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Telegram/SourceFiles/ui/controls/subsection_tabs_slider_reorder.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/effects/animations.h"
+
+namespace Ui {
+
+class RpWidget;
+class ScrollArea;
+class SubsectionButton;
+class SubsectionSlider;
+
+class SubsectionSliderReorder final {
+public:
+	using ProxyCallback = Fn<not_null<Ui::RpWidget*>(int)>;
+	enum class State : uchar {
+		Started,
+		Applied,
+		Cancelled,
+	};
+	struct Single {
+		not_null<SubsectionButton*> widget;
+		int oldPosition = 0;
+		int newPosition = 0;
+		State state = State::Started;
+	};
+
+	SubsectionSliderReorder(
+		not_null<SubsectionSlider*> slider,
+		not_null<ScrollArea*> scroll);
+	SubsectionSliderReorder(not_null<SubsectionSlider*> slider);
+	~SubsectionSliderReorder();
+
+	void start();
+	void cancel();
+	void finishReordering();
+	void addPinnedInterval(int from, int length);
+	void clearPinnedIntervals();
+	void setMouseEventProxy(ProxyCallback callback);
+	[[nodiscard]] rpl::producer<Single> updates() const;
+
+private:
+	struct Entry {
+		not_null<SubsectionButton*> button;
+		Ui::Animations::Simple shiftAnimation;
+		int shift = 0;
+		int finalShift = 0;
+		int deltaShift = 0;
+	};
+	struct Interval {
+		[[nodiscard]] bool isIn(int index) const;
+		int from = 0;
+		int length = 0;
+	};
+
+	void mouseMove(not_null<SubsectionButton*> button, QPoint position);
+	void mousePress(
+		not_null<SubsectionButton*> button,
+		Qt::MouseButton mouseButton,
+		QPoint position);
+	void mouseRelease(Qt::MouseButton button);
+
+	void checkForStart(QPoint position);
+	void updateOrder(int index, QPoint position);
+	void cancelCurrent();
+	void finishCurrent();
+	void cancelCurrent(int index);
+
+	[[nodiscard]] int indexOf(not_null<SubsectionButton*> button) const;
+	void moveToShift(int index, int shift);
+	void updateShift(not_null<SubsectionButton*> button, int indexHint);
+
+	void updateScrollCallback();
+	void checkForScrollAnimation();
+	[[nodiscard]] int deltaFromEdge();
+
+	[[nodiscard]] bool isIndexPinned(int index) const;
+
+	const not_null<Ui::SubsectionSlider*> _slider;
+	Ui::ScrollArea *_scroll = nullptr;
+
+	Ui::Animations::Basic _scrollAnimation;
+
+	std::vector<Interval> _pinnedIntervals;
+
+	ProxyCallback _proxyButtonCallback = nullptr;
+
+	SubsectionButton *_currentButton = nullptr;
+	int _currentStart = 0;
+	int _currentDesiredIndex = 0;
+	State _currentState = State::Cancelled;
+	std::vector<Entry> _entries;
+	rpl::event_stream<Single> _updates;
+	rpl::lifetime _lifetime;
+};
+
+} // namespace Ui