Merge "Stop assuming the existence of displays when tasks appear" into tm-qpr-dev

libs/WindowManager/Shell/src/com/android/wm/shell/windowdecor/CaptionWindowDecoration.java

@@ -95,6 +95,7 @@ public class CaptionWindowDecoration extends WindowDecoration<WindowDecorLinearL
         mDragResizeCallback = dragResizeCallback;
     }
 
+    @Override
     void relayout(ActivityManager.RunningTaskInfo taskInfo) {
         final int shadowRadiusDp = taskInfo.isFocused
                 ? DECOR_SHADOW_FOCUSED_THICKNESS_IN_DIP : DECOR_SHADOW_UNFOCUSED_THICKNESS_IN_DIP;
@@ -119,8 +120,8 @@ public class CaptionWindowDecoration extends WindowDecoration<WindowDecorLinearL
         });
 
         if (mResult.mRootView == null) {
-            // This means the task is hidden. Nothing is set up in this case including the
+            // This means something blocks the window decor from showing, e.g. the task is hidden.
-            // decoration surface.
+            // Nothing is set up in this case including the decoration surface.
             return;
         }
         if (oldRootView != mResult.mRootView) {

libs/WindowManager/Shell/src/com/android/wm/shell/windowdecor/WindowDecoration.java

@@ -38,6 +38,8 @@ import android.window.WindowContainerTransaction;
 import com.android.wm.shell.ShellTaskOrganizer;
 import com.android.wm.shell.common.DisplayController;
 
+import java.util.function.Supplier;
+
 /**
  * Manages a container surface and a windowless window to show window decoration. Responsible to
  * update window decoration window state and layout parameters on task info changes and so that
@@ -53,7 +55,8 @@ import com.android.wm.shell.common.DisplayController;
  *
  * @param <T> The type of the root view
  */
-public class WindowDecoration<T extends View & TaskFocusStateConsumer> implements AutoCloseable {
+public abstract class WindowDecoration<T extends View & TaskFocusStateConsumer>
+        implements AutoCloseable {
     private static final int[] CAPTION_INSETS_TYPES = { InsetsState.ITYPE_CAPTION_BAR };
 
     /**
@@ -62,6 +65,20 @@ public class WindowDecoration<T extends View & TaskFocusStateConsumer> implement
     final Context mContext;
     final DisplayController mDisplayController;
     final ShellTaskOrganizer mTaskOrganizer;
+    final Supplier<SurfaceControl.Builder> mSurfaceControlBuilderSupplier;
+    final SurfaceControlViewHostFactory mSurfaceControlViewHostFactory;
+    private final DisplayController.OnDisplaysChangedListener mOnDisplaysChangedListener =
+            new DisplayController.OnDisplaysChangedListener() {
+                @Override
+                public void onDisplayAdded(int displayId) {
+                    if (mTaskInfo.displayId != displayId) {
+                        return;
+                    }
+
+                    mDisplayController.removeDisplayWindowListener(this);
+                    relayout(mTaskInfo);
+                }
+            };
 
     RunningTaskInfo mTaskInfo;
     final SurfaceControl mTaskSurface;
@@ -71,7 +88,7 @@ public class WindowDecoration<T extends View & TaskFocusStateConsumer> implement
     SurfaceControl mDecorationContainerSurface;
     SurfaceControl mTaskBackgroundSurface;
 
-    private CaptionWindowManager mCaptionWindowManager;
+    private final CaptionWindowManager mCaptionWindowManager;
     private SurfaceControlViewHost mViewHost;
 
     private final Rect mCaptionInsetsRect = new Rect();
@@ -84,11 +101,25 @@ public class WindowDecoration<T extends View & TaskFocusStateConsumer> implement
             ShellTaskOrganizer taskOrganizer,
             RunningTaskInfo taskInfo,
             SurfaceControl taskSurface) {
+        this(context, displayController, taskOrganizer, taskInfo, taskSurface,
+                SurfaceControl.Builder::new, new SurfaceControlViewHostFactory() {});
+    }
+
+    WindowDecoration(
+            Context context,
+            DisplayController displayController,
+            ShellTaskOrganizer taskOrganizer,
+            RunningTaskInfo taskInfo,
+            SurfaceControl taskSurface,
+            Supplier<SurfaceControl.Builder> surfaceControlBuilderSupplier,
+            SurfaceControlViewHostFactory surfaceControlViewHostFactory) {
         mContext = context;
         mDisplayController = displayController;
         mTaskOrganizer = taskOrganizer;
         mTaskInfo = taskInfo;
         mTaskSurface = taskSurface;
+        mSurfaceControlBuilderSupplier = surfaceControlBuilderSupplier;
+        mSurfaceControlViewHostFactory = surfaceControlViewHostFactory;
 
         mDisplay = mDisplayController.getDisplay(mTaskInfo.displayId);
         mDecorWindowContext = mContext.createConfigurationContext(mTaskInfo.getConfiguration());
@@ -99,6 +130,15 @@ public class WindowDecoration<T extends View & TaskFocusStateConsumer> implement
                 new CaptionWindowManager(mTaskInfo.getConfiguration(), mTaskSurface);
     }
 
+    /**
+     * Used by {@link WindowDecoration} to trigger a new relayout because the requirements for a
+     * relayout weren't satisfied are satisfied now.
+     *
+     * @param taskInfo The previous {@link RunningTaskInfo} passed into {@link #relayout} or the
+     *                 constructor.
+     */
+    abstract void relayout(RunningTaskInfo taskInfo);
+
     void relayout(RunningTaskInfo taskInfo, int layoutResId, T rootView, float captionHeightDp,
             Rect outsetsDp, float shadowRadiusDp, SurfaceControl.Transaction t,
             WindowContainerTransaction wct, RelayoutResult<T> outResult) {
@@ -110,7 +150,7 @@ public class WindowDecoration<T extends View & TaskFocusStateConsumer> implement
         }
 
         if (!mTaskInfo.isVisible) {
-            close();
+            releaseViews();
             t.hide(mTaskSurface);
             return;
         }
@@ -123,10 +163,14 @@ public class WindowDecoration<T extends View & TaskFocusStateConsumer> implement
         rootView = null; // Clear it just in case we use it accidentally
         final Configuration taskConfig = mTaskInfo.getConfiguration();
         if (oldTaskConfig.densityDpi != taskConfig.densityDpi
+                || mDisplay == null
                 || mDisplay.getDisplayId() != mTaskInfo.displayId) {
-            close();
+            releaseViews();
 
-            mDisplay = mDisplayController.getDisplay(mTaskInfo.displayId);
+            if (!obtainDisplayOrRegisterListener()) {
+                outResult.mRootView = null;
+                return;
+            }
             mDecorWindowContext = mContext.createConfigurationContext(taskConfig);
             if (layoutResId != 0) {
                 outResult.mRootView =
@@ -141,7 +185,7 @@ public class WindowDecoration<T extends View & TaskFocusStateConsumer> implement
 
         // DecorationContainerSurface
         if (mDecorationContainerSurface == null) {
-            final SurfaceControl.Builder builder = new SurfaceControl.Builder();
+            final SurfaceControl.Builder builder = mSurfaceControlBuilderSupplier.get();
             mDecorationContainerSurface = builder
                     .setName("Decor container of Task=" + mTaskInfo.taskId)
                     .setContainerLayer()
@@ -168,7 +212,7 @@ public class WindowDecoration<T extends View & TaskFocusStateConsumer> implement
 
         // TaskBackgroundSurface
         if (mTaskBackgroundSurface == null) {
-            final SurfaceControl.Builder builder = new SurfaceControl.Builder();
+            final SurfaceControl.Builder builder = mSurfaceControlBuilderSupplier.get();
             mTaskBackgroundSurface = builder
                     .setName("Background of Task=" + mTaskInfo.taskId)
                     .setEffectLayer()
@@ -195,7 +239,7 @@ public class WindowDecoration<T extends View & TaskFocusStateConsumer> implement
         lp.setTitle("Caption of Task=" + mTaskInfo.taskId);
         lp.setTrustedOverlay();
         if (mViewHost == null) {
-            mViewHost = new SurfaceControlViewHost(mDecorWindowContext, mDisplay,
+            mViewHost = mSurfaceControlViewHostFactory.create(mDecorWindowContext, mDisplay,
                     mCaptionWindowManager, true);
             mViewHost.setView(outResult.mRootView, lp);
         } else {
@@ -225,8 +269,22 @@ public class WindowDecoration<T extends View & TaskFocusStateConsumer> implement
                 .show(mTaskSurface);
     }
 
-    @Override
+    /**
-    public void close() {
+     * Obtains the {@link Display} instance for the display ID in {@link #mTaskInfo} if it exists or
+     * registers {@link #mOnDisplaysChangedListener} if it doesn't.
+     *
+     * @return {@code true} if the {@link Display} instance exists; or {@code false} otherwise
+     */
+    private boolean obtainDisplayOrRegisterListener() {
+        mDisplay = mDisplayController.getDisplay(mTaskInfo.displayId);
+        if (mDisplay == null) {
+            mDisplayController.addDisplayWindowListener(mOnDisplaysChangedListener);
+            return false;
+        }
+        return true;
+    }
+
+    private void releaseViews() {
         if (mViewHost != null) {
             mViewHost.release();
             mViewHost = null;
@@ -243,6 +301,12 @@ public class WindowDecoration<T extends View & TaskFocusStateConsumer> implement
         }
     }
 
+    @Override
+    public void close() {
+        mDisplayController.removeDisplayWindowListener(mOnDisplaysChangedListener);
+        releaseViews();
+    }
+
     static class RelayoutResult<T extends View & TaskFocusStateConsumer> {
         int mWidth;
         int mHeight;
@@ -267,4 +331,11 @@ public class WindowDecoration<T extends View & TaskFocusStateConsumer> implement
             super.setConfiguration(configuration);
         }
     }
+
+    interface SurfaceControlViewHostFactory {
+        default SurfaceControlViewHost create(
+                Context c, Display d, WindowlessWindowManager wmm, boolean useSfChoreographer) {
+            return new SurfaceControlViewHost(c, d, wmm, useSfChoreographer);
+        }
+    }
 }

libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/MockSurfaceControlHelper.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.wm.shell;
+
+import static org.mockito.Mockito.RETURNS_SELF;
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.mock;
+
+import android.view.SurfaceControl;
+
+/**
+ * Helper class to provide mocks for {@link SurfaceControl.Builder} and
+ * {@link SurfaceControl.Transaction} with method chaining support.
+ */
+public class MockSurfaceControlHelper {
+    private MockSurfaceControlHelper() {}
+
+    /**
+     * Creates a mock {@link SurfaceControl.Builder} that supports method chaining and return the
+     * given {@link SurfaceControl} when calling {@link SurfaceControl.Builder#build()}.
+     *
+     * @param mockSurfaceControl the first {@link SurfaceControl} to return
+     * @param mockSurfaceControls following {@link SurfaceControl} to return
+     * @return the mock of {@link SurfaceControl.Builder}
+     */
+    public static SurfaceControl.Builder createMockSurfaceControlBuilder(
+            SurfaceControl mockSurfaceControl, SurfaceControl... mockSurfaceControls) {
+        final SurfaceControl.Builder mockBuilder = mock(SurfaceControl.Builder.class, RETURNS_SELF);
+        doReturn(mockSurfaceControl, (Object[]) mockSurfaceControls)
+                .when(mockBuilder)
+                .build();
+        return mockBuilder;
+    }
+
+    /**
+     * Creates a mock {@link SurfaceControl.Transaction} that supports method chaining.
+     * @return the mock of {@link SurfaceControl.Transaction}
+     */
+    public static SurfaceControl.Transaction createMockSurfaceControlTransaction() {
+        return mock(SurfaceControl.Transaction.class, RETURNS_SELF);
+    }
+}

libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/TestRunningTaskInfoBuilder.java

@@ -25,8 +25,10 @@ import static org.mockito.Mockito.mock;
 
 import android.app.ActivityManager;
 import android.app.WindowConfiguration;
+import android.graphics.Point;
 import android.graphics.Rect;
 import android.os.IBinder;
+import android.view.Display;
 import android.window.IWindowContainerToken;
 import android.window.WindowContainerToken;
 
@@ -38,6 +40,10 @@ public final class TestRunningTaskInfoBuilder {
     private int mParentTaskId = INVALID_TASK_ID;
     private @WindowConfiguration.ActivityType int mActivityType = ACTIVITY_TYPE_STANDARD;
     private @WindowConfiguration.WindowingMode int mWindowingMode = WINDOWING_MODE_UNDEFINED;
+    private int mDisplayId = Display.DEFAULT_DISPLAY;
+    private ActivityManager.TaskDescription.Builder mTaskDescriptionBuilder = null;
+    private final Point mPositionInParent = new Point();
+    private boolean mIsVisible = false;
 
     public static WindowContainerToken createMockWCToken() {
         final IWindowContainerToken itoken = mock(IWindowContainerToken.class);
@@ -68,17 +74,42 @@ public final class TestRunningTaskInfoBuilder {
         return this;
     }
 
+    public TestRunningTaskInfoBuilder setDisplayId(int displayId) {
+        mDisplayId = displayId;
+        return this;
+    }
+
+    public TestRunningTaskInfoBuilder setTaskDescriptionBuilder(
+            ActivityManager.TaskDescription.Builder builder) {
+        mTaskDescriptionBuilder = builder;
+        return this;
+    }
+
+    public TestRunningTaskInfoBuilder setPositionInParent(int x, int y) {
+        mPositionInParent.set(x, y);
+        return this;
+    }
+
+    public TestRunningTaskInfoBuilder setVisible(boolean isVisible) {
+        mIsVisible = isVisible;
+        return this;
+    }
+
     public ActivityManager.RunningTaskInfo build() {
         final ActivityManager.RunningTaskInfo info = new ActivityManager.RunningTaskInfo();
-        info.parentTaskId = INVALID_TASK_ID;
         info.taskId = sNextTaskId++;
         info.parentTaskId = mParentTaskId;
+        info.displayId = mDisplayId;
         info.configuration.windowConfiguration.setBounds(mBounds);
         info.configuration.windowConfiguration.setActivityType(mActivityType);
         info.configuration.windowConfiguration.setWindowingMode(mWindowingMode);
         info.token = mToken;
         info.isResizeable = true;
         info.supportsMultiWindow = true;
+        info.taskDescription =
+                mTaskDescriptionBuilder != null ? mTaskDescriptionBuilder.build() : null;
+        info.positionInParent = mPositionInParent;
+        info.isVisible = mIsVisible;
         return info;
     }
 }

libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/pip/PipAnimationControllerTest.java

@@ -21,6 +21,7 @@ import static android.view.Surface.ROTATION_0;
 import static android.view.Surface.ROTATION_270;
 import static android.view.Surface.ROTATION_90;
 
+import static com.android.wm.shell.MockSurfaceControlHelper.createMockSurfaceControlTransaction;
 import static com.android.wm.shell.pip.PipAnimationController.TRANSITION_DIRECTION_LEAVE_PIP;
 import static com.android.wm.shell.pip.PipAnimationController.TRANSITION_DIRECTION_TO_PIP;
 
@@ -37,6 +38,7 @@ import android.view.SurfaceControl;
 
 import androidx.test.filters.SmallTest;
 
+import com.android.wm.shell.MockSurfaceControlHelper;
 import com.android.wm.shell.ShellTestCase;
 
 import org.junit.Before;
@@ -103,7 +105,8 @@ public class PipAnimationControllerTest extends ShellTestCase {
         final PipAnimationController.PipTransitionAnimator oldAnimator = mPipAnimationController
                 .getAnimator(mTaskInfo, mLeash, baseValue, startValue, endValue1, null,
                         TRANSITION_DIRECTION_TO_PIP, 0, ROTATION_0);
-        oldAnimator.setSurfaceControlTransactionFactory(PipDummySurfaceControlTx::new);
+        oldAnimator.setSurfaceControlTransactionFactory(
+                MockSurfaceControlHelper::createMockSurfaceControlTransaction);
         oldAnimator.start();
 
         final PipAnimationController.PipTransitionAnimator newAnimator = mPipAnimationController
@@ -133,7 +136,7 @@ public class PipAnimationControllerTest extends ShellTestCase {
 
     @Test
     public void pipTransitionAnimator_rotatedEndValue() {
-        final PipDummySurfaceControlTx tx = new PipDummySurfaceControlTx();
+        final SurfaceControl.Transaction tx = createMockSurfaceControlTransaction();
         final Rect startBounds = new Rect(200, 700, 400, 800);
         final Rect endBounds = new Rect(0, 0, 500, 1000);
         // Fullscreen to PiP.
@@ -183,7 +186,8 @@ public class PipAnimationControllerTest extends ShellTestCase {
         final PipAnimationController.PipTransitionAnimator animator = mPipAnimationController
                 .getAnimator(mTaskInfo, mLeash, baseValue, startValue, endValue, null,
                         TRANSITION_DIRECTION_TO_PIP, 0, ROTATION_0);
-        animator.setSurfaceControlTransactionFactory(PipDummySurfaceControlTx::new);
+        animator.setSurfaceControlTransactionFactory(
+                MockSurfaceControlHelper::createMockSurfaceControlTransaction);
 
         animator.setPipAnimationCallback(mPipAnimationCallback);
 

libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/pip/PipDummySurfaceControlTx.java

@@ -1,66 +0,0 @@
-/*
- * Copyright (C) 2022 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package com.android.wm.shell.pip;
-
-import android.graphics.Matrix;
-import android.view.SurfaceControl;
-
-/**
- * A dummy {@link SurfaceControl.Transaction} class for testing purpose and supports
- * method chaining.
- */
-public class PipDummySurfaceControlTx extends SurfaceControl.Transaction {
-    @Override
-    public SurfaceControl.Transaction setAlpha(SurfaceControl leash, float alpha) {
-        return this;
-    }
-
-    @Override
-    public SurfaceControl.Transaction setPosition(SurfaceControl leash, float x, float y) {
-        return this;
-    }
-
-    @Override
-    public SurfaceControl.Transaction setWindowCrop(SurfaceControl leash, int w, int h) {
-        return this;
-    }
-
-    @Override
-    public SurfaceControl.Transaction setCornerRadius(SurfaceControl leash, float radius) {
-        return this;
-    }
-
-    @Override
-    public SurfaceControl.Transaction setShadowRadius(SurfaceControl leash, float radius) {
-        return this;
-    }
-
-    @Override
-    public SurfaceControl.Transaction setMatrix(SurfaceControl leash, Matrix matrix,
-            float[] float9) {
-        return this;
-    }
-
-    @Override
-    public SurfaceControl.Transaction setFrameTimelineVsync(long frameTimelineVsyncId) {
-        return this;
-    }
-
-    @Override
-    public void apply() {}
-}
-

libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/pip/PipTaskOrganizerTest.java

@@ -44,6 +44,7 @@ import android.util.Size;
 import android.view.DisplayInfo;
 import android.window.WindowContainerToken;
 
+import com.android.wm.shell.MockSurfaceControlHelper;
 import com.android.wm.shell.ShellTaskOrganizer;
 import com.android.wm.shell.ShellTestCase;
 import com.android.wm.shell.TestShellExecutor;
@@ -246,7 +247,8 @@ public class PipTaskOrganizerTest extends ShellTestCase {
         mPipBoundsState.setDisplayLayout(new DisplayLayout(info,
                 mContext.getResources(), true, true));
         mSpiedPipTaskOrganizer.setOneShotAnimationType(PipAnimationController.ANIM_TYPE_ALPHA);
-        mSpiedPipTaskOrganizer.setSurfaceControlTransactionFactory(PipDummySurfaceControlTx::new);
+        mSpiedPipTaskOrganizer.setSurfaceControlTransactionFactory(
+                MockSurfaceControlHelper::createMockSurfaceControlTransaction);
         doNothing().when(mSpiedPipTaskOrganizer).enterPipWithAlphaAnimation(any(), anyLong());
         doNothing().when(mSpiedPipTaskOrganizer).scheduleAnimateResizePip(any(), anyInt(), any());
     }

libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/windowdecor/WindowDecorationTests.java

@@ -0,0 +1,178 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.wm.shell.windowdecor;
+
+import static com.android.wm.shell.MockSurfaceControlHelper.createMockSurfaceControlBuilder;
+import static com.android.wm.shell.MockSurfaceControlHelper.createMockSurfaceControlTransaction;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import static org.mockito.Mockito.any;
+import static org.mockito.Mockito.anyBoolean;
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.eq;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.same;
+import static org.mockito.Mockito.verify;
+
+import android.app.ActivityManager;
+import android.content.Context;
+import android.graphics.Color;
+import android.graphics.Rect;
+import android.testing.AndroidTestingRunner;
+import android.view.Display;
+import android.view.SurfaceControl;
+import android.view.SurfaceControlViewHost;
+import android.view.View;
+import android.window.WindowContainerTransaction;
+
+import androidx.test.filters.SmallTest;
+
+import com.android.wm.shell.ShellTaskOrganizer;
+import com.android.wm.shell.ShellTestCase;
+import com.android.wm.shell.TestRunningTaskInfoBuilder;
+import com.android.wm.shell.common.DisplayController;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Mock;
+
+import java.util.function.Supplier;
+
+/**
+ * Tests for {@link WindowDecoration}.
+ *
+ * Build/Install/Run:
+ * atest WMShellUnitTests:WindowDecorationTests
+ */
+@SmallTest
+@RunWith(AndroidTestingRunner.class)
+public class WindowDecorationTests extends ShellTestCase {
+    private static final int CAPTION_HEIGHT_DP = 32;
+    private static final int SHADOW_RADIUS_DP = 5;
+
+    private final Rect mOutsetsDp = new Rect();
+    private final WindowDecoration.RelayoutResult<TestView> mRelayoutResult =
+            new WindowDecoration.RelayoutResult<>();
+
+    @Mock
+    private DisplayController mMockDisplayController;
+    @Mock
+    private ShellTaskOrganizer mMockShellTaskOrganizer;
+    @Mock
+    private WindowDecoration.SurfaceControlViewHostFactory mMockSurfaceControlViewHostFactory;
+    @Mock
+    private SurfaceControlViewHost mMockSurfaceControlViewHost;
+    @Mock
+    private TestView mMockView;
+    @Mock
+    private WindowContainerTransaction mMockWindowContainerTransaction;
+
+    private SurfaceControl.Builder mMockSurfaceControlBuilder;
+    private SurfaceControl.Transaction mMockSurfaceControlTransaction;
+
+    @Before
+    public void setUp() {
+        mMockSurfaceControlBuilder = createMockSurfaceControlBuilder(mock(SurfaceControl.class));
+        mMockSurfaceControlTransaction = createMockSurfaceControlTransaction();
+
+        doReturn(mMockSurfaceControlViewHost).when(mMockSurfaceControlViewHostFactory)
+                .create(any(), any(), any(), anyBoolean());
+    }
+
+    @Test
+    public void testNotCrashWhenDisplayAppearsAfterTask() {
+        doReturn(mock(Display.class)).when(mMockDisplayController)
+                .getDisplay(Display.DEFAULT_DISPLAY);
+
+        final int displayId = Display.DEFAULT_DISPLAY + 1;
+        final ActivityManager.TaskDescription.Builder taskDescriptionBuilder =
+                new ActivityManager.TaskDescription.Builder()
+                        .setBackgroundColor(Color.BLACK);
+        final ActivityManager.RunningTaskInfo taskInfo = new TestRunningTaskInfoBuilder()
+                .setDisplayId(displayId)
+                .setTaskDescriptionBuilder(taskDescriptionBuilder)
+                .setVisible(true)
+                .build();
+
+        final TestWindowDecoration windowDecor =
+                createWindowDecoration(taskInfo, new SurfaceControl());
+        windowDecor.relayout(taskInfo);
+
+        // It shouldn't show the window decoration when it can't obtain the display instance.
+        assertThat(mRelayoutResult.mRootView).isNull();
+
+        final ArgumentCaptor<DisplayController.OnDisplaysChangedListener> listenerArgumentCaptor =
+                ArgumentCaptor.forClass(DisplayController.OnDisplaysChangedListener.class);
+        verify(mMockDisplayController).addDisplayWindowListener(listenerArgumentCaptor.capture());
+        final DisplayController.OnDisplaysChangedListener listener =
+                listenerArgumentCaptor.getValue();
+
+        // Adding an irrelevant display shouldn't change the result.
+        listener.onDisplayAdded(Display.DEFAULT_DISPLAY);
+        assertThat(mRelayoutResult.mRootView).isNull();
+
+        final Display mockDisplay = mock(Display.class);
+        doReturn(mockDisplay).when(mMockDisplayController).getDisplay(displayId);
+
+        listener.onDisplayAdded(displayId);
+
+        // The listener should be removed when the display shows up.
+        verify(mMockDisplayController).removeDisplayWindowListener(same(listener));
+
+        assertThat(mRelayoutResult.mRootView).isSameInstanceAs(mMockView);
+        verify(mMockSurfaceControlViewHostFactory)
+                .create(any(), eq(mockDisplay), any(), anyBoolean());
+        verify(mMockSurfaceControlViewHost).setView(same(mMockView), any());
+    }
+
+    private TestWindowDecoration createWindowDecoration(
+            ActivityManager.RunningTaskInfo taskInfo, SurfaceControl testSurface) {
+        return new TestWindowDecoration(mContext, mMockDisplayController, mMockShellTaskOrganizer,
+                taskInfo, testSurface, () -> mMockSurfaceControlBuilder,
+                mMockSurfaceControlViewHostFactory);
+    }
+
+    private static class TestView extends View implements TaskFocusStateConsumer {
+        private TestView(Context context) {
+            super(context);
+        }
+
+        @Override
+        public void setTaskFocusState(boolean focused) {}
+    }
+
+    private class TestWindowDecoration extends WindowDecoration<TestView> {
+        TestWindowDecoration(Context context, DisplayController displayController,
+                ShellTaskOrganizer taskOrganizer, ActivityManager.RunningTaskInfo taskInfo,
+                SurfaceControl taskSurface,
+                Supplier<SurfaceControl.Builder> surfaceControlBuilderSupplier,
+                SurfaceControlViewHostFactory surfaceControlViewHostFactory) {
+            super(context, displayController, taskOrganizer, taskInfo, taskSurface,
+                    surfaceControlBuilderSupplier, surfaceControlViewHostFactory);
+        }
+
+        @Override
+        void relayout(ActivityManager.RunningTaskInfo taskInfo) {
+            relayout(null /* taskInfo */, 0 /* layoutResId */, mMockView, CAPTION_HEIGHT_DP,
+                    mOutsetsDp, SHADOW_RADIUS_DP, mMockSurfaceControlTransaction,
+                    mMockWindowContainerTransaction, mRelayoutResult);
+        }
+    }
+}