Handle migration to supergroups in boxes.

Telegram/Resources/langs/lang.strings

@@ -128,6 +128,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 "lng_gif_error" = "An error has occurred while reading GIF animation :(";
 "lng_edit_error" = "You cannot edit this message";
 "lng_join_channel_error" = "Sorry, you have joined too many channels and supergroups. Please leave some before joining this one.";
+"lng_migrate_error" = "This action will convert the group to a supergroup. Unfortunately, you are a member of too many supergroups and channels. Please leave some of the channels or groups you don't need before proceeding.";
 "lng_error_phone_flood" = "Sorry, you have deleted and re-created your account too many times recently. Please wait for a few days before signing up again.";
 "lng_error_start_minimized_passcoded" = "You have set a local passcode, so Telegram Desktop can't be launched minimised; it will ask you to enter your passcode before it can start working.";
 "lng_error_pinned_max#one" = "Sorry, you can pin no more than {count} chat to the top.";
@@ -797,6 +798,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 "lng_manage_history_visibility_shown_about" = "New members will see messages that were sent before they joined.";
 "lng_manage_history_visibility_hidden" = "Hidden";
 "lng_manage_history_visibility_hidden_about" = "New members won't see earlier messages.";
+"lng_manage_history_visibility_hidden_legacy" = "New members won't see more than 100 previous messages.";
 
 "lng_report_title" = "Report channel";
 "lng_report_group_title" = "Report group";
@@ -957,8 +959,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 "lng_profile_convert_feature4" = "— Creator can set a public link for the group";
 "lng_profile_convert_warning" = "{bold_start}Note:{bold_end} This action can not be undone";
 "lng_profile_convert_confirm" = "Convert";
-"lng_profile_add_more_after_upgrade#one" = "You will be able to add up to {count} member after you upgrade your group to a supergroup.";
-"lng_profile_add_more_after_upgrade#other" = "You will be able to add up to {count} members after you upgrade your group to a supergroup.";
+"lng_profile_add_more_after_create" = "You will be able to add more members after you create the group.";
 
 "lng_channel_not_accessible" = "Sorry, this channel is not accessible.";
 "lng_group_not_accessible" = "Sorry, this group is not accessible.";

Telegram/SourceFiles/apiwrap.cpp

@@ -886,6 +886,7 @@ void ApiWrap::requestFullPeer(not_null<PeerData*> peer) {
 	const auto requestId = [&] {
 		const auto failHandler = [=](const RPCError &error) {
 			_fullPeerRequests.remove(peer);
+			migrateFail(peer, error);
 		};
 		if (const auto user = peer->asUser()) {
 			if (_session->supportMode()) {
@@ -911,6 +912,7 @@ void ApiWrap::requestFullPeer(not_null<PeerData*> peer) {
 					const MTPmessages_ChatFull &result,
 					mtpRequestId requestId) {
 				gotChatFull(peer, result, requestId);
+				migrateDone(channel, channel);
 			}).fail(failHandler).send();
 		}
 		Unexpected("Peer type in requestFullPeer.");
@@ -993,40 +995,18 @@ void ApiWrap::gotChatFull(
 		channel->setUserpicPhoto(f.vchat_photo);
 		if (f.has_migrated_from_chat_id()) {
 			channel->addFlags(MTPDchannel::Flag::f_megagroup);
-			auto cfrom = App::chat(peerFromChat(f.vmigrated_from_chat_id));
-			bool updatedTo = (cfrom->migrateToPtr != channel), updatedFrom = (channel->mgInfo->migrateFromPtr != cfrom);
-			if (updatedTo) {
-				cfrom->migrateToPtr = channel;
-			}
-			if (updatedFrom) {
-				channel->mgInfo->migrateFromPtr = cfrom;
-				if (auto h = App::historyLoaded(cfrom->id)) {
-					if (auto hto = App::historyLoaded(channel->id)) {
-						if (!h->isEmpty()) {
-							h->unloadBlocks();
-						}
-						if (hto->inChatList(Dialogs::Mode::All) && h->inChatList(Dialogs::Mode::All)) {
-							App::main()->removeDialog(h);
-						}
-					}
-				}
-				Notify::migrateUpdated(channel);
-			}
-			if (updatedTo) {
-				Notify::migrateUpdated(cfrom);
-			}
+			const auto chat = channel->owner().chat(
+				peerFromChat(f.vmigrated_from_chat_id));
+			Data::ApplyMigration(chat, channel);
 		}
-		auto &v = f.vbot_info.v;
-		for_const (auto &item, v) {
-			switch (item.type()) {
-			case mtpc_botInfo: {
-				auto &b = item.c_botInfo();
-				if (auto user = App::userLoaded(b.vuser_id.v)) {
+		for (const auto &item : f.vbot_info.v) {
+			auto &owner = channel->owner();
+			item.match([&](const MTPDbotInfo &info) {
+				if (const auto user = owner.userLoaded(info.vuser_id.v)) {
 					user->setBotInfo(item);
 					fullPeerUpdated().notify(user);
 				}
-			} break;
-			}
+			});
 		}
 		channel->setAbout(qs(f.vabout));
 		channel->setMembersCount(f.has_participants_count() ? f.vparticipants_count.v : 0);
@@ -1179,56 +1159,81 @@ void ApiWrap::migrateChat(
 	if (i != end(_migrateCallbacks)) {
 		i->second.push_back(callback());
 		return;
-	} else if (const auto channel = chat->migrateTo()) {
+	}
+	_migrateCallbacks.emplace(chat).first->second.push_back(callback());
+	if (const auto channel = chat->migrateTo()) {
 		Notify::peerUpdatedDelayed(
 			chat,
 			Notify::PeerUpdate::Flag::MigrationChanged);
-		crl::on_main([=, done = std::move(done)]() mutable {
-			Notify::peerUpdatedSendDelayed();
-			done(channel);
+		crl::on_main([=] {
+			migrateDone(chat, channel);
 		});
 	} else if (chat->isDeactivated()) {
-		crl::on_main([fail = std::move(fail)]() mutable {
-			fail(RPCError::Local(
-				"BAD_MIGRATION",
-				"Chat is already deactivated"));
+		crl::on_main([=] {
+			migrateFail(
+				chat,
+				RPCError::Local(
+					"BAD_MIGRATION",
+					"Chat is already deactivated"));
 		});
 		return;
 	} else if (!chat->amCreator()) {
-		crl::on_main([fail = std::move(fail)]() mutable {
-			fail(RPCError::Local(
-				"BAD_MIGRATION",
-				"Current user is not the creator of that chat"));
+		crl::on_main([=] {
+			migrateFail(
+				chat,
+				RPCError::Local(
+					"BAD_MIGRATION",
+					"Current user is not the creator of that chat"));
 		});
 		return;
 	}
 
-	_migrateCallbacks.emplace(chat).first->second.push_back(callback());
 	request(MTPmessages_MigrateChat(
 		chat->inputChat
 	)).done([=](const MTPUpdates &result) {
 		applyUpdates(result);
 		Notify::peerUpdatedSendDelayed();
 
-		const auto channel = chat->migrateTo();
-		if (auto handlers = _migrateCallbacks.take(chat)) {
-			for (auto &handler : *handlers) {
-				if (channel) {
-					handler.done(channel);
-				} else {
-					handler.fail(RPCError::Local(
-						"MIGRATION_FAIL",
-						"No channel"));
-				}
+		if (const auto channel = chat->migrateTo()) {
+			if (auto handlers = _migrateCallbacks.take(chat)) {
+				_migrateCallbacks.emplace(channel, std::move(*handlers));
 			}
+			requestFullPeer(channel);
+		} else {
+			migrateFail(
+				chat,
+				RPCError::Local("MIGRATION_FAIL", "No channel"));
 		}
 	}).fail([=](const RPCError &error) {
-		if (auto handlers = _migrateCallbacks.take(chat)) {
-			for (auto &handler : *handlers) {
+		migrateFail(chat, error);
+	}).send();
+}
+
+void ApiWrap::migrateDone(
+		not_null<PeerData*> peer,
+		not_null<ChannelData*> channel) {
+	Notify::peerUpdatedSendDelayed();
+	if (auto handlers = _migrateCallbacks.take(peer)) {
+		for (auto &handler : *handlers) {
+			if (handler.done) {
+				handler.done(channel);
+			}
+		}
+	}
+}
+
+void ApiWrap::migrateFail(not_null<PeerData*> peer, const RPCError &error) {
+	const auto &type = error.type();
+	if (type == qstr("CHANNELS_TOO_MUCH")) {
+		Ui::show(Box<InformBox>(lang(lng_migrate_error)));
+	}
+	if (auto handlers = _migrateCallbacks.take(peer)) {
+		for (auto &handler : *handlers) {
+			if (handler.fail) {
 				handler.fail(error);
 			}
 		}
-	}).send();
+	}
 }
 
 void ApiWrap::markMediaRead(
@@ -5059,6 +5064,7 @@ void ApiWrap::requestSupportContact(FnMut<void(const MTPUser &)> callback) {
 }
 
 void ApiWrap::uploadPeerPhoto(not_null<PeerData*> peer, QImage &&image) {
+	peer = peer->migrateToOrMe();
 	const auto ready = PreparePeerPhoto(peer->id, std::move(image));
 
 	const auto fakeId = FullMsgId(peerToChannel(peer->id), clientMsgId());

Telegram/SourceFiles/apiwrap.h

@@ -587,6 +587,11 @@ private:
 
 	void setSelfDestructDays(int days);
 
+	void migrateDone(
+		not_null<PeerData*> peer,
+		not_null<ChannelData*> channel);
+	void migrateFail(not_null<PeerData*> peer, const RPCError &error);
+
 	not_null<AuthSession*> _session;
 
 	MessageDataRequests _messageDataRequests;
@@ -737,7 +742,7 @@ private:
 		FnMut<void(const RPCError&)> fail;
 	};
 	base::flat_map<
-		not_null<ChatData*>,
+		not_null<PeerData*>,
 		std::vector<MigrateCallbacks>> _migrateCallbacks;
 
 	std::vector<FnMut<void(const MTPUser &)>> _supportContactCallbacks;

Telegram/SourceFiles/boxes/abstract_box.h

@@ -348,3 +348,45 @@ enum CreatingGroupType {
 	CreatingGroupGroup,
 	CreatingGroupChannel,
 };
+
+class BoxPointer {
+public:
+	BoxPointer() = default;
+	BoxPointer(const BoxPointer &other) = default;
+	BoxPointer(BoxPointer &&other) : _value(base::take(other._value)) {
+	}
+	BoxPointer &operator=(const BoxPointer &other) {
+		if (_value != other._value) {
+			destroy();
+			_value = other._value;
+		}
+		return *this;
+	}
+	BoxPointer &operator=(BoxPointer &&other) {
+		if (_value != other._value) {
+			destroy();
+			_value = base::take(other._value);
+		}
+		return *this;
+	}
+	BoxPointer &operator=(BoxContent *other) {
+		if (_value != other) {
+			destroy();
+			_value = other;
+		}
+		return *this;
+	}
+	~BoxPointer() {
+		destroy();
+	}
+
+private:
+	void destroy() {
+		if (const auto value = base::take(_value)) {
+			value->closeBox();
+		}
+	}
+
+	QPointer<BoxContent> _value;
+
+};

Telegram/SourceFiles/boxes/peers/add_participants_box.cpp

@@ -86,11 +86,8 @@ void AddParticipantsBoxController::rowClicked(not_null<PeerListRow*> row) {
 		}
 	} else if (count >= Global::ChatSizeMax()
 		&& count < Global::MegagroupSizeMax()) {
-		// #TODO groups new error about "after creating"
 		Ui::show(
-			Box<InformBox>(lng_profile_add_more_after_upgrade(
-				lt_count,
-				Global::MegagroupSizeMax())),
+			Box<InformBox>(lang(lng_profile_add_more_after_create)),
 			LayerOption::KeepOther);
 	}
 }
@@ -454,11 +451,7 @@ void AddSpecialBoxController::showAdmin(
 	if (!checkInfoLoaded(user, [=] { showAdmin(user); })) {
 		return;
 	}
-
-	if (sure && _editBox) {
-		// Close the confirmation box.
-		_editBox->closeBox();
-	}
+	_editBox = nullptr;
 
 	const auto chat = _peer->asChat();
 	const auto channel = _peer->asChannel();
@@ -555,9 +548,7 @@ void AddSpecialBoxController::showAdmin(
 			editAdminDone(user, newRights);
 		});
 		const auto fail = crl::guard(this, [=] {
-			if (_editBox) {
-				_editBox->closeBox();
-			}
+			_editBox = nullptr;
 		});
 		box->setSaveCallback(SaveAdminCallback(_peer, user, done, fail));
 	}
@@ -567,7 +558,7 @@ void AddSpecialBoxController::showAdmin(
 void AddSpecialBoxController::editAdminDone(
 		not_null<UserData*> user,
 		const MTPChatAdminRights &rights) {
-	if (_editBox) _editBox->closeBox();
+	_editBox = nullptr;
 
 	const auto date = unixtime(); // Incorrect, but ignored.
 	if (rights.c_chatAdminRights().vflags.v == 0) {
@@ -597,11 +588,7 @@ void AddSpecialBoxController::showRestricted(
 	if (!checkInfoLoaded(user, [=] { showRestricted(user); })) {
 		return;
 	}
-
-	if (sure && _editBox) {
-		// Close the confirmation box.
-		_editBox->closeBox();
-	}
+	_editBox = nullptr;
 
 	const auto chat = _peer->asChat();
 	const auto channel = _peer->asChannel();
@@ -650,9 +637,7 @@ void AddSpecialBoxController::showRestricted(
 			editRestrictedDone(user, newRights);
 		});
 		const auto fail = crl::guard(this, [=] {
-			if (_editBox) {
-				_editBox->closeBox();
-			}
+			_editBox = nullptr;
 		});
 		box->setSaveCallback(
 			SaveRestrictedCallback(_peer, user, done, fail));
@@ -663,7 +648,7 @@ void AddSpecialBoxController::showRestricted(
 void AddSpecialBoxController::editRestrictedDone(
 		not_null<UserData*> user,
 		const MTPChatBannedRights &rights) {
-	if (_editBox) _editBox->closeBox();
+	_editBox = nullptr;
 
 	const auto date = unixtime(); // Incorrect, but ignored.
 	if (rights.c_chatBannedRights().vflags.v == 0) {
@@ -731,6 +716,8 @@ void AddSpecialBoxController::kickUser(
 			LayerOption::KeepOther);
 		return;
 	}
+
+	_editBox = nullptr;
 	const auto restrictedRights = _additional.restrictedRights(user);
 	const auto currentRights = restrictedRights
 		? *restrictedRights

Telegram/SourceFiles/boxes/peers/add_participants_box.h

@@ -115,7 +115,7 @@ private:
 	bool _allLoaded = false;
 	ParticipantsAdditionalData _additional;
 	std::unique_ptr<ParticipantsOnlineSorter> _onlineSorter;
-	QPointer<BoxContent> _editBox;
+	BoxPointer _editBox;
 	AdminDoneCallback _adminDoneCallback;
 	BannedDoneCallback _bannedDoneCallback;
 

Telegram/SourceFiles/boxes/peers/edit_participant_box.cpp

@@ -212,17 +212,20 @@ void EditAdminBox::prepare() {
 	const auto chat = peer()->asChat();
 	const auto channel = peer()->asChannel();
 	const auto prepareRights = hadRights ? _oldRights : Defaults(peer());
+	const auto disabledByDefaults = DisabledByDefaultRestrictions(peer());
 	const auto filterByMyRights = canSave()
 		&& !hadRights
 		&& channel
 		&& !channel->amCreator();
-	const auto prepareFlags = prepareRights.c_chatAdminRights().vflags.v
-		& (filterByMyRights ? channel->adminRights() : ~Flag(0));
+	const auto prepareFlags = disabledByDefaults
+		| (prepareRights.c_chatAdminRights().vflags.v
+			& (filterByMyRights ? channel->adminRights() : ~Flag(0)));
 
 	const auto disabledFlags = canSave()
-		? ((!channel || channel->amCreator())
-			? Flags(0)
-			: ~channel->adminRights())
+		? (disabledByDefaults
+			| ((!channel || channel->amCreator())
+				? Flags(0)
+				: ~channel->adminRights()))
 		: ~Flags(0);
 
 	const auto anyoneCanAddMembers = chat

Telegram/SourceFiles/boxes/peers/edit_participants_box.cpp

@@ -802,6 +802,7 @@ void ParticipantsBoxController::addNewItem() {
 	const auto initBox = [](not_null<PeerListBox*> box) {
 		box->addButton(langFactory(lng_cancel), [=] { box->closeBox(); });
 	};
+
 	_addBox = Ui::show(
 		Box<PeerListBox>(
 			std::make_unique<AddSpecialBoxController>(
@@ -1352,9 +1353,7 @@ void ParticipantsBoxController::showAdmin(not_null<UserData*> user) {
 			editAdminDone(user, newRights);
 		});
 		const auto fail = crl::guard(this, [=] {
-			if (_editBox) {
-				_editBox->closeBox();
-			}
+			_editBox = nullptr;
 		});
 		box->setSaveCallback(SaveAdminCallback(_peer, user, done, fail));
 	}
@@ -1364,12 +1363,9 @@ void ParticipantsBoxController::showAdmin(not_null<UserData*> user) {
 void ParticipantsBoxController::editAdminDone(
 		not_null<UserData*> user,
 		const MTPChatAdminRights &rights) {
-	if (_editBox) {
-		_editBox->closeBox();
-	}
-	if (_addBox) {
-		_addBox->closeBox();
-	}
+	_addBox = nullptr;
+	_editBox = nullptr;
+
 	const auto date = unixtime(); // Incorrect, but ignored.
 	if (rights.c_chatAdminRights().vflags.v == 0) {
 		_additional.applyParticipant(MTP_channelParticipant(
@@ -1420,9 +1416,7 @@ void ParticipantsBoxController::showRestricted(not_null<UserData*> user) {
 			editRestrictedDone(user, newRights);
 		});
 		const auto fail = crl::guard(this, [=] {
-			if (_editBox) {
-				_editBox->closeBox();
-			}
+			_editBox = nullptr;
 		});
 		box->setSaveCallback(
 			SaveRestrictedCallback(_peer, user, done, fail));
@@ -1433,12 +1427,9 @@ void ParticipantsBoxController::showRestricted(not_null<UserData*> user) {
 void ParticipantsBoxController::editRestrictedDone(
 		not_null<UserData*> user,
 		const MTPChatBannedRights &rights) {
-	if (_editBox) {
-		_editBox->closeBox();
-	}
-	if (_addBox) {
-		_addBox->closeBox();
-	}
+	_addBox = nullptr;
+	_editBox = nullptr;
+
 	const auto date = unixtime(); // Incorrect, but ignored.
 	if (rights.c_chatBannedRights().vflags.v == 0) {
 		_additional.applyParticipant(MTP_channelParticipant(
@@ -1495,9 +1486,8 @@ void ParticipantsBoxController::kickMember(not_null<UserData*> user) {
 }
 
 void ParticipantsBoxController::kickMemberSure(not_null<UserData*> user) {
-	if (_editBox) {
-		_editBox->closeBox();
-	}
+	_editBox = nullptr;
+
 	const auto restrictedRights = _additional.restrictedRights(user);
 	const auto currentRights = restrictedRights
 		? *restrictedRights
@@ -1529,9 +1519,8 @@ void ParticipantsBoxController::removeAdmin(not_null<UserData*> user) {
 }
 
 void ParticipantsBoxController::removeAdminSure(not_null<UserData*> user) {
-	if (_editBox) {
-		_editBox->closeBox();
-	}
+	_editBox = nullptr;
+
 	if (const auto chat = _peer->asChat()) {
 		SaveChatAdmin(chat, user, false, crl::guard(this, [=] {
 			editAdminDone(user, MTP_chatAdminRights(MTP_flags(0)));

Telegram/SourceFiles/boxes/peers/edit_participants_box.h

@@ -234,8 +234,8 @@ private:
 	bool _allLoaded = false;
 	ParticipantsAdditionalData _additional;
 	std::unique_ptr<ParticipantsOnlineSorter> _onlineSorter;
-	QPointer<BoxContent> _editBox;
-	QPointer<PeerListBox> _addBox;
+	BoxPointer _editBox;
+	BoxPointer _addBox;
 
 };
 

Telegram/SourceFiles/boxes/peers/edit_peer_info_box.cpp

@@ -23,6 +23,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "boxes/add_contact_box.h"
 #include "boxes/stickers_box.h"
 #include "boxes/peer_list_controllers.h"
+#include "boxes/peers/edit_participants_box.h"
 #include "data/data_peer.h"
 #include "data/data_chat.h"
 #include "data/data_channel.h"
@@ -114,6 +115,7 @@ private:
 	object_ptr<Ui::RpWidget> createDeleteButton();
 
 	QString inviteLinkText() const;
+	void observeInviteLink();
 
 	void submitTitle();
 	void submitDescription();
@@ -157,6 +159,9 @@ private:
 	void continueSave();
 	void cancelSave();
 
+	void subscribeToMigration();
+	void migrate(not_null<ChannelData*> channel);
+
 	not_null<BoxContent*> _box;
 	not_null<PeerData*> _peer;
 	bool _isGroup = false;
@@ -171,6 +176,8 @@ private:
 	std::deque<FnMut<void()>> _saveStagesQueue;
 	Saving _savingData;
 
+	rpl::lifetime _lifetime;
+
 };
 
 Controller::Controller(
@@ -179,7 +186,7 @@ Controller::Controller(
 : _box(box)
 , _peer(peer)
 , _isGroup(_peer->isChat() || _peer->isMegagroup())
-, _checkUsernameTimer([this] { checkUsernameAvailability(); }) {
+, _checkUsernameTimer([=] { checkUsernameAvailability(); }) {
 	_box->setTitle(computeTitle());
 	_box->addButton(langFactory(lng_settings_save), [this] {
 		save();
@@ -187,6 +194,21 @@ Controller::Controller(
 	_box->addButton(langFactory(lng_cancel), [this] {
 		_box->closeBox();
 	});
+	subscribeToMigration();
+	_peer->updateFull();
+}
+
+void Controller::subscribeToMigration() {
+	SubscribeToMigration(
+		_peer,
+		_lifetime,
+		[=](not_null<ChannelData*> channel) { migrate(channel); });
+}
+
+void Controller::migrate(not_null<ChannelData*> channel) {
+	_peer = channel;
+	observeInviteLink();
+	_peer->updateFull();
 }
 
 Fn<QString()> Controller::computeTitle() const {
@@ -222,10 +244,10 @@ void Controller::setFocus() {
 object_ptr<Ui::RpWidget> Controller::createPhotoAndTitleEdit() {
 	Expects(_wrap != nullptr);
 
-	auto canEdit = [&] {
-		if (auto channel = _peer->asChannel()) {
+	const auto canEdit = [&] {
+		if (const auto channel = _peer->asChannel()) {
 			return channel->canEditInformation();
-		} else if (auto chat = _peer->asChat()) {
+		} else if (const auto chat = _peer->asChat()) {
 			return chat->canEditInformation();
 		}
 		return false;
@@ -516,7 +538,7 @@ void Controller::checkUsernameAvailability() {
 	if (_checkUsernameRequestId) {
 		request(_checkUsernameRequestId).cancel();
 	}
-	const auto channel = _peer->asChannel();
+	const auto channel = _peer->migrateToOrMe()->asChannel();
 	const auto username = channel ? channel->username : QString();
 	_checkUsernameRequestId = request(MTPchannels_CheckUsername(
 		channel ? channel->inputChannel : MTP_inputChannelEmpty(),
@@ -534,7 +556,7 @@ void Controller::checkUsernameAvailability() {
 		}
 	}).fail([=](const RPCError &error) {
 		_checkUsernameRequestId = 0;
-		auto type = error.type();
+		const auto &type = error.type();
 		_usernameState = UsernameState::Normal;
 		if (type == qstr("CHANNEL_PUBLIC_GROUP_NA")) {
 			_usernameState = UsernameState::NotAvailable;
@@ -643,10 +665,10 @@ void Controller::revokeInviteLink() {
 void Controller::exportInviteLink(const QString &confirmation) {
 	auto boxPointer = std::make_shared<QPointer<ConfirmBox>>();
 	auto callback = crl::guard(this, [=] {
-		if (auto strong = *boxPointer) {
+		if (const auto strong = *boxPointer) {
 			strong->closeBox();
 		}
-		Auth().api().exportInviteLink(_peer);
+		Auth().api().exportInviteLink(_peer->migrateToOrMe());
 	});
 	auto box = Box<ConfirmBox>(
 		confirmation,
@@ -656,12 +678,11 @@ void Controller::exportInviteLink(const QString &confirmation) {
 
 bool Controller::canEditInviteLink() const {
 	if (const auto channel = _peer->asChannel()) {
-		if (channel->canEditUsername()) {
-			return true;
-		}
-		return (!channel->isPublic() && channel->canAddMembers());
+		return channel->amCreator()
+			|| (channel->adminRights() & ChatAdminRight::f_invite_users);
 	} else if (const auto chat = _peer->asChat()) {
-		return chat->amCreator() || !chat->inviteLink().isEmpty();
+		return chat->amCreator()
+			|| (chat->adminRights() & ChatAdminRight::f_invite_users);
 	}
 	return false;
 }
@@ -680,6 +701,18 @@ QString Controller::inviteLinkText() const {
 	return QString();
 }
 
+void Controller::observeInviteLink() {
+	if (!_controls.editInviteLinkWrap) {
+		return;
+	}
+	Notify::PeerUpdateValue(
+		_peer,
+		Notify::PeerUpdate::Flag::InviteLinkChanged
+	) | rpl::start_with_next([=] {
+		refreshEditInviteLink();
+	}, _controls.editInviteLinkWrap->lifetime());
+}
+
 object_ptr<Ui::RpWidget> Controller::createInviteLinkEdit() {
 	Expects(_wrap != nullptr);
 
@@ -721,14 +754,9 @@ object_ptr<Ui::RpWidget> Controller::createInviteLinkEdit() {
 		container,
 		lang(lng_group_invite_create_new),
 		st::editPeerInviteLinkButton)
-	)->addClickHandler([this] { revokeInviteLink(); });
+	)->addClickHandler([=] { revokeInviteLink(); });
 
-	Notify::PeerUpdateValue(
-		_peer,
-		Notify::PeerUpdate::Flag::InviteLinkChanged
-	) | rpl::start_with_next([this] {
-		refreshEditInviteLink();
-	}, _controls.editInviteLinkWrap->lifetime());
+	observeInviteLink();
 
 	return std::move(result);
 }
@@ -788,12 +816,7 @@ object_ptr<Ui::RpWidget> Controller::createInviteLinkCreate() {
 	});
 	_controls.createInviteLinkWrap = result.data();
 
-	Notify::PeerUpdateValue(
-		_peer,
-		Notify::PeerUpdate::Flag::InviteLinkChanged
-	) | rpl::start_with_next([this] {
-		refreshCreateInviteLink();
-	}, _controls.createInviteLinkWrap->lifetime());
+	observeInviteLink();
 
 	return std::move(result);
 }
@@ -865,7 +888,9 @@ object_ptr<Ui::RpWidget> Controller::createHistoryVisibilityEdit() {
 	addButton(
 		HistoryVisibility::Hidden,
 		lng_manage_history_visibility_hidden,
-		lng_manage_history_visibility_hidden_about);
+		(_peer->isChat()
+			? lng_manage_history_visibility_hidden_legacy
+			: lng_manage_history_visibility_hidden_about));
 
 	refreshHistoryVisibility();
 
@@ -1258,7 +1283,7 @@ void Controller::saveHistoryVisibility() {
 
 		Auth().api().applyUpdates(result);
 		continueSave();
-	}).fail([this](const RPCError &error) {
+	}).fail([=](const RPCError &error) {
 		if (error.type() == qstr("CHAT_NOT_MODIFIED")) {
 			continueSave();
 		} else {
@@ -1340,7 +1365,7 @@ void Controller::deleteChannel() {
 EditPeerInfoBox::EditPeerInfoBox(
 	QWidget*,
 	not_null<PeerData*> peer)
-: _peer(peer) {
+: _peer(peer->migrateToOrMe()) {
 }
 
 void EditPeerInfoBox::prepare() {

Telegram/SourceFiles/boxes/peers/edit_peer_permissions_box.cpp

@@ -215,10 +215,40 @@ ChatRestrictions DisabledByAdminRights(not_null<PeerData*> peer) {
 
 } // namespace
 
+ChatAdminRights DisabledByDefaultRestrictions(not_null<PeerData*> peer) {
+	using Flag = ChatAdminRight;
+	using Restriction = ChatRestriction;
+
+	const auto restrictions = [&] {
+		if (const auto chat = peer->asChat()) {
+			return chat->defaultRestrictions();
+		} else if (const auto channel = peer->asChannel()) {
+			return channel->defaultRestrictions();
+		}
+		Unexpected("User in DisabledByDefaultRestrictions.");
+	}();
+	return Flag(0)
+		| ((restrictions & Restriction::f_pin_messages)
+			? Flag(0)
+			: Flag::f_pin_messages)
+		//
+		// We allow to edit 'invite_users' admin right no matter what
+		// is chosen in default permissions for 'invite_users', because
+		// if everyone can 'invite_users' it handles invite link for admins.
+		//
+		//| ((restrictions & Restriction::f_invite_users)
+		//	? Flag(0)
+		//	: Flag::f_invite_users)
+		//
+		| ((restrictions & Restriction::f_change_info)
+			? Flag(0)
+			: Flag::f_change_info);
+}
+
 EditPeerPermissionsBox::EditPeerPermissionsBox(
 	QWidget*,
 	not_null<PeerData*> peer)
-: _peer(peer) {
+: _peer(peer->migrateToOrMe()) {
 }
 
 auto EditPeerPermissionsBox::saveEvents() const
@@ -282,12 +312,18 @@ void EditPeerPermissionsBox::prepare() {
 
 void EditPeerPermissionsBox::addBannedButtons(
 		not_null<Ui::VerticalLayout*> container) {
+	if (const auto chat = _peer->asChat()) {
+		if (!chat->amCreator()) {
+			return;
+		}
+	}
+	const auto channel = _peer->asChannel();
+
 	container->add(
 		object_ptr<BoxContentDivider>(container),
 		{ 0, st::infoProfileSkip, 0, st::infoProfileSkip });
 
 	const auto navigation = App::wnd()->controller();
-	const auto channel = _peer->asChannel();
 	ManagePeerBox::CreateButton(
 		container,
 		Lang::Viewer(lng_manage_peer_exceptions),

Telegram/SourceFiles/boxes/peers/edit_peer_permissions_box.h

@@ -55,3 +55,5 @@ EditFlagsControl<MTPDchatAdminRights::Flags> CreateEditAdminRights(
 	MTPDchatAdminRights::Flags disabled,
 	bool isGroup,
 	bool anyoneCanAddMembers);
+
+ChatAdminRights DisabledByDefaultRestrictions(not_null<PeerData*> peer);

Telegram/SourceFiles/boxes/peers/manage_peer_box.cpp

@@ -107,8 +107,8 @@ void ShowEditPermissions(not_null<PeerData*> peer) {
 				box->closeBox();
 			}
 		});
-		Auth().api().saveDefaultRestrictions(
-			peer,
+		peer->session().api().saveDefaultRestrictions(
+			peer->migrateToOrMe(),
 			MTP_chatBannedRights(MTP_flags(restrictions), MTP_int(0)),
 			callback);
 	}, box->lifetime());

Telegram/SourceFiles/data/data_channel.cpp

@@ -10,6 +10,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "data/data_peer_values.h"
 #include "data/data_channel_admins.h"
 #include "data/data_user.h"
+#include "data/data_chat.h"
 #include "data/data_session.h"
 #include "data/data_feed.h"
 #include "observer_peer.h"
@@ -22,13 +23,21 @@ using UpdateFlag = Notify::PeerUpdate::Flag;
 
 } // namespace
 
+ChatData *MegagroupInfo::getMigrateFromChat() const {
+	return _migratedFrom;
+}
+
+void MegagroupInfo::setMigrateFromChat(ChatData *chat) {
+	_migratedFrom = chat;
+}
+
 ChannelData::ChannelData(not_null<Data::Session*> owner, PeerId id)
 : PeerData(owner, id)
 , inputChannel(MTP_inputChannel(MTP_int(bareId()), MTP_long(0))) {
 	Data::PeerFlagValue(
 		this,
 		MTPDchannel::Flag::f_megagroup
-	) | rpl::start_with_next([this](bool megagroup) {
+	) | rpl::start_with_next([=](bool megagroup) {
 		if (megagroup) {
 			if (!mgInfo) {
 				mgInfo = std::make_unique<MegagroupInfo>();
@@ -37,6 +46,17 @@ ChannelData::ChannelData(not_null<Data::Session*> owner, PeerId id)
 			mgInfo = nullptr;
 		}
 	}, _lifetime);
+
+	Data::PeerFlagsValue(
+		this,
+		MTPDchannel::Flag::f_left | MTPDchannel_ClientFlag::f_forbidden
+	) | rpl::distinct_until_changed(
+	) | rpl::start_with_next([=] {
+		if (const auto chat = getMigrateFromChat()) {
+			Notify::peerUpdatedDelayed(chat, UpdateFlag::MigrationChanged);
+			Notify::peerUpdatedDelayed(this, UpdateFlag::MigrationChanged);
+		}
+	}, _lifetime);
 }
 
 void ChannelData::setPhoto(const MTPChatPhoto &photo) {
@@ -365,7 +385,8 @@ bool ChannelData::canEditInformation() const {
 }
 
 bool ChannelData::canEditPermissions() const {
-	return isMegagroup() && (hasAdminRights() || amCreator());
+	return isMegagroup()
+		&& ((adminRights() & AdminRight::f_ban_users) || amCreator());
 }
 
 bool ChannelData::canEditSignatures() const {
@@ -495,8 +516,36 @@ auto ChannelData::applyUpdateVersion(int version) -> UpdateStatus {
 	return UpdateStatus::Good;
 }
 
+ChatData *ChannelData::getMigrateFromChat() const {
+	if (const auto info = mgInfo.get()) {
+		return info->getMigrateFromChat();
+	}
+	return nullptr;
+}
+
+void ChannelData::setMigrateFromChat(ChatData *chat) {
+	Expects(mgInfo != nullptr);
+
+	const auto info = mgInfo.get();
+	if (chat != info->getMigrateFromChat()) {
+		info->setMigrateFromChat(chat);
+		if (amIn()) {
+			Notify::peerUpdatedDelayed(this, UpdateFlag::MigrationChanged);
+		}
+	}
+}
+
 namespace Data {
 
+void ApplyMigration(
+		not_null<ChatData*> chat,
+		not_null<ChannelData*> channel) {
+	Expects(channel->isMegagroup());
+
+	chat->setMigrateToChannel(channel);
+	channel->setMigrateFromChat(chat);
+}
+
 void ApplyChannelUpdate(
 		not_null<ChannelData*> channel,
 		const MTPDupdateChatDefaultBannedRights &update) {

Telegram/SourceFiles/data/data_channel.h

@@ -10,7 +10,8 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "data/data_peer.h"
 #include "data/data_pts_waiter.h"
 
-struct MegagroupInfo {
+class MegagroupInfo {
+public:
 	struct Admin {
 		explicit Admin(MTPChatAdminRights rights)
 		: rights(rights) {
@@ -30,6 +31,9 @@ struct MegagroupInfo {
 		MTPChatBannedRights rights;
 	};
 
+	ChatData *getMigrateFromChat() const;
+	void setMigrateFromChat(ChatData *chat);
+
 	std::deque<not_null<UserData*>> lastParticipants;
 	base::flat_map<not_null<UserData*>, Admin> lastAdmins;
 	base::flat_map<not_null<UserData*>, Restricted> lastRestricted;
@@ -51,7 +55,8 @@ struct MegagroupInfo {
 	mutable int lastParticipantsStatus = LastParticipantsUpToDate;
 	int lastParticipantsCount = 0;
 
-	ChatData *migrateFromPtr = nullptr;
+private:
+	ChatData *_migratedFrom = nullptr;
 
 };
 
@@ -60,6 +65,7 @@ public:
 	static constexpr auto kEssentialFlags = 0
 		| MTPDchannel::Flag::f_creator
 		| MTPDchannel::Flag::f_left
+		| MTPDchannel_ClientFlag::f_forbidden
 		| MTPDchannel::Flag::f_broadcast
 		| MTPDchannel::Flag::f_verified
 		| MTPDchannel::Flag::f_megagroup
@@ -339,6 +345,9 @@ public:
 	}
 	UpdateStatus applyUpdateVersion(int version);
 
+	ChatData *getMigrateFromChat() const;
+	void setMigrateFromChat(ChatData *chat);
+
 	// Still public data members.
 	uint64 access = 0;
 
@@ -384,6 +393,10 @@ private:
 
 namespace Data {
 
+void ApplyMigration(
+	not_null<ChatData*> chat,
+	not_null<ChannelData*> channel);
+
 void ApplyChannelUpdate(
 	not_null<ChannelData*> channel,
 	const MTPDupdateChatDefaultBannedRights &update);

Telegram/SourceFiles/data/data_chat.cpp

@@ -8,6 +8,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "data/data_chat.h"
 
 #include "data/data_user.h"
+#include "data/data_channel.h"
 #include "data/data_session.h"
 #include "history/history.h"
 #include "auth_session.h"
@@ -64,7 +65,7 @@ bool ChatData::canEditInformation() const {
 
 bool ChatData::canEditPermissions() const {
 	return !actionsUnavailable()
-		&& (amCreator() || hasAdminRights());
+		&& (amCreator() || (adminRights() & AdminRight::f_ban_users));
 }
 
 bool ChatData::canEditUsername() const {
@@ -177,6 +178,19 @@ auto ChatData::applyUpdateVersion(int version) -> UpdateStatus {
 	return UpdateStatus::Good;
 }
 
+ChannelData *ChatData::getMigrateToChannel() const {
+	return _migratedTo;
+}
+
+void ChatData::setMigrateToChannel(ChannelData *channel) {
+	if (_migratedTo != channel) {
+		_migratedTo = channel;
+		if (channel->amIn()) {
+			Notify::peerUpdatedDelayed(this, UpdateFlag::MigrationChanged);
+		}
+	}
+}
+
 namespace Data {
 
 void ApplyChatUpdate(

Telegram/SourceFiles/data/data_chat.h

@@ -156,11 +156,12 @@ public:
 	}
 	UpdateStatus applyUpdateVersion(int version);
 
+	ChannelData *getMigrateToChannel() const;
+	void setMigrateToChannel(ChannelData *channel);
+
 	// Still public data members.
 	MTPint inputChat;
 
-	ChannelData *migrateToPtr = nullptr;
-
 	int count = 0;
 	TimeId date = 0;
 	UserId creator = 0;
@@ -184,6 +185,8 @@ private:
 	AdminRightFlags _adminRights;
 	int _version = 0;
 
+	ChannelData *_migratedTo = nullptr;
+
 };
 
 namespace Data {

Telegram/SourceFiles/data/data_peer.cpp

@@ -520,7 +520,7 @@ const ChannelData *PeerData::asChannelOrMigrated() const {
 ChatData *PeerData::migrateFrom() const {
 	if (const auto megagroup = asMegagroup()) {
 		return megagroup->amIn()
-			? megagroup->mgInfo->migrateFromPtr
+			? megagroup->getMigrateFromChat()
 			: nullptr;
 	}
 	return nullptr;
@@ -528,13 +528,27 @@ ChatData *PeerData::migrateFrom() const {
 
 ChannelData *PeerData::migrateTo() const {
 	if (const auto chat = asChat()) {
-		if (const auto migrateTo = chat->migrateToPtr) {
-			return migrateTo->amIn() ? migrateTo : nullptr;
+		if (const auto result = chat->getMigrateToChannel()) {
+			return result->amIn() ? result : nullptr;
 		}
 	}
 	return nullptr;
 }
 
+not_null<PeerData*> PeerData::migrateToOrMe() {
+	if (const auto channel = migrateTo()) {
+		return channel;
+	}
+	return this;
+}
+
+not_null<const PeerData*> PeerData::migrateToOrMe() const {
+	if (const auto channel = migrateTo()) {
+		return channel;
+	}
+	return this;
+}
+
 Data::Feed *PeerData::feed() const {
 	if (const auto channel = asChannel()) {
 		return channel->feed();

Telegram/SourceFiles/data/data_peer.h

@@ -117,6 +117,8 @@ public:
 
 	[[nodiscard]] ChatData *migrateFrom() const;
 	[[nodiscard]] ChannelData *migrateTo() const;
+	[[nodiscard]] not_null<PeerData*> migrateToOrMe();
+	[[nodiscard]] not_null<const PeerData*> migrateToOrMe() const;
 	[[nodiscard]] Data::Feed *feed() const;
 
 	void updateFull();

Telegram/SourceFiles/data/data_session.cpp

@@ -11,7 +11,6 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "auth_session.h"
 #include "apiwrap.h"
 #include "messenger.h"
-#include "mainwidget.h" // for main()->removeDialog
 #include "core/crash_reports.h" // for CrashReports::SetAnnotation
 #include "ui/image/image.h"
 #include "export/export_controller.h"
@@ -455,35 +454,13 @@ not_null<PeerData*> Session::chat(const MTPChat &data) {
 			const auto channel = this->channel(input.vchannel_id.v);
 			channel->addFlags(MTPDchannel::Flag::f_megagroup);
 			if (!channel->access) {
-				channel->input = MTP_inputPeerChannel(input.vchannel_id, input.vaccess_hash);
-				channel->inputChannel = data.vmigrated_to;
+				channel->input = MTP_inputPeerChannel(
+					input.vchannel_id,
+					input.vaccess_hash);
+				channel->inputChannel = migratedTo;
 				channel->access = input.vaccess_hash.v;
 			}
-			const auto updatedTo = (chat->migrateToPtr != channel);
-			const auto updatedFrom = (channel->mgInfo->migrateFromPtr != chat);
-			if (updatedTo) {
-				chat->migrateToPtr = channel;
-			}
-			if (updatedFrom) {
-				channel->mgInfo->migrateFromPtr = chat;
-				if (const auto h = historyLoaded(chat->id)) {
-					if (const auto hto = historyLoaded(channel->id)) {
-						if (!h->isEmpty()) {
-							h->unloadBlocks();
-						}
-						if (hto->inChatList(Dialogs::Mode::All)
-							&& h->inChatList(Dialogs::Mode::All)) {
-							App::main()->removeDialog(h);
-						}
-					}
-				}
-				Notify::migrateUpdated(channel);
-				update.flags |= UpdateFlag::MigrationChanged;
-			}
-			if (updatedTo) {
-				Notify::migrateUpdated(chat);
-				update.flags |= UpdateFlag::MigrationChanged;
-			}
+			ApplyMigration(chat, channel);
 		}, [](const MTPDinputChannelEmpty &) {
 		});
 

Telegram/SourceFiles/dialogs/dialogs_inner_widget.cpp

@@ -139,8 +139,9 @@ DialogsInner::DialogsInner(QWidget *parent, not_null<Window::Controller*> contro
 		| UpdateFlag::NameChanged
 		| UpdateFlag::PhotoChanged
 		| UpdateFlag::UserIsContact
-		| UpdateFlag::UserOccupiedChanged;
-	subscribe(Notify::PeerUpdated(), Notify::PeerUpdatedHandler(changes, [this](const Notify::PeerUpdate &update) {
+		| UpdateFlag::UserOccupiedChanged
+		| UpdateFlag::MigrationChanged;
+	subscribe(Notify::PeerUpdated(), Notify::PeerUpdatedHandler(changes, [=](const Notify::PeerUpdate &update) {
 		if (update.flags & UpdateFlag::ChatPinnedChanged) {
 			stopReorderPinned();
 		}
@@ -156,6 +157,11 @@ DialogsInner::DialogsInner(QWidget *parent, not_null<Window::Controller*> contro
 				userIsContactUpdated(user);
 			}
 		}
+		if (update.flags & UpdateFlag::MigrationChanged) {
+			if (const auto chat = update.peer->asChat()) {
+				handleChatMigration(chat);
+			}
+		}
 	}));
 	Auth().data().feedUpdated(
 	) | rpl::start_with_next([=](const Data::FeedUpdate &update) {
@@ -175,6 +181,22 @@ DialogsInner::DialogsInner(QWidget *parent, not_null<Window::Controller*> contro
 	setupShortcuts();
 }
 
+void DialogsInner::handleChatMigration(not_null<ChatData*> chat) {
+	const auto channel = chat->migrateTo();
+	if (!channel) {
+		return;
+	}
+
+	if (const auto from = chat->owner().historyLoaded(chat)) {
+		if (const auto to = chat->owner().historyLoaded(channel)) {
+			if (to->inChatList(Dialogs::Mode::All)
+				&& from->inChatList(Dialogs::Mode::All)) {
+				removeDialog(from);
+			}
+		}
+	}
+}
+
 int DialogsInner::dialogsOffset() const {
 	return _dialogsImportant ? st::dialogsImportantBarHeight : 0;
 }

Telegram/SourceFiles/dialogs/dialogs_inner_widget.h

@@ -289,6 +289,7 @@ private:
 	int countPinnedIndex(Dialogs::Row *ofRow);
 	void savePinnedOrder();
 	void step_pinnedShifting(TimeMs ms, bool timer);
+	void handleChatMigration(not_null<ChatData*> chat);
 
 	not_null<Window::Controller*> _controller;
 

Telegram/SourceFiles/dialogs/dialogs_widget.cpp

@@ -310,7 +310,7 @@ void DialogsWidget::createDialog(Dialogs::Key key) {
 		if (const auto migrated = App::historyLoaded(
 				history->peer->migrateFrom())) {
 			if (migrated->inChatList(Dialogs::Mode::All)) {
-				removeDialog(migrated);
+				_inner->removeDialog(migrated);
 			}
 		}
 	}

Telegram/SourceFiles/facades.cpp

@@ -321,10 +321,6 @@ bool switchInlineBotButtonReceived(const QString &query, UserData *samePeerBot,
 	return false;
 }
 
-void migrateUpdated(PeerData *peer) {
-	if (MainWidget *m = App::main()) m->notify_migrateUpdated(peer);
-}
-
 void historyMuteUpdated(History *history) {
 	if (MainWidget *m = App::main()) m->notify_historyMuteUpdated(history);
 }

Telegram/SourceFiles/facades.h

@@ -149,8 +149,6 @@ void replyMarkupUpdated(const HistoryItem *item);
 void inlineKeyboardMoved(const HistoryItem *item, int oldKeyboardTop, int newKeyboardTop);
 bool switchInlineBotButtonReceived(const QString &query, UserData *samePeerBot = nullptr, MsgId samePeerReplyTo = 0);
 
-void migrateUpdated(PeerData *peer);
-
 void historyMuteUpdated(History *history);
 void unreadCounterUpdated();
 
@@ -323,7 +321,7 @@ DeclareRefVar(base::Variable<DBIWorkMode>, WorkMode);
 
 DeclareRefVar(base::Observable<void>, UnreadCounterUpdate);
 DeclareRefVar(base::Observable<void>, PeerChooseCancel);
-	
+
 DeclareVar(QString, CallOutputDeviceID);
 DeclareVar(QString, CallInputDeviceID);
 DeclareVar(int, CallOutputVolume);

Telegram/SourceFiles/history/history_widget.cpp

@@ -430,11 +430,7 @@ HistoryWidget::HistoryWidget(
 				unreadCountUpdated();
 			}
 			if (update.flags & UpdateFlag::MigrationChanged) {
-				if (auto channel = _peer->migrateTo()) {
-					Ui::showPeerHistory(channel, ShowAtUnreadMsgId);
-					Auth().api().requestParticipantsCountDelayed(channel);
-					return;
-				}
+				handlePeerMigration();
 			}
 			if (update.flags & UpdateFlag::NotificationsEnabled) {
 				updateNotifyControls();
@@ -1338,27 +1334,6 @@ void HistoryWidget::notify_userIsBotChanged(UserData *user) {
 	}
 }
 
-void HistoryWidget::notify_migrateUpdated(PeerData *peer) {
-	if (_peer) {
-		if (_peer == peer) {
-			if (peer->migrateTo()) {
-				showHistory(peer->migrateTo()->id, (_showAtMsgId > 0) ? (-_showAtMsgId) : _showAtMsgId, true);
-			} else if ((_migrated ? _migrated->peer.get() : nullptr) != peer->migrateFrom()) {
-				auto migrated = _history->migrateFrom();
-				if (_migrated || (migrated && migrated->unreadCount() > 0)) {
-					showHistory(peer->id, peer->migrateFrom() ? _showAtMsgId : ((_showAtMsgId < 0 && -_showAtMsgId < ServerMaxMsgId) ? ShowAtUnreadMsgId : _showAtMsgId), true);
-				} else {
-					_migrated = migrated;
-					_list->notifyMigrateUpdated();
-					updateHistoryGeometry();
-				}
-			}
-		} else if (_migrated && _migrated->peer == peer && peer->migrateTo() != _peer) {
-			showHistory(_peer->id, _showAtMsgId, true);
-		}
-	}
-}
-
 void HistoryWidget::setupShortcuts() {
 	Shortcuts::Requests(
 	) | rpl::filter([=] {
@@ -1516,7 +1491,10 @@ void HistoryWidget::applyCloudDraft(History *history) {
 	}
 }
 
-void HistoryWidget::showHistory(const PeerId &peerId, MsgId showAtMsgId, bool reload) {
+void HistoryWidget::showHistory(
+		const PeerId &peerId,
+		MsgId showAtMsgId,
+		bool reload) {
 	MsgId wasMsgId = _showAtMsgId;
 	History *wasHistory = _history;
 
@@ -1671,6 +1649,11 @@ void HistoryWidget::showHistory(const PeerId &peerId, MsgId showAtMsgId, bool re
 
 		_history = App::history(_peer);
 		_migrated = _history->migrateFrom();
+		if (_migrated
+			&& !_migrated->isEmpty()
+			&& (!_history->loadedAtTop() || !_migrated->loadedAtBottom())) {
+			_migrated->unloadBlocks();
+		}
 
 		_topBar->setActiveChat(_history);
 		updateTopBarSelection();
@@ -5173,6 +5156,35 @@ void HistoryWidget::keyPressEvent(QKeyEvent *e) {
 	}
 }
 
+void HistoryWidget::handlePeerMigration() {
+	const auto current = _peer->migrateToOrMe();
+	const auto chat = current->migrateFrom();
+	if (!chat) {
+		return;
+	}
+	const auto channel = current->asChannel();
+	Assert(channel != nullptr);
+
+	if (_peer != channel) {
+		showHistory(
+			channel->id,
+			(_showAtMsgId > 0) ? (-_showAtMsgId) : _showAtMsgId);
+		channel->session().api().requestParticipantsCountDelayed(channel);
+	} else {
+		_migrated = _history->migrateFrom();
+		_list->notifyMigrateUpdated();
+		updateHistoryGeometry();
+	}
+	const auto from = chat->owner().historyLoaded(chat);
+	const auto to = channel->owner().historyLoaded(channel);
+	if (from
+		&& to
+		&& !from->isEmpty()
+		&& (!from->loadedAtBottom() || !to->loadedAtTop())) {
+		from->unloadBlocks();
+	}
+}
+
 void HistoryWidget::replyToPreviousMessage() {
 	if (!_history || _editMsgId) {
 		return;

Telegram/SourceFiles/history/history_widget.h

@@ -288,7 +288,6 @@ public:
 	void notify_inlineKeyboardMoved(const HistoryItem *item, int oldKeyboardTop, int newKeyboardTop);
 	bool notify_switchInlineBotButtonReceived(const QString &query, UserData *samePeerBot, MsgId samePeerReplyTo);
 	void notify_userIsBotChanged(UserData *user);
-	void notify_migrateUpdated(PeerData *peer);
 
 	~HistoryWidget();
 
@@ -503,6 +502,8 @@ private:
 	bool showNextChat();
 	bool showPreviousChat();
 
+	void handlePeerMigration();
+
 	MsgId _replyToId = 0;
 	Text _replyToName;
 	int _replyToNameVersion = 0;

Telegram/SourceFiles/mainwidget.cpp

@@ -621,10 +621,6 @@ void MainWidget::notify_userIsBotChanged(UserData *bot) {
 	_history->notify_userIsBotChanged(bot);
 }
 
-void MainWidget::notify_migrateUpdated(PeerData *peer) {
-	_history->notify_migrateUpdated(peer);
-}
-
 void MainWidget::notify_historyMuteUpdated(History *history) {
 	_dialogs->notify_historyMuteUpdated(history);
 }
@@ -874,7 +870,7 @@ void MainWidget::deleteConversation(
 		removeDialog(history);
 		if (const auto channel = peer->asMegagroup()) {
 			channel->addFlags(MTPDchannel::Flag::f_left);
-			if (const auto from = channel->mgInfo->migrateFromPtr) {
+			if (const auto from = channel->getMigrateFromChat()) {
 				if (const auto migrated = App::historyLoaded(from)) {
 					migrated->updateChatListExistence();
 				}
@@ -2832,15 +2828,17 @@ void MainWidget::searchInChat(Dialogs::Key chat) {
 void MainWidget::feedUpdateVector(
 		const MTPVector<MTPUpdate> &updates,
 		bool skipMessageIds) {
-	for_const (auto &update, updates.v) {
-		if (skipMessageIds && update.type() == mtpc_updateMessageID) continue;
+	for (const auto &update : updates.v) {
+		if (skipMessageIds && update.type() == mtpc_updateMessageID) {
+			continue;
+		}
 		feedUpdate(update);
 	}
 	Auth().data().sendHistoryChangeNotifications();
 }
 
 void MainWidget::feedMessageIds(const MTPVector<MTPUpdate> &updates) {
-	for_const (auto &update, updates.v) {
+	for (const auto &update : updates.v) {
 		if (update.type() == mtpc_updateMessageID) {
 			feedUpdate(update);
 		}

Telegram/SourceFiles/mainwidget.h

@@ -290,7 +290,6 @@ public:
 	void notify_inlineKeyboardMoved(const HistoryItem *item, int oldKeyboardTop, int newKeyboardTop);
 	bool notify_switchInlineBotButtonReceived(const QString &query, UserData *samePeerBot, MsgId samePeerReplyTo);
 	void notify_userIsBotChanged(UserData *bot);
-	void notify_migrateUpdated(PeerData *peer);
 	void notify_historyMuteUpdated(History *history);
 
 	~MainWidget();