Qwt源码解读之QwtSystemClock类和QwtSamplingThread类

QwtSystemClock类提供了一个高分辨率的时钟功能（依赖于特定的系统）。

代码分析：

class QWT_EXPORT QwtSystemClock
{
public:
    QwtSystemClock();
    virtual ~QwtSystemClock();

    bool isNull() const;

    void start();
    double restart();
    double elapsed() const;

    static double precision();

private:
    class PrivateData;
    PrivateData *d_data;
};

QwtSystemClock类在QwtSamplingThread类里被用作了采样时钟。

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QwtSamplingThread类：定期采集样品的线程，继承自QThread。

QwtSamplingThread自身也是一个抽象基类。

代码分析

class QWT_EXPORT QwtSamplingThread: public QThread
{
    Q_OBJECT

public:
    virtual ~QwtSamplingThread();

    double interval() const;
    double elapsed() const;

public Q_SLOTS:
    void setInterval( double interval );
    void stop();

protected:
    explicit QwtSamplingThread( QObject *parent = NULL );

    virtual void run();

    /*!
       Collect a sample

       \param elapsed Time since the thread was started in miliseconds
     */
    virtual void sample( double elapsed ) = 0; // 需重新实现

private:
    class PrivateData;
    PrivateData *d_data;
};

在D:\qwt-6.0.1\examples\oscilloscope\oscilloscope.pro例子中有对以上两个类使用的示例。