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Telegram/SourceFiles/info/info_flexible_scroll.h

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+/*
+This file is part of Telegram Desktop,
+the official desktop application for the Telegram messaging service.
+
+For license and copyright information please follow this link:
+https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
+*/
+#pragma once
+
+#include "ui/widgets/scroll_area.h"
+#include "ui/effects/animations.h"
+#include "ui/rp_widget.h"
+
+namespace Info {
+
+extern const char kAlternativeScrollProcessing[];
+
+struct FlexibleScrollData {
+	rpl::event_stream<int> contentHeightValue;
+	rpl::event_stream<int> fillerWidthValue;
+	rpl::event_stream<> backButtonEnables;
+};
+
+class FlexibleScrollHelper final {
+public:
+	FlexibleScrollHelper(
+		not_null<Ui::ScrollArea*> scroll,
+		not_null<Ui::RpWidget*> inner,
+		not_null<Ui::RpWidget*> pinnedToTop,
+		Fn<void(QMargins)> setPaintPadding,
+		Fn<void(rpl::producer<not_null<QEvent*>>&&)> setViewport,
+		FlexibleScrollData &data);
+
+private:
+	void setupScrollAnimation();
+	void setupScrollHandling();
+	void setupScrollHandlingWithFilter();
+	void scrollToY(int value);
+	void applyScrollToPinnedLayout(int scrollCurrent);
+
+	const not_null<Ui::ScrollArea*> _scroll;
+	const not_null<Ui::RpWidget*> _inner;
+	const not_null<Ui::RpWidget*> _pinnedToTop;
+	const Fn<void(QMargins)> _setPaintPadding;
+	const Fn<void(rpl::producer<not_null<QEvent*>>&&)> _setViewport;
+	FlexibleScrollData &_data;
+
+	Ui::Animations::Basic _scrollAnimation;
+	int _scrollTopFrom = 0;
+	int _scrollTopTo = 0;
+	crl::time _timeOffset = 0;
+	int _lastScrollApplied = 0;
+	int _scrollTopPrevious = 0;
+	bool _applyingFakeScrollState = false;
+	rpl::lifetime _filterLifetime;
+};
+
+} // namespace Info