diff --git a/Telegram/SourceFiles/application.cpp b/Telegram/SourceFiles/application.cpp
index c2eeae415..f899532f7 100644
--- a/Telegram/SourceFiles/application.cpp
+++ b/Telegram/SourceFiles/application.cpp
@@ -33,6 +33,7 @@ Copyright (c) 2014-2016 John Preston, https://desktop.telegram.org
 #include "autoupdater.h"
 #include "core/observer.h"
 #include "observer_peer.h"
+#include "core/observer.h"
 
 namespace {
 	void mtpStateChanged(int32 dc, int32 state) {
@@ -922,6 +923,10 @@ void AppClass::call_handleDelayedPeerUpdates() {
 	Notify::peerUpdatedSendDelayed();
 }
 
+void AppClass::call_handleObservables() {
+	base::HandleObservables();
+}
+
 void AppClass::killDownloadSessions() {
 	uint64 ms = getms(), left = MTPAckSendWaiting + MTPKillFileSessionTimeout;
 	for (QMap<int32, uint64>::iterator i = killDownloadSessionTimes.begin(); i != killDownloadSessionTimes.end(); ) {
diff --git a/Telegram/SourceFiles/application.h b/Telegram/SourceFiles/application.h
index 78983d070..025164cd6 100644
--- a/Telegram/SourceFiles/application.h
+++ b/Telegram/SourceFiles/application.h
@@ -205,6 +205,7 @@ public slots:
 	void call_handleUnreadCounterUpdate();
 	void call_handleFileDialogQueue();
 	void call_handleDelayedPeerUpdates();
+	void call_handleObservables();
 
 private:
 
diff --git a/Telegram/SourceFiles/core/basic_types.h b/Telegram/SourceFiles/core/basic_types.h
index 943772903..8bb5d3efb 100644
--- a/Telegram/SourceFiles/core/basic_types.h
+++ b/Telegram/SourceFiles/core/basic_types.h
@@ -33,13 +33,6 @@ T *getPointerAndReset(T *&ptr) {
 	return result;
 }
 
-template <typename T>
-T createAndSwap(T &value) {
-	T result = T();
-	std::swap(result, value);
-	return result;
-}
-
 struct NullType {
 };
 
@@ -491,6 +484,13 @@ struct is_base_of {
 
 } // namespace std_
 
+template <typename T>
+T createAndSwap(T &value) {
+	T result = T();
+	std::swap(result, value);
+	return std_::move(result);
+}
+
 #include "logs.h"
 
 static volatile int *t_assert_nullptr = nullptr;
diff --git a/Telegram/SourceFiles/core/observer.cpp b/Telegram/SourceFiles/core/observer.cpp
index 6ec33a341..cc9b9497f 100644
--- a/Telegram/SourceFiles/core/observer.cpp
+++ b/Telegram/SourceFiles/core/observer.cpp
@@ -113,3 +113,62 @@ void observerRegisteredDefault(Observer *observer, ConnectionId connection) {
 
 } // namespace internal
 } // namespace Notify
+
+namespace base {
+namespace internal {
+namespace {
+
+bool CantUseObservables = false;
+
+struct ObservableListWrap {
+	~ObservableListWrap() {
+		CantUseObservables = true;
+	}
+	OrderedSet<ObservableCallHandlers*> list;
+};
+
+ObservableListWrap &PendingObservables() {
+	static ObservableListWrap result;
+	return result;
+}
+
+ObservableListWrap &ActiveObservables() {
+	static ObservableListWrap result;
+	return result;
+}
+
+} // namespace
+
+void RegisterPendingObservable(ObservableCallHandlers *handlers) {
+	if (CantUseObservables) return;
+	PendingObservables().list.insert(handlers);
+	Global::RefHandleObservables().call();
+}
+
+void UnregisterActiveObservable(ObservableCallHandlers *handlers) {
+	if (CantUseObservables) return;
+	ActiveObservables().list.remove(handlers);
+}
+
+void UnregisterObservable(ObservableCallHandlers *handlers) {
+	if (CantUseObservables) return;
+	PendingObservables().list.remove(handlers);
+	ActiveObservables().list.remove(handlers);
+}
+
+} // namespace internal
+
+void HandleObservables() {
+	if (internal::CantUseObservables) return;
+	auto &active = internal::ActiveObservables().list;
+	qSwap(active, internal::PendingObservables().list);
+	while (!active.empty()) {
+		auto first = *active.begin();
+		(*first)();
+		if (!active.empty() && *active.begin() == first) {
+			active.erase(active.begin());
+		}
+	}
+}
+
+} // namespace base
diff --git a/Telegram/SourceFiles/core/observer.h b/Telegram/SourceFiles/core/observer.h
index 7b0df81a2..02fc10bac 100644
--- a/Telegram/SourceFiles/core/observer.h
+++ b/Telegram/SourceFiles/core/observer.h
@@ -240,3 +240,324 @@ inline void observerRegistered(ObserverType *observer, ConnectionId connection)
 }
 
 } // namespace Notify
+
+namespace base {
+namespace internal {
+
+using ObservableCallHandlers = base::lambda_unique<void()>;
+void RegisterPendingObservable(ObservableCallHandlers *handlers);
+void UnregisterActiveObservable(ObservableCallHandlers *handlers);
+void UnregisterObservable(ObservableCallHandlers *handlers);
+
+template <typename EventType>
+struct SubscriptionHandlerHelper {
+	using type = base::lambda_unique<void(const EventType &)>;
+};
+
+template <>
+struct SubscriptionHandlerHelper<void> {
+	using type = base::lambda_unique<void()>;
+};
+
+template <typename EventType>
+using SubscriptionHandler = typename SubscriptionHandlerHelper<EventType>::type;
+
+// Required because QShared/WeakPointer can't point to void.
+class BaseObservableData {
+};
+
+template <typename EventType>
+class CommonObservableData;
+
+template <typename EventType>
+class ObservableData;
+
+} // namespace internal
+
+class Subscription {
+public:
+	Subscription() = default;
+	Subscription(const Subscription &) = delete;
+	Subscription &operator=(const Subscription &) = delete;
+	Subscription(Subscription &&other) : _node(createAndSwap(other._node)), _removeMethod(other._removeMethod) {
+	}
+	Subscription &operator=(Subscription &&other) {
+		qSwap(_node, other._node);
+		qSwap(_removeMethod, other._removeMethod);
+		return *this;
+	}
+	void destroy() {
+		if (_node) {
+			(*_removeMethod)(_node);
+			delete _node;
+			_node = nullptr;
+		}
+	}
+	~Subscription() {
+		destroy();
+	}
+
+private:
+	struct Node {
+		Node(const QSharedPointer<internal::BaseObservableData> &observable) : observable(observable) {
+		}
+		Node *next = nullptr;
+		Node *prev = nullptr;
+		QWeakPointer<internal::BaseObservableData> observable;
+	};
+	using RemoveMethod = void(*)(Node*);
+	Subscription(Node *node, RemoveMethod removeMethod) : _node(node), _removeMethod(removeMethod) {
+	}
+
+	Node *_node = nullptr;
+	RemoveMethod _removeMethod;
+
+	template <typename EventType>
+	friend class internal::CommonObservableData;
+
+	template <typename EventType>
+	friend class internal::ObservableData;
+
+};
+
+template <typename EventType>
+class Observable;
+
+namespace internal {
+
+template <typename EventType>
+class CommonObservable {
+public:
+	using Handler = typename CommonObservableData<EventType>::Handler;
+
+	Subscription subscribe(Handler &&handler) {
+		if (_data) {
+			_data->append(std_::forward<Handler>(handler));
+		} else {
+			_data = MakeShared<ObservableData<EventType>>(this, std_::forward<Handler>(handler));
+		}
+		return _data->last();
+	}
+
+private:
+	QSharedPointer<ObservableData<EventType>> _data;
+
+	friend class CommonObservableData<EventType>;
+	friend class Observable<EventType>;
+
+};
+
+} // namespace internal
+
+template <typename EventType>
+class Observable : public internal::CommonObservable<EventType> {
+public:
+	void notify(EventType &&event) {
+		if (_data) {
+			_data->notify(std_::move(event));
+		}
+	}
+
+};
+
+namespace internal {
+
+template <typename EventType>
+class CommonObservableData : public BaseObservableData {
+public:
+	using Handler = SubscriptionHandler<EventType>;
+
+	CommonObservableData(CommonObservable<EventType> *observable, Handler &&handler) : _observable(observable)
+		, _begin(new Node(observable->_data, std_::forward<Handler>(handler)))
+		, _end(_begin) {
+	}
+
+	void append(Handler &&handler) {
+		auto node = new Node(_observable->_data, std_::forward<Handler>(handler));
+
+		_end->next = node;
+		node->prev = _end;
+		_end = node;
+	}
+
+	Subscription last() {
+		return { _end, &CommonObservableData::destroyNode };
+	}
+
+	bool empty() const {
+		return !_begin;
+	}
+
+private:
+	struct Node : public Subscription::Node {
+		Node(const QSharedPointer<BaseObservableData> &observer, Handler &&handler) : Subscription::Node(observer), handler(std_::move(handler)) {
+		}
+		Handler handler;
+	};
+
+	void remove(Subscription::Node *node) {
+		if (node->prev) {
+			node->prev->next = node->next;
+		}
+		if (node->next) {
+			node->next->prev = node->prev;
+		}
+		if (_begin == node) {
+			_begin = static_cast<Node*>(node->next);
+		}
+		if (_end == node) {
+			_end = static_cast<Node*>(node->prev);
+		}
+		if (_current == node) {
+			_current = static_cast<Node*>(node->prev);
+		} else if (!_begin) {
+			_observable->_data.reset();
+		}
+	}
+
+	static void destroyNode(Subscription::Node *node) {
+		if (auto that = node->observable.lock()) {
+			static_cast<CommonObservableData*>(that.data())->remove(node);
+		}
+	}
+
+	template <typename CallCurrent>
+	void notifyEnumerate(CallCurrent callCurrent) {
+		_current = _begin;
+		do {
+			callCurrent();
+			if (_current) {
+				_current = static_cast<Node*>(_current->next);
+			} else if (_begin) {
+				_current = _begin;
+			} else {
+				break;
+			}
+		} while (_current);
+
+		if (!_begin) {
+			_observable->_data.reset();
+		}
+	}
+
+	CommonObservable<EventType> *_observable = nullptr;
+	Node *_begin;
+	Node *_current = nullptr;
+	Node *_end;
+	ObservableCallHandlers _callHandlers;
+
+	friend class ObservableData<EventType>;
+
+};
+
+template <typename EventType>
+class ObservableData : public CommonObservableData<EventType> {
+public:
+	using CommonObservableData<EventType>::CommonObservableData;
+
+	void notify(EventType &&event) {
+		if (!_callHandlers) {
+			_callHandlers = [this]() {
+				callHandlers();
+			};
+		}
+		if (_events.empty()) {
+			RegisterPendingObservable(&_callHandlers);
+		}
+		_events.push_back(std_::move(event));
+	}
+
+	~ObservableData() {
+		UnregisterObservable(&_callHandlers);
+	}
+
+private:
+	void callHandlers() {
+		auto events = createAndSwap(_events);
+		for (auto &event : events) {
+			notifyEnumerate([this, &event]() {
+				_current->handler(event);
+			});
+		}
+		UnregisterActiveObservable(&_callHandlers);
+	}
+
+	std_::vector_of_moveable<EventType> _events;
+
+};
+
+template <>
+class ObservableData<void> : public CommonObservableData<void> {
+public:
+	using CommonObservableData<void>::CommonObservableData;
+
+	void notify() {
+		if (!_callHandlers) {
+			_callHandlers = [this]() {
+				callHandlers();
+			};
+		}
+		if (!_eventsCount) {
+			RegisterPendingObservable(&_callHandlers);
+		}
+		++_eventsCount;
+	}
+
+	~ObservableData() {
+		UnregisterObservable(&_callHandlers);
+	}
+
+private:
+	void callHandlers() {
+		auto eventsCount = createAndSwap(_eventsCount);
+		for (int i = 0; i != eventsCount; ++i) {
+			notifyEnumerate([this]() {
+				_current->handler();
+			});
+		}
+		UnregisterActiveObservable(&_callHandlers);
+	}
+
+	int _eventsCount = 0;
+
+};
+
+} // namespace internal
+
+template <>
+class Observable<void> : public internal::CommonObservable<void> {
+public:
+	void notify() {
+		if (_data) {
+			_data->notify();
+		}
+	}
+
+};
+
+class Subscriber {
+protected:
+	template <typename EventType, typename Lambda>
+	int subscribe(base::Observable<EventType> &observable, Lambda &&handler) {
+		_subscriptions.push_back(observable.subscribe(std_::forward<Lambda>(handler)));
+		return _subscriptions.size() - 1;
+	}
+
+	template <typename EventType, typename Lambda>
+	int subscribe(base::Observable<EventType> *observable, Lambda &&handler) {
+		return subscribe(*observable, std_::forward<Lambda>(handler));
+	}
+
+	void unsubscribe(int index) {
+		t_assert(index >= 0 && index < _subscriptions.size());
+		_subscriptions[index].destroy();
+	}
+
+private:
+	std_::vector_of_moveable<base::Subscription> _subscriptions;
+
+};
+
+void HandleObservables();
+
+} // namespace base
diff --git a/Telegram/SourceFiles/core/vector_of_moveable.h b/Telegram/SourceFiles/core/vector_of_moveable.h
index 608bb0796..6119a9678 100644
--- a/Telegram/SourceFiles/core/vector_of_moveable.h
+++ b/Telegram/SourceFiles/core/vector_of_moveable.h
@@ -30,6 +30,21 @@ class vector_of_moveable {
 	void *_plaindata = nullptr;
 
 public:
+	vector_of_moveable() = default;
+	vector_of_moveable(const vector_of_moveable &other) = delete;
+	vector_of_moveable &operator=(const vector_of_moveable &other) = delete;
+	vector_of_moveable(vector_of_moveable &&other)
+		: _size(createAndSwap(other._size))
+		, _capacity(createAndSwap(other._capacity))
+		, _plaindata(createAndSwap(other._plaindata)) {
+	}
+	vector_of_moveable &operator=(vector_of_moveable &&other) {
+		std::swap(_size, other._size);
+		std::swap(_capacity, other._capacity);
+		std::swap(_plaindata, other._plaindata);
+		return *this;
+	}
+
 	inline T *data() {
 		return reinterpret_cast<T*>(_plaindata);
 	}
diff --git a/Telegram/SourceFiles/facades.cpp b/Telegram/SourceFiles/facades.cpp
index 4cfdfd51c..a4294ff16 100644
--- a/Telegram/SourceFiles/facades.cpp
+++ b/Telegram/SourceFiles/facades.cpp
@@ -577,6 +577,7 @@ struct Data {
 	SingleDelayedCall HandleUnreadCounterUpdate = { App::app(), "call_handleUnreadCounterUpdate" };
 	SingleDelayedCall HandleFileDialogQueue = { App::app(), "call_handleFileDialogQueue" };
 	SingleDelayedCall HandleDelayedPeerUpdates = { App::app(), "call_handleDelayedPeerUpdates" };
+	SingleDelayedCall HandleObservables = { App::app(), "call_handleObservables" };
 
 	Adaptive::Layout AdaptiveLayout = Adaptive::NormalLayout;
 	bool AdaptiveForWide = true;
@@ -654,6 +655,7 @@ DefineRefVar(Global, SingleDelayedCall, HandleHistoryUpdate);
 DefineRefVar(Global, SingleDelayedCall, HandleUnreadCounterUpdate);
 DefineRefVar(Global, SingleDelayedCall, HandleFileDialogQueue);
 DefineRefVar(Global, SingleDelayedCall, HandleDelayedPeerUpdates);
+DefineRefVar(Global, SingleDelayedCall, HandleObservables);
 
 DefineVar(Global, Adaptive::Layout, AdaptiveLayout);
 DefineVar(Global, bool, AdaptiveForWide);
diff --git a/Telegram/SourceFiles/facades.h b/Telegram/SourceFiles/facades.h
index c0b0a4613..2fdd64591 100644
--- a/Telegram/SourceFiles/facades.h
+++ b/Telegram/SourceFiles/facades.h
@@ -230,6 +230,7 @@ DeclareRefVar(SingleDelayedCall, HandleHistoryUpdate);
 DeclareRefVar(SingleDelayedCall, HandleUnreadCounterUpdate);
 DeclareRefVar(SingleDelayedCall, HandleFileDialogQueue);
 DeclareRefVar(SingleDelayedCall, HandleDelayedPeerUpdates);
+DeclareRefVar(SingleDelayedCall, HandleObservables);
 
 DeclareVar(Adaptive::Layout, AdaptiveLayout);
 DeclareVar(bool, AdaptiveForWide);
diff --git a/Telegram/SourceFiles/ui/twidget.h b/Telegram/SourceFiles/ui/twidget.h
index 6760a2698..7b6c12261 100644
--- a/Telegram/SourceFiles/ui/twidget.h
+++ b/Telegram/SourceFiles/ui/twidget.h
@@ -275,16 +275,16 @@ public:
 	SingleDelayedCall(QObject *parent, const char *member) : QObject(parent), _member(member) {
 	}
 	void call() {
-		if (!_pending.loadAcquire()) {
-			_pending.storeRelease(1);
+		if (_pending.testAndSetOrdered(0, 1)) {
 			QMetaObject::invokeMethod(this, "makeDelayedCall", Qt::QueuedConnection);
 		}
 	}
 
 private slots:
 	void makeDelayedCall() {
-		_pending.storeRelease(0);
-		QMetaObject::invokeMethod(parent(), _member);
+		if (_pending.testAndSetOrdered(1, 0)) {
+			QMetaObject::invokeMethod(parent(), _member);
+		}
 	}
 
 private:
diff --git a/Telegram/gyp/Telegram.gyp b/Telegram/gyp/Telegram.gyp
index 0532b5024..01b17232b 100644
--- a/Telegram/gyp/Telegram.gyp
+++ b/Telegram/gyp/Telegram.gyp
@@ -187,6 +187,7 @@
       '<(src_loc)/core/observer.h',
       '<(src_loc)/core/qthelp_url.cpp',
       '<(src_loc)/core/qthelp_url.h',
+      '<(src_loc)/core/vector_of_moveable.h',
       '<(src_loc)/data/data_abstract_structure.cpp',
       '<(src_loc)/data/data_abstract_structure.h',
       '<(src_loc)/data/data_drafts.cpp',