diff --git a/Telegram/SourceFiles/base/flags.h b/Telegram/SourceFiles/base/flags.h
new file mode 100644
index 0000000000..d51e84f1a4
--- /dev/null
+++ b/Telegram/SourceFiles/base/flags.h
@@ -0,0 +1,370 @@
+/*
+This file is part of Telegram Desktop,
+the official desktop version of Telegram messaging app, see https://telegram.org
+
+Telegram Desktop is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+It is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+In addition, as a special exception, the copyright holders give permission
+to link the code of portions of this program with the OpenSSL library.
+
+Full license: https://github.com/telegramdesktop/tdesktop/blob/master/LICENSE
+Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
+*/
+#pragma once
+
+#include <type_traits>
+
+#if defined _MSC_VER && _MSC_VER < 1910
+#define FLAGS_CONSTEXPR
+#else // MSVS2015
+#define FLAGS_CONSTEXPR constexpr
+#endif // MSVS2015
+
+namespace base {
+
+template <typename EnumType>
+class flags;
+
+template <typename ExtendedEnum>
+struct extended_flags;
+
+template <typename ExtendedEnum>
+using extended_flags_t = typename extended_flags<ExtendedEnum>::type;
+
+namespace details {
+
+struct flags_zero_helper_struct {
+};
+
+using flags_zero_helper = void(base::details::flags_zero_helper_struct::*)();
+
+template <typename ExtendedEnum,
+	typename Enum = typename base::extended_flags<ExtendedEnum>::type>
+inline constexpr auto extended_flag_convert(ExtendedEnum value) {
+	return static_cast<Enum>(value);
+}
+
+template <typename ExtendedEnum,
+	typename Enum = typename base::extended_flags<ExtendedEnum>::type>
+inline constexpr auto extended_flags_convert(ExtendedEnum value) {
+	return flags<Enum>(extended_flag_convert(value));
+}
+
+} // namespace details
+
+template <typename EnumType>
+class flags {
+public:
+	using Enum = EnumType;
+	using Type = std::underlying_type_t<Enum>;
+
+	constexpr flags() = default;
+	constexpr flags(details::flags_zero_helper) noexcept {
+	}
+	constexpr flags(Enum value) noexcept : _value(static_cast<Type>(value)) {
+	}
+	explicit constexpr flags(Type value) noexcept : _value(value) {
+	}
+
+	constexpr auto value() const noexcept {
+		return _value;
+	}
+	constexpr operator Type() const noexcept {
+		return value();
+	}
+
+	FLAGS_CONSTEXPR auto &operator|=(flags b) noexcept {
+		_value |= b.value();
+		return *this;
+	}
+	FLAGS_CONSTEXPR auto &operator&=(flags b) noexcept {
+		_value &= b.value();
+		return *this;
+	}
+	FLAGS_CONSTEXPR auto &operator^=(flags b) noexcept {
+		_value ^= b.value();
+		return *this;
+	}
+
+	FLAGS_CONSTEXPR auto operator~() const noexcept {
+		return flags(~value());
+	}
+
+	FLAGS_CONSTEXPR auto operator|(flags b) const noexcept {
+		return (flags(*this) |= b);
+	}
+	FLAGS_CONSTEXPR auto operator&(flags b) const noexcept {
+		return (flags(*this) &= b);
+	}
+	FLAGS_CONSTEXPR auto operator^(flags b) const noexcept {
+		return (flags(*this) ^= b);
+	}
+
+	FLAGS_CONSTEXPR auto operator|(Enum b) const noexcept {
+		return (flags(*this) |= b);
+	}
+	FLAGS_CONSTEXPR auto operator&(Enum b) const noexcept {
+		return (flags(*this) &= b);
+	}
+	FLAGS_CONSTEXPR auto operator^(Enum b) const noexcept {
+		return (flags(*this) ^= b);
+	}
+
+	constexpr auto operator==(Enum b) const noexcept {
+		return (value() == static_cast<Type>(b));
+	}
+	constexpr auto operator!=(Enum b) const noexcept {
+		return !(*this == b);
+	}
+	constexpr auto operator<(Enum b) const noexcept {
+		return value() < static_cast<Type>(b);
+	}
+	constexpr auto operator>(Enum b) const noexcept {
+		return (b < *this);
+	}
+	constexpr auto operator<=(Enum b) const noexcept {
+		return !(b < *this);
+	}
+	constexpr auto operator>=(Enum b) const noexcept {
+		return !(*this < b);
+	}
+
+private:
+	Type _value = 0;
+
+};
+
+template <typename Enum>
+constexpr auto make_flags(Enum value) noexcept {
+	return flags<Enum>(value);
+}
+
+template <typename Enum,
+	typename = std::enable_if_t<std::is_enum<Enum>::value>,
+	typename = std::enable_if_t<is_flag_type(Enum{})>>
+inline constexpr auto operator|(Enum a, flags<Enum> b) noexcept {
+	return b | a;
+}
+
+template <typename Enum,
+	typename = std::enable_if_t<std::is_enum<Enum>::value>,
+	typename = std::enable_if_t<is_flag_type(Enum{})>>
+inline constexpr auto operator&(Enum a, flags<Enum> b) noexcept {
+	return b & a;
+}
+
+template <typename Enum,
+	typename = std::enable_if_t<std::is_enum<Enum>::value>,
+	typename = std::enable_if_t<is_flag_type(Enum{})>>
+inline constexpr auto operator^(Enum a, flags<Enum> b) noexcept {
+	return b ^ a;
+}
+
+template <typename ExtendedEnum,
+	typename = typename extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator|(flags<extended_flags_t<ExtendedEnum>> a, ExtendedEnum b) {
+	return a | details::extended_flags_convert(b);
+}
+
+template <typename ExtendedEnum,
+	typename = typename extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator|(ExtendedEnum a, flags<extended_flags_t<ExtendedEnum>> b) {
+	return b | a;
+}
+
+template <typename ExtendedEnum,
+	typename = extended_flags_t<ExtendedEnum>>
+inline constexpr auto operator&(flags<extended_flags_t<ExtendedEnum>> a, ExtendedEnum b) {
+	return a & details::extended_flags_convert(b);
+}
+
+template <typename ExtendedEnum,
+	typename = typename extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator&(ExtendedEnum a, flags<extended_flags_t<ExtendedEnum>> b) {
+	return b & a;
+}
+
+template <typename ExtendedEnum,
+	typename = extended_flags_t<ExtendedEnum>>
+inline constexpr auto operator^(flags<extended_flags_t<ExtendedEnum>> a, ExtendedEnum b) {
+	return a ^ details::extended_flags_convert(b);
+}
+
+template <typename ExtendedEnum,
+	typename = typename extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator^(ExtendedEnum a, flags<extended_flags_t<ExtendedEnum>> b) {
+	return b ^ a;
+}
+
+template <typename ExtendedEnum,
+	typename = typename extended_flags<ExtendedEnum>::type>
+inline constexpr auto &operator&=(flags<extended_flags_t<ExtendedEnum>> &a, ExtendedEnum b) {
+	return (a &= details::extended_flags_convert(b));
+}
+
+template <typename ExtendedEnum,
+	typename = typename extended_flags<ExtendedEnum>::type>
+inline constexpr auto &operator|=(flags<extended_flags_t<ExtendedEnum>> &a, ExtendedEnum b) {
+	return (a |= details::extended_flags_convert(b));
+}
+
+template <typename ExtendedEnum,
+	typename = typename extended_flags<ExtendedEnum>::type>
+inline constexpr auto &operator^=(flags<extended_flags_t<ExtendedEnum>> &a, ExtendedEnum b) {
+	return (a ^= details::extended_flags_convert(b));
+}
+
+template <typename ExtendedEnum,
+	typename = typename extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator==(flags<extended_flags_t<ExtendedEnum>> a, ExtendedEnum b) {
+	return a == details::extended_flags_convert(b);
+}
+
+template <typename ExtendedEnum,
+	typename = typename extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator==(ExtendedEnum a, flags<extended_flags_t<ExtendedEnum>> b) {
+	return (b == a);
+}
+
+template <typename ExtendedEnum,
+	typename = typename extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator!=(flags<extended_flags_t<ExtendedEnum>> a, ExtendedEnum b) {
+	return !(a == b);
+}
+
+template <typename ExtendedEnum,
+	typename = typename extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator!=(ExtendedEnum a, flags<extended_flags_t<ExtendedEnum>> b) {
+	return !(a == b);
+}
+
+template <typename ExtendedEnum,
+	typename = typename extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator<(flags<extended_flags_t<ExtendedEnum>> a, ExtendedEnum b) {
+	return a < details::extended_flags_convert(b);
+}
+
+template <typename ExtendedEnum,
+	typename = typename extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator<(ExtendedEnum a, flags<extended_flags_t<ExtendedEnum>> b) {
+	return details::extended_flags_convert(a) < b;
+}
+
+template <typename ExtendedEnum,
+	typename = typename extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator>(flags<extended_flags_t<ExtendedEnum>> a, ExtendedEnum b) {
+	return (b < a);
+}
+
+template <typename ExtendedEnum,
+	typename = typename extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator>(ExtendedEnum a, flags<extended_flags_t<ExtendedEnum>> b) {
+	return (b < a);
+}
+
+template <typename ExtendedEnum,
+	typename = typename extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator<=(flags<extended_flags_t<ExtendedEnum>> a, ExtendedEnum b) {
+	return !(b < a);
+}
+
+template <typename ExtendedEnum,
+	typename = typename extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator<=(ExtendedEnum a, flags<extended_flags_t<ExtendedEnum>> b) {
+	return !(b < a);
+}
+
+template <typename ExtendedEnum,
+	typename = typename extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator>=(flags<extended_flags_t<ExtendedEnum>> a, ExtendedEnum b) {
+	return !(a < b);
+}
+
+template <typename ExtendedEnum,
+	typename = typename extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator>=(ExtendedEnum a, flags<extended_flags_t<ExtendedEnum>> b) {
+	return !(a < b);
+}
+
+} // namespace base
+
+#undef FLAGS_CONSTEXPR
+
+template <typename Enum,
+	typename = std::enable_if_t<std::is_enum<Enum>::value>,
+	typename = std::enable_if_t<is_flag_type(Enum{})>>
+inline constexpr auto operator!(Enum a) noexcept {
+	return !base::make_flags(a);
+}
+
+template <typename Enum,
+	typename = std::enable_if_t<std::is_enum<Enum>::value>,
+	typename = std::enable_if_t<is_flag_type(Enum{})>>
+inline constexpr auto operator~(Enum a) noexcept {
+	return ~base::make_flags(a);
+}
+
+template <typename Enum,
+	typename = std::enable_if_t<std::is_enum<Enum>::value>,
+	typename = std::enable_if_t<is_flag_type(Enum{})>>
+inline constexpr auto operator|(Enum a, Enum b) noexcept {
+	return base::make_flags(a) | b;
+}
+
+template <typename Enum,
+	typename = std::enable_if_t<std::is_enum<Enum>::value>,
+	typename = std::enable_if_t<is_flag_type(Enum{})>>
+inline constexpr auto operator|(Enum a, base::details::flags_zero_helper) noexcept {
+	return base::make_flags(a);
+}
+
+template <typename Enum,
+	typename = std::enable_if_t<std::is_enum<Enum>::value>,
+	typename = std::enable_if_t<is_flag_type(Enum{})>>
+inline constexpr auto operator|(base::details::flags_zero_helper, Enum b) noexcept {
+	return base::make_flags(b);
+}
+
+template <typename ExtendedEnum,
+	typename = typename base::extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator|(ExtendedEnum a, ExtendedEnum b) {
+	return base::details::extended_flags_convert(a) | b;
+}
+
+template <typename ExtendedEnum,
+	typename = typename base::extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator|(ExtendedEnum a, typename base::extended_flags<ExtendedEnum>::type b) {
+	return base::details::extended_flags_convert(a) | b;
+}
+
+template <typename ExtendedEnum,
+	typename = typename base::extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator|(typename base::extended_flags<ExtendedEnum>::type a, ExtendedEnum b) {
+	return b | a;
+}
+
+template <typename ExtendedEnum,
+	typename = typename base::extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator|(base::details::flags_zero_helper, ExtendedEnum b) {
+	return 0 | base::details::extended_flag_convert(b);
+}
+
+template <typename ExtendedEnum,
+	typename = typename base::extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator|(ExtendedEnum a, base::details::flags_zero_helper) {
+	return base::details::extended_flag_convert(a) | 0;
+}
+
+template <typename ExtendedEnum,
+	typename = typename base::extended_flags<ExtendedEnum>::type>
+inline constexpr auto operator~(ExtendedEnum b) {
+	return ~base::details::extended_flags_convert(b);
+}
diff --git a/Telegram/SourceFiles/base/flags_tests.cpp b/Telegram/SourceFiles/base/flags_tests.cpp
new file mode 100644
index 0000000000..f2da24d53b
--- /dev/null
+++ b/Telegram/SourceFiles/base/flags_tests.cpp
@@ -0,0 +1,142 @@
+/*
+This file is part of Telegram Desktop,
+the official desktop version of Telegram messaging app, see https://telegram.org
+
+Telegram Desktop is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+It is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+In addition, as a special exception, the copyright holders give permission
+to link the code of portions of this program with the OpenSSL library.
+
+Full license: https://github.com/telegramdesktop/tdesktop/blob/master/LICENSE
+Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
+*/
+#include "catch.hpp"
+
+#include "base/flags.h"
+
+namespace MethodNamespace {
+
+template <typename Enum>
+void TestFlags(Enum a, Enum b, Enum c) {
+	auto abc = a | b;
+	abc |= c;
+	auto test = abc != a;
+	CHECK(abc != a);
+	CHECK(abc != (a | b));
+	CHECK((abc & a) == a);
+	CHECK((abc & b) == b);
+	CHECK((abc & c) == c);
+	CHECK((abc & ~a) == (b | c));
+	CHECK((abc & ~(b | c)) == a);
+	CHECK((abc ^ a) == (abc & ~a));
+
+	auto another = a | b;
+	another |= c;
+	CHECK(abc == another);
+	another &= ~b;
+	CHECK(another == (a | c));
+	another ^= a;
+	CHECK(another == c);
+	another = 0;
+	another = nullptr;
+	auto is_zero = ((another & abc) == 0);
+	CHECK(is_zero);
+	CHECK(!(another & abc));
+	auto more = a | another;
+	auto just = a | 0;
+	CHECK(more == just);
+	CHECK(just);
+}
+
+} // namespace MethodNamespace
+
+namespace FlagsNamespace {
+
+enum class Flag : int {
+	one = (1 << 0),
+	two = (1 << 1),
+	three = (1 << 2),
+};
+inline constexpr auto is_flag_type(Flag) { return true; }
+
+class Class {
+public:
+	enum class Public : long {
+		one = (1 << 2),
+		two = (1 << 1),
+		three = (1 << 0),
+	};
+	friend inline constexpr auto is_flag_type(Public) { return true; }
+
+	static void TestPrivate();
+
+private:
+	enum class Private : long {
+		one = (1 << 0),
+		two = (1 << 1),
+		three = (1 << 2),
+	};
+	friend inline constexpr auto is_flag_type(Private) { return true; }
+
+};
+
+void Class::TestPrivate() {
+	MethodNamespace::TestFlags(Private::one, Private::two, Private::three);
+}
+
+} // namespace FlagsNamespace
+
+namespace ExtendedNamespace {
+
+enum class Flag : int {
+	one = (1 << 3),
+	two = (1 << 4),
+	three = (1 << 5),
+};
+
+} // namespace ExtendedNamespace
+
+namespace base {
+
+template<>
+struct extended_flags<ExtendedNamespace::Flag> {
+	using type = FlagsNamespace::Flag;
+};
+
+} // namespace base
+
+TEST_CASE("flags operators on scoped enums", "[flags]") {
+	SECTION("testing non-member flags") {
+		MethodNamespace::TestFlags(
+			FlagsNamespace::Flag::one,
+			FlagsNamespace::Flag::two,
+			FlagsNamespace::Flag::three);
+	}
+	SECTION("testing public member flags") {
+		MethodNamespace::TestFlags(
+			FlagsNamespace::Class::Public::one,
+			FlagsNamespace::Class::Public::two,
+			FlagsNamespace::Class::Public::three);
+	}
+	SECTION("testing private member flags") {
+		FlagsNamespace::Class::TestPrivate();
+	}
+	SECTION("testing extended flags") {
+		MethodNamespace::TestFlags(
+			ExtendedNamespace::Flag::one,
+			ExtendedNamespace::Flag::two,
+			ExtendedNamespace::Flag::three);
+
+		auto onetwo = FlagsNamespace::Flag::one | ExtendedNamespace::Flag::two;
+		auto twoone = ExtendedNamespace::Flag::two | FlagsNamespace::Flag::one;
+		CHECK(onetwo == twoone);
+	}
+}
diff --git a/Telegram/gyp/tests/tests.gyp b/Telegram/gyp/tests/tests.gyp
index 105554be9e..42284ddffb 100644
--- a/Telegram/gyp/tests/tests.gyp
+++ b/Telegram/gyp/tests/tests.gyp
@@ -73,5 +73,14 @@
       '<(src_loc)/base/flat_set.h',
       '<(src_loc)/base/flat_set_tests.cpp',
     ],
+  }, {
+    'target_name': 'tests_flags',
+    'includes': [
+      'common_test.gypi',
+    ],
+    'sources': [
+      '<(src_loc)/base/flags.h',
+      '<(src_loc)/base/flags_tests.cpp',
+    ],
   }],
 }
diff --git a/Telegram/gyp/tests/tests_list.txt b/Telegram/gyp/tests/tests_list.txt
index 6d79c8e1e5..6cb15eda32 100644
--- a/Telegram/gyp/tests/tests_list.txt
+++ b/Telegram/gyp/tests/tests_list.txt
@@ -1,2 +1,3 @@
 tests_flat_map
 tests_flat_set
+tests_flags