From d9ea032b739df157d9229ee214bb562cbb88508b Mon Sep 17 00:00:00 2001
From: Charles Chen <charlesccchen@google.com>
Date: Fri, 16 Apr 2021 16:09:44 +0800
Subject: [PATCH] Fix WindowContext is removed unexpectedly

Previously WindowContext is removed if the associated WindowContainer
is removed. However, it causes an issue that WindowContext is removed
unexpectedly after the last window is removed by WM#removeView().
When the last view is removed, WMS will remove the WindowToken
in postWindowRemoveCleanupLocked(), and if the WindowToken is created
by WindowContext, the associated WindowContext is also removed
unexpectedly.

This CL makes WindowContext switch back to listen to the previous
DisplayArea if the last window is removed.

Test: atest WindowContextListenerControllerTests
Bug: 185460076

Change-Id: I9c1d0c15c77bbfb3662355f8c72f0d8c70ed6748
---
 .../wm/WindowContextListenerController.java   | 15 ++++++++++++
 .../WindowContextListenerControllerTests.java | 23 +++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/services/core/java/com/android/server/wm/WindowContextListenerController.java b/services/core/java/com/android/server/wm/WindowContextListenerController.java
index 5e75996b00120..a127611b2cce7 100644
--- a/services/core/java/com/android/server/wm/WindowContextListenerController.java
+++ b/services/core/java/com/android/server/wm/WindowContextListenerController.java
@@ -271,6 +271,21 @@ class WindowContextListenerController {
             if (mDeathRecipient == null) {
                 throw new IllegalStateException("Invalid client token: " + mClientToken);
             }
+            final WindowToken windowToken = mContainer.asWindowToken();
+            if (windowToken != null && windowToken.isFromClient()) {
+                // If the WindowContext created WindowToken is removed by
+                // WMS#postWindowRemoveCleanupLocked, the WindowContext should switch back to
+                // listen to previous associated DisplayArea.
+                final DisplayContent dc = windowToken.mWmService.mRoot
+                        .getDisplayContent(mLastReportedDisplay);
+                // If we cannot obtain the DisplayContent, the DisplayContent may also be removed.
+                // We should proceed the removal process.
+                if (dc != null) {
+                    final DisplayArea da = dc.findAreaForToken(windowToken);
+                    updateContainer(da);
+                    return;
+                }
+            }
             mDeathRecipient.unlinkToDeath();
             IWindowToken windowTokenClient = IWindowToken.Stub.asInterface(mClientToken);
             try {
diff --git a/services/tests/wmtests/src/com/android/server/wm/WindowContextListenerControllerTests.java b/services/tests/wmtests/src/com/android/server/wm/WindowContextListenerControllerTests.java
index 73b9173ba1438..5d0fe170885a2 100644
--- a/services/tests/wmtests/src/com/android/server/wm/WindowContextListenerControllerTests.java
+++ b/services/tests/wmtests/src/com/android/server/wm/WindowContextListenerControllerTests.java
@@ -17,8 +17,11 @@
 package com.android.server.wm;
 
 import static android.view.Display.DEFAULT_DISPLAY;
+import static android.view.WindowManager.LayoutParams.TYPE_ACCESSIBILITY_MAGNIFICATION_OVERLAY;
 import static android.view.WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;
 
+import static com.google.common.truth.Truth.assertThat;
+
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
@@ -162,6 +165,26 @@ public class WindowContextListenerControllerTests extends WindowTestsBase {
                 false /* callerCanManagerAppTokens */, ANOTHER_UID);
     }
 
+    @Test
+    public void testWindowContextCreatedWindowTokenRemoved_SwitchToListenToDA() {
+        WindowToken windowContextCreatedToken = new WindowToken.Builder(mWm, mClientToken,
+                TYPE_ACCESSIBILITY_MAGNIFICATION_OVERLAY)
+                .setDisplayContent(mDefaultDisplay)
+                .setFromClientToken(true)
+                .build();
+        final DisplayArea da = windowContextCreatedToken.getDisplayArea();
+
+        mController.registerWindowContainerListener(mClientToken, windowContextCreatedToken,
+                TEST_UID, TYPE_ACCESSIBILITY_MAGNIFICATION_OVERLAY, null /* options */);
+
+        assertThat(mController.getContainer(mClientToken)).isEqualTo(windowContextCreatedToken);
+
+        // Remove WindowToken
+        windowContextCreatedToken.removeImmediately();
+
+        assertThat(mController.getContainer(mClientToken)).isEqualTo(da);
+    }
+
     private class TestWindowTokenClient extends IWindowToken.Stub {
         private Configuration mConfiguration;
         private int mDisplayId;