Shows navbar in SUW if the a11y button is requested

Adds a utility class to detect the state of the accessibility
button.

Test: Robolectric tests in 2110420 to verify behavior.
Bug: 37295649
Change-Id: I25828a0daaeb7f0048fe63741bc929ffac084336

packages/SettingsLib/src/com/android/settingslib/accessibility/AccessibilityButtonHelper.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright (C) 2017 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.accessibility;
+
+import android.accessibilityservice.AccessibilityServiceInfo;
+import android.content.Context;
+import android.content.res.Resources;
+import android.provider.Settings;
+import android.view.accessibility.AccessibilityManager;
+
+import java.util.List;
+
+/**
+ * A helper class to assist determining the state of the accessibility button that can appear
+ * within the software-rendered navigation area.
+ */
+public class AccessibilityButtonHelper {
+    public static boolean isRequestedByMagnification(Context ctx) {
+        return Settings.Secure.getInt(ctx.getContentResolver(),
+                Settings.Secure.ACCESSIBILITY_DISPLAY_MAGNIFICATION_NAVBAR_ENABLED, 0) == 1;
+    }
+
+    public static boolean isRequestedByAccessibilityService(Context ctx) {
+        final AccessibilityManager accessibilityManager = ctx.getSystemService(
+                AccessibilityManager.class);
+        List<AccessibilityServiceInfo> services =
+                accessibilityManager.getEnabledAccessibilityServiceList(
+                        AccessibilityServiceInfo.FEEDBACK_ALL_MASK);
+        if (services != null) {
+            for (int i = 0, size = services.size(); i < size; i++) {
+                if ((services.get(i).flags
+                        & AccessibilityServiceInfo.FLAG_REQUEST_ACCESSIBILITY_BUTTON)
+                        != 0) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
+    public static boolean isRequested(Context ctx) {
+        return isRequestedByMagnification(ctx) || isRequestedByAccessibilityService(ctx);
+    }
+
+    public static boolean isDeviceSupported(Resources res) {
+        return res.getBoolean(com.android.internal.R.bool.config_showNavigationBar);
+    }
+}