                 && !ENABLE_SHELL_TRANSITIONS) {
             // Clear the divider remote animating flag as the divider will be re-rendered to apply
             // the new rotation config.
-            mIsDividerRemoteAnimating = false;
+            mIsSplitEntering = false;
             mSplitLayout.update(null /* t */);
             onLayoutSizeChanged(mSplitLayout);
         }
@@ -1423,6 +1450,33 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         });
     }
 
+    void onChildTaskAppeared(StageListenerImpl stageListener, int taskId) {
+        if (stageListener == mSideStageListener && isSplitScreenRunningBackground()) {
+            // Handle entring split case here if split already running background.
+            if (mIsDropEntering) {
+                mSplitLayout.resetDividerPosition();
+            } else {
+                mSplitLayout.setDividerAtBorder(mSideStagePosition == SPLIT_POSITION_TOP_OR_LEFT);
+            }
+            final WindowContainerTransaction wct = new WindowContainerTransaction();
+            mMainStage.evictAllChildren(wct);
+            mSideStage.evictOtherChildren(wct, taskId);
+            mMainStage.reparentTopTask(wct);
+            updateWindowBounds(mSplitLayout, wct);
+            wct.reorder(mRootTaskInfo.token, true);
+
+            mSyncQueue.queue(wct);
+            mSyncQueue.runInSync(t -> {
+                if (mIsDropEntering) {
+                    updateSurfaceBounds(mSplitLayout, t, false /* applyResizingOffset */);
+                    mIsDropEntering = false;
+                } else {
+                    mSplitLayout.flingDividerToCenter();
+                }
+            });
+        }
+    }
+
     private void onRootTaskVanished() {
         final WindowContainerTransaction wct = new WindowContainerTransaction();
         if (mRootTaskInfo != null) {
@@ -1441,20 +1495,20 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
             return;
         }
 
+        final WindowContainerTransaction wct = new WindowContainerTransaction();
         if (!mainStageVisible) {
+            wct.setReparentLeafTaskIfRelaunch(mRootTaskInfo.token,
+                    true /* setReparentLeafTaskIfRelaunch */);
             // Both stages are not visible, check if it needs to dismiss split screen.
-            if (mExitSplitScreenOnHide
+            if (mExitSplitScreenOnHide) {
-                    // Don't dismiss split screen when both stages are not visible due to sleeping
-                    // display.
-                    || (!mMainStage.mRootTaskInfo.isSleeping
-                    && !mSideStage.mRootTaskInfo.isSleeping)) {
                 exitSplitScreen(null /* childrenToTop */, EXIT_REASON_RETURN_HOME);
             }
+        } else {
+            wct.setReparentLeafTaskIfRelaunch(mRootTaskInfo.token,
+                    false /* setReparentLeafTaskIfRelaunch */);
         }
-
+        mSyncQueue.queue(wct);
         mSyncQueue.runInSync(t -> {
-            t.setVisibility(mSideStage.mRootLeash, sideStageVisible)
-                    .setVisibility(mMainStage.mRootLeash, mainStageVisible);
             setDividerVisibility(mainStageVisible, t);
         });
     }
@@ -1479,7 +1533,7 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         mDividerVisible = visible;
         sendSplitVisibilityChanged();
 
-        if (mIsDividerRemoteAnimating) {
+        if (mIsSplitEntering) {
             ProtoLog.d(ShellProtoLogGroup.WM_SHELL_SPLIT_SCREEN,
                     "   Skip animating divider bar due to it's remote animating.");
             return;
@@ -1499,7 +1553,7 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
                     "   Skip animating divider bar due to divider leash not ready.");
             return;
         }
-        if (mIsDividerRemoteAnimating) {
+        if (mIsSplitEntering) {
             ProtoLog.d(ShellProtoLogGroup.WM_SHELL_SPLIT_SCREEN,
                     "   Skip animating divider bar due to it's remote animating.");
             return;
@@ -1555,26 +1609,22 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         if (!hasChildren && !mIsExiting && mMainStage.isActive()) {
             if (isSideStage && mMainStageListener.mVisible) {
                 // Exit to main stage if side stage no longer has children.
-                if (ENABLE_SHELL_TRANSITIONS) {
-                    exitSplitScreen(mMainStage, EXIT_REASON_APP_FINISHED);
-                } else {
                 mSplitLayout.flingDividerToDismiss(
                         mSideStagePosition == SPLIT_POSITION_BOTTOM_OR_RIGHT,
                         EXIT_REASON_APP_FINISHED);
-                }
             } else if (!isSideStage && mSideStageListener.mVisible) {
                 // Exit to side stage if main stage no longer has children.
-                if (ENABLE_SHELL_TRANSITIONS) {
-                    exitSplitScreen(mSideStage, EXIT_REASON_APP_FINISHED);
-                } else {
                 mSplitLayout.flingDividerToDismiss(
                         mSideStagePosition != SPLIT_POSITION_BOTTOM_OR_RIGHT,
                         EXIT_REASON_APP_FINISHED);
-                }
+            } else if (isSplitScreenRunningBackground()) {
+                // Do not exit to any stage due to running background.
+                exitSplitScreen(null /* childrenToTop */, EXIT_REASON_APP_FINISHED);
             }
         } else if (isSideStage && hasChildren && !mMainStage.isActive()) {
-            final WindowContainerTransaction wct = new WindowContainerTransaction();
             mSplitLayout.init();
+
+            final WindowContainerTransaction wct = new WindowContainerTransaction();
             if (mLogger.isEnterRequestedByDrag()) {
                 prepareEnterSplitScreen(wct);
             } else {
@@ -1589,8 +1639,9 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
 
             mSyncQueue.queue(wct);
             mSyncQueue.runInSync(t -> {
-                if (mLogger.isEnterRequestedByDrag()) {
+                if (mIsDropEntering) {
                     updateSurfaceBounds(mSplitLayout, t, false /* applyResizingOffset */);
+                    mIsDropEntering = false;
                 } else {
                     mShowDecorImmediately = true;
                     mSplitLayout.flingDividerToCenter();
@@ -1945,10 +1996,6 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         }
     }
 
-    public boolean isSplitActive() {
-        return mMainStage.isActive();
-    }
-
     @Override
     public void mergeAnimation(IBinder transition, TransitionInfo info,
             SurfaceControl.Transaction t, IBinder mergeTarget,
@@ -2304,10 +2351,28 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
     /**
      * Sets drag info to be logged when splitscreen is next entered.
      */
-    public void logOnDroppedToSplit(@SplitPosition int position, InstanceId dragSessionId) {
+    public void onDroppedToSplit(@SplitPosition int position, InstanceId dragSessionId) {
+        if (!isSplitScreenVisible()) {
+            mIsDropEntering = true;
+        }
+        if (isSplitScreenRunningBackground()) {
+            // Split running background, log exit first and start new enter request.
+            logExit(EXIT_REASON_RECREATE_SPLIT);
+        }
         mLogger.enterRequestedByDrag(position, dragSessionId);
     }
 
+    /**
+     * Sets info to be logged when splitscreen is next entered.
+     */
+    public void onRequestToSplit(InstanceId sessionId, int enterReason) {
+        if (isSplitScreenRunningBackground()) {
+            // Split running background, log exit first and start new enter request.
+            logExit(EXIT_REASON_RECREATE_SPLIT);
+        }
+        mLogger.enterRequested(sessionId, enterReason);
+    }
+
     /**
      * Logs the exit of splitscreen.
      */
@@ -2342,6 +2407,11 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
             StageCoordinator.this.onRootTaskAppeared();
         }
 
+        @Override
+        public void onChildTaskAppeared(int taskId) {
+            StageCoordinator.this.onChildTaskAppeared(this, taskId);
+        }
+
         @Override
         public void onStatusChanged(boolean visible, boolean hasChildren) {
             if (!mHasRootTask) return;

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

@@ -22,6 +22,7 @@ import static android.app.WindowConfiguration.WINDOWING_MODE_UNDEFINED;
 import static android.view.RemoteAnimationTarget.MODE_OPENING;
 
 import static com.android.wm.shell.common.split.SplitScreenConstants.CONTROLLED_ACTIVITY_TYPES;
+import static com.android.wm.shell.common.split.SplitScreenConstants.CONTROLLED_WINDOWING_MODES;
 import static com.android.wm.shell.common.split.SplitScreenConstants.CONTROLLED_WINDOWING_MODES_WHEN_ACTIVE;
 import static com.android.wm.shell.transition.Transitions.ENABLE_SHELL_TRANSITIONS;
 
@@ -69,6 +70,8 @@ class StageTaskListener implements ShellTaskOrganizer.TaskListener {
     public interface StageListenerCallbacks {
         void onRootTaskAppeared();
 
+        void onChildTaskAppeared(int taskId);
+
         void onStatusChanged(boolean visible, boolean hasChildren);
 
         void onChildTaskStatusChanged(int taskId, boolean present, boolean visible);
@@ -185,6 +188,7 @@ class StageTaskListener implements ShellTaskOrganizer.TaskListener {
                 // Status is managed/synchronized by the transition lifecycle.
                 return;
             }
+            mCallbacks.onChildTaskAppeared(taskId);
             sendStatusChanged();
         } else {
             throw new IllegalArgumentException(this + "\n Unknown task: " + taskInfo
@@ -338,6 +342,14 @@ class StageTaskListener implements ShellTaskOrganizer.TaskListener {
         }
     }
 
+    void evictOtherChildren(WindowContainerTransaction wct, int taskId) {
+        for (int i = mChildrenTaskInfo.size() - 1; i >= 0; i--) {
+            final ActivityManager.RunningTaskInfo taskInfo = mChildrenTaskInfo.valueAt(i);
+            if (taskId == taskInfo.taskId) continue;
+            wct.reparent(taskInfo.token, null /* parent */, false /* onTop */);
+        }
+    }
+
     void evictNonOpeningChildren(RemoteAnimationTarget[] apps, WindowContainerTransaction wct) {
         final SparseArray<ActivityManager.RunningTaskInfo> toBeEvict = mChildrenTaskInfo.clone();
         for (int i = 0; i < apps.length; i++) {
@@ -360,6 +372,12 @@ class StageTaskListener implements ShellTaskOrganizer.TaskListener {
         }
     }
 
+    void reparentTopTask(WindowContainerTransaction wct) {
+        wct.reparentTasks(null /* currentParent */, mRootTaskInfo.token,
+                CONTROLLED_WINDOWING_MODES, CONTROLLED_ACTIVITY_TYPES,
+                true /* onTop */, true /* reparentTopOnly */);
+    }
+
     void resetBounds(WindowContainerTransaction wct) {
         wct.setBounds(mRootTaskInfo.token, null);
         wct.setAppBounds(mRootTaskInfo.token, null);

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

@@ -111,7 +111,7 @@ public class DefaultMixedHandler implements Transitions.TransitionHandler {
     @Override
     public WindowContainerTransaction handleRequest(@NonNull IBinder transition,
             @NonNull TransitionRequestInfo request) {
-        if (mPipHandler.requestHasPipEnter(request) && mSplitHandler.isSplitActive()) {
+        if (mPipHandler.requestHasPipEnter(request) && mSplitHandler.isSplitScreenVisible()) {
             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) {