Display information about proxy sponsor.

Telegram/Resources/langs/lang.strings

@@ -444,6 +444,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 "lng_proxy_description" = "Your saved proxy list will be here.";
 "lng_proxy_sponsor" = "Proxy sponsor";
 "lng_proxy_sponsor_about" = "This channel is shown by your proxy server.\nTo remove this channel from your chats list,\ndisable the proxy in Telegram Settings.";
+"lng_proxy_sponsor_warning" = "This proxy may display a sponsored channel in your chat list. This doesn't reveal any of your Telegram traffic.";
 
 "lng_settings_blocked_users" = "Blocked users";
 "lng_settings_last_seen_privacy" = "Last seen privacy";

Telegram/SourceFiles/boxes/boxes.style

@@ -781,3 +781,4 @@ proxyDropdownDownPosition: point(-2px, 35px);
 proxyDropdownUpPosition: point(-2px, 20px);
 
 proxyAboutPadding: margins(22px, 7px, 22px, 14px);
+proxyAboutSponsorPadding: margins(22px, 7px, 22px, 0px);

Telegram/SourceFiles/boxes/connection_box.cpp

@@ -155,6 +155,7 @@ private:
 
 	std::shared_ptr<Ui::RadioenumGroup<Type>> _type;
 
+	QPointer<Ui::SlideWrap<>> _aboutSponsored;
 	QPointer<Ui::InputField> _host;
 	QPointer<Ui::PortInput> _port;
 	QPointer<Ui::InputField> _user;
@@ -763,6 +764,16 @@ void ProxyBox::setupTypes() {
 				label),
 			st::proxyEditTypePadding);
 	}
+	_aboutSponsored = _content->add(object_ptr<Ui::SlideWrap<>>(
+		_content,
+		object_ptr<Ui::PaddingWrap<>>(
+			_content,
+			object_ptr<Ui::FlatLabel>(
+				_content,
+				lang(lng_proxy_sponsor_warning),
+				Ui::FlatLabel::InitType::Simple,
+				st::boxDividerLabel),
+			st::proxyAboutSponsorPadding)));
 }
 
 void ProxyBox::setupSocketAddress(const ProxyData &data) {
@@ -875,6 +886,9 @@ void ProxyBox::setupControls(const ProxyData &data) {
 		_mtprotoCredentials->toggle(
 			type == Type::Mtproto,
 			anim::type::instant);
+		_aboutSponsored->toggle(
+			type == Type::Mtproto,
+			anim::type::instant);
 	};
 	_type->setChangedCallback([=](Type type) {
 		handleType(type);
@@ -1046,7 +1060,10 @@ void ProxiesBoxController::ShowApplyConfirmation(
 			lt_server,
 			server,
 			lt_port,
-			QString::number(port));
+			QString::number(port))
+			+ (proxy.type == Type::Mtproto
+				? "\n\n" + lang(lng_proxy_sponsor_warning)
+				: QString());
 		*box = Ui::show(Box<ConfirmBox>(text, lang(lng_sure_enable), [=] {
 			auto &proxies = Global::RefProxiesList();
 			if (ranges::find(proxies, proxy) == end(proxies)) {