feat: Implement forum topics support

app/src/main/java/org/thunderdog/challegram/MainActivity.java

@@ -783,8 +783,9 @@ public void onPasscodeShowing (BaseActivity context, boolean isShowing) {
         }
       }
       long messageId = intent.getLongExtra("message_id", 0);
+      long messageThreadId = intent.getLongExtra("message_thread_id", 0);
       if (accountId != TdlibAccount.NO_ID && chatId != 0) {
-        openMessagesController(accountId, chatId, messageId);
+        openMessagesController(accountId, chatId, messageId, messageThreadId);
         return true;
       } else {
         Log.e("Cannot open chat, no information found: %s", intent);
@@ -1384,7 +1385,7 @@ private void openMainController (int accountId) {
     }
   }
 
-  private void openMessagesController (int accountId, long chatId, long specificMessageId) {
+  private void openMessagesController (int accountId, long chatId, long specificMessageId, long messageThreadId) {
     final Tdlib tdlib = TdlibManager.instanceForAccountId(accountId).account(accountId).tdlib();
     tdlib.awaitInitialization(() -> {
       tdlib.incrementUiReferenceCount();
@@ -1393,6 +1394,10 @@ private void openMessagesController (int accountId, long chatId, long specificMe
         final TdlibUi.ChatOpenParameters params = new TdlibUi.ChatOpenParameters().onDone(tdlib::decrementUiReferenceCount);
         if (specificMessageId != 0)
           params.highlightMessage(new MessageId(chatId, specificMessageId));
+        // Handle forum topic opening
+        if (messageThreadId != 0) {
+          params.messageTopic(new TdApi.MessageTopicForum((int) messageThreadId));
+        }
         tdlib.ui().openChat(context, chatId, params);
       });
     });

app/src/main/java/org/thunderdog/challegram/component/chat/ChatHeaderView.java

@@ -15,30 +15,48 @@
 package org.thunderdog.challegram.component.chat;
 
 import android.content.Context;
+import android.graphics.Canvas;
 import android.view.MotionEvent;
 
+import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 
 import org.drinkless.tdlib.TdApi;
+import org.thunderdog.challegram.data.AvatarPlaceholder;
 import org.thunderdog.challegram.data.ThreadInfo;
 import org.thunderdog.challegram.loader.AvatarReceiver;
+import org.thunderdog.challegram.loader.ComplexReceiver;
+import org.thunderdog.challegram.loader.ImageFile;
+import org.thunderdog.challegram.loader.gif.GifFile;
 import org.thunderdog.challegram.navigation.ComplexHeaderView;
 import org.thunderdog.challegram.navigation.HeaderView;
 import org.thunderdog.challegram.navigation.ViewController;
 import org.thunderdog.challegram.telegram.Tdlib;
+import org.thunderdog.challegram.telegram.TdlibAccentColor;
+import org.thunderdog.challegram.telegram.TdlibEmojiManager;
+import org.thunderdog.challegram.theme.Theme;
 import org.thunderdog.challegram.theme.ThemeDeprecated;
+import org.thunderdog.challegram.tool.Paints;
 import org.thunderdog.challegram.tool.Screen;
+import org.thunderdog.challegram.util.text.Letters;
 
 import me.vkryl.core.StringUtils;
 import tgx.td.ChatId;
 
-public class ChatHeaderView extends ComplexHeaderView {
+public class ChatHeaderView extends ComplexHeaderView implements TdlibEmojiManager.Watcher {
   public interface Callback {
     void onChatHeaderClick ();
   }
 
   private Callback callback;
 
+  // Topic icon support
+  private long topicCustomEmojiId;
+  private TdlibEmojiManager.Entry topicCustomEmoji;
+  private ComplexReceiver topicIconReceiver;
+  private ImageFile topicImageFile;
+  private GifFile topicGifFile;
+
   public ChatHeaderView (Context context, Tdlib tdlib, @Nullable ViewController<?> parent) {
     super(context, tdlib, parent);
     setPhotoOpenDisabled(true);
@@ -50,6 +68,81 @@ public ChatHeaderView (Context context, Tdlib tdlib, @Nullable ViewController<?>
     setUseDefaultClickListener(true);
     setBackgroundResource(ThemeDeprecated.headerSelector());
     setInnerMargins(Screen.dp(56f), Screen.dp(49f));
+    topicIconReceiver = new ComplexReceiver(this);
+  }
+
+  @Override
+  protected void onAttachedToWindow () {
+    super.onAttachedToWindow();
+    topicIconReceiver.attach();
+  }
+
+  @Override
+  protected void onDetachedFromWindow () {
+    super.onDetachedFromWindow();
+    topicIconReceiver.detach();
+  }
+
+  @Override
+  public void onCustomEmojiLoaded (TdlibEmojiManager context, TdlibEmojiManager.Entry entry) {
+    if (entry.customEmojiId == topicCustomEmojiId) {
+      topicCustomEmoji = entry;
+      loadTopicEmojiFiles();
+      invalidate();
+    }
+  }
+
+  private void loadTopicEmojiFiles () {
+    if (topicCustomEmoji == null || topicCustomEmoji.isNotFound()) {
+      topicImageFile = null;
+      topicGifFile = null;
+      topicIconReceiver.clear();
+      return;
+    }
+
+    TdApi.Sticker sticker = topicCustomEmoji.value;
+    if (sticker == null) {
+      topicImageFile = null;
+      topicGifFile = null;
+      topicIconReceiver.clear();
+      return;
+    }
+
+    int size = Screen.dp(40f); // Avatar size
+    // Check sticker format to determine file type
+    // WebP stickers use ImageFile, TGS and WEBM use GifFile
+    switch (sticker.format.getConstructor()) {
+      case TdApi.StickerFormatWebp.CONSTRUCTOR: {
+        topicImageFile = new ImageFile(tdlib, sticker.sticker);
+        topicImageFile.setSize(size);
+        topicImageFile.setScaleType(ImageFile.CENTER_CROP);
+        topicGifFile = null;
+        topicIconReceiver.getImageReceiver(0).requestFile(topicImageFile);
+        break;
+      }
+      case TdApi.StickerFormatTgs.CONSTRUCTOR:
+      case TdApi.StickerFormatWebm.CONSTRUCTOR: {
+        topicGifFile = new GifFile(tdlib, sticker);
+        topicGifFile.setOptimizationMode(GifFile.OptimizationMode.EMOJI);
+        topicGifFile.setRequestedSize(size);
+        topicImageFile = null;
+        topicIconReceiver.getGifReceiver(0).requestFile(topicGifFile);
+        break;
+      }
+    }
+  }
+
+  private void clearTopicEmoji () {
+    if (topicCustomEmojiId != 0 && topicCustomEmoji == null && tdlib != null) {
+      tdlib.emoji().forgetWatcher(topicCustomEmojiId, this);
+    }
+    topicCustomEmojiId = 0;
+    topicCustomEmoji = null;
+    topicImageFile = null;
+    topicGifFile = null;
+    if (topicIconReceiver != null) {
+      topicIconReceiver.clear();
+    }
   }
 
   private CharSequence forcedSubtitle;
@@ -91,20 +184,68 @@ public boolean onTouchEvent (MotionEvent e) {
   }
 
   public void setChat (Tdlib tdlib, TdApi.Chat chat, @Nullable ThreadInfo messageThread) {
+    setChat(tdlib, chat, messageThread, null);
+  }
+
+  public void setChat (Tdlib tdlib, TdApi.Chat chat, @Nullable ThreadInfo messageThread, @Nullable TdApi.ForumTopic forumTopic) {
     this.tdlib = tdlib;
 
+    // Clear previous topic emoji
+    clearTopicEmoji();
+
     if (chat == null) {
       setText("Debug controller", "nobody should find this view");
       return;
     }
 
-    getAvatarReceiver().requestChat(tdlib, chat.id, AvatarReceiver.Options.FULL_SIZE);
+    // For forum topics, show topic icon instead of chat avatar
+    if (forumTopic != null) {
+      TdApi.ForumTopicIcon icon = forumTopic.info.icon;
+      int topicColor = icon != null ? icon.color : 0x6FB9F0;
+      // Ensure color has alpha
+      if (topicColor < 0x01000000) {
+        topicColor = 0xFF000000 | topicColor;
+      }
+
+      // Check if topic has custom emoji icon
+      if (icon != null && icon.customEmojiId != 0) {
+        // Request custom emoji
+        topicCustomEmojiId = icon.customEmojiId;
+        topicCustomEmoji = tdlib.emoji().findOrPostponeRequest(topicCustomEmojiId, this);
+        if (topicCustomEmoji != null) {
+          loadTopicEmojiFiles();
+        }
+        // Use placeholder while loading or as fallback
+        String letter = forumTopic.info.forumTopicId == 1 ? "#" :
+          (!StringUtils.isEmpty(forumTopic.info.name) ? forumTopic.info.name.substring(0, 1).toUpperCase() : "?");
+        TdlibAccentColor accentColor = new TdlibAccentColor(topicColor);
+        AvatarPlaceholder.Metadata metadata = new AvatarPlaceholder.Metadata(accentColor, new Letters(letter));
+        getAvatarReceiver().requestPlaceholder(tdlib, metadata, AvatarReceiver.Options.FULL_SIZE);
+      } else {
+        // No custom emoji - show colored placeholder with letter/hash
+        String letter = forumTopic.info.forumTopicId == 1 ? "#" :
+          (!StringUtils.isEmpty(forumTopic.info.name) ? forumTopic.info.name.substring(0, 1).toUpperCase() : "?");
+        TdlibAccentColor accentColor = new TdlibAccentColor(topicColor);
+        AvatarPlaceholder.Metadata metadata = new AvatarPlaceholder.Metadata(accentColor, new Letters(letter));
+        getAvatarReceiver().requestPlaceholder(tdlib, metadata, AvatarReceiver.Options.FULL_SIZE);
+      }
+    } else {
+      getAvatarReceiver().requestChat(tdlib, chat.id, AvatarReceiver.Options.FULL_SIZE);
+    }
+
     setShowVerify(tdlib.chatVerified(chat));
     setShowScam(tdlib.chatScam(chat));
     setShowFake(tdlib.chatFake(chat));
     setShowMute(tdlib.chatNeedsMuteIcon(chat));
     setShowLock(ChatId.isSecret(chat.id));
-    if (messageThread != null) {
+    if (forumTopic != null) {
+      // Forum topic: show topic name as title, chat name as subtitle
+      setEmojiStatus(null);
+      setText(forumTopic.info.name, !StringUtils.isEmpty(forcedSubtitle) ? forcedSubtitle : tdlib.chatTitle(chat));
+      setExpandedSubtitle(null);
+      setUseRedHighlight(false);
+      attachChatStatus(chat.id, new TdApi.MessageTopicForum(forumTopic.info.forumTopicId));
+    } else if (messageThread != null) {
       setEmojiStatus(null);
       setText(messageThread.chatHeaderTitle(), !StringUtils.isEmpty(forcedSubtitle) ? forcedSubtitle : messageThread.chatHeaderSubtitle());
       setExpandedSubtitle(null);
@@ -129,4 +270,32 @@ public void updateUserStatus (TdApi.Chat chat) {
       setExpandedSubtitle(tdlib.status().chatStatusExpanded(chat));
     }
   }
+
+  @Override
+  protected void onDraw (@NonNull Canvas c) {
+    super.onDraw(c);
+
+    // Draw topic custom emoji icon on top of avatar if loaded
+    if (topicCustomEmojiId != 0 && topicCustomEmoji != null && !topicCustomEmoji.isNotFound()) {
+      AvatarReceiver avatarReceiver = getAvatarReceiver();
+      int left = avatarReceiver.getLeft();
+      int top = avatarReceiver.getTop();
+      int right = avatarReceiver.getRight();
+      int bottom = avatarReceiver.getBottom();
+      float centerX = (left + right) / 2f;
+      float centerY = (top + bottom) / 2f;
+      float radius = (right - left) / 2f;
+
+      // Cover the placeholder with header background before drawing emoji
+      c.drawCircle(centerX, centerY, radius, Paints.fillingPaint(Theme.headerColor()));
+
+      if (topicImageFile != null) {
+        topicIconReceiver.getImageReceiver(0).setBounds(left, top, right, bottom);
+        topicIconReceiver.getImageReceiver(0).draw(c);
+      } else if (topicGifFile != null) {
+        topicIconReceiver.getGifReceiver(0).setBounds(left, top, right, bottom);
+        topicIconReceiver.getGifReceiver(0).draw(c);
+      }
+    }
+  }
 }

app/src/main/java/org/thunderdog/challegram/component/chat/MessagesLoader.java

@@ -1151,6 +1151,11 @@ private void load (final MessageId fromMessageId, final int offset, final int li
             loadingLocal = false;
             Log.ensureReturnType(TdApi.GetMessageThreadHistory.class, TdApi.Messages.class);
             function = new TdApi.GetMessageThreadHistory(sourceChatId, messageThread.getOldestMessageId(), (lastFromMessageId = fromMessageId).getMessageId(), lastOffset = offset, lastLimit = limit);
+          } else if (topicId != null && topicId.getConstructor() == TdApi.MessageTopicForum.CONSTRUCTOR) {
+            loadingLocal = false;
+            Log.ensureReturnType(TdApi.GetForumTopicHistory.class, TdApi.Messages.class);
+            int forumTopicId = ((TdApi.MessageTopicForum) topicId).forumTopicId;
+            function = new TdApi.GetForumTopicHistory(sourceChatId, forumTopicId, (lastFromMessageId = fromMessageId).getMessageId(), lastOffset = offset, lastLimit = limit);
           } else {
             Log.ensureReturnType(TdApi.GetChatHistory.class, TdApi.Messages.class);
             function = new TdApi.GetChatHistory(sourceChatId, (lastFromMessageId = fromMessageId).getMessageId(), lastOffset = offset, lastLimit = limit, loadingLocal);

app/src/main/java/org/thunderdog/challegram/component/chat/MessagesManager.java

@@ -601,7 +601,7 @@ public void openSearch (TdApi.Chat chat, String query, TdApi.MessageSender sende
     loader.setSearchParameters(query, sender, filter);
     adapter.setChatType(chat.type);
     if (filter != null && Td.isPinnedFilter(filter)) {
-      initPinned(chat.id, 1, 1);
+      initPinned(chat.id, null, 1, 1);
     }
     if (highlightMessageId != null) {
       loadFromMessage(highlightMessageId, highlightMode, true);
@@ -692,8 +692,8 @@ private void setPinnedMessagesAvailable (boolean areAvailable) {
     }
   }
 
-  private void initPinned (long chatId, int initialLoadCount, int loadCount) {
-    this.pinnedMessages = new MessageListManager(tdlib, initialLoadCount, loadCount, pinnedMessageListener, chatId, 0, null, null, null, new TdApi.SearchMessagesFilterPinned());
+  private void initPinned (long chatId, @Nullable TdApi.MessageTopic topicId, int initialLoadCount, int loadCount) {
+    this.pinnedMessages = new MessageListManager(tdlib, initialLoadCount, loadCount, pinnedMessageListener, chatId, 0, topicId, null, null, new TdApi.SearchMessagesFilterPinned());
     this.pinnedMessages.addMaxMessageIdListener(pinnedMessageAvailabilityChangeListener);
     this.pinnedMessages.addChangeListener(new MessageListManager.ChangeListener() {
       @Override
@@ -718,7 +718,7 @@ public void openChat (TdApi.Chat chat, @Nullable ThreadInfo messageThread, @Null
       // readOneShot = true;
     }
     if (chat.id != 0 && messageThread == null && !areScheduled && needPinnedMessages) {
-      initPinned(chat.id, 10, 50);
+      initPinned(chat.id, topicId, 10, 50);
     } else {
       this.pinnedMessages = null;
     }
@@ -781,6 +781,13 @@ public boolean onMessageViewed (TdlibMessageViewer.Viewport viewport, View view,
 
       @Override
       public boolean needForceRead (TdlibMessageViewer.Viewport viewport) {
+        // For forum topics opened at first unread position, don't force-read on initial load
+        // to avoid marking all visible messages as read on the server
+        TdApi.MessageTopic topicId = loader.getTopicId();
+        if (topicId != null && topicId.getConstructor() == TdApi.MessageTopicForum.CONSTRUCTOR) {
+          // Only force-read after user has scrolled
+          return canRead() && wasScrollByUser;
+        }
         return canRead();
       }
 
@@ -1838,8 +1845,11 @@ private void updateNewMessage (TGMessage message) {
       case MessagesLoader.SPECIAL_MODE_SEARCH:
         return;
     }
-    TdApi.MessageTopic topicId = loader.getMessageTopicId();
-    if (!Td.matchesTopic(message.getMessageTopicId(), topicId)) {
+    // Check both messageThread topic (for comment threads) and forum topicId (for forum tabs)
+    TdApi.MessageTopic messageThreadTopicId = loader.getMessageTopicId();
+    TdApi.MessageTopic forumTopicId = loader.getTopicId();
+    TdApi.MessageTopic effectiveTopicId = messageThreadTopicId != null ? messageThreadTopicId : forumTopicId;
+    if (!Td.matchesTopic(message.getMessageTopicId(), effectiveTopicId)) {
       return;
     }
     ThreadInfo messageThread = loader.getMessageThread();
@@ -2551,10 +2561,9 @@ private void saveScrollPosition () {
         if (view != null && view.getParent() != null) {
           scrollOffsetInPixels = calculateOffsetInPixels(view, message.getExtraPadding());
         }
-        if (readFully && scrollOffsetInPixels == 0) {
-          scrollMessageId = scrollMessageChatId = 0;
-          scrollMessageOtherIds = null;
-        } else if (isBottomSponsored) {
+        // Don't clear scroll position when at bottom - keep it so we can restore to bottom on re-entry.
+        // The readFully flag is still saved in SavedMessageId to indicate user was at the end.
+        if (isBottomSponsored) {
           if (message.isSponsoredMessage()) {
             // the bottom VISIBLE message is sponsored - no need to save that data
             scrollMessageId = scrollMessageChatId = scrollOffsetInPixels = 0;

app/src/main/java/org/thunderdog/challegram/component/dialogs/ChatsAdapter.java

@@ -439,6 +439,14 @@ public int updateChatUnreadMentionCount (long chatId, int unreadMentionCount) {
     return -1;
   }
 
+  public int updateForumUnreadTopicCount (long chatId) {
+    int index = indexOfChat(chatId);
+    if (index != -1 && chats.get(index).updateForumUnreadTopicCount(chatId)) {
+      return getItemPositionByChatIndex(index);
+    }
+    return -1;
+  }
+
   public int updateChatHasScheduledMessages (long chatId, boolean hasScheduledMessages) {
     int index = indexOfChat(chatId);
     if (index != -1 && chats.get(index).updateChatHasScheduledMessages(chatId, hasScheduledMessages)) {