feat(#AlwaysOnMagnifier): add preference for enabling Always On Magnification to Settings

Hide behind feature flag so no one sees the preference unless its enabled.

Defaults to enabled.

Bug: b/265086261

Test: manual

Change-Id: Ic32353f2b139772fe905137c9ec137925ef6ebb9

src/com/android/settings/accessibility/MagnificationAlwaysOnPreferenceController.java

@@ -0,0 +1,94 @@
+/*
+ * 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.settings.accessibility;
+
+import static com.android.settings.accessibility.AccessibilityUtil.State.OFF;
+import static com.android.settings.accessibility.AccessibilityUtil.State.ON;
+
+import android.content.Context;
+import android.provider.Settings;
+
+import androidx.lifecycle.Lifecycle;
+import androidx.lifecycle.LifecycleObserver;
+import androidx.lifecycle.OnLifecycleEvent;
+import androidx.preference.PreferenceScreen;
+import androidx.preference.SwitchPreference;
+
+import com.android.settings.R;
+import com.android.settings.core.TogglePreferenceController;
+
+/**
+ * Controller that accesses and switches the preference status of the magnification always on
+ * feature, where the magnifier will not deactivate on Activity transitions; it will only zoom out
+ * to 100%.
+ */
+public class MagnificationAlwaysOnPreferenceController extends TogglePreferenceController
+        implements LifecycleObserver {
+
+    private static final String TAG =
+            MagnificationAlwaysOnPreferenceController.class.getSimpleName();
+    static final String PREF_KEY = Settings.Secure.ACCESSIBILITY_MAGNIFICATION_ALWAYS_ON_ENABLED;
+
+    private SwitchPreference mSwitchPreference;
+
+    public MagnificationAlwaysOnPreferenceController(Context context, String preferenceKey) {
+        super(context, preferenceKey);
+    }
+
+    @Override
+    public int getAvailabilityStatus() {
+        return AVAILABLE;
+    }
+
+    @Override
+    public boolean isChecked() {
+        return Settings.Secure.getInt(mContext.getContentResolver(),
+                Settings.Secure.ACCESSIBILITY_MAGNIFICATION_ALWAYS_ON_ENABLED, ON) == ON;
+    }
+
+    @Override
+    public boolean setChecked(boolean isChecked) {
+        return Settings.Secure.putInt(mContext.getContentResolver(),
+                Settings.Secure.ACCESSIBILITY_MAGNIFICATION_ALWAYS_ON_ENABLED,
+                (isChecked ? ON : OFF));
+    }
+
+    @Override
+    public int getSliceHighlightMenuRes() {
+        return R.string.menu_key_accessibility;
+    }
+
+    @Override
+    public void displayPreference(PreferenceScreen screen) {
+        super.displayPreference(screen);
+        mSwitchPreference = screen.findPreference(getPreferenceKey());
+    }
+
+    // TODO(b/186731461): Remove it when this controller is used in DashBoardFragment only.
+    @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
+    void onResume() {
+        updateState();
+    }
+
+    /**
+     * Updates the state of preference components which has been displayed by
+     * {@link MagnificationAlwaysOnPreferenceController#displayPreference}.
+     */
+    void updateState() {
+        updateState(mSwitchPreference);
+    }
+}

src/com/android/settings/accessibility/ToggleScreenMagnificationPreferenceFragment.java

@@ -31,6 +31,7 @@ import android.content.pm.PackageManager;
 import android.icu.text.CaseMap;
 import android.net.Uri;
 import android.os.Bundle;
+import android.provider.DeviceConfig;
 import android.provider.Settings;
 import android.text.TextUtils;
 import android.view.LayoutInflater;
@@ -212,6 +213,32 @@ public class ToggleScreenMagnificationPreferenceFragment extends
                 getContext(), MagnificationFollowTypingPreferenceController.PREF_KEY);
         getSettingsLifecycle().addObserver(mFollowTypingPreferenceController);
         mFollowTypingPreferenceController.displayPreference(getPreferenceScreen());
+
+        addAlwaysOnSetting(generalCategory);
+    }
+
+    private void addAlwaysOnSetting(PreferenceCategory generalCategory) {
+        if (!DeviceConfig.getBoolean(
+                DeviceConfig.NAMESPACE_WINDOW_MANAGER,
+                "AlwaysOnMagnifier__enable_always_on_magnifier",
+                false
+        )) {
+            return;
+        }
+
+        var alwaysOnPreference = new SwitchPreference(getPrefContext());
+        alwaysOnPreference.setTitle(
+                R.string.accessibility_screen_magnification_always_on_title);
+        alwaysOnPreference.setSummary(
+                R.string.accessibility_screen_magnification_always_on_summary);
+        alwaysOnPreference.setKey(
+                MagnificationAlwaysOnPreferenceController.PREF_KEY);
+        generalCategory.addPreference(alwaysOnPreference);
+
+        var alwaysOnPreferenceController = new MagnificationAlwaysOnPreferenceController(
+                getContext(), MagnificationAlwaysOnPreferenceController.PREF_KEY);
+        getSettingsLifecycle().addObserver(alwaysOnPreferenceController);
+        alwaysOnPreferenceController.displayPreference(getPreferenceScreen());
     }
 
     @Override