add lockscreen PIN input layout scrambling toggle

res/values/strings_ext.xml

@@ -11,6 +11,7 @@
 
     <string name="app_exploit_protection_category">App exploit protection</string>
 
+    <string name="scramble_pin_title">Scramble PIN input layout</string>
 
     <string name="auto_grant_OTHER_SENSORS_permission_title">Allow Sensors permission to apps by default</string>
     <string name="auto_grant_OTHER_SENSORS_permission_summary_on">Sensors is a non-standard permission, apps may malfunction if it’s denied.</string>

res/xml/screen_lock_settings.xml

@@ -33,6 +33,11 @@
         android:title="@string/lock_screen_auto_pin_confirm_title"
         android:summary="@string/lock_screen_auto_pin_confirm_summary" />
 
+    <SwitchPreferenceCompat
+        android:key="scramble_pin_layout"
+        android:title="@string/scramble_pin_title"
+        settings:controller="com.android.settings.security.screenlock.PinScramblingPrefController" />
+
     <SwitchPreferenceCompat
         android:key="enhancedPinPrivacy"
         android:title="@string/lockpattern_settings_enhanced_pin_privacy_title"

src/com/android/settings/security/screenlock/PinScramblingPrefController.java

@@ -0,0 +1,33 @@
+package com.android.settings.security.screenlock;
+
+import android.content.Context;
+import android.ext.settings.ExtSettings;
+
+import com.android.internal.widget.LockPatternUtils;
+import com.android.settings.ext.BoolSettingPrefController;
+import com.android.settings.overlay.FeatureFactory;
+
+public class PinScramblingPrefController extends BoolSettingPrefController {
+
+    private final LockPatternUtils lockPatternUtils;
+
+    public PinScramblingPrefController(Context ctx, String key) {
+        super(ctx, key, ExtSettings.SCRAMBLE_LOCKSCREEN_PIN_LAYOUT);
+
+        lockPatternUtils = FeatureFactory.getFeatureFactory()
+                .getSecurityFeatureProvider()
+                .getLockPatternUtils(ctx);
+    }
+
+    @Override
+    public int getAvailabilityStatus() {
+        int res = super.getAvailabilityStatus();
+        if (res == AVAILABLE) {
+            if (lockPatternUtils.getCredentialTypeForUser(mContext.getUserId())
+                    != LockPatternUtils.CREDENTIAL_TYPE_PIN) {
+                return CONDITIONALLY_UNAVAILABLE;
+            }
+        }
+        return res;
+    }
+}