QT仪表盘小工具

头文件：

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** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
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** This file is part of the examples of the Qt Toolkit.
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** $QT_BEGIN_LICENSE:BSD$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
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** as follows:
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** "Redistribution and use in source and binary forms, with or without
** modificatio