Hide "Magnify with button" if no navbar is shown

Devices without a software-rendered navigation bar will be unable to
use "Magnify with button" as no accessibility button trigger for
magnification can be shown.

In this case, we hide the setting by preventing
MagnificationPreferenceFragment from showing the list of mag
modes, instead launching directly into the PreferenceFragment for
"Magnify with triple-tap"

Bug: 36862906
Test: Manual - Configured marlin to disable the navigation bar and
      verified behavior in SUW and Settings

Change-Id: Ie614ec292d7779044274b7c79eaed1df080c0fd1

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

@@ -387,6 +387,7 @@ public class AccessibilitySettings extends SettingsPreferenceFragment implements
         // Display magnification.
         mDisplayMagnificationPreferenceScreen = findPreference(
                 DISPLAY_MAGNIFICATION_PREFERENCE_SCREEN);
+        configureMagnificationPreferenceIfNeeded(mDisplayMagnificationPreferenceScreen);
 
         // Font size.
         mFontSizePreferenceScreen = findPreference(FONT_SIZE_PREFERENCE_SCREEN);
@@ -678,6 +679,19 @@ public class AccessibilitySettings extends SettingsPreferenceFragment implements
         }
     }
 
+    private static void configureMagnificationPreferenceIfNeeded(Preference preference) {
+        // Some devices support only a single magnification mode. In these cases, we redirect to
+        // the magnification mode's UI directly, rather than showing a PreferenceScreen with a
+        // single list item.
+        final Context context = preference.getContext();
+        if (!MagnificationPreferenceFragment.isApplicable(context.getResources())) {
+            preference.setFragment(ToggleScreenMagnificationPreferenceFragment.class.getName());
+            final Bundle extras = preference.getExtras();
+            MagnificationPreferenceFragment.populateMagnificationGesturesPreferenceExtras(extras,
+                    context);
+        }
+    }
+
     public static final SearchIndexProvider SEARCH_INDEX_DATA_PROVIDER =
             new BaseSearchIndexProvider() {
         @Override

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

@@ -18,9 +18,9 @@ package com.android.settings.accessibility;
 
 import android.accessibilityservice.AccessibilityServiceInfo;
 import android.content.ComponentName;
+import android.content.Context;
 import android.content.pm.ServiceInfo;
 import android.os.Bundle;
-import android.provider.Settings;
 import android.support.v7.preference.Preference;
 import android.text.TextUtils;
 import android.view.accessibility.AccessibilityManager;
@@ -79,6 +79,7 @@ public class AccessibilitySettingsForSetupWizard extends SettingsPreferenceFragm
                 findService(SCREEN_READER_PACKAGE_NAME, SCREEN_READER_SERVICE_NAME));
         updateAccessibilityServicePreference(mSelectToSpeakPreference,
                 findService(SELECT_TO_SPEAK_PACKAGE_NAME, SELECT_TO_SPEAK_SERVICE_NAME));
+        configureMagnificationPreferenceIfNeeded(mDisplayMagnificationPreference);
     }
 
     @Override
@@ -145,4 +146,18 @@ public class AccessibilitySettingsForSetupWizard extends SettingsPreferenceFragm
         }
         extras.putString(AccessibilitySettings.EXTRA_SUMMARY, description);
     }
+
+    private static void configureMagnificationPreferenceIfNeeded(Preference preference) {
+        // Some devices support only a single magnification mode. In these cases, we redirect to
+        // the magnification mode's UI directly, rather than showing a PreferenceScreen with a
+        // single list item.
+        final Context context = preference.getContext();
+        if (!MagnificationPreferenceFragment.isApplicable(context.getResources())) {
+            preference.setFragment(
+                    ToggleScreenMagnificationPreferenceFragmentForSetupWizard.class.getName());
+            final Bundle extras = preference.getExtras();
+            MagnificationPreferenceFragment.populateMagnificationGesturesPreferenceExtras(extras,
+                    context);
+        }
+    }
 }

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

@@ -19,6 +19,7 @@ package com.android.settings.accessibility;
 import android.accessibilityservice.AccessibilityServiceInfo;
 import android.content.ComponentName;
 import android.content.Context;
+import android.content.res.Resources;
 import android.os.Bundle;
 import android.provider.SearchIndexableResource;
 import android.provider.Settings;
@@ -34,6 +35,7 @@ import com.android.settings.search.BaseSearchIndexProvider;
 import com.android.settings.search.Indexable;
 
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 
 public final class MagnificationPreferenceFragment extends SettingsPreferenceFragment implements
@@ -123,18 +125,7 @@ public final class MagnificationPreferenceFragment extends SettingsPreferenceFra
 
     private void handleMagnificationGesturesPreferenceScreenClick() {
         Bundle extras = mMagnificationGesturesPreference.getExtras();
-        extras.putString(AccessibilitySettings.EXTRA_PREFERENCE_KEY,
+        populateMagnificationGesturesPreferenceExtras(extras, getContext());
-                Settings.Secure.ACCESSIBILITY_DISPLAY_MAGNIFICATION_ENABLED);
-        extras.putString(AccessibilitySettings.EXTRA_TITLE, getString(
-                R.string.accessibility_screen_magnification_gestures_title));
-        extras.putCharSequence(AccessibilitySettings.EXTRA_SUMMARY,
-                getActivity().getResources().getText(
-                        R.string.accessibility_screen_magnification_summary));
-        extras.putBoolean(AccessibilitySettings.EXTRA_CHECKED,
-                Settings.Secure.getInt(getContentResolver(),
-                        Settings.Secure.ACCESSIBILITY_DISPLAY_MAGNIFICATION_ENABLED, 0) == 1);
-        extras.putInt(AccessibilitySettings.EXTRA_VIDEO_RAW_RESOURCE_ID,
-                R.raw.accessibility_screen_magnification);
         extras.putBoolean(AccessibilitySettings.EXTRA_LAUNCHED_FROM_SUW, mLaunchedFromSuw);
     }
 
@@ -188,14 +179,40 @@ public final class MagnificationPreferenceFragment extends SettingsPreferenceFra
         return null;
     }
 
+    static void populateMagnificationGesturesPreferenceExtras(Bundle extras, Context context) {
+        extras.putString(AccessibilitySettings.EXTRA_PREFERENCE_KEY,
+                Settings.Secure.ACCESSIBILITY_DISPLAY_MAGNIFICATION_ENABLED);
+        extras.putString(AccessibilitySettings.EXTRA_TITLE, context.getString(
+                R.string.accessibility_screen_magnification_gestures_title));
+        extras.putCharSequence(AccessibilitySettings.EXTRA_SUMMARY, context.getResources().getText(
+                R.string.accessibility_screen_magnification_summary));
+        extras.putBoolean(AccessibilitySettings.EXTRA_CHECKED,
+                Settings.Secure.getInt(context.getContentResolver(),
+                        Settings.Secure.ACCESSIBILITY_DISPLAY_MAGNIFICATION_ENABLED, 0) == 1);
+        extras.putInt(AccessibilitySettings.EXTRA_VIDEO_RAW_RESOURCE_ID,
+                R.raw.accessibility_screen_magnification);
+    }
+
+    /**
+     * @return {@code true} if this fragment should be shown, {@code false} otherwise. This
+     * fragment is shown in the case that more than one magnification mode is available.
+     */
+    static boolean isApplicable(Resources res) {
+        return res.getBoolean(com.android.internal.R.bool.config_showNavigationBar);
+    }
+
     public static final Indexable.SearchIndexProvider SEARCH_INDEX_DATA_PROVIDER =
             new BaseSearchIndexProvider() {
                 @Override
                 public List<SearchIndexableResource> getXmlResourcesToIndex(Context context,
                         boolean enabled) {
-                    final SearchIndexableResource sir = new SearchIndexableResource(context);
+                    if (isApplicable(context.getResources())) {
-                    sir.xmlResId = R.xml.accessibility_magnification_settings;
+                        final SearchIndexableResource sir = new SearchIndexableResource(context);
-                    return Arrays.asList(sir);
+                        sir.xmlResId = R.xml.accessibility_magnification_settings;
+                        return Arrays.asList(sir);
+                    } else {
+                        return Collections.emptyList();
+                    }
                 }
             };
 }