From 05ad942626b230b41d5cf9654ed86d6e436b1f70 Mon Sep 17 00:00:00 2001
From: Louis Chang <louischang@google.com>
Date: Wed, 22 Jul 2020 16:07:02 +0800
Subject: Do not reposition leaf tasks from grandparent tasks

A leaf task was added to be the child of its grandparent while
switch user, which caused exception while reparenting split-screen
tasks to fullscreen.

Bug: 161167885
Test: switch user in split-screen
Test: atest TaskTests
Change-Id: Iffde4ddfbe315d0226961f7d98a897b34062c376
Merged-In: Iffde4ddfbe315d0226961f7d98a897b34062c376
---
 .../core/java/com/android/server/wm/ActivityStack.java    |  9 +++------
 .../com/android/server/wm/WindowOrganizerController.java  |  2 +-
 .../wmtests/src/com/android/server/wm/TaskTests.java      | 15 +++++++++++++++
 3 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/services/core/java/com/android/server/wm/ActivityStack.java b/services/core/java/com/android/server/wm/ActivityStack.java
index e9768a26f571..cf1d59ff2fe4 100644
--- a/services/core/java/com/android/server/wm/ActivityStack.java
+++ b/services/core/java/com/android/server/wm/ActivityStack.java
@@ -928,12 +928,9 @@ class ActivityStack extends Task {
         mCurrentUser = userId;
 
         super.switchUser(userId);
-        forAllLeafTasks((t) -> {
-            if (t.showToCurrentUser() && t != this) {
-                mChildren.remove(t);
-                mChildren.add(t);
-            }
-        }, true /* traverseTopToBottom */);
+        if (isLeafTask() && showToCurrentUser()) {
+            getParent().positionChildAt(POSITION_TOP, this, false /*includeParents*/);
+        }
     }
 
     void minimalResumeActivityLocked(ActivityRecord r) {
diff --git a/services/core/java/com/android/server/wm/WindowOrganizerController.java b/services/core/java/com/android/server/wm/WindowOrganizerController.java
index 930bfded39a4..21a76ff763a8 100644
--- a/services/core/java/com/android/server/wm/WindowOrganizerController.java
+++ b/services/core/java/com/android/server/wm/WindowOrganizerController.java
@@ -335,7 +335,7 @@ class WindowOrganizerController extends IWindowOrganizerController.Stub
                     }
                 }
             } else {
-                throw new RuntimeException("Reparenting leaf Tasks is not supported now.");
+                throw new RuntimeException("Reparenting leaf Tasks is not supported now. " + task);
             }
         } else {
             // Ugh, of course ActivityStack has its own special reorder logic...
diff --git a/services/tests/wmtests/src/com/android/server/wm/TaskTests.java b/services/tests/wmtests/src/com/android/server/wm/TaskTests.java
index 9d88ada5a90c..9feb83fde4fa 100644
--- a/services/tests/wmtests/src/com/android/server/wm/TaskTests.java
+++ b/services/tests/wmtests/src/com/android/server/wm/TaskTests.java
@@ -186,4 +186,19 @@ public class TaskTests extends WindowTestsBase {
             assertTrue(r.finishing);
         });
     }
+
+    @Test
+    public void testSwitchUser() {
+        final Task rootTask = createTaskStackOnDisplay(mDisplayContent);
+        final Task childTask = createTaskInStack((ActivityStack) rootTask, 0 /* userId */);
+        final Task leafTask1 = createTaskInStack((ActivityStack) childTask, 10 /* userId */);
+        final Task leafTask2 = createTaskInStack((ActivityStack) childTask, 0 /* userId */);
+        assertEquals(1, rootTask.getChildCount());
+        assertEquals(leafTask2, childTask.getTopChild());
+
+        doReturn(true).when(leafTask1).showToCurrentUser();
+        rootTask.switchUser(10);
+        assertEquals(1, rootTask.getChildCount());
+        assertEquals(leafTask1, childTask.getTopChild());
+    }
 }
-- 
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