Added Gmail label support

FAQ.md

@@ -380,6 +380,7 @@ The low priority status bar notification shows the number of pending operations,
 * *answered*: mark message as answered in remote folder
 * *flag*: add/remove star in remote folder
 * *keyword*: add/remove IMAP flag in remote folder
+* *label*: set/reset Gmail label in remote folder
 * *headers*: download message headers
 * *raw*: download raw message
 * *body*: download message text

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

@@ -156,6 +156,7 @@ import java.io.UnsupportedEncodingException;
 import java.lang.reflect.Field;
 import java.nio.charset.StandardCharsets;
 import java.security.NoSuchAlgorithmException;
+import java.text.Collator;
 import java.text.DateFormat;
 import java.text.NumberFormat;
 import java.text.SimpleDateFormat;
@@ -241,6 +242,7 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
     private String subject_ellipsize;
 
     private boolean keywords_header;
+    private boolean labels_header;
     private boolean flags;
     private boolean flags_background;
     private boolean preview;
@@ -341,6 +343,7 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
         private TextView tvSubject;
         private TextView tvKeywords;
         private TextView tvFolder;
+        private TextView tvLabels;
         private TextView tvCount;
         private ImageView ivThread;
         private TextView tvExpand;
@@ -410,6 +413,7 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
         private ImageButton ibRule;
         private ImageButton ibUnsubscribe;
         private ImageButton ibAnswer;
+        private ImageButton ibLabels;
         private ImageButton ibMove;
         private ImageButton ibArchive;
         private ImageButton ibTrash;
@@ -493,6 +497,7 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
             tvExpand = itemView.findViewById(R.id.tvExpand);
             tvPreview = itemView.findViewById(R.id.tvPreview);
             tvFolder = itemView.findViewById(R.id.tvFolder);
+            tvLabels = itemView.findViewById(R.id.tvLabels);
             tvCount = itemView.findViewById(R.id.tvCount);
             ivThread = itemView.findViewById(R.id.ivThread);
             tvError = itemView.findViewById(R.id.tvError);
@@ -611,6 +616,7 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
             ibRule = vsBody.findViewById(R.id.ibRule);
             ibUnsubscribe = vsBody.findViewById(R.id.ibUnsubscribe);
             ibAnswer = vsBody.findViewById(R.id.ibAnswer);
+            ibLabels = vsBody.findViewById(R.id.ibLabels);
             ibMove = vsBody.findViewById(R.id.ibMove);
             ibArchive = vsBody.findViewById(R.id.ibArchive);
             ibTrash = vsBody.findViewById(R.id.ibTrash);
@@ -701,6 +707,7 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
                 ibVerify.setOnClickListener(this);
                 ibUndo.setOnClickListener(this);
                 ibAnswer.setOnClickListener(this);
+                ibLabels.setOnClickListener(this);
                 ibMove.setOnClickListener(this);
                 ibArchive.setOnClickListener(this);
                 ibTrash.setOnClickListener(this);
@@ -788,6 +795,7 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
                 ibVerify.setOnClickListener(null);
                 ibUndo.setOnClickListener(null);
                 ibAnswer.setOnClickListener(null);
+                ibLabels.setOnClickListener(null);
                 ibMove.setOnClickListener(null);
                 ibArchive.setOnClickListener(null);
                 ibTrash.setOnClickListener(null);
@@ -841,6 +849,7 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
             tvSubject.setText(null);
             tvKeywords.setVisibility(View.GONE);
             tvFolder.setText(null);
+            tvLabels.setVisibility(View.GONE);
             tvCount.setText(null);
             ivThread.setVisibility(View.GONE);
             tvExpand.setVisibility(View.GONE);
@@ -876,6 +885,7 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
                 tvSubject.setTextSize(TypedValue.COMPLEX_UNIT_PX, fz_subject);
                 tvKeywords.setTextSize(TypedValue.COMPLEX_UNIT_PX, textSize * 0.9f);
                 tvFolder.setTextSize(TypedValue.COMPLEX_UNIT_PX, textSize * 0.9f);
+                tvLabels.setTextSize(TypedValue.COMPLEX_UNIT_PX, textSize * 0.9f);
                 tvPreview.setTextSize(TypedValue.COMPLEX_UNIT_PX, textSize * 0.9f);
 
                 if (avatars) {
@@ -920,6 +930,7 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
                 tvSubject.setAlpha(dim ? Helper.LOW_LIGHT : 1.0f);
                 tvKeywords.setAlpha(dim ? Helper.LOW_LIGHT : 1.0f);
                 tvFolder.setAlpha(dim ? Helper.LOW_LIGHT : 1.0f);
+                tvLabels.setAlpha(dim ? Helper.LOW_LIGHT : 1.0f);
                 tvCount.setAlpha(dim ? Helper.LOW_LIGHT : 1.0f);
                 ivThread.setAlpha(dim ? Helper.LOW_LIGHT : 1.0f);
                 tvPreview.setAlpha(dim ? Helper.LOW_LIGHT : 1.0f);
@@ -1055,6 +1066,11 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
 
             tvFolder.setVisibility(compact && viewType != ViewType.THREAD ? View.GONE : View.VISIBLE);
 
+            tvLabels.setText(message.labels == null ? null : TextUtils.join(", ", message.labels));
+            tvLabels.setVisibility(
+                    labels_header && message.labels != null && message.labels.length > 0
+                            ? View.VISIBLE : View.GONE);
+
             boolean selected = properties.getValue("selected", message.id);
             if (viewType == ViewType.THREAD || (!threading && !selected)) {
                 tvCount.setVisibility(View.GONE);
@@ -1282,6 +1298,7 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
             ibRule.setVisibility(View.GONE);
             ibUnsubscribe.setVisibility(View.GONE);
             ibAnswer.setVisibility(View.GONE);
+            ibLabels.setVisibility(View.GONE);
             ibMove.setVisibility(View.GONE);
             ibArchive.setVisibility(View.GONE);
             ibTrash.setVisibility(View.GONE);
@@ -1412,6 +1429,7 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
             ibRule.setVisibility(View.GONE);
             ibUnsubscribe.setVisibility(View.GONE);
             ibAnswer.setVisibility(View.GONE);
+            ibLabels.setVisibility(View.GONE);
             ibMove.setVisibility(View.GONE);
             ibArchive.setVisibility(View.GONE);
             ibTrash.setVisibility(View.GONE);
@@ -1485,8 +1503,13 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
             new SimpleTask<List<EntityFolder>>() {
                 @Override
                 protected List<EntityFolder> onExecute(Context context, Bundle args) {
-                    long account = args.getLong("account");
+                    long aid = args.getLong("account");
-                    return DB.getInstance(context).folder().getSystemFolders(account);
+
+                    DB db = DB.getInstance(context);
+                    EntityAccount account = db.account().getAccount(aid);
+                    args.putBoolean("labels", account != null && account.isGmail());
+
+                    return db.folder().getSystemFolders(aid);
                 }
 
                 @Override
@@ -1500,6 +1523,8 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
                     if (!show_expanded)
                         return;
 
+                    boolean labels = args.getBoolean("labels");
+
                     boolean hasArchive = false;
                     boolean hasTrash = false;
                     boolean hasJunk = false;
@@ -1542,6 +1567,7 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
                             message.accountProtocol == EntityAccount.TYPE_IMAP ? View.VISIBLE : View.GONE);
                     ibUnsubscribe.setVisibility(!tools || message.unsubscribe == null ? View.GONE : View.VISIBLE);
                     ibAnswer.setVisibility(!tools || outbox || (!expand_all && expand_one) ? View.GONE : View.VISIBLE);
+                    ibLabels.setVisibility(tools && labels_header && labels ? View.VISIBLE : View.GONE);
                     ibMove.setVisibility(tools && move ? View.VISIBLE : View.GONE);
                     ibArchive.setVisibility(tools && extras && archive ? View.VISIBLE : View.GONE);
                     ibTrash.setVisibility(tools && extras && trash ? View.VISIBLE : View.GONE);
@@ -2742,6 +2768,9 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
                     case R.id.ibAnswer:
                         onActionAnswer(message, ibAnswer);
                         break;
+                    case R.id.ibLabels:
+                        onActionLabels(message);
+                        break;
                     case R.id.ibMove:
                         onActionMove(message, false);
                         break;
@@ -3530,6 +3559,50 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
             properties.reply(message, getSelectedText(), anchor);
         }
 
+        private void onActionLabels(final TupleMessageEx message) {
+            Bundle args = new Bundle();
+            args.putLong("id", message.id);
+            args.putLong("account", message.account);
+
+            new SimpleTask<String[]>() {
+                @Override
+                protected String[] onExecute(Context context, Bundle args) {
+                    long account = args.getLong("account");
+
+                    DB db = DB.getInstance(context);
+                    List<EntityFolder> folders = db.folder().getFolders(account, true, true);
+
+                    List<String> result = new ArrayList<>();
+                    if (folders != null)
+                        for (EntityFolder folder : folders)
+                            if (!EntityFolder.INBOX.equals(folder.type))
+                                result.add(folder.name);
+
+                    Collator collator = Collator.getInstance(Locale.getDefault());
+                    collator.setStrength(Collator.SECONDARY); // Case insensitive, process accents etc
+
+                    Collections.sort(result, collator);
+
+                    return result.toArray(new String[0]);
+                }
+
+                @Override
+                protected void onExecuted(Bundle args, String[] folders) {
+                    args.putStringArray("labels", message.labels);
+                    args.putStringArray("folders", folders);
+
+                    FragmentDialogLabelsManage fragment = new FragmentDialogLabelsManage();
+                    fragment.setArguments(args);
+                    fragment.show(parentFragment.getParentFragmentManager(), "labels:manage");
+                }
+
+                @Override
+                protected void onException(Bundle args, Throwable ex) {
+                    Log.unexpectedError(parentFragment.getParentFragmentManager(), ex);
+                }
+            }.execute(context, owner, args, "labels:fetch");
+        }
+
         private void onActionMove(TupleMessageEx message, final boolean copy) {
             Bundle args = new Bundle();
             args.putString("title", context.getString(copy ? R.string.title_copy_to : R.string.title_move_to_folder));
@@ -4849,6 +4922,7 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
         this.subject_italic = prefs.getBoolean("subject_italic", true);
         this.subject_ellipsize = prefs.getString("subject_ellipsize", "middle");
         this.keywords_header = prefs.getBoolean("keywords_header", false);
+        this.labels_header = prefs.getBoolean("labels_header", true);
         this.flags = prefs.getBoolean("flags", true);
         this.flags_background = prefs.getBoolean("flags_background", false);
         this.preview = prefs.getBoolean("preview", false);
@@ -5047,6 +5121,10 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
                     same = false;
                     log("keywords changed", next.id);
                 }
+                if (!Helper.equal(prev.labels, next.labels)) {
+                    same = false;
+                    log("labels changed", next.id);
+                }
                 // notifying
                 // fts
                 if (!prev.ui_seen.equals(next.ui_seen)) {
@@ -6044,4 +6122,59 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
                     .create();
         }
     }
+
+    public static class FragmentDialogLabelsManage extends FragmentDialogBase {
+        @NonNull
+        @Override
+        public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
+            final long id = getArguments().getLong("id");
+            String[] labels = getArguments().getStringArray("labels");
+            final String[] folders = getArguments().getStringArray("folders");
+
+            List<String> l = new ArrayList<>();
+            if (labels != null)
+                l.addAll(Arrays.asList(labels));
+
+            boolean[] checked = new boolean[folders.length];
+            for (int i = 0; i < folders.length; i++)
+                if (l.contains(folders[i]))
+                    checked[i] = true;
+
+            return new AlertDialog.Builder(getContext())
+                    .setTitle(R.string.title_manage_labels)
+                    .setMultiChoiceItems(folders, checked, new DialogInterface.OnMultiChoiceClickListener() {
+                        @Override
+                        public void onClick(DialogInterface dialog, int which, boolean isChecked) {
+                            Bundle args = new Bundle();
+                            args.putLong("id", id);
+                            args.putString("label", folders[which]);
+                            args.putBoolean("set", isChecked);
+
+                            new SimpleTask<Void>() {
+                                @Override
+                                protected Void onExecute(Context context, Bundle args) {
+                                    long id = args.getLong("id");
+                                    String label = args.getString("label");
+                                    boolean set = args.getBoolean("set");
+
+                                    DB db = DB.getInstance(context);
+                                    EntityMessage message = db.message().getMessage(id);
+                                    if (message == null)
+                                        return null;
+
+                                    EntityOperation.queue(context, message, EntityOperation.LABEL, label, set);
+
+                                    return null;
+                                }
+
+                                @Override
+                                protected void onException(Bundle args, Throwable ex) {
+                                    Log.unexpectedError(getParentFragmentManager(), ex);
+                                }
+                            }.execute(FragmentDialogLabelsManage.this, args, "label:set");
+                        }
+                    })
+                    .create();
+        }
+    }
 }

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

@@ -499,8 +499,10 @@ public class BoundaryCallbackMessages extends PagedList.BoundaryCallback<TupleMe
                 //fp.add(IMAPFolder.FetchProfileItem.MESSAGE);
                 fp.add(FetchProfile.Item.SIZE);
                 fp.add(IMAPFolder.FetchProfileItem.INTERNALDATE);
-                if (account.isGmail())
+                if (account.isGmail()) {
                     fp.add(GmailFolder.FetchProfileItem.THRID);
+                    fp.add(GmailFolder.FetchProfileItem.LABELS);
+                }
                 state.ifolder.fetch(add.toArray(new Message[0]), fp);
             }
 

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

@@ -43,6 +43,7 @@ import androidx.localbroadcastmanager.content.LocalBroadcastManager;
 import androidx.preference.PreferenceManager;
 
 import com.sun.mail.gimap.GmailFolder;
+import com.sun.mail.gimap.GmailMessage;
 import com.sun.mail.iap.BadCommandException;
 import com.sun.mail.iap.CommandFailedException;
 import com.sun.mail.iap.ConnectionException;
@@ -324,6 +325,10 @@ class Core {
                                     onKeyword(context, jargs, folder, message, (IMAPFolder) ifolder);
                                     break;
 
+                                case EntityOperation.LABEL:
+                                    onLabel(context, jargs, folder, message, (IMAPStore) istore, (IMAPFolder) ifolder, state);
+                                    break;
+
                                 case EntityOperation.ADD:
                                     onAdd(context, jargs, folder, message, (IMAPStore) istore, (IMAPFolder) ifolder, state);
                                     break;
@@ -688,6 +693,26 @@ class Core {
         imessage.setFlags(flags, set);
     }
 
+    private static void onLabel(Context context, JSONArray jargs, EntityFolder folder, EntityMessage message, IMAPStore istore, IMAPFolder ifolder, State state) throws JSONException, MessagingException, IOException {
+        // Set/clear Gmail label
+        String label = jargs.getString(0);
+        boolean set = jargs.getBoolean(1);
+
+        Message imessage = ifolder.getMessageByUID(message.uid);
+        if (imessage == null)
+            throw new MessageRemovedException();
+
+        if (!(imessage instanceof GmailMessage))
+            throw new IllegalArgumentException("GmailMessage");
+
+        ((GmailMessage) imessage).setLabels(new String[]{label}, set);
+
+        // Gmail does not push label changes
+        JSONArray fargs = new JSONArray();
+        fargs.put(message.uid);
+        onFetch(context, fargs, folder, istore, ifolder, state);
+    }
+
     private static void onAdd(Context context, JSONArray jargs, EntityFolder folder, EntityMessage message, IMAPStore istore, IMAPFolder ifolder, State state) throws MessagingException, IOException {
         // Add message
         DB db = DB.getInstance(context);
@@ -985,8 +1010,10 @@ class Core {
                 //fp.add(IMAPFolder.FetchProfileItem.MESSAGE);
                 fp.add(FetchProfile.Item.SIZE);
                 fp.add(IMAPFolder.FetchProfileItem.INTERNALDATE);
-                if (account.isGmail())
+                if (account.isGmail()) {
                     fp.add(GmailFolder.FetchProfileItem.THRID);
+                    fp.add(GmailFolder.FetchProfileItem.LABELS);
+                }
                 ifolder.fetch(new Message[]{imessage}, fp);
 
                 EntityMessage message = synchronizeMessage(context, account, folder, istore, ifolder, imessage, false, download, rules, state);
@@ -1895,6 +1922,8 @@ class Core {
             FetchProfile fp = new FetchProfile();
             fp.add(UIDFolder.FetchProfileItem.UID); // To check if message exists
             fp.add(FetchProfile.Item.FLAGS); // To update existing messages
+            if (account.isGmail())
+                fp.add(GmailFolder.FetchProfileItem.LABELS);
             ifolder.fetch(imessages, fp);
 
             long fetch = SystemClock.elapsedRealtime();
@@ -2213,6 +2242,7 @@ class Core {
         boolean flagged = helper.getFlagged();
         String flags = helper.getFlags();
         String[] keywords = helper.getKeywords();
+        String[] labels = helper.getLabels();
         boolean update = false;
         boolean process = false;
 
@@ -2324,6 +2354,7 @@ class Core {
             message.flagged = flagged;
             message.flags = flags;
             message.keywords = keywords;
+            message.labels = labels;
             message.ui_seen = seen;
             message.ui_answered = answered;
             message.ui_flagged = flagged;
@@ -2557,6 +2588,13 @@ class Core {
                         " keywords=" + TextUtils.join(" ", keywords));
             }
 
+            if (!Helper.equal(message.labels, labels)) {
+                update = true;
+                message.labels = labels;
+                Log.i(folder.name + " updated id=" + message.id + " uid=" + message.uid +
+                        " labels=" + (labels == null ? null : TextUtils.join(" ", labels)));
+            }
+
             if (message.hash == null || process) {
                 update = true;
                 message.hash = helper.getHash();
@@ -2859,8 +2897,10 @@ class Core {
             //fp.add(IMAPFolder.FetchProfileItem.MESSAGE);
             //fp.add(FetchProfile.Item.SIZE);
             //fp.add(IMAPFolder.FetchProfileItem.INTERNALDATE);
-            //if (account.isGmail())
+            //if (account.isGmail()) {
             //    fp.add(GmailFolder.FetchProfileItem.THRID);
+            //    fp.add(GmailFolder.FetchProfileItem.LABELS);
+            //}
             //ifolder.fetch(new Message[]{imessage}, fp);
 
             MessageHelper helper = new MessageHelper(imessage, context);

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

@@ -3,6 +3,7 @@ package eu.faircode.email;
 import android.content.Context;
 import android.content.SharedPreferences;
 import android.database.Cursor;
+import android.net.Uri;
 import android.text.TextUtils;
 
 import androidx.annotation.NonNull;
@@ -60,7 +61,7 @@ import io.requery.android.database.sqlite.SQLiteDatabase;
 // https://developer.android.com/topic/libraries/architecture/room.html
 
 @Database(
-        version = 166,
+        version = 167,
         entities = {
                 EntityIdentity.class,
                 EntityAccount.class,
@@ -1641,6 +1642,13 @@ public abstract class DB extends RoomDatabase {
                     public void migrate(@NonNull SupportSQLiteDatabase db) {
                         db.execSQL("DROP INDEX `index_attachment_message_type`");
                     }
+                })
+                .addMigrations(new Migration(166, 167) {
+                    @Override
+                    public void migrate(@NonNull SupportSQLiteDatabase db) {
+                        Log.i("DB migration from version " + startVersion + " to " + endVersion);
+                        db.execSQL("ALTER TABLE `message` ADD COLUMN `labels` TEXT");
+                    }
                 });
     }
 
@@ -1667,16 +1675,25 @@ public abstract class DB extends RoomDatabase {
         public static String[] toStringArray(String value) {
             if (value == null)
                 return new String[0];
-            else
+            else {
-                return TextUtils.split(value, " ");
+                String[] result = TextUtils.split(value, " ");
+                for (int i = 0; i < result.length; i++)
+                    result[i] = Uri.decode(result[i]);
+                return result;
+            }
         }
 
         @TypeConverter
         public static String fromStringArray(String[] value) {
             if (value == null || value.length == 0)
                 return null;
-            else
+            else {
-                return TextUtils.join(" ", value);
+                String[] copy = new String[value.length];
+                System.arraycopy(value, 0, copy, 0, value.length);
+                for (int i = 0; i < copy.length; i++)
+                    copy[i] = Uri.encode(copy[i]);
+                return TextUtils.join(" ", copy);
+            }
         }
 
         @TypeConverter

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

@@ -161,6 +161,7 @@ public class EntityMessage implements Serializable {
     public Boolean flagged = false;
     public String flags; // system flags
     public String[] keywords; // user flags
+    public String[] labels; // Gmail
     @NonNull
     public Integer notifying = 0;
     @NonNull

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

@@ -89,6 +89,7 @@ public class EntityOperation {
     static final String ANSWERED = "answered";
     static final String FLAG = "flag";
     static final String KEYWORD = "keyword";
+    static final String LABEL = "label"; // Gmail
     static final String HEADERS = "headers";
     static final String RAW = "raw";
     static final String BODY = "body";

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

@@ -83,7 +83,7 @@ public class FragmentOptions extends FragmentBase {
             "avatars", "gravatars", "generated_icons", "identicons", "circular", "saturation", "brightness", "threshold",
             "name_email", "prefer_contact", "distinguish_contacts", "show_recipients", "authentication",
             "subject_top", "font_size_sender", "font_size_subject", "subject_italic", "highlight_subject", "subject_ellipsize",
-            "keywords_header", "flags", "flags_background", "preview", "preview_italic", "preview_lines",
+            "keywords_header", "labels_header", "flags", "flags_background", "preview", "preview_italic", "preview_lines",
             "addresses", "attachments_alt",
             "contrast", "monospaced", "text_color", "text_size",
             "inline_images", "collapse_quotes", "seekbar", "actionbar", "actionbar_color", "navbar_colorize",

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

@@ -95,6 +95,7 @@ public class FragmentOptionsDisplay extends FragmentBase implements SharedPrefer
     private SwitchCompat swHighlightSubject;
     private Spinner spSubjectEllipsize;
     private SwitchCompat swKeywords;
+    private SwitchCompat swLabels;
     private SwitchCompat swFlags;
     private SwitchCompat swFlagsBackground;
     private SwitchCompat swPreview;
@@ -122,7 +123,7 @@ public class FragmentOptionsDisplay extends FragmentBase implements SharedPrefer
             "avatars", "gravatars", "generated_icons", "identicons", "circular", "saturation", "brightness", "threshold",
             "name_email", "prefer_contact", "distinguish_contacts", "show_recipients",
             "subject_top", "font_size_sender", "font_size_subject", "subject_italic", "highlight_subject", "subject_ellipsize",
-            "keywords_header", "flags", "flags_background",
+            "keywords_header", "labels_header", "flags", "flags_background",
             "preview", "preview_italic", "preview_lines",
             "addresses",
             "contrast", "monospaced", "text_color", "text_size", "text_align",
@@ -180,6 +181,7 @@ public class FragmentOptionsDisplay extends FragmentBase implements SharedPrefer
         swHighlightSubject = view.findViewById(R.id.swHighlightSubject);
         spSubjectEllipsize = view.findViewById(R.id.spSubjectEllipsize);
         swKeywords = view.findViewById(R.id.swKeywords);
+        swLabels = view.findViewById(R.id.swLabels);
         swFlags = view.findViewById(R.id.swFlags);
         swFlagsBackground = view.findViewById(R.id.swFlagsBackground);
         swPreview = view.findViewById(R.id.swPreview);
@@ -529,6 +531,13 @@ public class FragmentOptionsDisplay extends FragmentBase implements SharedPrefer
             }
         });
 
+        swLabels.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
+            @Override
+            public void onCheckedChanged(CompoundButton compoundButton, boolean checked) {
+                prefs.edit().putBoolean("labels_header", checked).apply();
+            }
+        });
+
         swFlags.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
             @Override
             public void onCheckedChanged(CompoundButton compoundButton, boolean checked) {
@@ -776,6 +785,7 @@ public class FragmentOptionsDisplay extends FragmentBase implements SharedPrefer
             }
 
         swKeywords.setChecked(prefs.getBoolean("keywords_header", false));
+        swLabels.setChecked(prefs.getBoolean("labels_header", true));
         swFlags.setChecked(prefs.getBoolean("flags", true));
         swFlagsBackground.setChecked(prefs.getBoolean("flags_background", false));
         swPreview.setChecked(prefs.getBoolean("preview", false));

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

@@ -1387,6 +1387,12 @@ public class Helper {
     }
 
     static boolean equal(String[] a1, String[] a2) {
+        if (a1 == null && a2 == null)
+            return true;
+
+        if (a1 == null || a2 == null)
+            return false;
+
         if (a1.length != a2.length)
             return false;
 

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

@@ -944,6 +944,20 @@ public class MessageHelper {
         return thread;
     }
 
+    String[] getLabels() throws MessagingException {
+        //ensureMessage(false);
+
+        List<String> labels = new ArrayList<>();
+        if (imessage instanceof GmailMessage)
+            for (String label : ((GmailMessage) imessage).getLabels())
+                if (!label.startsWith("\\"))
+                    labels.add(label);
+
+        Collections.sort(labels);
+
+        return labels.toArray(new String[0]);
+    }
+
     Integer getPriority() throws MessagingException {
         Integer priority = null;
 

app/src/main/res/drawable/baseline_label_24.xml

@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24"
+    android:tint="?attr/colorControlNormal">
+  <path
+      android:fillColor="@android:color/white"
+      android:pathData="M17.63,5.84C17.27,5.33 16.67,5 16,5L5,5.01C3.9,5.01 3,5.9 3,7v10c0,1.1 0.9,1.99 2,1.99L16,19c0.67,0 1.27,-0.33 1.63,-0.84L22,12l-4.37,-6.16z"/>
+</vector>

app/src/main/res/layout/fragment_options_display.xml

@@ -661,6 +661,17 @@
             app:layout_constraintTop_toBottomOf="@id/spSubjectEllipsize"
             app:switchPadding="12dp" />
 
+        <androidx.appcompat.widget.SwitchCompat
+            android:id="@+id/swLabels"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="12dp"
+            android:text="@string/title_advanced_labels"
+            app:layout_constraintEnd_toEndOf="parent"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toBottomOf="@id/swKeywords"
+            app:switchPadding="12dp" />
+
         <androidx.appcompat.widget.SwitchCompat
             android:id="@+id/swFlags"
             android:layout_width="0dp"
@@ -670,7 +681,7 @@
             android:text="@string/title_advanced_flags"
             app:layout_constraintEnd_toEndOf="parent"
             app:layout_constraintStart_toStartOf="parent"
-            app:layout_constraintTop_toBottomOf="@id/swKeywords"
+            app:layout_constraintTop_toBottomOf="@id/swLabels"
             app:switchPadding="12dp" />
 
         <androidx.appcompat.widget.SwitchCompat

app/src/main/res/layout/include_message_compact.xml

@@ -316,6 +316,18 @@
         app:layout_constraintStart_toEndOf="@id/ibAvatar"
         app:layout_constraintTop_toBottomOf="@id/tvKeywords" />
 
+    <eu.faircode.email.FixedTextView
+        android:id="@+id/tvLabels"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_marginStart="6dp"
+        android:layout_marginEnd="6dp"
+        android:text="label1,label2,label3"
+        android:textAppearance="@style/TextAppearance.AppCompat.Small"
+        app:layout_constraintEnd_toStartOf="@+id/paddingEnd"
+        app:layout_constraintStart_toEndOf="@id/paddingStart"
+        app:layout_constraintTop_toBottomOf="@id/tvFolder" />
+
     <eu.faircode.email.FixedTextView
         android:id="@+id/tvExpand"
         android:layout_width="0dp"
@@ -328,7 +340,7 @@
         android:textStyle="bold"
         app:layout_constraintEnd_toStartOf="@+id/paddingEnd"
         app:layout_constraintStart_toEndOf="@id/paddingStart"
-        app:layout_constraintTop_toBottomOf="@id/tvFolder" />
+        app:layout_constraintTop_toBottomOf="@id/tvLabels" />
 
     <eu.faircode.email.FixedTextView
         android:id="@+id/tvPreview"

app/src/main/res/layout/include_message_navigation.xml

@@ -41,7 +41,7 @@
         android:layout_width="0dp"
         android:layout_height="wrap_content"
         android:layout_marginEnd="3dp"
-        app:constraint_referenced_ids="ibMore,ibInbox,ibJunk,ibTrash,ibArchive,ibMove,ibAnswer,ibUnsubscribe,ibRule,ibUndo"
+        app:constraint_referenced_ids="ibMore,ibInbox,ibJunk,ibTrash,ibArchive,ibMove,ibLabels,ibAnswer,ibUnsubscribe,ibRule,ibUndo"
         app:flow_horizontalBias="0"
         app:flow_horizontalGap="3dp"
         app:flow_horizontalStyle="packed"
@@ -122,6 +122,16 @@
         app:srcCompat="@drawable/baseline_folder_24"
         tools:ignore="MissingConstraints" />
 
+    <ImageButton
+        android:id="@+id/ibLabels"
+        android:layout_width="36dp"
+        android:layout_height="36dp"
+        android:background="?android:attr/selectableItemBackgroundBorderless"
+        android:padding="6dp"
+        android:scaleType="fitCenter"
+        app:srcCompat="@drawable/baseline_label_24"
+        tools:ignore="MissingConstraints" />
+
     <ImageButton
         android:id="@+id/ibAnswer"
         android:layout_width="36dp"

app/src/main/res/layout/include_message_normal.xml

@@ -311,6 +311,19 @@
         app:layout_constraintTop_toTopOf="@+id/tvFolder"
         app:srcCompat="@drawable/baseline_message_24" />
 
+    <eu.faircode.email.FixedTextView
+        android:id="@+id/tvLabels"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_marginStart="6dp"
+        android:layout_marginTop="3dp"
+        android:layout_marginEnd="6dp"
+        android:text="label1,label2,label3"
+        android:textAppearance="@style/TextAppearance.AppCompat.Small"
+        app:layout_constraintEnd_toStartOf="@+id/paddingEnd"
+        app:layout_constraintStart_toEndOf="@id/paddingStart"
+        app:layout_constraintTop_toBottomOf="@id/tvFolder" />
+
     <eu.faircode.email.FixedTextView
         android:id="@+id/tvExpand"
         android:layout_width="0dp"
@@ -324,7 +337,7 @@
         android:textStyle="bold"
         app:layout_constraintEnd_toStartOf="@+id/paddingEnd"
         app:layout_constraintStart_toEndOf="@id/paddingStart"
-        app:layout_constraintTop_toBottomOf="@id/tvFolder" />
+        app:layout_constraintTop_toBottomOf="@id/tvLabels" />
 
     <eu.faircode.email.FixedTextView
         android:id="@+id/tvPreview"

app/src/main/res/values/strings.xml

@@ -347,6 +347,7 @@
     <string name="title_advanced_subject_italic">Show subject in italics</string>
     <string name="title_advanced_subject_elipsed">When needed, shorten the subject</string>
     <string name="title_advanced_keywords">Show keywords in message header</string>
+    <string name="title_advanced_labels">Show Gmail labels in message header</string>
     <string name="title_advanced_flags">Show stars</string>
     <string name="title_advanced_flags_background">Show colored background instead of colored stars</string>
     <string name="title_advanced_preview">Show message preview</string>
@@ -746,6 +747,7 @@
     <string name="title_raw_save">Save raw message</string>
     <string name="title_raw_send">Send as attachment</string>
     <string name="title_manage_keywords">Manage keywords</string>
+    <string name="title_manage_labels">Manage Gmail labels</string>
     <string name="title_add_keyword">Add keyword</string>
     <string name="title_show_inline">Show inline attachments</string>
     <string name="title_download_all">Download all</string>