Don't change dc after qr request / phone submit.

Telegram/SourceFiles/intro/intro_phone.cpp

@@ -132,7 +132,9 @@ void PhoneWidget::phoneChanged() {
 }
 
 void PhoneWidget::submit() {
-	if (_sentRequest || isHidden()) return;
+	if (_sentRequest || isHidden()) {
+		return;
+	}
 
 	const auto phone = fullNumber();
 	if (!AllowPhoneAttempt(phone)) {
@@ -141,6 +143,8 @@ void PhoneWidget::submit() {
 		return;
 	}
 
+	cancelNearestDcRequest();
+
 	// Check if such account is authorized already.
 	const auto digitsOnly = [](QString value) {
 		return value.replace(QRegularExpression("[^0-9]"), QString());

Telegram/SourceFiles/intro/intro_qr.cpp

@@ -179,6 +179,8 @@ QrWidget::QrWidget(
 	setDescriptionText(rpl::single(QString()));
 	setErrorCentered(true);
 
+	cancelNearestDcRequest();
+
 	account->mtpUpdates(
 	) | rpl::start_with_next([=](const MTPUpdates &updates) {
 		checkForTokenUpdate(updates);

Telegram/SourceFiles/intro/intro_step.cpp

@@ -502,6 +502,10 @@ void Step::setShowTermsCallback(Fn<void()> callback) {
 	_showTermsCallback = std::move(callback);
 }
 
+void Step::setCancelNearestDcCallback(Fn<void()> callback) {
+	_cancelNearestDcCallback = std::move(callback);
+}
+
 void Step::setAcceptTermsCallback(
 		Fn<void(Fn<void()> callback)> callback) {
 	_acceptTermsCallback = std::move(callback);

Telegram/SourceFiles/intro/intro_step.h

@@ -58,8 +58,8 @@ public:
 	void setGoCallback(
 		Fn<void(Step *step, StackAction action, Animate animate)> callback);
 	void setShowResetCallback(Fn<void()> callback);
-	void setShowTermsCallback(
-		Fn<void()> callback);
+	void setShowTermsCallback(Fn<void()> callback);
+	void setCancelNearestDcCallback(Fn<void()> callback);
 	void setAcceptTermsCallback(
 		Fn<void(Fn<void()> callback)> callback);
 
@@ -130,6 +130,9 @@ protected:
 			_acceptTermsCallback(callback);
 		}
 	}
+	void cancelNearestDcRequest() {
+		if (_cancelNearestDcCallback) _cancelNearestDcCallback();
+	}
 
 	virtual int errorTop() const;
 
@@ -176,6 +179,7 @@ private:
 	Fn<void(Step *step, StackAction action, Animate animate)> _goCallback;
 	Fn<void()> _showResetCallback;
 	Fn<void()> _showTermsCallback;
+	Fn<void()> _cancelNearestDcCallback;
 	Fn<void(Fn<void()> callback)> _acceptTermsCallback;
 
 	rpl::variable<QString> _titleText;

Telegram/SourceFiles/intro/intro_widget.cpp

@@ -65,6 +65,8 @@ Widget::Widget(
 		rpl::single(true))) {
 	Core::App().setDefaultFloatPlayerDelegate(floatPlayerDelegate());
 
+	getNearestDC();
+
 	switch (point) {
 	case EnterPoint::Start:
 		appendStep(new StartWidget(this, _account, getData()));
@@ -104,8 +106,6 @@ Widget::Widget(
 
 	_settings->entity()->setClickedCallback([] { App::wnd()->showSettings(); });
 
-	getNearestDC();
-
 	if (_changeLanguage) {
 		_changeLanguage->finishAnimating();
 	}
@@ -378,9 +378,14 @@ void Widget::appendStep(Step *step) {
 	step->setShowResetCallback([=] {
 		showResetButton();
 	});
-	step->setShowTermsCallback([=]() {
+	step->setShowTermsCallback([=] {
 		showTerms();
 	});
+	step->setCancelNearestDcCallback([=] {
+		if (_api) {
+			_api->request(base::take(_nearestDcRequestId)).cancel();
+		}
+	});
 	step->setAcceptTermsCallback([=](Fn<void()> callback) {
 		acceptTerms(callback);
 	});
@@ -519,8 +524,9 @@ void Widget::getNearestDC() {
 	if (!_api) {
 		return;
 	}
-	_api->request(MTPhelp_GetNearestDc(
+	_nearestDcRequestId = _api->request(MTPhelp_GetNearestDc(
 	)).done([=](const MTPNearestDc &result) {
+		_nearestDcRequestId = 0;
 		const auto &nearest = result.c_nearestDc();
 		DEBUG_LOG(("Got nearest dc, country: %1, nearest: %2, this: %3"
 			).arg(qs(nearest.vcountry())

Telegram/SourceFiles/intro/intro_widget.h

@@ -167,6 +167,7 @@ private:
 
 	const not_null<Main::Account*> _account;
 	std::optional<MTP::Sender> _api;
+	mtpRequestId _nearestDcRequestId = 0;
 
 	Ui::Animations::Simple _a_show;
 	bool _showBack = false;

Telegram/SourceFiles/mtproto/mtp_instance.cpp

@@ -417,8 +417,9 @@ void Instance::Private::setGoodProxyDomain(
 }
 
 void Instance::Private::suggestMainDcId(DcId mainDcId) {
-	if (_mainDcIdForced) return;
-	setMainDcId(mainDcId);
+	if (!_mainDcIdForced) {
+		setMainDcId(mainDcId);
+	}
 }
 
 void Instance::Private::setMainDcId(DcId mainDcId) {