From 0a9db8533b34a665c52b1eebe64d5f1992b8a0c1 Mon Sep 17 00:00:00 2001
From: John Preston <johnprestonmail@gmail.com>
Date: Sat, 24 Jun 2017 20:05:32 +0300
Subject: [PATCH] Save admin log state to memento and restore it.

---
 .../history/history_admin_log_inner.cpp       | 65 ++++++++++---------
 .../history/history_admin_log_inner.h         |  9 ++-
 .../history/history_admin_log_section.cpp     | 18 ++---
 .../history/history_admin_log_section.h       | 44 +++++++++++--
 Telegram/SourceFiles/mainwidget.cpp           | 38 ++++++-----
 Telegram/SourceFiles/mainwidget.h             |  4 +-
 .../profile/profile_block_widget.h            |  4 +-
 .../profile/profile_common_groups_section.cpp | 18 ++---
 .../profile/profile_common_groups_section.h   | 16 ++---
 .../profile/profile_inner_widget.cpp          |  4 +-
 .../profile/profile_inner_widget.h            |  4 +-
 .../profile/profile_section_memento.cpp       |  2 +-
 .../profile/profile_section_memento.h         |  2 +-
 .../SourceFiles/profile/profile_widget.cpp    | 12 ++--
 Telegram/SourceFiles/profile/profile_widget.h | 10 +--
 Telegram/SourceFiles/window/section_memento.h |  2 +-
 Telegram/SourceFiles/window/section_widget.h  |  8 ++-
 17 files changed, 152 insertions(+), 108 deletions(-)

diff --git a/Telegram/SourceFiles/history/history_admin_log_inner.cpp b/Telegram/SourceFiles/history/history_admin_log_inner.cpp
index 865cc53156..d38b33e60a 100644
--- a/Telegram/SourceFiles/history/history_admin_log_inner.cpp
+++ b/Telegram/SourceFiles/history/history_admin_log_inner.cpp
@@ -335,35 +335,22 @@ QPoint InnerWidget::tooltipPos() const {
 	return _mousePosition;
 }
 
-void InnerWidget::saveState(gsl::not_null<SectionMemento*> memento) const {
-	//if (auto count = _items.size()) {
-	//	QList<gsl::not_null<PeerData*>> groups;
-	//	groups.reserve(count);
-	//	for_const (auto item, _items) {
-	//		groups.push_back(item->peer);
-	//	}
-	//	memento->setCommonGroups(groups);
-	//}
+void InnerWidget::saveState(gsl::not_null<SectionMemento*> memento) {
+	memento->setItems(std::move(_items), std::move(_itemsByIds), _upLoaded, _downLoaded);
+	memento->setIdManager(std::move(_idManager));
+	_upLoaded = _downLoaded = true; // Don't load or handle anything anymore.
 }
 
-void InnerWidget::restoreState(gsl::not_null<const SectionMemento*> memento) {
-	//auto list = memento->getCommonGroups();
-	//_allLoaded = false;
-	//if (!list.empty()) {
-	//	showInitial(list);
-	//}
+void InnerWidget::restoreState(gsl::not_null<SectionMemento*> memento) {
+	_items = memento->takeItems();
+	_itemsByIds = memento->takeItemsByIds();
+	_idManager = memento->takeIdManager();
+	_upLoaded = memento->upLoaded();
+	_downLoaded = memento->downLoaded();
+	updateMinMaxIds();
+	updateSize();
 }
 
-//void InnerWidget::showInitial(const QList<PeerData*> &list) {
-//	for_const (auto group, list) {
-//		if (auto item = computeItem(group)) {
-//			_items.push_back(item);
-//		}
-//		_preloadGroupId = group->bareId();
-//	}
-//	updateSize();
-//}
-
 void InnerWidget::preloadMore(Direction direction) {
 	auto &requestId = (direction == Direction::Up) ? _preloadUpRequestId : _preloadDownRequestId;
 	auto &loadedFlag = (direction == Direction::Up) ? _upLoaded : _downLoaded;
@@ -394,6 +381,10 @@ void InnerWidget::preloadMore(Direction direction) {
 		auto &results = result.c_channels_adminLogResults();
 		App::feedUsers(results.vusers);
 		App::feedChats(results.vchats);
+
+		if (loadedFlag) {
+			return;
+		}
 		auto &events = results.vevents.v;
 		if (!events.empty()) {
 			auto oldItemsCount = _items.size();
@@ -401,10 +392,14 @@ void InnerWidget::preloadMore(Direction direction) {
 			for_const (auto &event, events) {
 				t_assert(event.type() == mtpc_channelAdminLogEvent);
 				auto &data = event.c_channelAdminLogEvent();
+				if (_itemsByIds.find(data.vid.v) != _itemsByIds.cend()) {
+					continue;
+				}
+
 				auto count = 0;
 				GenerateItems(_history, _idManager, data, [this, id = data.vid.v, &count](HistoryItemOwned item) {
-					_items.push_back(std::move(item));
 					_itemsByIds.emplace(id, item.get());
+					_items.push_back(std::move(item));
 					++count;
 				});
 				if (count > 1) {
@@ -433,11 +428,7 @@ void InnerWidget::preloadMore(Direction direction) {
 						}
 					}
 				}
-				_maxId = (--_itemsByIds.end())->first;
-				_minId = _itemsByIds.begin()->first;
-				if (_minId == 1) {
-					_upLoaded = true;
-				}
+				updateMinMaxIds();
 				itemsAdded(direction);
 			}
 		} else {
@@ -449,6 +440,18 @@ void InnerWidget::preloadMore(Direction direction) {
 	}).send();
 }
 
+void InnerWidget::updateMinMaxIds() {
+	if (_itemsByIds.empty()) {
+		_maxId = _minId = 0;
+	} else {
+		_maxId = (--_itemsByIds.end())->first;
+		_minId = _itemsByIds.begin()->first;
+		if (_minId == 1) {
+			_upLoaded = true;
+		}
+	}
+}
+
 void InnerWidget::itemsAdded(Direction direction) {
 	updateSize();
 }
diff --git a/Telegram/SourceFiles/history/history_admin_log_inner.h b/Telegram/SourceFiles/history/history_admin_log_inner.h
index 1eb839d920..a64bdf504c 100644
--- a/Telegram/SourceFiles/history/history_admin_log_inner.h
+++ b/Telegram/SourceFiles/history/history_admin_log_inner.h
@@ -76,8 +76,8 @@ public:
 		return TWidget::resizeToWidth(newWidth);
 	}
 
-	void saveState(gsl::not_null<SectionMemento*> memento) const;
-	void restoreState(gsl::not_null<const SectionMemento*> memento);
+	void saveState(gsl::not_null<SectionMemento*> memento);
+	void restoreState(gsl::not_null<SectionMemento*> memento);
 	void setCancelledCallback(base::lambda<void()> callback) {
 		_cancelledCallback = std::move(callback);
 	}
@@ -151,6 +151,7 @@ private:
 	void preloadMore(Direction direction);
 	void itemsAdded(Direction direction);
 	void updateSize();
+	void updateMinMaxIds();
 	void paintEmpty(Painter &p);
 
 	void toggleScrollDateShown();
@@ -213,7 +214,9 @@ private:
 	uint64 _minId = 0;
 	mtpRequestId _preloadUpRequestId = 0;
 	mtpRequestId _preloadDownRequestId = 0;
-	bool _upLoaded = false;
+
+	// Don't load anything until the memento was read.
+	bool _upLoaded = true;
 	bool _downLoaded = true;
 
 	MouseAction _mouseAction = MouseAction::None;
diff --git a/Telegram/SourceFiles/history/history_admin_log_section.cpp b/Telegram/SourceFiles/history/history_admin_log_section.cpp
index 78c17e91b6..35bc07232a 100644
--- a/Telegram/SourceFiles/history/history_admin_log_section.cpp
+++ b/Telegram/SourceFiles/history/history_admin_log_section.cpp
@@ -61,7 +61,7 @@ private:
 
 };
 
-object_ptr<Window::SectionWidget> SectionMemento::createWidget(QWidget *parent, gsl::not_null<Window::Controller*> controller, const QRect &geometry) const {
+object_ptr<Window::SectionWidget> SectionMemento::createWidget(QWidget *parent, gsl::not_null<Window::Controller*> controller, const QRect &geometry) {
 	auto result = object_ptr<Widget>(parent, controller, _channel);
 	result->setInternalState(geometry, this);
 	return std::move(result);
@@ -168,34 +168,34 @@ void Widget::doSetInnerFocus() {
 	_inner->setFocus();
 }
 
-bool Widget::showInternal(const Window::SectionMemento *memento) {
-	if (auto profileMemento = dynamic_cast<const SectionMemento*>(memento)) {
-		if (profileMemento->getChannel() == channel()) {
-			restoreState(profileMemento);
+bool Widget::showInternal(gsl::not_null<Window::SectionMemento*> memento) {
+	if (auto logMemento = dynamic_cast<SectionMemento*>(memento.get())) {
+		if (logMemento->getChannel() == channel()) {
+			restoreState(logMemento);
 			return true;
 		}
 	}
 	return false;
 }
 
-void Widget::setInternalState(const QRect &geometry, gsl::not_null<const SectionMemento*> memento) {
+void Widget::setInternalState(const QRect &geometry, gsl::not_null<SectionMemento*> memento) {
 	setGeometry(geometry);
 	myEnsureResized(this);
 	restoreState(memento);
 }
 
-std::unique_ptr<Window::SectionMemento> Widget::createMemento() const {
+std::unique_ptr<Window::SectionMemento> Widget::createMemento() {
 	auto result = std::make_unique<SectionMemento>(channel());
 	saveState(result.get());
 	return std::move(result);
 }
 
-void Widget::saveState(gsl::not_null<SectionMemento*> memento) const {
+void Widget::saveState(gsl::not_null<SectionMemento*> memento) {
 	memento->setScrollTop(_scroll->scrollTop());
 	_inner->saveState(memento);
 }
 
-void Widget::restoreState(gsl::not_null<const SectionMemento*> memento) {
+void Widget::restoreState(gsl::not_null<SectionMemento*> memento) {
 	_inner->restoreState(memento);
 	auto scrollTop = memento->getScrollTop();
 	_scroll->scrollToY(scrollTop);
diff --git a/Telegram/SourceFiles/history/history_admin_log_section.h b/Telegram/SourceFiles/history/history_admin_log_section.h
index a0188ebecc..6a8c29663a 100644
--- a/Telegram/SourceFiles/history/history_admin_log_section.h
+++ b/Telegram/SourceFiles/history/history_admin_log_section.h
@@ -22,6 +22,8 @@ Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
 
 #include "window/section_widget.h"
 #include "window/section_memento.h"
+#include "history/history_admin_log_item.h"
+#include "history/history_admin_log_inner.h"
 
 namespace Notify {
 struct PeerUpdate;
@@ -58,10 +60,10 @@ public:
 
 	QPixmap grabForShowAnimation(const Window::SectionSlideParams &params) override;
 
-	bool showInternal(const Window::SectionMemento *memento) override;
-	std::unique_ptr<Window::SectionMemento> createMemento() const override;
+	bool showInternal(gsl::not_null<Window::SectionMemento*> memento) override;
+	std::unique_ptr<Window::SectionMemento> createMemento() override;
 
-	void setInternalState(const QRect &geometry, gsl::not_null<const SectionMemento*> memento);
+	void setInternalState(const QRect &geometry, gsl::not_null<SectionMemento*> memento);
 
 	// Float player interface.
 	bool wheelEventFromFloatPlayer(QEvent *e, Window::Column myColumn, Window::Column playerColumn) override;
@@ -81,8 +83,8 @@ protected:
 private:
 	void onScroll();
 	void updateAdaptiveLayout();
-	void saveState(gsl::not_null<SectionMemento*> memento) const;
-	void restoreState(gsl::not_null<const SectionMemento*> memento);
+	void saveState(gsl::not_null<SectionMemento*> memento);
+	void restoreState(gsl::not_null<SectionMemento*> memento);
 
 	object_ptr<Ui::ScrollArea> _scroll;
 	QPointer<InnerWidget> _inner;
@@ -97,7 +99,7 @@ public:
 	SectionMemento(gsl::not_null<ChannelData*> channel) : _channel(channel) {
 	}
 
-	object_ptr<Window::SectionWidget> createWidget(QWidget *parent, gsl::not_null<Window::Controller*> controller, const QRect &geometry) const override;
+	object_ptr<Window::SectionWidget> createWidget(QWidget *parent, gsl::not_null<Window::Controller*> controller, const QRect &geometry) override;
 
 	gsl::not_null<ChannelData*> getChannel() const {
 		return _channel;
@@ -109,9 +111,39 @@ public:
 		return _scrollTop;
 	}
 
+	void setItems(std::vector<HistoryItemOwned> &&items, std::map<uint64, HistoryItem*> &&itemsByIds, bool upLoaded, bool downLoaded) {
+		_items = std::move(items);
+		_itemsByIds = std::move(itemsByIds);
+		_upLoaded = upLoaded;
+		_downLoaded = downLoaded;
+	}
+	void setIdManager(LocalIdManager &&manager) {
+		_idManager = std::move(manager);
+	}
+	std::vector<HistoryItemOwned> takeItems() {
+		return std::move(_items);
+	}
+	std::map<uint64, HistoryItem*> takeItemsByIds() {
+		return std::move(_itemsByIds);
+	}
+	LocalIdManager takeIdManager() {
+		return std::move(_idManager);
+	}
+	bool upLoaded() const {
+		return _upLoaded;
+	}
+	bool downLoaded() const {
+		return _downLoaded;
+	}
+
 private:
 	gsl::not_null<ChannelData*> _channel;
 	int _scrollTop = 0;
+	std::vector<HistoryItemOwned> _items;
+	std::map<uint64, HistoryItem*> _itemsByIds;
+	bool _upLoaded = false;
+	bool _downLoaded = true;
+	LocalIdManager _idManager;
 
 };
 
diff --git a/Telegram/SourceFiles/mainwidget.cpp b/Telegram/SourceFiles/mainwidget.cpp
index 21e972996b..823686d4bd 100644
--- a/Telegram/SourceFiles/mainwidget.cpp
+++ b/Telegram/SourceFiles/mainwidget.cpp
@@ -2517,15 +2517,6 @@ void MainWidget::ui_showPeerHistory(quint64 peerId, qint32 showAtMsgId, Ui::Show
 		}
 	}
 
-	dlgUpdated();
-	if (back || (way == Ui::ShowWay::ClearStack)) {
-		_peerInStack = nullptr;
-		_msgIdInStack = 0;
-	} else {
-		saveSectionInStack();
-	}
-	dlgUpdated();
-
 	auto wasActivePeer = activePeer();
 
 	Ui::hideSettingsAndLayer();
@@ -2556,6 +2547,16 @@ void MainWidget::ui_showPeerHistory(quint64 peerId, qint32 showAtMsgId, Ui::Show
 
 	auto animationParams = animatedShow() ? prepareHistoryAnimation(peerId) : Window::SectionSlideParams();
 
+	dlgUpdated();
+	if (back || (way == Ui::ShowWay::ClearStack)) {
+		_peerInStack = nullptr;
+		_msgIdInStack = 0;
+	} else {
+		// This may modify the current section, for example remove its contents.
+		saveSectionInStack();
+	}
+	dlgUpdated();
+
 	if (_history->peer() && _history->peer()->id != peerId && way != Ui::ShowWay::Forward) {
 		clearBotStartToken(_history->peer());
 	}
@@ -2708,11 +2709,11 @@ void MainWidget::showMediaOverview(PeerData *peer, MediaOverviewType type, bool
 		return false;
 	};
 	auto animationParams = animatedShow() ? prepareOverviewAnimation() : Window::SectionSlideParams();
+	setFocus(); // otherwise dialogs widget could be focused.
+
 	if (!back) {
 		saveSectionInStack();
 	}
-
-	setFocus(); // otherwise dialogs widget could be focused.
 	if (_overview) {
 		_overview->hide();
 		_overview->clear();
@@ -2751,12 +2752,12 @@ void MainWidget::showMediaOverview(PeerData *peer, MediaOverviewType type, bool
 	orderWidgets();
 }
 
-void MainWidget::showWideSection(const Window::SectionMemento &memento) {
+void MainWidget::showWideSection(Window::SectionMemento &&memento) {
 	Ui::hideSettingsAndLayer();
 	if (_wideSection && _wideSection->showInternal(&memento)) {
 		return;
 	}
-	showNewWideSection(&memento, false, true);
+	showNewWideSection(std::move(memento), false, true);
 }
 
 Window::SectionSlideParams MainWidget::prepareShowAnimation(bool willHaveTopBarShadow, bool willHaveTabbedSection) {
@@ -2856,7 +2857,7 @@ Window::SectionSlideParams MainWidget::prepareDialogsAnimation() {
 	return prepareShowAnimation(false, false);
 }
 
-void MainWidget::showNewWideSection(const Window::SectionMemento *memento, bool back, bool saveInStack) {
+void MainWidget::showNewWideSection(Window::SectionMemento &&memento, bool back, bool saveInStack) {
 	QPixmap animCache;
 
 	_controller->dialogsListFocused().set(false, true);
@@ -2864,7 +2865,7 @@ void MainWidget::showNewWideSection(const Window::SectionMemento *memento, bool
 
 	auto sectionTop = getSectionTop();
 	auto newWideGeometry = QRect(_history->x(), sectionTop, _history->width(), height() - sectionTop);
-	auto newWideSection = memento->createWidget(this, _controller, newWideGeometry);
+	auto newWideSection = memento.createWidget(this, _controller, newWideGeometry);
 	auto animatedShow = [this] {
 		if (_a_show.animating() || App::passcoded()) {
 			return false;
@@ -2876,11 +2877,12 @@ void MainWidget::showNewWideSection(const Window::SectionMemento *memento, bool
 	};
 	auto animationParams = animatedShow() ? prepareWideSectionAnimation(newWideSection) : Window::SectionSlideParams();
 
+	setFocus(); // otherwise dialogs widget could be focused.
+
 	if (saveInStack) {
+		// This may modify the current section, for example remove its contents.
 		saveSectionInStack();
 	}
-
-	setFocus(); // otherwise dialogs widget could be focused.
 	if (_overview) {
 		_overview->hide();
 		_overview->clear();
@@ -2949,7 +2951,7 @@ void MainWidget::showBackFromStack() {
 		_history->setReplyReturns(historyItem->peer->id, historyItem->replyReturns);
 	} else if (item->type() == SectionStackItem) {
 		auto sectionItem = static_cast<StackItemSection*>(item.get());
-		showNewWideSection(sectionItem->memento(), true, false);
+		showNewWideSection(std::move(*sectionItem->memento()), true, false);
 	} else if (item->type() == OverviewStackItem) {
 		auto overviewItem = static_cast<StackItemOverview*>(item.get());
 		showMediaOverview(overviewItem->peer, overviewItem->mediaType, true, overviewItem->lastScrollTop);
diff --git a/Telegram/SourceFiles/mainwidget.h b/Telegram/SourceFiles/mainwidget.h
index e594fc4998..b5cfcbb927 100644
--- a/Telegram/SourceFiles/mainwidget.h
+++ b/Telegram/SourceFiles/mainwidget.h
@@ -215,7 +215,7 @@ public:
 	int backgroundFromY() const;
 	PeerData *overviewPeer();
 	bool showMediaTypeSwitch() const;
-	void showWideSection(const Window::SectionMemento &memento);
+	void showWideSection(Window::SectionMemento &&memento);
 	void showMediaOverview(PeerData *peer, MediaOverviewType type, bool back = false, int32 lastScrollTop = -1);
 	bool stackIsEmpty() const;
 	void showBackFromStack();
@@ -521,7 +521,7 @@ private:
 	void mediaOverviewUpdated(const Notify::PeerUpdate &update);
 
 	Window::SectionSlideParams prepareShowAnimation(bool willHaveTopBarShadow, bool willHaveTabbedSection);
-	void showNewWideSection(const Window::SectionMemento *memento, bool back, bool saveInStack);
+	void showNewWideSection(Window::SectionMemento &&memento, bool back, bool saveInStack);
 
 	// All this methods use the prepareShowAnimation().
 	Window::SectionSlideParams prepareWideSectionAnimation(Window::SectionWidget *section);
diff --git a/Telegram/SourceFiles/profile/profile_block_widget.h b/Telegram/SourceFiles/profile/profile_block_widget.h
index fc4c451e7b..0e73317f9b 100644
--- a/Telegram/SourceFiles/profile/profile_block_widget.h
+++ b/Telegram/SourceFiles/profile/profile_block_widget.h
@@ -35,9 +35,9 @@ public:
 	virtual void showFinished() {
 	}
 
-	virtual void saveState(SectionMemento *memento) const {
+	virtual void saveState(gsl::not_null<SectionMemento*> memento) {
 	}
-	virtual void restoreState(const SectionMemento *memento) {
+	virtual void restoreState(gsl::not_null<SectionMemento*> memento) {
 	}
 
 protected:
diff --git a/Telegram/SourceFiles/profile/profile_common_groups_section.cpp b/Telegram/SourceFiles/profile/profile_common_groups_section.cpp
index 26835862b4..77b25cc2ae 100644
--- a/Telegram/SourceFiles/profile/profile_common_groups_section.cpp
+++ b/Telegram/SourceFiles/profile/profile_common_groups_section.cpp
@@ -42,7 +42,7 @@ constexpr int kCommonGroupsPerPage = 40;
 
 } // namespace
 
-object_ptr<Window::SectionWidget> SectionMemento::createWidget(QWidget *parent, gsl::not_null<Window::Controller*> controller, const QRect &geometry) const {
+object_ptr<Window::SectionWidget> SectionMemento::createWidget(QWidget *parent, gsl::not_null<Window::Controller*> controller, const QRect &geometry) {
 	auto result = object_ptr<Widget>(parent, controller, _user);
 	result->setInternalState(geometry, this);
 	return std::move(result);
@@ -118,7 +118,7 @@ void InnerWidget::checkPreloadMore() {
 	}
 }
 
-void InnerWidget::saveState(SectionMemento *memento) const {
+void InnerWidget::saveState(gsl::not_null<SectionMemento*> memento) {
 	if (auto count = _items.size()) {
 		QList<gsl::not_null<PeerData*>> groups;
 		groups.reserve(count);
@@ -129,7 +129,7 @@ void InnerWidget::saveState(SectionMemento *memento) const {
 	}
 }
 
-void InnerWidget::restoreState(const SectionMemento *memento) {
+void InnerWidget::restoreState(gsl::not_null<SectionMemento*> memento) {
 	auto list = memento->getCommonGroups();
 	_allLoaded = false;
 	if (!list.empty()) {
@@ -374,8 +374,8 @@ void Widget::doSetInnerFocus() {
 	_inner->setFocus();
 }
 
-bool Widget::showInternal(const Window::SectionMemento *memento) {
-	if (auto profileMemento = dynamic_cast<const SectionMemento*>(memento)) {
+bool Widget::showInternal(gsl::not_null<Window::SectionMemento*> memento) {
+	if (auto profileMemento = dynamic_cast<SectionMemento*>(memento.get())) {
 		if (profileMemento->getUser() == user()) {
 			restoreState(profileMemento);
 			return true;
@@ -384,24 +384,24 @@ bool Widget::showInternal(const Window::SectionMemento *memento) {
 	return false;
 }
 
-void Widget::setInternalState(const QRect &geometry, const SectionMemento *memento) {
+void Widget::setInternalState(const QRect &geometry, gsl::not_null<SectionMemento*> memento) {
 	setGeometry(geometry);
 	myEnsureResized(this);
 	restoreState(memento);
 }
 
-std::unique_ptr<Window::SectionMemento> Widget::createMemento() const {
+std::unique_ptr<Window::SectionMemento> Widget::createMemento() {
 	auto result = std::make_unique<SectionMemento>(user());
 	saveState(result.get());
 	return std::move(result);
 }
 
-void Widget::saveState(SectionMemento *memento) const {
+void Widget::saveState(gsl::not_null<SectionMemento*> memento) {
 	memento->setScrollTop(_scroll->scrollTop());
 	_inner->saveState(memento);
 }
 
-void Widget::restoreState(const SectionMemento *memento) {
+void Widget::restoreState(gsl::not_null<SectionMemento*> memento) {
 	_inner->restoreState(memento);
 	auto scrollTop = memento->getScrollTop();
 	_scroll->scrollToY(scrollTop);
diff --git a/Telegram/SourceFiles/profile/profile_common_groups_section.h b/Telegram/SourceFiles/profile/profile_common_groups_section.h
index 6eea2da6a0..808990dafa 100644
--- a/Telegram/SourceFiles/profile/profile_common_groups_section.h
+++ b/Telegram/SourceFiles/profile/profile_common_groups_section.h
@@ -43,7 +43,7 @@ public:
 	SectionMemento(gsl::not_null<UserData*> user) : _user(user) {
 	}
 
-	object_ptr<Window::SectionWidget> createWidget(QWidget *parent, gsl::not_null<Window::Controller*> controller, const QRect &geometry) const override;
+	object_ptr<Window::SectionWidget> createWidget(QWidget *parent, gsl::not_null<Window::Controller*> controller, const QRect &geometry) override;
 
 	gsl::not_null<UserData*> getUser() const {
 		return _user;
@@ -110,8 +110,8 @@ public:
 		return TWidget::resizeToWidth(newWidth);
 	}
 
-	void saveState(SectionMemento *memento) const;
-	void restoreState(const SectionMemento *memento);
+	void saveState(gsl::not_null<SectionMemento*> memento);
+	void restoreState(gsl::not_null<SectionMemento*> memento);
 
 	~InnerWidget();
 
@@ -184,10 +184,10 @@ public:
 
 	QPixmap grabForShowAnimation(const Window::SectionSlideParams &params) override;
 
-	bool showInternal(const Window::SectionMemento *memento) override;
-	std::unique_ptr<Window::SectionMemento> createMemento() const override;
+	bool showInternal(gsl::not_null<Window::SectionMemento*> memento) override;
+	std::unique_ptr<Window::SectionMemento> createMemento() override;
 
-	void setInternalState(const QRect &geometry, const SectionMemento *memento);
+	void setInternalState(const QRect &geometry, gsl::not_null<SectionMemento*> memento);
 
 	// Float player interface.
 	bool wheelEventFromFloatPlayer(QEvent *e, Window::Column myColumn, Window::Column playerColumn) override;
@@ -205,8 +205,8 @@ private slots:
 
 private:
 	void updateAdaptiveLayout();
-	void saveState(SectionMemento *memento) const;
-	void restoreState(const SectionMemento *memento);
+	void saveState(gsl::not_null<SectionMemento*> memento);
+	void restoreState(gsl::not_null<SectionMemento*> memento);
 
 	object_ptr<Ui::ScrollArea> _scroll;
 	QPointer<InnerWidget> _inner;
diff --git a/Telegram/SourceFiles/profile/profile_inner_widget.cpp b/Telegram/SourceFiles/profile/profile_inner_widget.cpp
index a54323babd..2c7a187c5d 100644
--- a/Telegram/SourceFiles/profile/profile_inner_widget.cpp
+++ b/Telegram/SourceFiles/profile/profile_inner_widget.cpp
@@ -89,13 +89,13 @@ bool InnerWidget::shareContactButtonShown() const {
 	return _cover->shareContactButtonShown();
 }
 
-void InnerWidget::saveState(SectionMemento *memento) const {
+void InnerWidget::saveState(gsl::not_null<SectionMemento*> memento) {
 	for_const (auto &blockData, _blocks) {
 		blockData.block->saveState(memento);
 	}
 }
 
-void InnerWidget::restoreState(const SectionMemento *memento) {
+void InnerWidget::restoreState(gsl::not_null<SectionMemento*> memento) {
 	for_const (auto &blockData, _blocks) {
 		blockData.block->restoreState(memento);
 	}
diff --git a/Telegram/SourceFiles/profile/profile_inner_widget.h b/Telegram/SourceFiles/profile/profile_inner_widget.h
index 701b4aaea8..aa3b5d7891 100644
--- a/Telegram/SourceFiles/profile/profile_inner_widget.h
+++ b/Telegram/SourceFiles/profile/profile_inner_widget.h
@@ -49,8 +49,8 @@ public:
 	// It should show it only if it is hidden in the cover.
 	bool shareContactButtonShown() const;
 
-	void saveState(SectionMemento *memento) const;
-	void restoreState(const SectionMemento *memento);
+	void saveState(gsl::not_null<SectionMemento*> memento);
+	void restoreState(gsl::not_null<SectionMemento*> memento);
 
 	void showFinished();
 
diff --git a/Telegram/SourceFiles/profile/profile_section_memento.cpp b/Telegram/SourceFiles/profile/profile_section_memento.cpp
index 5998c86e98..c07bbe4118 100644
--- a/Telegram/SourceFiles/profile/profile_section_memento.cpp
+++ b/Telegram/SourceFiles/profile/profile_section_memento.cpp
@@ -24,7 +24,7 @@ Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
 
 namespace Profile {
 
-object_ptr<Window::SectionWidget> SectionMemento::createWidget(QWidget *parent, gsl::not_null<Window::Controller*> controller, const QRect &geometry) const {
+object_ptr<Window::SectionWidget> SectionMemento::createWidget(QWidget *parent, gsl::not_null<Window::Controller*> controller, const QRect &geometry) {
 	auto result = object_ptr<Widget>(parent, controller, _peer);
 	result->setInternalState(geometry, this);
 	return std::move(result);
diff --git a/Telegram/SourceFiles/profile/profile_section_memento.h b/Telegram/SourceFiles/profile/profile_section_memento.h
index 979a32fb3c..cc7140ad79 100644
--- a/Telegram/SourceFiles/profile/profile_section_memento.h
+++ b/Telegram/SourceFiles/profile/profile_section_memento.h
@@ -31,7 +31,7 @@ public:
 	SectionMemento(PeerData *peer) : _peer(peer) {
 	}
 
-	object_ptr<Window::SectionWidget> createWidget(QWidget *parent, gsl::not_null<Window::Controller*> controller, const QRect &geometry) const override;
+	object_ptr<Window::SectionWidget> createWidget(QWidget *parent, gsl::not_null<Window::Controller*> controller, const QRect &geometry) override;
 
 	PeerData *getPeer() const {
 		return _peer;
diff --git a/Telegram/SourceFiles/profile/profile_widget.cpp b/Telegram/SourceFiles/profile/profile_widget.cpp
index 1264e6e699..c70c2ef1aa 100644
--- a/Telegram/SourceFiles/profile/profile_widget.cpp
+++ b/Telegram/SourceFiles/profile/profile_widget.cpp
@@ -76,8 +76,8 @@ void Widget::doSetInnerFocus() {
 	_inner->setFocus();
 }
 
-bool Widget::showInternal(const Window::SectionMemento *memento) {
-	if (auto profileMemento = dynamic_cast<const SectionMemento*>(memento)) {
+bool Widget::showInternal(gsl::not_null<Window::SectionMemento*> memento) {
+	if (auto profileMemento = dynamic_cast<SectionMemento*>(memento.get())) {
 		if (profileMemento->getPeer() == peer()) {
 			restoreState(profileMemento);
 			return true;
@@ -86,24 +86,24 @@ bool Widget::showInternal(const Window::SectionMemento *memento) {
 	return false;
 }
 
-void Widget::setInternalState(const QRect &geometry, const SectionMemento *memento) {
+void Widget::setInternalState(const QRect &geometry, gsl::not_null<SectionMemento*> memento) {
 	setGeometry(geometry);
 	myEnsureResized(this);
 	restoreState(memento);
 }
 
-std::unique_ptr<Window::SectionMemento> Widget::createMemento() const {
+std::unique_ptr<Window::SectionMemento> Widget::createMemento() {
 	auto result = std::make_unique<SectionMemento>(peer());
 	saveState(result.get());
 	return std::move(result);
 }
 
-void Widget::saveState(SectionMemento *memento) const {
+void Widget::saveState(gsl::not_null<SectionMemento*> memento) {
 	memento->setScrollTop(_scroll->scrollTop());
 	_inner->saveState(memento);
 }
 
-void Widget::restoreState(const SectionMemento *memento) {
+void Widget::restoreState(gsl::not_null<SectionMemento*> memento) {
 	_inner->restoreState(memento);
 	auto scrollTop = memento->getScrollTop();
 	_scroll->scrollToY(scrollTop);
diff --git a/Telegram/SourceFiles/profile/profile_widget.h b/Telegram/SourceFiles/profile/profile_widget.h
index bd57297787..82438996dc 100644
--- a/Telegram/SourceFiles/profile/profile_widget.h
+++ b/Telegram/SourceFiles/profile/profile_widget.h
@@ -49,10 +49,10 @@ public:
 
 	QPixmap grabForShowAnimation(const Window::SectionSlideParams &params) override;
 
-	bool showInternal(const Window::SectionMemento *memento) override;
-	std::unique_ptr<Window::SectionMemento> createMemento() const override;
+	bool showInternal(gsl::not_null<Window::SectionMemento*> memento) override;
+	std::unique_ptr<Window::SectionMemento> createMemento() override;
 
-	void setInternalState(const QRect &geometry, const SectionMemento *memento);
+	void setInternalState(const QRect &geometry, gsl::not_null<SectionMemento*> memento);
 
 	// Float player interface.
 	bool wheelEventFromFloatPlayer(QEvent *e, Window::Column myColumn, Window::Column playerColumn) override;
@@ -71,8 +71,8 @@ private slots:
 private:
 	void updateScrollState();
 	void updateAdaptiveLayout();
-	void saveState(SectionMemento *memento) const;
-	void restoreState(const SectionMemento *memento);
+	void saveState(gsl::not_null<SectionMemento*> memento);
+	void restoreState(gsl::not_null<SectionMemento*> memento);
 
 	object_ptr<Ui::ScrollArea> _scroll;
 	QPointer<InnerWidget> _inner;
diff --git a/Telegram/SourceFiles/window/section_memento.h b/Telegram/SourceFiles/window/section_memento.h
index 46c22f3d91..9151fa49f8 100644
--- a/Telegram/SourceFiles/window/section_memento.h
+++ b/Telegram/SourceFiles/window/section_memento.h
@@ -27,7 +27,7 @@ class SectionWidget;
 
 class SectionMemento {
 public:
-	virtual object_ptr<Window::SectionWidget> createWidget(QWidget *parent, gsl::not_null<Window::Controller*> controller, const QRect &geometry) const = 0;
+	virtual object_ptr<Window::SectionWidget> createWidget(QWidget *parent, gsl::not_null<Window::Controller*> controller, const QRect &geometry) = 0;
 	virtual ~SectionMemento() {
 	}
 
diff --git a/Telegram/SourceFiles/window/section_widget.h b/Telegram/SourceFiles/window/section_widget.h
index 72dfc06b71..0a283e3445 100644
--- a/Telegram/SourceFiles/window/section_widget.h
+++ b/Telegram/SourceFiles/window/section_widget.h
@@ -96,10 +96,14 @@ public:
 	// Attempt to show the required section inside the existing one.
 	// For example if this section already shows exactly the required
 	// memento it can simply return true - it is shown already.
-	virtual bool showInternal(const SectionMemento *memento) = 0;
+	//
+	// If this method returns false it is not supposed to modify the memento.
+	// If this method returns true it may modify the memento ("take" heavy items).
+	virtual bool showInternal(gsl::not_null<SectionMemento*> memento) = 0;
 
 	// Create a memento of that section to store it in the history stack.
-	virtual std::unique_ptr<SectionMemento> createMemento() const = 0;
+	// This method may modify the section ("take" heavy items).
+	virtual std::unique_ptr<SectionMemento> createMemento() = 0;
 
 	void setInnerFocus() {
 		doSetInnerFocus();