Auto scroll up conversations

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

@@ -151,6 +151,18 @@ public interface DaoMessage {
             ", CASE WHEN folder.type = '" + EntityFolder.ARCHIVE + "' THEN 1 ELSE 0 END")
     DataSource.Factory<Integer, TupleMessageEx> pagedThread(long account, String thread, Long id, boolean debug);
 
+    @Query("SELECT account.name AS accountName" +
+            ", COUNT(message.id) AS count" +
+            ", SUM(message.ui_seen) AS seen" +
+            " FROM message" +
+            " JOIN account ON account.id = message.account" +
+            " WHERE message.account = :account" +
+            " AND message.thread = :thread" +
+            " AND (:id IS NULL OR message.id = :id)" +
+            " AND NOT message.ui_hide" +
+            " GROUP BY account.id")
+    LiveData<TupleThreadStats> liveThreadStats(long account, String thread, Long id);
+
     @Query("SELECT message.id FROM folder" +
             " JOIN message ON message.folder = folder.id" +
             " WHERE CASE WHEN :folder IS NULL THEN folder.unified ELSE folder.id = :folder END" +

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

@@ -1772,10 +1772,22 @@ public class FragmentMessages extends FragmentBase {
                 break;
 
             case THREAD:
-                db.account().liveAccount(account).observe(getViewLifecycleOwner(), new Observer<EntityAccount>() {
+                db.message().liveThreadStats(account, thread, null).observe(getViewLifecycleOwner(), new Observer<TupleThreadStats>() {
+                    Integer lastUnseen = null;
+
                     @Override
-                    public void onChanged(EntityAccount account) {
+                    public void onChanged(TupleThreadStats stats) {
-                        setSubtitle(getString(R.string.title_folder_thread, account == null ? "" : account.name));
+                        setSubtitle(getString(R.string.title_folder_thread,
+                                stats == null || stats.accountName == null ? "" : stats.accountName));
+
+                        if (stats != null && stats.count != null && stats.unseen != null) {
+                            int unseen = stats.count - stats.unseen;
+                            if (lastUnseen == null || lastUnseen != unseen) {
+                                if (autoscroll && lastUnseen != null && lastUnseen < unseen)
+                                    loadMessages(true);
+                                lastUnseen = unseen;
+                            }
+                        }
                     }
                 });
                 db.message().liveHidden(account, thread).observe(getViewLifecycleOwner(), new Observer<List<Long>>() {

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

@@ -0,0 +1,7 @@
+package eu.faircode.email;
+
+public class TupleThreadStats {
+    String accountName;
+    Integer count;
+    Integer unseen;
+}