diff --git a/Telegram/SourceFiles/apiwrap.cpp b/Telegram/SourceFiles/apiwrap.cpp
index cf1d5800ef..eb5229d9f2 100644
--- a/Telegram/SourceFiles/apiwrap.cpp
+++ b/Telegram/SourceFiles/apiwrap.cpp
@@ -33,23 +33,29 @@ Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
 #include "window/themes/window_theme.h"
 #include "window/notifications_manager.h"
 
+namespace {
+
+constexpr auto kReloadChannelMembersTimeout = 1000; // 1 second wait before reload members in channel after adding
+
+} // namespace
+
 ApiWrap::ApiWrap(QObject *parent) : QObject(parent)
-, _messageDataResolveDelayed(new SingleDelayedCall(this, "resolveMessageDatas")) {
+, _messageDataResolveDelayed([this] { resolveMessageDatas(); }) {
 	Window::Theme::Background()->start();
 
-	connect(&_webPagesTimer, SIGNAL(timeout()), this, SLOT(resolveWebPages()));
-	connect(&_draftsSaveTimer, SIGNAL(timeout()), this, SLOT(saveDraftsToCloud()));
+	connect(&_webPagesTimer, &QTimer::timeout, this, [this] { resolveWebPages(); });
+	connect(&_draftsSaveTimer, &QTimer::timeout, this, [this] { saveDraftsToCloud(); });
 }
 
 void ApiWrap::init() {
 }
 
 void ApiWrap::requestMessageData(ChannelData *channel, MsgId msgId, RequestMessageDataCallback callback) {
-	MessageDataRequest &req(channel ? _channelMessageDataRequests[channel][msgId] : _messageDataRequests[msgId]);
+	auto &req = (channel ? _channelMessageDataRequests[channel][msgId] : _messageDataRequests[msgId]);
 	if (callback) {
 		req.callbacks.append(callback);
 	}
-	if (!req.req) _messageDataResolveDelayed->call();
+	if (!req.req) _messageDataResolveDelayed.call();
 }
 
 ApiWrap::MessageIds ApiWrap::collectMessageIds(const MessageDataRequests &requests) {
@@ -202,7 +208,7 @@ void ApiWrap::gotChatFull(PeerData *peer, const MTPmessages_ChatFull &result, mt
 				if (auto user = App::userLoaded(b.vuser_id.v)) {
 					user->setBotInfo(item);
 					App::clearPeerUpdated(user);
-					emit fullPeerUpdated(user);
+					fullPeerUpdated().notify(user);
 				}
 			} break;
 			}
@@ -274,7 +280,7 @@ void ApiWrap::gotChatFull(PeerData *peer, const MTPmessages_ChatFull &result, mt
 				if (auto user = App::userLoaded(b.vuser_id.v)) {
 					user->setBotInfo(item);
 					App::clearPeerUpdated(user);
-					emit fullPeerUpdated(user);
+					fullPeerUpdated().notify(user);
 				}
 			} break;
 			}
@@ -320,7 +326,7 @@ void ApiWrap::gotChatFull(PeerData *peer, const MTPmessages_ChatFull &result, mt
 		requestPeer(peer);
 	}
 	App::clearPeerUpdated(peer);
-	emit fullPeerUpdated(peer);
+	fullPeerUpdated().notify(peer);
 }
 
 void ApiWrap::gotUserFull(PeerData *peer, const MTPUserFull &result, mtpRequestId req) {
@@ -353,7 +359,7 @@ void ApiWrap::gotUserFull(PeerData *peer, const MTPUserFull &result, mtpRequestI
 		}
 	}
 	App::clearPeerUpdated(peer);
-	emit fullPeerUpdated(peer);
+	fullPeerUpdated().notify(peer);
 }
 
 bool ApiWrap::gotPeerFullFailed(PeerData *peer, const RPCError &error) {
@@ -563,7 +569,7 @@ void ApiWrap::lastParticipantsDone(ChannelData *peer, const MTPchannels_ChannelP
 	}
 
 	peer->mgInfo->botStatus = botStatus;
-	if (App::main()) emit fullPeerUpdated(peer);
+	if (App::main()) fullPeerUpdated().notify(peer);
 }
 
 bool ApiWrap::lastParticipantsFail(ChannelData *peer, const RPCError &error, mtpRequestId req) {
@@ -669,7 +675,7 @@ void ApiWrap::kickParticipantDone(KickRequest kick, const MTPUpdates &result, mt
 		}
 	}
 	Notify::peerUpdatedDelayed(kick.first, Notify::PeerUpdate::Flag::MembersChanged);
-	emit fullPeerUpdated(kick.first);
+	fullPeerUpdated().notify(kick.first);
 }
 
 bool ApiWrap::kickParticipantFail(KickRequest kick, const RPCError &error, mtpRequestId req) {
@@ -1345,10 +1351,10 @@ void ApiWrap::resolveWebPages() {
 	if (m < INT_MAX) _webPagesTimer.start(m * 1000);
 }
 
-void ApiWrap::delayedRequestParticipantsCount() {
-	if (App::main() && App::main()->peer() && App::main()->peer()->isChannel()) {
-		requestFullPeer(App::main()->peer());
-	}
+void ApiWrap::requestParticipantsCountDelayed(ChannelData *channel) {
+	QTimer::singleShot(kReloadChannelMembersTimeout, this, [this, channel] {
+		channel->updateFull(true);
+	});
 }
 
 void ApiWrap::gotWebPages(ChannelData *channel, const MTPmessages_Messages &msgs, mtpRequestId req) {
diff --git a/Telegram/SourceFiles/apiwrap.h b/Telegram/SourceFiles/apiwrap.h
index cf1c6280f4..6fe06e5ee5 100644
--- a/Telegram/SourceFiles/apiwrap.h
+++ b/Telegram/SourceFiles/apiwrap.h
@@ -35,8 +35,6 @@ inline const MTPVector<MTPChat> *getChatsFromMessagesChats(const MTPmessages_Cha
 } // namespace Api
 
 class ApiWrap : public QObject, public RPCSender {
-	Q_OBJECT
-
 public:
 	ApiWrap(QObject *parent);
 	void init();
@@ -49,6 +47,7 @@ public:
 	void requestPeers(const QList<PeerData*> &peers);
 	void requestLastParticipants(ChannelData *peer, bool fromStart = true);
 	void requestBots(ChannelData *peer);
+	void requestParticipantsCountDelayed(ChannelData *channel);
 
 	void processFullPeer(PeerData *peer, const MTPmessages_ChatFull &result);
 	void processFullPeer(PeerData *peer, const MTPUserFull &result);
@@ -73,6 +72,7 @@ public:
 	void exportInviteLink(PeerData *peer);
 	void requestNotifySetting(PeerData *peer);
 
+	void saveDraftsToCloud();
 	void saveDraftToCloudDelayed(History *history);
 	bool hasUnsavedDrafts() const;
 
@@ -80,21 +80,16 @@ public:
 	void handlePrivacyChange(mtpTypeId keyTypeId, const MTPVector<MTPPrivacyRule> &rules);
 	int onlineTillFromStatus(const MTPUserStatus &status, int currentOnlineTill);
 
+	base::Observable<PeerData*> &fullPeerUpdated() {
+		return _fullPeerUpdated;
+	}
+
 	~ApiWrap();
 
-signals:
-	void fullPeerUpdated(PeerData *peer);
-
-public slots:
-	void resolveMessageDatas();
-	void resolveWebPages();
-
-	void delayedRequestParticipantsCount();
-	void saveDraftsToCloud();
-
 private:
 	void updatesReceived(const MTPUpdates &updates);
 
+	void resolveMessageDatas();
 	void gotMessageDatas(ChannelData *channel, const MTPmessages_Messages &result, mtpRequestId req);
 	struct MessageDataRequest {
 		using Callbacks = QList<RequestMessageDataCallback>;
@@ -105,7 +100,7 @@ private:
 	MessageDataRequests _messageDataRequests;
 	typedef QMap<ChannelData*, MessageDataRequests> ChannelMessageDataRequests;
 	ChannelMessageDataRequests _channelMessageDataRequests;
-	SingleDelayedCall *_messageDataResolveDelayed;
+	SingleQueuedInvokation _messageDataResolveDelayed;
 	typedef QVector<MTPint> MessageIds;
 	MessageIds collectMessageIds(const MessageDataRequests &requests);
 	MessageDataRequests *messageDataRequests(ChannelData *channel, bool onlyExisting = false);
@@ -138,6 +133,7 @@ private:
 	typedef QMap<ChannelData*, mtpRequestId> SelfParticipantRequests;
 	SelfParticipantRequests _selfParticipantRequests;
 
+	void resolveWebPages();
 	void gotWebPages(ChannelData *channel, const MTPmessages_Messages &result, mtpRequestId req);
 	typedef QMap<WebPageData*, mtpRequestId> WebPagesPending;
 	WebPagesPending _webPagesPending;
@@ -191,4 +187,6 @@ private:
 	void contactsStatusesDone(const MTPVector<MTPContactStatus> &result);
 	bool contactsStatusesFail(const RPCError &error);
 
+	base::Observable<PeerData*> _fullPeerUpdated;
+
 };
diff --git a/Telegram/SourceFiles/app.cpp b/Telegram/SourceFiles/app.cpp
index b69c1184dc..ffb648700d 100644
--- a/Telegram/SourceFiles/app.cpp
+++ b/Telegram/SourceFiles/app.cpp
@@ -2466,7 +2466,9 @@ namespace {
 		if (auto apiwrap = api()) {
 			if (apiwrap->hasUnsavedDrafts()) {
 				apiwrap->saveDraftsToCloud();
-				QTimer::singleShot(SaveDraftBeforeQuitTimeout, QCoreApplication::instance(), SLOT(quit()));
+				QTimer::singleShot(SaveDraftBeforeQuitTimeout, [] {
+					QCoreApplication::quit();
+				});
 				return;
 			}
 		}
diff --git a/Telegram/SourceFiles/application.cpp b/Telegram/SourceFiles/application.cpp
index fac7a256a1..aeb2d98384 100644
--- a/Telegram/SourceFiles/application.cpp
+++ b/Telegram/SourceFiles/application.cpp
@@ -26,7 +26,6 @@ Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
 #include "storage/localstorage.h"
 #include "autoupdater.h"
 #include "window/notifications_manager.h"
-#include "base/task_queue.h"
 #include "messenger.h"
 
 namespace {
@@ -347,10 +346,6 @@ void Application::closeApplication() {
 #endif // !TDESKTOP_DISABLE_AUTOUPDATE
 }
 
-void Application::onMainThreadTask() {
-	base::TaskQueue::ProcessMainTasks();
-}
-
 #ifndef TDESKTOP_DISABLE_AUTOUPDATE
 void Application::updateCheck() {
 	startUpdateCheck(false);
diff --git a/Telegram/SourceFiles/application.h b/Telegram/SourceFiles/application.h
index 52ba9eec0b..eec0ffc84b 100644
--- a/Telegram/SourceFiles/application.h
+++ b/Telegram/SourceFiles/application.h
@@ -51,8 +51,6 @@ public slots:
 	void startApplication(); // will be done in exec()
 	void closeApplication(); // will be done in aboutToQuit()
 
-	void onMainThreadTask();
-
 private:
 	typedef QPair<QLocalSocket*, QByteArray> LocalClient;
 	typedef QList<LocalClient> LocalClients;
diff --git a/Telegram/SourceFiles/boxes/add_contact_box.cpp b/Telegram/SourceFiles/boxes/add_contact_box.cpp
index a199670584..b3767f1878 100644
--- a/Telegram/SourceFiles/boxes/add_contact_box.cpp
+++ b/Telegram/SourceFiles/boxes/add_contact_box.cpp
@@ -1060,7 +1060,7 @@ bool EditChannelBox::onSaveFail(const RPCError &error, mtpRequestId req) {
 		if (err == qstr("CHAT_ABOUT_NOT_MODIFIED")) {
 			if (_channel->setAbout(_sentDescription)) {
 				if (App::api()) {
-					emit App::api()->fullPeerUpdated(_channel);
+					App::api()->fullPeerUpdated().notify(_channel);
 				}
 			}
 			saveSign();
@@ -1090,7 +1090,7 @@ void EditChannelBox::onSaveDescriptionDone(const MTPBool &result) {
 	_saveDescriptionRequestId = 0;
 	if (_channel->setAbout(_sentDescription)) {
 		if (App::api()) {
-			emit App::api()->fullPeerUpdated(_channel);
+			App::api()->fullPeerUpdated().notify(_channel);
 		}
 	}
 	saveSign();
diff --git a/Telegram/SourceFiles/boxes/confirm_box.cpp b/Telegram/SourceFiles/boxes/confirm_box.cpp
index 4bafcc5555..591a7e4d07 100644
--- a/Telegram/SourceFiles/boxes/confirm_box.cpp
+++ b/Telegram/SourceFiles/boxes/confirm_box.cpp
@@ -312,25 +312,21 @@ void ConvertToSupergroupBox::convertToSupergroup() {
 void ConvertToSupergroupBox::convertDone(const MTPUpdates &updates) {
 	Ui::hideLayer();
 	App::main()->sentUpdatesReceived(updates);
-	const QVector<MTPChat> *v = 0;
-	switch (updates.type()) {
-	case mtpc_updates: v = &updates.c_updates().vchats.v; break;
-	case mtpc_updatesCombined: v = &updates.c_updatesCombined().vchats.v; break;
-	default: LOG(("API Error: unexpected update cons %1 (ConvertToSupergroupBox::convertDone)").arg(updates.type())); break;
-	}
 
-	PeerData *peer = 0;
-	if (v && !v->isEmpty()) {
-		for (int32 i = 0, l = v->size(); i < l; ++i) {
-			if (v->at(i).type() == mtpc_channel) {
-				peer = App::channel(v->at(i).c_channel().vid.v);
-				Ui::showPeerHistory(peer, ShowAtUnreadMsgId);
-				QTimer::singleShot(ReloadChannelMembersTimeout, App::api(), SLOT(delayedRequestParticipantsCount()));
+	auto handleChats = [](auto &mtpChats) {
+		for_const (auto &mtpChat, mtpChats.v) {
+			if (mtpChat.type() == mtpc_channel) {
+				auto channel = App::channel(mtpChat.c_channel().vid.v);
+				Ui::showPeerHistory(channel, ShowAtUnreadMsgId);
+				App::api()->requestParticipantsCountDelayed(channel);
 			}
 		}
-	}
-	if (!peer) {
-		LOG(("API Error: channel not found in updates (ProfileInner::migrateDone)"));
+	};
+
+	switch (updates.type()) {
+	case mtpc_updates: handleChats(updates.c_updates().vchats); break;
+	case mtpc_updatesCombined: handleChats(updates.c_updatesCombined().vchats); break;
+	default: LOG(("API Error: unexpected update cons %1 (ConvertToSupergroupBox::convertDone)").arg(updates.type())); break;
 	}
 }
 
diff --git a/Telegram/SourceFiles/boxes/members_box.cpp b/Telegram/SourceFiles/boxes/members_box.cpp
index 9b2479c465..1dcf814b61 100644
--- a/Telegram/SourceFiles/boxes/members_box.cpp
+++ b/Telegram/SourceFiles/boxes/members_box.cpp
@@ -62,6 +62,12 @@ Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
 //	return mapFromGlobal(QCursor::pos()) - _st.rippleAreaPosition;
 //}
 
+namespace {
+
+constexpr auto kReloadChannelAdminsTimeout = 1000; // 1 second wait before reload admins in channel after adding
+
+} // namespace
+
 MembersBox::MembersBox(QWidget*, ChannelData *channel, MembersFilter filter)
 : _channel(channel)
 , _filter(filter) {
@@ -124,7 +130,7 @@ void MembersBox::onAdminAdded() {
 	if (!_addBox) return;
 	_addBox->closeBox();
 	_addBox = nullptr;
-	_loadTimer->start(ReloadChannelMembersTimeout);
+	_loadTimer->start(kReloadChannelAdminsTimeout);
 }
 
 MembersBox::Inner::Inner(QWidget *parent, ChannelData *channel, MembersFilter filter) : TWidget(parent)
diff --git a/Telegram/SourceFiles/config.h b/Telegram/SourceFiles/config.h
index eb269a1cd3..df28c96887 100644
--- a/Telegram/SourceFiles/config.h
+++ b/Telegram/SourceFiles/config.h
@@ -142,7 +142,6 @@ enum {
 	SessionsShortPollTimeout = 60000,
 
 	ChoosePeerByDragTimeout = 1000, // 1 second mouse not moved to choose dialog when dragging a file
-	ReloadChannelMembersTimeout = 1000, // 1 second wait before reload members in channel after adding
 };
 
 inline bool isNotificationsUser(uint64 id) {
diff --git a/Telegram/SourceFiles/facades.cpp b/Telegram/SourceFiles/facades.cpp
index 6a294454b8..a2fdfb84a9 100644
--- a/Telegram/SourceFiles/facades.cpp
+++ b/Telegram/SourceFiles/facades.cpp
@@ -28,6 +28,7 @@ Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
 #include "layerwidget.h"
 #include "lang.h"
 #include "base/observer.h"
+#include "base/task_queue.h"
 
 Q_DECLARE_METATYPE(ClickHandlerPtr);
 Q_DECLARE_METATYPE(Qt::MouseButton);
@@ -410,7 +411,7 @@ struct Data {
 } // namespace internal
 } // namespace Sandbox
 
-Sandbox::internal::Data *SandboxData = nullptr;
+std::unique_ptr<Sandbox::internal::Data> SandboxData;
 uint64 SandboxUserTag = 0;
 
 namespace Sandbox {
@@ -496,7 +497,7 @@ void WorkingDirReady() {
 	}
 }
 
-object_ptr<SingleDelayedCall> MainThreadTaskHandler = { nullptr };
+object_ptr<SingleQueuedInvokation> MainThreadTaskHandler = { nullptr };
 
 void MainThreadTaskAdded() {
 	if (!started()) {
@@ -507,8 +508,10 @@ void MainThreadTaskAdded() {
 }
 
 void start() {
-	MainThreadTaskHandler.create(QCoreApplication::instance(), "onMainThreadTask");
-	SandboxData = new internal::Data();
+	MainThreadTaskHandler.create([] {
+		base::TaskQueue::ProcessMainTasks();
+	});
+	SandboxData = std::make_unique<internal::Data>();
 
 	SandboxData->LangSystemISO = psCurrentLanguage();
 	if (SandboxData->LangSystemISO.isEmpty()) SandboxData->LangSystemISO = qstr("en");
@@ -526,8 +529,7 @@ bool started() {
 }
 
 void finish() {
-	delete SandboxData;
-	SandboxData = nullptr;
+	SandboxData.reset();
 	MainThreadTaskHandler.destroy();
 }
 
@@ -586,10 +588,10 @@ namespace internal {
 
 struct Data {
 	uint64 LaunchId = 0;
-	SingleDelayedCall HandleHistoryUpdate = { App::app(), "call_handleHistoryUpdate" };
-	SingleDelayedCall HandleUnreadCounterUpdate = { App::app(), "call_handleUnreadCounterUpdate" };
-	SingleDelayedCall HandleDelayedPeerUpdates = { App::app(), "call_handleDelayedPeerUpdates" };
-	SingleDelayedCall HandleObservables = { App::app(), "call_handleObservables" };
+	SingleQueuedInvokation HandleHistoryUpdate = { [] { App::app()->call_handleHistoryUpdate(); } };
+	SingleQueuedInvokation HandleUnreadCounterUpdate = { [] { App::app()->call_handleUnreadCounterUpdate(); } };
+	SingleQueuedInvokation HandleDelayedPeerUpdates = { [] { App::app()->call_handleDelayedPeerUpdates(); } };
+	SingleQueuedInvokation HandleObservables = { [] { App::app()->call_handleObservables(); } };
 
 	Adaptive::WindowLayout AdaptiveWindowLayout = Adaptive::WindowLayout::Normal;
 	Adaptive::ChatLayout AdaptiveChatLayout = Adaptive::ChatLayout::Normal;
@@ -709,10 +711,10 @@ void finish() {
 }
 
 DefineReadOnlyVar(Global, uint64, LaunchId);
-DefineRefVar(Global, SingleDelayedCall, HandleHistoryUpdate);
-DefineRefVar(Global, SingleDelayedCall, HandleUnreadCounterUpdate);
-DefineRefVar(Global, SingleDelayedCall, HandleDelayedPeerUpdates);
-DefineRefVar(Global, SingleDelayedCall, HandleObservables);
+DefineRefVar(Global, SingleQueuedInvokation, HandleHistoryUpdate);
+DefineRefVar(Global, SingleQueuedInvokation, HandleUnreadCounterUpdate);
+DefineRefVar(Global, SingleQueuedInvokation, HandleDelayedPeerUpdates);
+DefineRefVar(Global, SingleQueuedInvokation, HandleObservables);
 
 DefineVar(Global, Adaptive::WindowLayout, AdaptiveWindowLayout);
 DefineVar(Global, Adaptive::ChatLayout, AdaptiveChatLayout);
diff --git a/Telegram/SourceFiles/facades.h b/Telegram/SourceFiles/facades.h
index 7dac46ea39..26e806a869 100644
--- a/Telegram/SourceFiles/facades.h
+++ b/Telegram/SourceFiles/facades.h
@@ -292,10 +292,10 @@ void start();
 void finish();
 
 DeclareReadOnlyVar(uint64, LaunchId);
-DeclareRefVar(SingleDelayedCall, HandleHistoryUpdate);
-DeclareRefVar(SingleDelayedCall, HandleUnreadCounterUpdate);
-DeclareRefVar(SingleDelayedCall, HandleDelayedPeerUpdates);
-DeclareRefVar(SingleDelayedCall, HandleObservables);
+DeclareRefVar(SingleQueuedInvokation, HandleHistoryUpdate);
+DeclareRefVar(SingleQueuedInvokation, HandleUnreadCounterUpdate);
+DeclareRefVar(SingleQueuedInvokation, HandleDelayedPeerUpdates);
+DeclareRefVar(SingleQueuedInvokation, HandleObservables);
 
 DeclareVar(Adaptive::WindowLayout, AdaptiveWindowLayout);
 DeclareVar(Adaptive::ChatLayout, AdaptiveChatLayout);
diff --git a/Telegram/SourceFiles/historywidget.cpp b/Telegram/SourceFiles/historywidget.cpp
index 580d4606f3..a7f9ba1e36 100644
--- a/Telegram/SourceFiles/historywidget.cpp
+++ b/Telegram/SourceFiles/historywidget.cpp
@@ -152,7 +152,8 @@ HistoryInner::HistoryInner(HistoryWidget *historyWidget, Ui::ScrollArea *scroll,
 , _migrated(history->peer->migrateFrom() ? App::history(history->peer->migrateFrom()->id) : nullptr)
 , _history(history)
 , _widget(historyWidget)
-, _scroll(scroll) {
+, _scroll(scroll)
+, _scrollDateCheck([this] { onScrollDateCheck(); }) {
 	_touchSelectTimer.setSingleShot(true);
 	connect(&_touchSelectTimer, SIGNAL(timeout()), this, SLOT(onTouchSelect()));
 
@@ -2585,7 +2586,7 @@ void MessageField::focusInEvent(QFocusEvent *e) {
 	emit focused();
 }
 
-ReportSpamPanel::ReportSpamPanel(HistoryWidget *parent) : TWidget(parent),
+ReportSpamPanel::ReportSpamPanel(QWidget *parent) : TWidget(parent),
 _report(this, lang(lng_report_spam), st::reportSpamHide),
 _hide(this, lang(lng_report_spam_hide), st::reportSpamHide),
 _clear(this, lang(lng_profile_delete_conversation)) {
@@ -3369,8 +3370,9 @@ void HistoryWidget::start() {
 	connect(App::main(), SIGNAL(stickersUpdated()), this, SLOT(onStickersUpdated()));
 	updateRecentStickers();
 	AuthSession::Current().data().savedGifsUpdated().notify();
-
-	connect(App::api(), SIGNAL(fullPeerUpdated(PeerData*)), this, SLOT(onFullPeerUpdated(PeerData*)));
+	subscribe(App::api()->fullPeerUpdated(), [this](PeerData *peer) {
+		fullPeerUpdated(peer);
+	});
 }
 
 void HistoryWidget::onStickersUpdated() {
@@ -8397,8 +8399,8 @@ void HistoryWidget::onCancel() {
 	}
 }
 
-void HistoryWidget::onFullPeerUpdated(PeerData *data) {
-	if (_list && data == _peer) {
+void HistoryWidget::fullPeerUpdated(PeerData *peer) {
+	if (_list && peer == _peer) {
 		bool newCanSendMessages = canSendMessages(_peer);
 		if (newCanSendMessages != _canSendMessages) {
 			_canSendMessages = newCanSendMessages;
@@ -8422,9 +8424,9 @@ void HistoryWidget::onFullPeerUpdated(PeerData *data) {
 
 void HistoryWidget::peerUpdated(PeerData *data) {
 	if (data && data == _peer) {
-		if (data->migrateTo()) {
-			Ui::showPeerHistory(data->migrateTo(), ShowAtUnreadMsgId);
-			QTimer::singleShot(ReloadChannelMembersTimeout, App::api(), SLOT(delayedRequestParticipantsCount()));
+		if (auto channel = data->migrateTo()) {
+			Ui::showPeerHistory(channel, ShowAtUnreadMsgId);
+			App::api()->requestParticipantsCountDelayed(channel);
 			return;
 		}
 		QString restriction = _peer->restrictionReason();
diff --git a/Telegram/SourceFiles/historywidget.h b/Telegram/SourceFiles/historywidget.h
index e3efef33d6..5ce0ca6d09 100644
--- a/Telegram/SourceFiles/historywidget.h
+++ b/Telegram/SourceFiles/historywidget.h
@@ -286,7 +286,7 @@ private:
 
 	bool _scrollDateShown = false;
 	Animation _scrollDateOpacity;
-	SingleDelayedCall _scrollDateCheck = { this, "onScrollDateCheck" };
+	SingleQueuedInvokation _scrollDateCheck;
 	SingleTimer _scrollDateHideTimer;
 	HistoryItem *_scrollDateLastItem = nullptr;
 	int _scrollDateLastItemTop = 0;
@@ -358,12 +358,11 @@ private:
 
 };
 
-class HistoryWidget;
 class ReportSpamPanel : public TWidget {
 	Q_OBJECT
 
 public:
-	ReportSpamPanel(HistoryWidget *parent);
+	ReportSpamPanel(QWidget *parent);
 
 	void setReported(bool reported, PeerData *onPeer);
 
@@ -767,7 +766,6 @@ public slots:
 	void onPreviewTimeout();
 
 	void peerUpdated(PeerData *data);
-	void onFullPeerUpdated(PeerData *data);
 
 	void onPhotoUploaded(const FullMsgId &msgId, bool silent, const MTPInputFile &file);
 	void onDocumentUploaded(const FullMsgId &msgId, bool silent, const MTPInputFile &file);
@@ -856,6 +854,7 @@ private:
 		bool allFilesForCompress = true;
 	};
 
+	void fullPeerUpdated(PeerData *peer);
 	void topBarClick();
 
 	void animationCallback();
diff --git a/Telegram/SourceFiles/layout.h b/Telegram/SourceFiles/layout.h
index 2cecf01ab8..8dece22354 100644
--- a/Telegram/SourceFiles/layout.h
+++ b/Telegram/SourceFiles/layout.h
@@ -22,7 +22,7 @@ Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
 
 #include "base/runtime_composer.h"
 
-static constexpr TextSelection FullSelection = { 0xFFFF, 0xFFFF };
+constexpr auto FullSelection = TextSelection { 0xFFFF, 0xFFFF };
 
 extern TextParseOptions _textNameOptions, _textDlgOptions;
 extern TextParseOptions _historyTextOptions, _historyBotOptions, _historyTextNoMonoOptions, _historyBotNoMonoOptions;
diff --git a/Telegram/SourceFiles/mainwidget.cpp b/Telegram/SourceFiles/mainwidget.cpp
index ebcf0359b9..3e45d580e9 100644
--- a/Telegram/SourceFiles/mainwidget.cpp
+++ b/Telegram/SourceFiles/mainwidget.cpp
@@ -102,7 +102,6 @@ MainWidget::MainWidget(QWidget *parent, std::unique_ptr<Window::Controller> cont
 	connect(&_byPtsTimer, SIGNAL(timeout()), this, SLOT(onGetDifferenceTimeByPts()));
 	connect(&_byMinChannelTimer, SIGNAL(timeout()), this, SLOT(getDifference()));
 	connect(&_failDifferenceTimer, SIGNAL(timeout()), this, SLOT(onGetDifferenceTimeAfterFail()));
-	connect(_api.get(), SIGNAL(fullPeerUpdated(PeerData*)), this, SLOT(onFullPeerUpdated(PeerData*)));
 	connect(this, SIGNAL(peerUpdated(PeerData*)), _history, SLOT(peerUpdated(PeerData*)));
 	connect(_history, SIGNAL(historyShown(History*,MsgId)), this, SLOT(onHistoryShown(History*,MsgId)));
 	connect(&updateNotifySettingTimer, SIGNAL(timeout()), this, SLOT(onUpdateNotifySettings()));
@@ -111,7 +110,9 @@ MainWidget::MainWidget(QWidget *parent, std::unique_ptr<Window::Controller> cont
 			handleAudioUpdate(audioId);
 		}
 	});
-
+	subscribe(_api->fullPeerUpdated(), [this](PeerData *peer) {
+		emit peerUpdated(peer);
+	});
 	subscribe(Global::RefDialogsListFocused(), [this](bool) {
 		updateDialogsWidthAnimated();
 	});
@@ -2797,13 +2798,7 @@ bool MainWidget::deleteChannelFailed(const RPCError &error) {
 
 void MainWidget::inviteToChannelDone(ChannelData *channel, const MTPUpdates &updates) {
 	sentUpdatesReceived(updates);
-	QTimer::singleShot(ReloadChannelMembersTimeout, this, SLOT(onActiveChannelUpdateFull()));
-}
-
-void MainWidget::onActiveChannelUpdateFull() {
-	if (activePeer() && activePeer()->isChannel()) {
-		activePeer()->asChannel()->updateFull(true);
-	}
+	App::api()->requestParticipantsCountDelayed(channel);
 }
 
 void MainWidget::historyToDown(History *history) {
@@ -3830,10 +3825,6 @@ void MainWidget::onStickersInstalled(uint64 setId) {
 	_history->stickersInstalled(setId);
 }
 
-void MainWidget::onFullPeerUpdated(PeerData *peer) {
-	emit peerUpdated(peer);
-}
-
 void MainWidget::onSelfParticipantUpdated(ChannelData *channel) {
 	auto history = App::historyLoaded(channel->id);
 	if (_updatedChannels.contains(channel)) {
@@ -5062,7 +5053,7 @@ void MainWidget::feedUpdate(const MTPUpdate &update) {
 			if (channel->isMegagroup()) {
 				channel->mgInfo->pinnedMsgId = d.vid.v;
 				if (App::api()) {
-					emit App::api()->fullPeerUpdated(channel);
+					App::api()->fullPeerUpdated().notify(channel);
 				}
 			}
 		}
diff --git a/Telegram/SourceFiles/mainwidget.h b/Telegram/SourceFiles/mainwidget.h
index 90ed7844d9..52f198cad5 100644
--- a/Telegram/SourceFiles/mainwidget.h
+++ b/Telegram/SourceFiles/mainwidget.h
@@ -444,10 +444,8 @@ public slots:
 	void onUpdateMuted();
 
 	void onStickersInstalled(uint64 setId);
-	void onFullPeerUpdated(PeerData *peer);
 
 	void onViewsIncrement();
-	void onActiveChannelUpdateFull();
 
 	void ui_showPeerHistoryAsync(quint64 peerId, qint32 showAtMsgId, Ui::ShowWay way);
 	void ui_autoplayMediaInlineAsync(qint32 channelId, qint32 msgId);
diff --git a/Telegram/SourceFiles/media/media_audio_loaders.cpp b/Telegram/SourceFiles/media/media_audio_loaders.cpp
index 2cc36249ab..9fba602ae3 100644
--- a/Telegram/SourceFiles/media/media_audio_loaders.cpp
+++ b/Telegram/SourceFiles/media/media_audio_loaders.cpp
@@ -27,7 +27,7 @@ Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
 namespace Media {
 namespace Player {
 
-Loaders::Loaders(QThread *thread) : _fromVideoNotify(this, "onVideoSoundAdded") {
+Loaders::Loaders(QThread *thread) : _fromVideoNotify([this] { videoSoundAdded(); }) {
 	moveToThread(thread);
 	connect(thread, SIGNAL(started()), this, SLOT(onInit()));
 	connect(thread, SIGNAL(finished()), this, SLOT(deleteLater()));
@@ -59,7 +59,7 @@ void Loaders::stopFromVideo() {
 	startFromVideo(0);
 }
 
-void Loaders::onVideoSoundAdded() {
+void Loaders::videoSoundAdded() {
 	bool waitingAndAdded = false;
 	{
 		QMutexLocker lock(&_fromVideoMutex);
diff --git a/Telegram/SourceFiles/media/media_audio_loaders.h b/Telegram/SourceFiles/media/media_audio_loaders.h
index a0a676d9fe..e2efd57ed0 100644
--- a/Telegram/SourceFiles/media/media_audio_loaders.h
+++ b/Telegram/SourceFiles/media/media_audio_loaders.h
@@ -51,9 +51,8 @@ signals:
 	void onLoad(const AudioMsgId &audio);
 	void onCancel(const AudioMsgId &audio);
 
-	void onVideoSoundAdded();
-
 private:
+	void videoSoundAdded();
 	void clearFromVideoQueue();
 
 	AudioMsgId _audio, _song, _video;
@@ -64,7 +63,7 @@ private:
 	QMutex _fromVideoMutex;
 	uint64 _fromVideoPlayId;
 	QQueue<FFMpeg::AVPacketDataWrap> _fromVideoQueue;
-	SingleDelayedCall _fromVideoNotify;
+	SingleQueuedInvokation _fromVideoNotify;
 
 	void emitError(AudioMsgId::Type type);
 	AudioMsgId clear(AudioMsgId::Type type);
diff --git a/Telegram/SourceFiles/messenger.cpp b/Telegram/SourceFiles/messenger.cpp
index ea7803f09f..0d47b60054 100644
--- a/Telegram/SourceFiles/messenger.cpp
+++ b/Telegram/SourceFiles/messenger.cpp
@@ -55,8 +55,7 @@ struct Messenger::Private {
 };
 
 Messenger::Messenger() : QObject()
-, _private(std::make_unique<Private>())
-, _delayedLoadersDestroyer(this, "onDelayedDestroyLoaders") {
+, _private(std::make_unique<Private>()) {
 	t_assert(SingleInstance == nullptr);
 	SingleInstance = this;
 
@@ -697,7 +696,6 @@ void Messenger::prepareToDestroy() {
 
 	// Some MTP requests can be cancelled from data clearing.
 	App::clearHistories();
-	_delayedDestroyedLoaders.clear();
 	authSessionDestroy();
 
 	_mtproto.reset();
@@ -732,12 +730,3 @@ Messenger::~Messenger() {
 MainWindow *Messenger::mainWindow() {
 	return _window.get();
 }
-
-void Messenger::delayedDestroyLoader(std::unique_ptr<FileLoader> loader) {
-	_delayedDestroyedLoaders.push_back(std::move(loader));
-	_delayedLoadersDestroyer.call();
-}
-
-void Messenger::onDelayedDestroyLoaders() {
-	_delayedDestroyedLoaders.clear();
-}
diff --git a/Telegram/SourceFiles/messenger.h b/Telegram/SourceFiles/messenger.h
index f1230680c3..807e2069b3 100644
--- a/Telegram/SourceFiles/messenger.h
+++ b/Telegram/SourceFiles/messenger.h
@@ -105,8 +105,10 @@ public:
 	void handleAppActivated();
 	void handleAppDeactivated();
 
-	// Temporary here, when all Images and Documents are owned by AuthSession it'll have this.
-	void delayedDestroyLoader(std::unique_ptr<FileLoader> loader);
+	void call_handleHistoryUpdate();
+	void call_handleUnreadCounterUpdate();
+	void call_handleDelayedPeerUpdates();
+	void call_handleObservables();
 
 signals:
 	void peerPhotoDone(PeerId peer);
@@ -114,7 +116,6 @@ signals:
 
 public slots:
 	void onAllKeysDestroyed();
-	void onDelayedDestroyLoaders();
 
 	void photoUpdated(const FullMsgId &msgId, bool silent, const MTPInputFile &file);
 
@@ -125,11 +126,6 @@ public slots:
 	void killDownloadSessions();
 	void onAppStateChanged(Qt::ApplicationState state);
 
-	void call_handleHistoryUpdate();
-	void call_handleUnreadCounterUpdate();
-	void call_handleDelayedPeerUpdates();
-	void call_handleObservables();
-
 private:
 	void destroyMtpKeys(MTP::AuthKeysList &&keys);
 	void startLocalStorage();
@@ -154,7 +150,4 @@ private:
 	std::unique_ptr<AuthSession> _authSession;
 	base::Observable<void> _authSessionChanged;
 
-	SingleDelayedCall _delayedLoadersDestroyer;
-	std::vector<std::unique_ptr<FileLoader>> _delayedDestroyedLoaders;
-
 };
diff --git a/Telegram/SourceFiles/storage/file_download.cpp b/Telegram/SourceFiles/storage/file_download.cpp
index 959766feea..48aaa2a67c 100644
--- a/Telegram/SourceFiles/storage/file_download.cpp
+++ b/Telegram/SourceFiles/storage/file_download.cpp
@@ -29,6 +29,15 @@ Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
 
 namespace Storage {
 
+Downloader::Downloader()
+: _delayedLoadersDestroyer([this] { _delayedDestroyedLoaders.clear(); }) {
+}
+
+void Downloader::delayedDestroyLoader(std::unique_ptr<FileLoader> loader) {
+	_delayedDestroyedLoaders.push_back(std::move(loader));
+	_delayedLoadersDestroyer.call();
+}
+
 void Downloader::clearPriorities() {
 	++_priority;
 }
diff --git a/Telegram/SourceFiles/storage/file_download.h b/Telegram/SourceFiles/storage/file_download.h
index c80a564116..8ca8d46b58 100644
--- a/Telegram/SourceFiles/storage/file_download.h
+++ b/Telegram/SourceFiles/storage/file_download.h
@@ -27,11 +27,15 @@ namespace Storage {
 
 class Downloader final {
 public:
+	Downloader();
+
 	int currentPriority() const {
 		return _priority;
 	}
 	void clearPriorities();
 
+	void delayedDestroyLoader(std::unique_ptr<FileLoader> loader);
+
 	base::Observable<void> &taskFinished() {
 		return _taskFinishedObservable;
 	}
@@ -40,6 +44,9 @@ private:
 	base::Observable<void> _taskFinishedObservable;
 	int _priority = 1;
 
+	SingleQueuedInvokation _delayedLoadersDestroyer;
+	std::vector<std::unique_ptr<FileLoader>> _delayedDestroyedLoaders;
+
 };
 
 } // namespace Storage
diff --git a/Telegram/SourceFiles/structs.cpp b/Telegram/SourceFiles/structs.cpp
index cbebdc401c..9476bbced9 100644
--- a/Telegram/SourceFiles/structs.cpp
+++ b/Telegram/SourceFiles/structs.cpp
@@ -1535,7 +1535,7 @@ bool DocumentData::loaded(FilePathResolveType type) const {
 void DocumentData::destroyLoaderDelayed(mtpFileLoader *newValue) const {
 	_loader->stop();
 	auto loader = std::unique_ptr<FileLoader>(std::exchange(_loader, newValue));
-	Messenger::Instance().delayedDestroyLoader(std::move(loader));
+	AuthSession::Current().downloader().delayedDestroyLoader(std::move(loader));
 }
 
 bool DocumentData::loading() const {
@@ -1620,10 +1620,10 @@ void DocumentData::save(const QString &toFile, ActionOnLoad action, const FullMs
 void DocumentData::cancel() {
 	if (!loading()) return;
 
-	auto loader = std::exchange(_loader, CancelledMtpFileLoader);
+	auto loader = std::unique_ptr<FileLoader>(std::exchange(_loader, CancelledMtpFileLoader));
 	loader->cancel();
 	loader->stop();
-	Messenger::Instance().delayedDestroyLoader(std::unique_ptr<FileLoader>(loader));
+	AuthSession::Current().downloader().delayedDestroyLoader(std::move(loader));
 
 	notifyLayoutChanged();
 	if (auto main = App::main()) {
diff --git a/Telegram/SourceFiles/ui/images.cpp b/Telegram/SourceFiles/ui/images.cpp
index d4a9e70e70..2a32d943dd 100644
--- a/Telegram/SourceFiles/ui/images.cpp
+++ b/Telegram/SourceFiles/ui/images.cpp
@@ -23,7 +23,7 @@ Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
 #include "mainwidget.h"
 #include "storage/localstorage.h"
 #include "platform/platform_specific.h"
-#include "messenger.h"
+#include "auth_session.h"
 
 namespace Images {
 namespace {
@@ -858,7 +858,7 @@ void RemoteImage::doCheckload() const {
 void RemoteImage::destroyLoaderDelayed(FileLoader *newValue) const {
 	_loader->stop();
 	auto loader = std::unique_ptr<FileLoader>(std::exchange(_loader, newValue));
-	Messenger::Instance().delayedDestroyLoader(std::move(loader));
+	AuthSession::Current().downloader().delayedDestroyLoader(std::move(loader));
 }
 
 void RemoteImage::loadLocal() {
@@ -959,7 +959,7 @@ void RemoteImage::cancel() {
 	auto loader = std::exchange(_loader, CancelledFileLoader);
 	loader->cancel();
 	loader->stop();
-	Messenger::Instance().delayedDestroyLoader(std::unique_ptr<FileLoader>(loader));
+	AuthSession::Current().downloader().delayedDestroyLoader(std::unique_ptr<FileLoader>(loader));
 }
 
 float64 RemoteImage::progress() const {
diff --git a/Telegram/SourceFiles/ui/twidget.h b/Telegram/SourceFiles/ui/twidget.h
index 55fd4eb700..d3f7f5af6b 100644
--- a/Telegram/SourceFiles/ui/twidget.h
+++ b/Telegram/SourceFiles/ui/twidget.h
@@ -328,28 +328,23 @@ void myEnsureResized(QWidget *target);
 QPixmap myGrab(TWidget *target, QRect rect = QRect(), QColor bg = QColor(255, 255, 255, 0));
 QImage myGrabImage(TWidget *target, QRect rect = QRect(), QColor bg = QColor(255, 255, 255, 0));
 
-class SingleDelayedCall : public QObject {
-	Q_OBJECT
-
+class SingleQueuedInvokation : public QObject {
 public:
-	SingleDelayedCall(QObject *parent, const char *member) : QObject(parent), _member(member) {
+	SingleQueuedInvokation(base::lambda<void()> callback) : _callback(callback) {
 	}
 	void call() {
-		if (_pending.testAndSetOrdered(0, 1)) {
-			QMetaObject::invokeMethod(this, "makeDelayedCall", Qt::QueuedConnection);
-		}
-	}
-
-private slots:
-	void makeDelayedCall() {
-		if (_pending.testAndSetOrdered(1, 0)) {
-			QMetaObject::invokeMethod(parent(), _member);
+		if (_pending.testAndSetAcquire(0, 1)) {
+			InvokeQueued(this, [this] {
+				if (_pending.testAndSetRelease(1, 0)) {
+					_callback();
+				}
+			});
 		}
 	}
 
 private:
+	base::lambda<void()> _callback;
 	QAtomicInt _pending = { 0 };
-	const char *_member;
 
 };