From a4e60d74df7eeb2e904701cd9cde66d72eef4aad Mon Sep 17 00:00:00 2001
From: wilsonshih <wilsonshih@google.com>
Date: Wed, 3 Jun 2020 23:06:10 +0800
Subject: [PATCH] Fix the root task of secondary split screen could be
 overwritten.

When external display removed, the remaining tasks should be
reparent to correct parents depends on the status of default
display, if secondary split screen exists, reparent it to the
root task instead of display area.

Bug: 158067169
Test: atest MultiDisplayPolicyTests
Test: after test complete, verify the root of home task doesn't
remain in secondary-split-screen.

Change-Id: Ic4b836263f9acadad2641a19bd369a44aa806d96
---
 .../android/server/wm/TaskDisplayArea.java    | 31 +++++++++++++------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/services/core/java/com/android/server/wm/TaskDisplayArea.java b/services/core/java/com/android/server/wm/TaskDisplayArea.java
index 102c2a6364f4e..9a6fc8c5950ba 100644
--- a/services/core/java/com/android/server/wm/TaskDisplayArea.java
+++ b/services/core/java/com/android/server/wm/TaskDisplayArea.java
@@ -1741,21 +1741,23 @@ final class TaskDisplayArea extends DisplayArea<ActivityStack> {
         // reparenting stack finished.
         // Keep the order from bottom to top.
         int numStacks = getStackCount();
+
+        final boolean splitScreenActivated = toDisplayArea.isSplitScreenModeActivated();
+        final ActivityStack rootStack = splitScreenActivated ? toDisplayArea
+                .getTopStackInWindowingMode(WINDOWING_MODE_SPLIT_SCREEN_SECONDARY) : null;
         for (int stackNdx = 0; stackNdx < numStacks; stackNdx++) {
             final ActivityStack stack = getStackAt(stackNdx);
             // Always finish non-standard type stacks.
             if (destroyContentOnRemoval || !stack.isActivityTypeStandardOrUndefined()) {
                 stack.finishAllActivitiesImmediately();
             } else {
-                // If default display is in split-window mode, set windowing mode of the
-                // stack to split-screen secondary. Otherwise, set the windowing mode to
-                // undefined by default to let stack inherited the windowing mode from the
-                // new display.
-                final int windowingMode = toDisplayArea.isSplitScreenModeActivated()
-                        ? WINDOWING_MODE_SPLIT_SCREEN_SECONDARY
-                        : WINDOWING_MODE_UNDEFINED;
-                stack.reparent(toDisplayArea, true /* onTop */);
-                stack.setWindowingMode(windowingMode);
+                // Reparent the stack to the root task of secondary-split-screen or display area.
+                stack.reparent(stack.supportsSplitScreenWindowingMode() && rootStack != null
+                        ? rootStack : toDisplayArea, POSITION_TOP);
+
+                // Set the windowing mode to undefined by default to let the stack inherited the
+                // windowing mode.
+                stack.setWindowingMode(WINDOWING_MODE_UNDEFINED);
                 lastReparentedStack = stack;
             }
             // Stacks may be removed from this display. Ensure each stack will be processed
@@ -1763,6 +1765,17 @@ final class TaskDisplayArea extends DisplayArea<ActivityStack> {
             stackNdx -= numStacks - getStackCount();
             numStacks = getStackCount();
         }
+        if (lastReparentedStack != null && splitScreenActivated) {
+            if (!lastReparentedStack.supportsSplitScreenWindowingMode()) {
+                mAtmService.getTaskChangeNotificationController()
+                        .notifyActivityDismissingDockedStack();
+                toDisplayArea.onSplitScreenModeDismissed(lastReparentedStack);
+            } else if (rootStack != null) {
+                // update focus
+                rootStack.moveToFront("display-removed");
+            }
+        }
+
         mRemoved = true;
 
         return lastReparentedStack;