Extract a reusable Ui::ResizeArea class.

Telegram/SourceFiles/ui/resize_area.h

@@ -0,0 +1,91 @@
+/*
+This file is part of Telegram Desktop,
+the official desktop version of Telegram messaging app, see https://telegram.org
+
+Telegram Desktop is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+It is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+In addition, as a special exception, the copyright holders give permission
+to link the code of portions of this program with the OpenSSL library.
+
+Full license: https://github.com/telegramdesktop/tdesktop/blob/master/LICENSE
+Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
+*/
+#pragma once
+
+#include "ui/rp_widget.h"
+
+namespace Ui {
+
+class ResizeArea : public RpWidget {
+public:
+	ResizeArea(QWidget *parent) : RpWidget(parent) {
+		setCursor(style::cur_sizehor);
+	}
+
+	rpl::producer<int> moveLeft() const {
+		return _moveLeft.events();
+	}
+	template <typename Callback>
+	void addMoveLeftCallback(Callback &&callback) {
+		moveLeft()
+			| rpl::start_with_next(
+				std::forward<Callback>(callback),
+				lifetime());
+	}
+
+	rpl::producer<> moveFinished() const {
+		return _moveFinished.events();
+	}
+	template <typename Callback>
+	void addMoveFinishedCallback(Callback &&callback) {
+		moveFinished()
+			| rpl::start_with_next(
+				std::forward<Callback>(callback),
+				lifetime());
+	}
+
+	~ResizeArea() {
+		moveFinish();
+	}
+
+protected:
+	void mousePressEvent(QMouseEvent *e) override {
+		if (e->button() == Qt::LeftButton) {
+			_moving = true;
+			_moveStartLeft = e->pos().x();
+		}
+	}
+	void mouseReleaseEvent(QMouseEvent *e) override {
+		if (e->button() == Qt::LeftButton) {
+			moveFinish();
+		}
+	}
+	void mouseMoveEvent(QMouseEvent *e) override {
+		if (_moving) {
+			_moveLeft.fire(e->globalPos().x() - _moveStartLeft);
+		}
+	}
+
+private:
+	void moveFinish() {
+		if (base::take(_moving)) {
+			_moveFinished.fire({});
+		}
+	}
+
+	rpl::event_stream<int> _moveLeft;
+	rpl::event_stream<> _moveFinished;
+	int _moveStartLeft = 0;
+	bool _moving = false;
+
+};
+
+} // namespace Ui