Fix back stack for PiP from multi-activity Task

Details in design doc go/pip-and-back

Video: http://recall/-/aaaaaabFQoRHlzixHdtY/g8lbXnC8ln0t54ARxfPELo
Bug: 184758170
Test: ensure back stack works for Netflix, see video
Test: atest PinnedStackTests
Test: atest RootWindowContainerTests
Change-Id: I9e2f8d0d50dd107ff30fd7afe6273d8347aac803

core/api/test-current.txt

@@ -161,6 +161,7 @@ package android.app {
     method @RequiresPermission(android.Manifest.permission.MANAGE_ACTIVITY_TASKS) public void moveTaskToRootTask(int, int, boolean);
     method @RequiresPermission(android.Manifest.permission.MANAGE_ACTIVITY_TASKS) public void removeRootTasksInWindowingModes(@NonNull int[]);
     method @RequiresPermission(android.Manifest.permission.MANAGE_ACTIVITY_TASKS) public void removeRootTasksWithActivityTypes(@NonNull int[]);
+    method @RequiresPermission(android.Manifest.permission.MANAGE_ACTIVITY_TASKS) public boolean removeTask(int);
     method @RequiresPermission(android.Manifest.permission.MANAGE_ACTIVITY_TASKS) public void resizeTask(int, android.graphics.Rect);
     method @RequiresPermission(android.Manifest.permission.MANAGE_ACTIVITY_TASKS) public void startSystemLockTaskMode(int);
     method @RequiresPermission(android.Manifest.permission.MANAGE_ACTIVITY_TASKS) public void stopSystemLockTaskMode();

core/java/android/app/ActivityTaskManager.java

@@ -469,7 +469,8 @@ public class ActivityTaskManager {
         }
     }
 
-    /** @hide */
+    /** Removes task by a given taskId */
+    @RequiresPermission(android.Manifest.permission.MANAGE_ACTIVITY_TASKS)
     public boolean removeTask(int taskId) {
         try {
             return getService().removeTask(taskId);

core/proto/android/server/windowmanagerservice.proto

@@ -308,6 +308,7 @@ message TaskProto {
     optional float minimize_amount = 27;
     optional bool created_by_organizer = 28;
     optional string affinity = 29;
+    optional bool has_child_pip_activity = 30;
 }
 
 /* represents ActivityRecordProto */

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

@@ -587,7 +587,14 @@ final class ActivityRecord extends WindowToken implements WindowManagerService.A
 
     AnimatingActivityRegistry mAnimatingActivityRegistry;
 
-    private Task mLastParent;
+    // Set whenever the ActivityRecord gets reparented to a Task so we can know the last known
+    // parent was when the ActivityRecord is detached from the hierarchy
+    private Task mLastKnownParent;
+
+    // Set to the previous Task parent of the ActivityRecord when it is reparented to a new Task
+    // due to picture-in-picture. This gets cleared whenever this activity or the Task
+    // it references to gets removed. This should also be cleared when we move out of pip.
+    private Task mLastParentBeforePip;
 
     boolean firstWindowDrawn;
     /** Whether the visible window(s) of this activity is drawn. */
@@ -1096,6 +1103,9 @@ final class ActivityRecord extends WindowToken implements WindowManagerService.A
                 pw.println(prefix + "configChanges=0x" + Integer.toHexString(info.configChanges));
             }
         }
+        if (mLastParentBeforePip != null) {
+            pw.println(prefix + "lastParentTaskIdBeforePip=" + mLastParentBeforePip.mTaskId);
+        }
 
         dumpLetterboxInfo(pw, prefix);
     }
@@ -1349,7 +1359,7 @@ final class ActivityRecord extends WindowToken implements WindowManagerService.A
             if (getDisplayContent() != null) {
                 getDisplayContent().mClosingApps.remove(this);
             }
-        } else if (mLastParent != null && mLastParent.getRootTask() != null) {
+        } else if (mLastKnownParent != null && mLastKnownParent.getRootTask() != null) {
             task.getRootTask().mExitingActivities.remove(this);
         }
         final Task rootTask = getRootTask();
@@ -1362,7 +1372,11 @@ final class ActivityRecord extends WindowToken implements WindowManagerService.A
                 ? rootTask.getAnimatingActivityRegistry()
                 : null;
 
-        mLastParent = task;
+        mLastKnownParent = task;
+        if (mLastKnownParent == mLastParentBeforePip) {
+            // Activity's reparented back from pip, clear the links once established
+            clearLastParentBeforePip();
+        }
 
         updateColorTransform();
 
@@ -1381,6 +1395,26 @@ final class ActivityRecord extends WindowToken implements WindowManagerService.A
         }
     }
 
+    /**
+     * Sets {@link #mLastParentBeforePip} to the current parent Task, it's caller's job to ensure
+     * {@link #getTask()} is set before this is called.
+     */
+    void setLastParentBeforePip() {
+        mLastParentBeforePip = getTask();
+        mLastParentBeforePip.mChildPipActivity = this;
+    }
+
+    private void clearLastParentBeforePip() {
+        if (mLastParentBeforePip != null) {
+            mLastParentBeforePip.mChildPipActivity = null;
+            mLastParentBeforePip = null;
+        }
+    }
+
+    @Nullable Task getLastParentBeforePip() {
+        return mLastParentBeforePip;
+    }
+
     private void updateColorTransform() {
         if (mSurfaceControl != null && mLastAppSaturationInfo != null) {
             getPendingTransaction().setColorTransform(mSurfaceControl,
@@ -3434,6 +3468,7 @@ final class ActivityRecord extends WindowToken implements WindowManagerService.A
      */
     void cleanUp(boolean cleanServices, boolean setState) {
         task.cleanUpActivityReferences(this);
+        clearLastParentBeforePip();
 
         deferRelaunchUntilPaused = false;
         frozenBeforeDestroy = false;

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

@@ -1415,6 +1415,9 @@ class RecentTasks {
             return true;
         }
 
+        // The given task if always treated as in visible range if it is the origin of pinned task.
+        if (task.mChildPipActivity != null) return true;
+
         if (mMaxNumVisibleTasks >= 0) {
             // Always keep up to the max number of recent tasks, but return false afterwards
             return numVisibleTasks <= mMaxNumVisibleTasks;

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

@@ -2124,6 +2124,8 @@ class RootWindowContainer extends WindowContainer<DisplayContent>
                         .setDeferTaskAppear(true)
                         .setHasBeenVisible(true)
                         .build();
+                // Establish bi-directional link between the original and pinned task.
+                r.setLastParentBeforePip();
                 // It's possible the task entering PIP is in freeform, so save the last
                 // non-fullscreen bounds. Then when this new PIP task exits PIP, it can restore
                 // to its previous freeform bounds.

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

@@ -131,6 +131,7 @@ import static com.android.server.wm.TaskProto.BOUNDS;
 import static com.android.server.wm.TaskProto.CREATED_BY_ORGANIZER;
 import static com.android.server.wm.TaskProto.DISPLAY_ID;
 import static com.android.server.wm.TaskProto.FILLS_PARENT;
+import static com.android.server.wm.TaskProto.HAS_CHILD_PIP_ACTIVITY;
 import static com.android.server.wm.TaskProto.LAST_NON_FULLSCREEN_BOUNDS;
 import static com.android.server.wm.TaskProto.MIN_HEIGHT;
 import static com.android.server.wm.TaskProto.MIN_WIDTH;
@@ -836,6 +837,14 @@ class Task extends WindowContainer<WindowContainer> {
     // The task will be removed when TaskOrganizer, which is managing the task, is destroyed.
     boolean mRemoveWithTaskOrganizer;
 
+    /**
+     * Reference to the pinned activity that is logically parented to this task, ie.
+     * the previous top activity within this task is put into pinned mode.
+     * This always gets cleared in pair with the ActivityRecord-to-Task link as seen in
+     * {@link ActivityRecord#clearLastParentBeforePip()}.
+     */
+    ActivityRecord mChildPipActivity;
+
     private Task(ActivityTaskManagerService atmService, int _taskId, Intent _intent,
             Intent _affinityIntent, String _affinity, String _rootAffinity,
             ComponentName _realActivity, ComponentName _origActivity, boolean _rootWasReset,
@@ -1841,6 +1850,10 @@ class Task extends WindowContainer<WindowContainer> {
 
     /** Completely remove all activities associated with an existing task. */
     void performClearTask(String reason) {
+        // The original task is to be removed, try remove also the pinned task.
+        if (mChildPipActivity != null && mChildPipActivity.getTask() != null) {
+            mTaskSupervisor.removeRootTask(mChildPipActivity.getTask());
+        }
         // Broken down into to cases to avoid object create due to capturing mStack.
         if (getRootTask() == null) {
             forAllActivities((r) -> {
@@ -4449,6 +4462,7 @@ class Task extends WindowContainer<WindowContainer> {
         }
         pw.print(prefix); pw.print("taskId=" + mTaskId);
         pw.println(" rootTaskId=" + getRootTaskId());
+        pw.print(prefix); pw.println("hasChildPipActivity=" + (mChildPipActivity != null));
         pw.print(prefix); pw.print("mHasBeenVisible="); pw.println(getHasBeenVisible());
         pw.print(prefix); pw.print("mResizeMode=");
         pw.print(ActivityInfo.resizeModeToString(mResizeMode));
@@ -5328,7 +5342,6 @@ class Task extends WindowContainer<WindowContainer> {
             return;
         }
         final int currentMode = getWindowingMode();
-        final int currentOverrideMode = getRequestedOverrideWindowingMode();
         final Task topTask = getTopMostTask();
         int windowingMode = preferredWindowingMode;
 
@@ -5397,9 +5410,26 @@ class Task extends WindowContainer<WindowContainer> {
                 mTaskSupervisor.mNoAnimActivities.add(topActivity);
             }
             super.setWindowingMode(windowingMode);
-            // setWindowingMode triggers an onConfigurationChanged cascade which can result in a
+
-            // different resolved windowing mode (usually when preferredWindowingMode is UNDEFINED).
+            // Try reparent pinned activity back to its original task after onConfigurationChanged
-            windowingMode = getWindowingMode();
+            // cascade finishes. This is done on Task level instead of
+            // {@link ActivityRecord#onConfigurationChanged(Configuration)} since when we exit PiP,
+            // we set final windowing mode on the ActivityRecord first and then on its Task when
+            // the exit PiP transition finishes. Meanwhile, the exit transition is always
+            // performed on its original task, reparent immediately in ActivityRecord breaks it.
+            if (currentMode == WINDOWING_MODE_PINNED) {
+                if (topActivity != null && topActivity.getLastParentBeforePip() != null) {
+                    // Do not reparent if the pinned task is in removal, indicated by the
+                    // force hidden flag.
+                    if (!isForceHidden()) {
+                        final Task lastParentBeforePip = topActivity.getLastParentBeforePip();
+                        topActivity.reparent(lastParentBeforePip,
+                                lastParentBeforePip.getChildCount() /* top */,
+                                "movePinnedActivityToOriginalTask");
+                        lastParentBeforePip.moveToFront("movePinnedActivityToOriginalTask");
+                    }
+                }
+            }
 
             if (creating) {
                 // Nothing else to do if we don't have a window container yet. E.g. call from ctor.
@@ -7530,7 +7560,11 @@ class Task extends WindowContainer<WindowContainer> {
             final Task task = getBottomMostTask();
             setWindowingMode(WINDOWING_MODE_UNDEFINED);
 
-            getDisplayArea().positionChildAt(POSITION_TOP, this, false /* includingParents */);
+            // Task could have been removed from the hierarchy due to windowing mode change
+            // where its only child is reparented back to their original parent task.
+            if (isAttached()) {
+                getDisplayArea().positionChildAt(POSITION_TOP, this, false /* includingParents */);
+            }
 
             mTaskSupervisor.scheduleUpdatePictureInPictureModeIfNeeded(task, this);
         });
@@ -7831,6 +7865,7 @@ class Task extends WindowContainer<WindowContainer> {
 
         proto.write(CREATED_BY_ORGANIZER, mCreatedByOrganizer);
         proto.write(AFFINITY, affinity);
+        proto.write(HAS_CHILD_PIP_ACTIVITY, mChildPipActivity != null);
 
         proto.end(token);
     }