Extract common display density configuraiton code

We're currently importing the whole of SettingsLib into the Settings
Backup Agent just to access a single static method. This seems to
have contributed to a the regression which relates to b/139373401.

This CL separates the 3 related methods out into their own build
target so the amount of code included in SettingsBackupAgent is
much smaller.

A later CL will remove the original location after all usages
have been redirected to this new location

Bug: 139373401
Test: atest SettingsProviderTest SettingsLibRoboTests
Change-Id: I36fbc21daddcf068491b58db01b66f540ac26cf7

packages/SettingsLib/Android.bp

@@ -25,6 +25,7 @@ android_library {
         "SettingsLibAdaptiveIcon",
         "SettingsLibRadioButtonPreference",
         "WifiTrackerLib",
+        "SettingsLibDisplayDensityUtils",
     ],
 
     // ANDROIDMK TRANSLATION ERROR: unsupported assignment to LOCAL_SHARED_JAVA_LIBRARIES

packages/SettingsLib/DisplayDensityUtils/Android.bp

@@ -0,0 +1,7 @@
+android_library {
+    name: "SettingsLibDisplayDensityUtils",
+
+    srcs: ["src/**/*.java"],
+
+    min_sdk_version: "21",
+}

packages/SettingsLib/DisplayDensityUtils/AndroidManifest.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Copyright (C) 2019 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.
+  -->
+
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+          package="com.android.settingslib.display">
+
+</manifest>

packages/SettingsLib/DisplayDensityUtils/src/com/android/settingslib/display/DisplayDensityConfiguration.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright (C) 2019 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.settingslib.display;
+
+import android.os.AsyncTask;
+import android.os.RemoteException;
+import android.os.UserHandle;
+import android.util.Log;
+import android.view.IWindowManager;
+import android.view.WindowManagerGlobal;
+
+/** Utility methods for controlling the display density. */
+public class DisplayDensityConfiguration {
+    private static final String LOG_TAG = "DisplayDensityConfig";
+
+    /**
+     * Returns the default density for the specified display.
+     *
+     * @param displayId the identifier of the display
+     * @return the default density of the specified display, or {@code -1} if the display does not
+     *     exist or the density could not be obtained
+     */
+    static int getDefaultDisplayDensity(int displayId) {
+        try {
+            final IWindowManager wm = WindowManagerGlobal.getWindowManagerService();
+            return wm.getInitialDisplayDensity(displayId);
+        } catch (RemoteException exc) {
+            return -1;
+        }
+    }
+
+    /**
+     * Asynchronously applies display density changes to the specified display.
+     *
+     * <p>The change will be applied to the user specified by the value of {@link
+     * UserHandle#myUserId()} at the time the method is called.
+     *
+     * @param displayId the identifier of the display to modify
+     */
+    public static void clearForcedDisplayDensity(final int displayId) {
+        final int userId = UserHandle.myUserId();
+        AsyncTask.execute(
+                () -> {
+                    try {
+                        final IWindowManager wm = WindowManagerGlobal.getWindowManagerService();
+                        wm.clearForcedDisplayDensityForUser(displayId, userId);
+                    } catch (RemoteException exc) {
+                        Log.w(LOG_TAG, "Unable to clear forced display density setting");
+                    }
+                });
+    }
+
+    /**
+     * Asynchronously applies display density changes to the specified display.
+     *
+     * <p>The change will be applied to the user specified by the value of {@link
+     * UserHandle#myUserId()} at the time the method is called.
+     *
+     * @param displayId the identifier of the display to modify
+     * @param density the density to force for the specified display
+     */
+    public static void setForcedDisplayDensity(final int displayId, final int density) {
+        final int userId = UserHandle.myUserId();
+        AsyncTask.execute(
+                () -> {
+                    try {
+                        final IWindowManager wm = WindowManagerGlobal.getWindowManagerService();
+                        wm.setForcedDisplayDensityForUser(displayId, density, userId);
+                    } catch (RemoteException exc) {
+                        Log.w(LOG_TAG, "Unable to save forced display density setting");
+                    }
+                });
+    }
+}

packages/SettingsProvider/Android.bp

@@ -11,7 +11,7 @@ android_app {
     ],
     static_libs: [
         "junit",
-        "SettingsLib",
+        "SettingsLibDisplayDensityUtils",
     ],
     platform_apis: true,
     certificate: "platform",
@@ -30,7 +30,7 @@ android_test {
     ],
     static_libs: [
         "androidx.test.rules",
-        "SettingsLib",
+        "SettingsLibDisplayDensityUtils",
     ],
     libs: [
         "android.test.base",

packages/SettingsProvider/src/com/android/providers/settings/SettingsBackupAgent.java

@@ -45,7 +45,7 @@ import android.view.Display;
 import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.util.ArrayUtils;
 import com.android.internal.widget.LockPatternUtils;
-import com.android.settingslib.display.DisplayDensityUtils;
+import com.android.settingslib.display.DisplayDensityConfiguration;
 
 import java.io.BufferedOutputStream;
 import java.io.ByteArrayInputStream;
@@ -1035,7 +1035,8 @@ public class SettingsBackupAgent extends BackupAgentHelper {
 
         if (previousDensity == null || previousDensity != newDensity) {
             // From nothing to something is a change.
-            DisplayDensityUtils.setForcedDisplayDensity(Display.DEFAULT_DISPLAY, newDensity);
+            DisplayDensityConfiguration.setForcedDisplayDensity(
+                    Display.DEFAULT_DISPLAY, newDensity);
         }
     }