From 7c8a2474f1a77f3e023a8cec4ec5f848fd8b44f0 Mon Sep 17 00:00:00 2001
From: Vishnu Nair <vishnun@google.com>
Date: Fri, 17 Apr 2020 16:08:29 -0700
Subject: [PATCH] Consolidate TaskDisplayArea#addStack and
 TaskDisplayArea#addChild

When closing an app by swiping up, launcher runs a remote animation
on the home task and the closing app task. If the most recent running
task (via ATMS#getFilteredTasks) does not match the remote animation
 target task then the animation is not run and we see a flicker.

When dismissing split screen, the recency of the primary split screen
task is not updated. Fix this by eliminating two different code paths
to add a child to TaskDisplayArea and ensure we update
TaskDisplayArea#mPreferredTopFocusableStack.

Test: swipe up to dismiss app after exiting split-screen
Test: go/wm-smoke
Fixes: 153583420

Change-Id: I592199d95f3f2ae56ad5ff638612cb63a3549602
---
 .../com/android/server/wm/TaskDisplayArea.java   | 16 ++++------------
 .../com/android/server/wm/WindowContainer.java   |  8 +++++---
 .../android/server/wm/ActivityStackTests.java    |  2 +-
 3 files changed, 10 insertions(+), 16 deletions(-)

diff --git a/services/core/java/com/android/server/wm/TaskDisplayArea.java b/services/core/java/com/android/server/wm/TaskDisplayArea.java
index d71e56106e180..0722b8efd2cf4 100644
--- a/services/core/java/com/android/server/wm/TaskDisplayArea.java
+++ b/services/core/java/com/android/server/wm/TaskDisplayArea.java
@@ -266,16 +266,14 @@ final class TaskDisplayArea extends DisplayArea<ActivityStack> {
 
     @Override
     void addChild(ActivityStack stack, int position) {
+        if (DEBUG_STACK) Slog.d(TAG_WM, "Set stack=" + stack + " on taskDisplayArea=" + this);
         addStackReferenceIfNeeded(stack);
         position = findPositionForStack(position, stack, true /* adding */);
 
         super.addChild(stack, position);
         mAtmService.updateSleepIfNeededLocked();
 
-        // The reparenting case is handled in WindowContainer.
-        if (!stack.mReparenting) {
-            mDisplayContent.setLayoutNeeded();
-        }
+        positionStackAt(stack, position);
     }
 
     @Override
@@ -637,12 +635,6 @@ final class TaskDisplayArea extends DisplayArea<ActivityStack> {
         }
     }
 
-    void addStack(ActivityStack stack, int position) {
-        if (DEBUG_STACK) Slog.d(TAG_WM, "Set stack=" + stack + " on taskDisplayArea=" + this);
-        addChild(stack, position);
-        positionStackAt(stack, position);
-    }
-
     void onStackRemoved(ActivityStack stack) {
         if (ActivityTaskManagerDebugConfig.DEBUG_STACK) {
             Slog.v(TAG_STACK, "removeStack: detaching " + stack + " from displayId="
@@ -786,7 +778,7 @@ final class TaskDisplayArea extends DisplayArea<ActivityStack> {
                 }
             } else if (stack.getDisplayArea() != this || !stack.isRootTask()) {
                 if (stack.getParent() == null) {
-                    addStack(stack, position);
+                    addChild(stack, position);
                 } else {
                     stack.reparent(this, onTop);
                 }
@@ -942,7 +934,7 @@ final class TaskDisplayArea extends DisplayArea<ActivityStack> {
                 positionStackAtTop((ActivityStack) launchRootTask, false /* includingParents */);
             }
         } else {
-            addStack(stack, onTop ? POSITION_TOP : POSITION_BOTTOM);
+            addChild(stack, onTop ? POSITION_TOP : POSITION_BOTTOM);
             stack.setWindowingMode(windowingMode, true /* creating */);
         }
         return stack;
diff --git a/services/core/java/com/android/server/wm/WindowContainer.java b/services/core/java/com/android/server/wm/WindowContainer.java
index 899ab247077a2..f3e2992d59137 100644
--- a/services/core/java/com/android/server/wm/WindowContainer.java
+++ b/services/core/java/com/android/server/wm/WindowContainer.java
@@ -662,9 +662,11 @@ class WindowContainer<E extends WindowContainer> extends ConfigurationContainer<
                 //       position that takes into account the removed child (if the index of the
                 //       child < position, then the position should be adjusted). We should consider
                 //       doing this adjustment here and remove any adjustments in the callers.
-                mChildren.remove(child);
-                mChildren.add(position, child);
-                onChildPositionChanged(child);
+                if (mChildren.indexOf(child) != position) {
+                    mChildren.remove(child);
+                    mChildren.add(position, child);
+                    onChildPositionChanged(child);
+                }
         }
     }
 
diff --git a/services/tests/wmtests/src/com/android/server/wm/ActivityStackTests.java b/services/tests/wmtests/src/com/android/server/wm/ActivityStackTests.java
index 3bed05f383a8c..e8b74a34ecccf 100644
--- a/services/tests/wmtests/src/com/android/server/wm/ActivityStackTests.java
+++ b/services/tests/wmtests/src/com/android/server/wm/ActivityStackTests.java
@@ -1145,7 +1145,7 @@ public class ActivityStackTests extends ActivityTestsBase {
         mDefaultTaskDisplayArea.registerStackOrderChangedListener(listener);
         try {
             mStack.mReparenting = true;
-            mDefaultTaskDisplayArea.addStack(mStack, 0);
+            mDefaultTaskDisplayArea.addChild(mStack, 0);
         } finally {
             mDefaultTaskDisplayArea.unregisterStackOrderChangedListener(listener);
         }