Adapt swipe navigation to reading direction

FAQ.md

@@ -224,6 +224,7 @@ FairEmail follows all the best practices for an email client as decribed in [thi
 * [(128) How can I reset asked questions, for example to show images?](#user-content-faq128)
 * [(129) Is ProtonMail supported?](#user-content-faq129)
 * [(130) What does message error ... mean?](#user-content-faq130)
+* [(131) Can you change the direction for swiping to previous/next message?](#user-content-faq131)
 
 [I have another question.](#user-content-support)
 
@@ -2188,6 +2189,8 @@ ProtonMail uses a proprietary email protocol
 and [does not directly support IMAP](https://protonmail.com/support/knowledge-base/imap-smtp-and-pop3-setup/),
 so you cannot use FairEmail to access ProtonMail.
 
+<br />
+
 <a name="faq130"></a>
 **(130) What does message error ... mean?**
 
@@ -2203,6 +2206,18 @@ The error will almost always include a reason. Common reasons are that the messa
 
 Please see [here](#user-content-faq22) for other error messages in the outbox.
 
+<br />
+
+<a name="faq131"></a>
+**(131) Can you change the direction for swiping to previous/next message?**
+
+If you read from left to right, swiping to the left will show the next message.
+Similarly, if you read from right to left, swiping to the right will show the next message.
+
+This behavior seems quite natural to me.
+
+<br />
+
 ## Support
 
 If you have another question, want to request a feature or report a bug, you can use [this forum](https://forum.xda-developers.com/android/apps-games/source-email-t3824168).

app/src/main/java/eu/faircode/email/FragmentMessages.java

@@ -944,6 +944,8 @@ public class FragmentMessages extends FragmentBase implements SharedPreferences.
             if (swipenav) {
                 Log.i("Swipe navigation");
 
+                boolean ltr = (getContext().getResources().getConfiguration().getLayoutDirection() == View.LAYOUT_DIRECTION_LTR);
+
                 final SwipeListener swipeListener = new SwipeListener(getContext(), new SwipeListener.ISwipeListener() {
                     @Override
                     public boolean onSwipeRight() {
@@ -951,7 +953,7 @@ public class FragmentMessages extends FragmentBase implements SharedPreferences.
                             Animation bounce = AnimationUtils.loadAnimation(getContext(), R.anim.bounce_right);
                             view.startAnimation(bounce);
                         } else
-                            navigate(previous, true);
+                            navigate(previous, ltr);
 
                         return (previous != null);
                     }
@@ -962,7 +964,7 @@ public class FragmentMessages extends FragmentBase implements SharedPreferences.
                             Animation bounce = AnimationUtils.loadAnimation(getContext(), R.anim.bounce_left);
                             view.startAnimation(bounce);
                         } else
-                            navigate(next, false);
+                            navigate(next, !ltr);
 
                         return (next != null);
                     }