Add Context.getDisplayId() to avoid possible IPC

ContextImpl has an internal rule that when ContextImpl#mDisplay is
null the Context is associated with the default display.  The problem
is that, as discussed in Bug 117709581, when ContextImpl#mDisplay is
null ContextImpl#getDisplay() tries to get some non-null Display
object by making an IPC to the system server, which is redundant when
the display ID is the only thing that the caller wants to know.

By having an @hide method Context.getDisplayId(), we can ensure that
display ID can be obtained without any IPC.  This enables us to
re-submit my CL [1] that aimed to instantiate InputMethodManager (IMM)
for each display but then got reverted due to a performance regression
(Bug 117434607).

There should be no developer-observable behavior change.

 [1]: I7242e765426353672823fcc8277f20ac361930d7
      c53d78e992694e471ddaae73f9a30977db9cdb75

Fix: 117712745
Test: atest FrameworksCoreTests:android.content.ContextTest
Test: prebuilts/checkstyle/checkstyle.py -f \
      frameworks/base/core/tests/coretests/src/android/content/ContextTest.java
Change-Id: I2534530a5ce90e2620c5039d793a6454a0a1e154

12 files changed, 100 insertions, 16 deletions

diff --git a/core/java/android/app/ActivityThread.java b/core/java/android/app/ActivityThread.java
index ff6aca6fa6c4..9d3c5c6417af 100644
--- a/core/java/android/app/ActivityThread.java
+++ b/core/java/android/app/ActivityThread.java
@@ -5054,7 +5054,7 @@ public final class ActivityThread extends ClientTransactionHandler {
     private void performConfigurationChangedForActivity(ActivityClientRecord r,
             Configuration newBaseConfig) {
         performConfigurationChangedForActivity(r, newBaseConfig,
-                r.activity.getDisplay().getDisplayId(), false /* movedToDifferentDisplay */);
+                r.activity.getDisplayId(), false /* movedToDifferentDisplay */);
     }
 
     /**
@@ -5406,7 +5406,7 @@ public final class ActivityThread extends ClientTransactionHandler {
             return;
         }
         final boolean movedToDifferentDisplay = displayId != INVALID_DISPLAY
-                && displayId != r.activity.getDisplay().getDisplayId();
+                && displayId != r.activity.getDisplayId();
 
         // Perform updates.
         r.overrideConfig = overrideConfig;
diff --git a/core/java/android/app/ContextImpl.java b/core/java/android/app/ContextImpl.java
index 77f639535b15..dc707e892d9a 100644
--- a/core/java/android/app/ContextImpl.java
+++ b/core/java/android/app/ContextImpl.java
@@ -2088,8 +2088,7 @@ class ContextImpl extends Context {
             ContextImpl c = new ContextImpl(this, mMainThread, pi, null, mActivityToken,
                     new UserHandle(UserHandle.getUserId(application.uid)), flags, null);
 
-            final int displayId = mDisplay != null
-                    ? mDisplay.getDisplayId() : Display.DEFAULT_DISPLAY;
+            final int displayId = getDisplayId();
 
             c.setResources(createResources(mActivityToken, pi, null, displayId, null,
                     getDisplayAdjustments(displayId).getCompatibilityInfo()));
@@ -2124,8 +2123,7 @@ class ContextImpl extends Context {
             ContextImpl c = new ContextImpl(this, mMainThread, pi, null, mActivityToken, user,
                     flags, null);
 
-            final int displayId = mDisplay != null
-                    ? mDisplay.getDisplayId() : Display.DEFAULT_DISPLAY;
+            final int displayId = getDisplayId();
 
             c.setResources(createResources(mActivityToken, pi, null, displayId, null,
                     getDisplayAdjustments(displayId).getCompatibilityInfo()));
@@ -2152,8 +2150,7 @@ class ContextImpl extends Context {
         final ContextImpl context = new ContextImpl(this, mMainThread, mPackageInfo, splitName,
                 mActivityToken, mUser, mFlags, classLoader);
 
-        final int displayId = mDisplay != null
-                ? mDisplay.getDisplayId() : Display.DEFAULT_DISPLAY;
+        final int displayId = getDisplayId();
 
         context.setResources(ResourcesManager.getInstance().getResources(
                 mActivityToken,
@@ -2177,7 +2174,7 @@ class ContextImpl extends Context {
         ContextImpl context = new ContextImpl(this, mMainThread, mPackageInfo, mSplitName,
                 mActivityToken, mUser, mFlags, mClassLoader);
 
-        final int displayId = mDisplay != null ? mDisplay.getDisplayId() : Display.DEFAULT_DISPLAY;
+        final int displayId = getDisplayId();
         context.setResources(createResources(mActivityToken, mPackageInfo, mSplitName, displayId,
                 overrideConfiguration, getDisplayAdjustments(displayId).getCompatibilityInfo()));
         return context;
@@ -2250,6 +2247,11 @@ class ContextImpl extends Context {
     }
 
     @Override
+    public int getDisplayId() {
+        return mDisplay != null ? mDisplay.getDisplayId() : Display.DEFAULT_DISPLAY;
+    }
+
+    @Override
     public void updateDisplay(int displayId) {
         mDisplay = mResourcesManager.getAdjustedDisplay(displayId, mResources);
     }
diff --git a/core/java/android/content/Context.java b/core/java/android/content/Context.java
index db4adcfaaf35..31973524ceaf 100644
--- a/core/java/android/content/Context.java
+++ b/core/java/android/content/Context.java
@@ -4982,6 +4982,14 @@ public abstract class Context {
     public abstract Display getDisplay();
 
     /**
+     * Gets the display ID.
+     *
+     * @return display ID associated with this {@link Context}.
+     * @hide
+     */
+    public abstract int getDisplayId();
+
+    /**
      * @hide
      */
     public abstract void updateDisplay(int displayId);
diff --git a/core/java/android/content/ContextWrapper.java b/core/java/android/content/ContextWrapper.java
index c5dce017430b..bfad2b42bc94 100644
--- a/core/java/android/content/ContextWrapper.java
+++ b/core/java/android/content/ContextWrapper.java
@@ -921,6 +921,14 @@ public class ContextWrapper extends Context {
      * @hide
      */
     @Override
+    public int getDisplayId() {
+        return mBase.getDisplayId();
+    }
+
+    /**
+     * @hide
+     */
+    @Override
     public void updateDisplay(int displayId) {
         mBase.updateDisplay(displayId);
     }
diff --git a/core/java/android/hardware/display/DisplayManager.java b/core/java/android/hardware/display/DisplayManager.java
index 09113e5d175d..01ef58e987d7 100644
--- a/core/java/android/hardware/display/DisplayManager.java
+++ b/core/java/android/hardware/display/DisplayManager.java
@@ -397,7 +397,7 @@ public final class DisplayManager {
         if (display == null) {
             // TODO: We cannot currently provide any override configurations for metrics on displays
             // other than the display the context is associated with.
-            final Context context = mContext.getDisplay().getDisplayId() == displayId
+            final Context context = mContext.getDisplayId() == displayId
                     ? mContext : mContext.getApplicationContext();
 
             display = mGlobal.getCompatibleDisplay(displayId, context.getResources());
diff --git a/core/java/android/widget/Toast.java b/core/java/android/widget/Toast.java
index 10cf70215747..c256d57a6af6 100644
--- a/core/java/android/widget/Toast.java
+++ b/core/java/android/widget/Toast.java
@@ -137,7 +137,7 @@ public class Toast {
         String pkg = mContext.getOpPackageName();
         TN tn = mTN;
         tn.mNextView = mNextView;
-        final int displayId = mContext.getDisplay().getDisplayId();
+        final int displayId = mContext.getDisplayId();
 
         try {
             service.enqueueToast(pkg, tn, mDuration, displayId);
diff --git a/core/java/com/android/internal/policy/PhoneWindow.java b/core/java/com/android/internal/policy/PhoneWindow.java
index 87515173e8de..3b7ce0a22b18 100644
--- a/core/java/com/android/internal/policy/PhoneWindow.java
+++ b/core/java/com/android/internal/policy/PhoneWindow.java
@@ -1387,7 +1387,7 @@ public class PhoneWindow extends Window implements MenuBuilder.Callback {
     private int getOptionsPanelGravity() {
         try {
             return WindowManagerHolder.sWindowManager.getPreferredOptionsPanelGravity(
-                    getContext().getDisplay().getDisplayId());
+                    getContext().getDisplayId());
         } catch (RemoteException ex) {
             Log.e(TAG, "Couldn't getOptionsPanelGravity; using default", ex);
             return Gravity.CENTER | Gravity.BOTTOM;
@@ -3642,7 +3642,7 @@ public class PhoneWindow extends Window implements MenuBuilder.Callback {
                 if (!mIsWatching) {
                     try {
                         WindowManagerHolder.sWindowManager.watchRotation(this,
-                                phoneWindow.getContext().getDisplay().getDisplayId());
+                                phoneWindow.getContext().getDisplayId());
                         mHandler = new Handler();
                         mIsWatching = true;
                     } catch (RemoteException ex) {
diff --git a/core/tests/coretests/src/android/content/ContextTest.java b/core/tests/coretests/src/android/content/ContextTest.java
new file mode 100644
index 000000000000..c8a3098690be
--- /dev/null
+++ b/core/tests/coretests/src/android/content/ContextTest.java
@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) 2018 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 android.content;
+
+import static org.junit.Assert.assertEquals;
+
+import android.app.ActivityThread;
+import android.support.test.InstrumentationRegistry;
+import android.support.test.filters.SmallTest;
+import android.support.test.runner.AndroidJUnit4;
+import android.view.WindowManager;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+@SmallTest
+@RunWith(AndroidJUnit4.class)
+public class ContextTest {
+    @Test
+    public void testDisplayIdForSystemContext() {
+        final Context systemContext =
+                ActivityThread.currentActivityThread().getSystemContext();
+
+        assertEquals(systemContext.getDisplay().getDisplayId(), systemContext.getDisplayId());
+    }
+
+    @Test
+    public void testDisplayIdForTestContext() {
+        final Context testContext =
+                InstrumentationRegistry.getInstrumentation().getTargetContext();
+
+        assertEquals(testContext.getDisplay().getDisplayId(), testContext.getDisplayId());
+    }
+
+    @Test
+    public void testDisplayIdForDefaultDisplayContext() {
+        final Context testContext =
+                InstrumentationRegistry.getInstrumentation().getTargetContext();
+        final WindowManager wm = testContext.getSystemService(WindowManager.class);
+        final Context defaultDisplayContext =
+                testContext.createDisplayContext(wm.getDefaultDisplay());
+
+        assertEquals(defaultDisplayContext.getDisplay().getDisplayId(),
+                defaultDisplayContext.getDisplayId());
+    }
+}
diff --git a/packages/SystemUI/shared/src/com/android/systemui/shared/system/RotationWatcher.java b/packages/SystemUI/shared/src/com/android/systemui/shared/system/RotationWatcher.java
index 5a28a5e28d91..7c8c23eba73b 100644
--- a/packages/SystemUI/shared/src/com/android/systemui/shared/system/RotationWatcher.java
+++ b/packages/SystemUI/shared/src/com/android/systemui/shared/system/RotationWatcher.java
@@ -48,7 +48,7 @@ public abstract class RotationWatcher {
         if (!mIsWatching) {
             try {
                 WindowManagerGlobal.getWindowManagerService().watchRotation(mWatcher,
-                        mContext.getDisplay().getDisplayId());
+                        mContext.getDisplayId());
                 mIsWatching = true;
             } catch (RemoteException e) {
                 Log.w(TAG, "Failed to set rotation watcher", e);
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarFragment.java b/packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarFragment.java
index 6bccf31b04a6..99a2cdc9a545 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarFragment.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarFragment.java
@@ -236,7 +236,7 @@ public class NavigationBarFragment extends Fragment implements Callbacks {
 
         try {
             WindowManagerGlobal.getWindowManagerService()
-                    .watchRotation(mRotationWatcher, getContext().getDisplay().getDisplayId());
+                    .watchRotation(mRotationWatcher, getContext().getDisplayId());
         } catch (RemoteException e) {
             throw e.rethrowFromSystemServer();
         }
diff --git a/services/tests/servicestests/src/com/android/server/wm/ScreenDecorWindowTests.java b/services/tests/servicestests/src/com/android/server/wm/ScreenDecorWindowTests.java
index 60025f0f03fe..ae40f7e7d235 100644
--- a/services/tests/servicestests/src/com/android/server/wm/ScreenDecorWindowTests.java
+++ b/services/tests/servicestests/src/com/android/server/wm/ScreenDecorWindowTests.java
@@ -334,7 +334,7 @@ public class ScreenDecorWindowTests {
         final Activity activity = mInstrumentation.startActivitySync(intent, options.toBundle());
         waitForIdle();
 
-        assertEquals(displayId, activity.getDisplay().getDisplayId());
+        assertEquals(displayId, activity.getDisplayId());
         return activity;
     }
 
diff --git a/test-mock/src/android/test/mock/MockContext.java b/test-mock/src/android/test/mock/MockContext.java
index 9d260ebf7231..fa5b896ea126 100644
--- a/test-mock/src/android/test/mock/MockContext.java
+++ b/test-mock/src/android/test/mock/MockContext.java
@@ -774,6 +774,12 @@ public class MockContext extends Context {
 
     /** @hide */
     @Override
+    public int getDisplayId() {
+        throw new UnsupportedOperationException();
+    }
+
+    /** @hide */
+    @Override
     public void updateDisplay(int displayId) {
         throw new UnsupportedOperationException();
     }