Send start in bots auto in existing bot chats.

Telegram/SourceFiles/data/data_msg_id.h

@@ -86,6 +86,7 @@ constexpr auto SpecialMsgIdShift = EndStoryMsgId.bare;
 constexpr auto ShowAtTheEndMsgId = MsgId(SpecialMsgIdShift + 1);
 constexpr auto SwitchAtTopMsgId = MsgId(SpecialMsgIdShift + 2);
 constexpr auto ShowAndStartBotMsgId = MsgId(SpecialMsgIdShift + 4);
+constexpr auto ShowAndMaybeStartBotMsgId = MsgId(SpecialMsgIdShift + 5);
 constexpr auto ShowForChooseMessagesMsgId = MsgId(SpecialMsgIdShift + 6);
 
 static_assert(SpecialMsgIdShift + 0xFF < 0);

Telegram/SourceFiles/history/history_widget.cpp

@@ -2181,7 +2181,8 @@ void HistoryWidget::showHistory(
 
 	const auto wasState = controller()->currentDialogsEntryState();
 	const auto startBot = (showAtMsgId == ShowAndStartBotMsgId);
-	if (startBot) {
+	_showAndMaybeSendStart = (showAtMsgId == ShowAndMaybeStartBotMsgId);
+	if (startBot || _showAndMaybeSendStart) {
 		showAtMsgId = ShowAtTheEndMsgId;
 	}
 
@@ -2283,8 +2284,8 @@ void HistoryWidget::showHistory(
 
 			if (const auto user = _peer->asUser()) {
 				if (const auto &info = user->botInfo) {
-					if (startBot) {
+					if (startBot || clearMaybeSendStart()) {
-						if (wasState.key) {
+						if (startBot && wasState.key) {
 							info->inlineReturnTo = wasState;
 						}
 						sendBotStartCommand();
@@ -2519,8 +2520,9 @@ void HistoryWidget::showHistory(
 
 		if (const auto user = _peer->asUser()) {
 			if (const auto &info = user->botInfo) {
-				if (startBot) {
+				if (startBot
-					if (wasState.key) {
+					|| (!_history->isEmpty() && clearMaybeSendStart())) {
+					if (startBot && wasState.key) {
 						info->inlineReturnTo = wasState;
 					}
 					sendBotStartCommand();
@@ -3582,6 +3584,21 @@ void HistoryWidget::historyLoaded() {
 	doneShow();
 }
 
+bool HistoryWidget::clearMaybeSendStart() {
+	if (!_showAndMaybeSendStart) {
+		return false;
+	}
+	_showAndMaybeSendStart = false;
+	if (const auto user = _history ? _history->peer->asUser() : nullptr) {
+		if (const auto info = user->botInfo.get()) {
+			if (!info->startToken.isEmpty()) {
+				return true;
+			}
+		}
+	}
+	return false;
+}
+
 void HistoryWidget::windowShown() {
 	updateControlsGeometry();
 }
@@ -3944,6 +3961,11 @@ void HistoryWidget::preloadHistoryIfNeeded() {
 		preloadHistoryByScroll();
 		checkReplyReturns();
 	}
+	if (_history && _history->loadedAtTop() && _history->loadedAtBottom()) {
+		if (clearMaybeSendStart() && !_history->isDisplayedEmpty()) {
+			sendBotStartCommand();
+		}
+	}
 }
 
 void HistoryWidget::preloadHistoryByScroll() {

Telegram/SourceFiles/history/history_widget.h

@@ -391,6 +391,7 @@ private:
 	void fileChosen(ChatHelpers::FileChosen &&data);
 
 	void updateFieldSubmitSettings();
+	bool clearMaybeSendStart();
 
 	// Checks if we are too close to the top or to the bottom
 	// in the scroll area and preloads history if needed.
@@ -726,6 +727,7 @@ private:
 	base::flat_set<MsgId> _topicsRequested;
 	TextWithEntities _showAtMsgHighlightPart;
 	int _showAtMsgHighlightPartOffsetHint = 0;
+	bool _showAndMaybeSendStart = false;
 
 	int _firstLoadRequest = 0; // Not real mtpRequestId.
 	int _preloadRequest = 0; // Not real mtpRequestId.

Telegram/SourceFiles/window/window_session_controller.cpp

@@ -690,6 +690,8 @@ void SessionNavigation::showPeerByLinkResolved(
 			? info.messageId
 			: info.startAutoSubmit
 			? ShowAndStartBotMsgId
+			: (bot && !info.startToken.isEmpty())
+			? ShowAndMaybeStartBotMsgId
 			: ShowAtUnreadMsgId;
 		const auto attachBotUsername = info.attachBotUsername;
 		if (bot && bot->botInfo->startToken != info.startToken) {