Don't push sublists to stack endlessly.

Telegram/SourceFiles/history/view/history_view_sublist_section.cpp

@@ -293,6 +293,10 @@ bool SublistWidget::showInternal(
 	return false;
 }
 
+bool SublistWidget::sameTypeAs(not_null<Window::SectionMemento*> memento) {
+	return dynamic_cast<SublistMemento*>(memento.get()) != nullptr;
+}
+
 void SublistWidget::setInternalState(
 		const QRect &geometry,
 		not_null<SublistMemento*> memento) {

Telegram/SourceFiles/history/view/history_view_sublist_section.h

@@ -58,6 +58,8 @@ public:
 	bool showInternal(
 		not_null<Window::SectionMemento*> memento,
 		const Window::SectionShow &params) override;
+	bool sameTypeAs(not_null<Window::SectionMemento*> memento) override;
+
 	std::shared_ptr<Window::SectionMemento> createMemento() override;
 	bool showMessage(
 		PeerId peerId,

Telegram/SourceFiles/info/saved/info_saved_sublists_widget.cpp

@@ -60,9 +60,12 @@ SublistsWidget::SublistsWidget(
 
 	_list->chosenRow() | rpl::start_with_next([=](Dialogs::ChosenRow row) {
 		if (const auto sublist = row.key.sublist()) {
+			using namespace Window;
+			auto params = SectionShow(SectionShow::Way::Forward);
+			params.dropSameFromStack = true;
 			controller->showSection(
 				std::make_shared<HistoryView::SublistMemento>(sublist),
-				Window::SectionShow::Way::Forward);
+				params);
 		}
 	}, _list->lifetime());
 

Telegram/SourceFiles/mainwidget.cpp

@@ -1379,7 +1379,7 @@ void MainWidget::showHistory(
 
 	if (!back && (way != Way::ClearStack)) {
 		// This may modify the current section, for example remove its contents.
-		saveSectionInStack();
+		saveSectionInStack(params);
 	}
 
 	if (_history->peer()
@@ -1501,13 +1501,23 @@ Ui::ChatTheme *MainWidget::customChatTheme() const {
 	return _history->customChatTheme();
 }
 
-void MainWidget::saveSectionInStack() {
+bool MainWidget::saveSectionInStack(
+		const SectionShow &params,
+		Window::SectionWidget *newMainSection) {
 	if (_mainSection) {
 		if (auto memento = _mainSection->createMemento()) {
+			if (params.dropSameFromStack
+				&& newMainSection
+				&& newMainSection->sameTypeAs(memento.get())) {
+				// When choosing saved sublist we want to save the original
+				// "Saved Messages" in the stack, but don't save every
+				// sublist in a new stack entry when clicking them through.
+				return false;
+			}
 			_stack.push_back(std::make_unique<StackItemSection>(
 				std::move(memento)));
 		} else {
-			return;
+			return false;
 		}
 	} else if (const auto history = _history->history()) {
 		_stack.push_back(std::make_unique<StackItemHistory>(
@@ -1515,7 +1525,7 @@ void MainWidget::saveSectionInStack() {
 			_history->msgId(),
 			_history->replyReturns()));
 	} else {
-		return;
+		return false;
 	}
 	const auto raw = _stack.back().get();
 	raw->setThirdSectionWeak(_thirdSection.data());
@@ -1528,6 +1538,7 @@ void MainWidget::saveSectionInStack() {
 			}
 		}
 	}, raw->lifetime());
+	return true;
 }
 
 void MainWidget::showSection(
@@ -1730,7 +1741,11 @@ void MainWidget::showNewSection(
 
 	if (saveInStack) {
 		// This may modify the current section, for example remove its contents.
-		saveSectionInStack();
+		if (!saveSectionInStack(params, newMainSection)) {
+			saveInStack = false;
+			animatedShow = false;
+			animationParams = Window::SectionSlideParams();
+		}
 	}
 	auto &settingSection = newThirdSection
 		? _thirdSection

Telegram/SourceFiles/mainwidget.h

@@ -286,7 +286,9 @@ private:
 	Window::SectionSlideParams prepareHistoryAnimation(PeerId historyPeerId);
 	Window::SectionSlideParams prepareDialogsAnimation();
 
-	void saveSectionInStack();
+	bool saveSectionInStack(
+		const SectionShow &params,
+		Window::SectionWidget *newMainSection = nullptr);
 
 	int getMainSectionTop() const;
 	int getThirdSectionTop() const;

Telegram/SourceFiles/window/section_widget.h

@@ -138,6 +138,9 @@ public:
 	virtual bool showInternal(
 		not_null<SectionMemento*> memento,
 		const SectionShow &params) = 0;
+	virtual bool sameTypeAs(not_null<SectionMemento*> memento) {
+		return false;
+	}
 
 	virtual bool showMessage(
 			PeerId peerId,

Telegram/SourceFiles/window/window_session_controller.h

@@ -162,6 +162,7 @@ struct SectionShow {
 	bool childColumn = false;
 	bool forbidLayer = false;
 	bool reapplyLocalDraft = false;
+	bool dropSameFromStack = false;
 	Origin origin;
 
 };