采用Qt快速绘制多条曲线（折线），跟随鼠标动态显示线上点的值（基于Qt的开源绘图控件QCustomPlot进行二次开发）

qcustomplot是一个开源的基于qt的第三方绘图库，能够绘制漂亮的2d图形。

qcustomplot的官方网址：

从官网下载qcustomplot的源文件，包括qcustomplot.h和qcustomplot.cpp。

 

本程序的源码下载地址： https://github.com/xiongxw/xcustomplot.git

 

 

1 自定义鼠标显示跟随类xxwtracer和xxwtraceline：

xxwtracer用于在图表中显示鼠标所在位置的x,y值

xxwtraceline用于在图中显示水平或垂直的虚线

头文件xxwtracer.h

#ifndef mytracer_h
#define mytracer_h

#include <qobject>
#include "qcustomplot.h"

///
/// \brief the xxwtracer class:在图表中显示鼠标所在位置的x,y值的追踪显示器
///
class xxwtracer : public qobject
{
q_object

public:
enum tracertype
{
        xaxistracer,//依附在x轴上显示x值
        yaxistracer,//依附在y轴上显示y值
        datatracer//在图中显示x,y值
};
    explicit xxwtracer(qcustomplot *_plot, tracertype _type, qobject *parent = q_nullptr);
    ~xxwtracer();
void setpen(const qpen &pen);
void setbrush(const qbrush &brush);
void settext(const qstring &text);
void setlabelpen(const qpen &pen);
void updateposition(double xvalue, double yvalue);
    void setvisible(bool m_visible);

protected:
    bool m_visible;//是否可见
    tracertype m_type;//类型
    qcustomplot *m_plot;//图表
    qcpitemtracer *m_tracer;//跟踪的点
    qcpitemtext *m_label;//显示的数值
    qcpitemline *m_arrow;//箭头
};


///
/// \brief the xxwcrossline class:用于显示鼠标移动过程中的鼠标位置的直线
///
class xxwtraceline : public qobject
{
public:
    enum linetype
    {
        verticalline,//垂直线
        horizonline, //水平线
        both//同时显示水平和垂直线
    };
    explicit xxwtraceline(qcustomplot *_plot, linetype _type = verticalline, qobject *parent = q_nullptr);
    ~xxwtraceline();
    void initline();
    void updateposition(double xvalue, double yvalue);

    void setvisible(bool vis)
    {
        if(m_linev)
            m_linev->setvisible(vis);
        if(m_lineh)
            m_lineh->setvisible(vis);
    }

protected:
    bool m_visible;//是否可见
    linetype m_type;//类型
    qcustomplot *m_plot;//图表
    qcpitemstraightline *m_linev; //垂直线
    qcpitemstraightline *m_lineh; //水平线
};

#endif // mytracer_h

源文件mytracer.cpp

#include "mytracer.h"

xxwtracer::xxwtracer(qcustomplot *_plot, tracertype _type, qobject *parent)
    : qobject(parent),
      m_plot(_plot),
      m_type(_type)
{
    m_visible = true;
    m_tracer = q_nullptr;// 跟踪的点
    m_label = q_nullptr;// 显示的数值
    m_arrow = q_nullptr;// 箭头
    if (m_plot)
    {
        qcolor clrdefault(qt::red);
        qbrush brushdefault(qt::nobrush);
        qpen pendefault(clrdefault);
        //        pendefault.setbrush(brushdefault);
        pendefault.setwidthf(0.5);

        m_tracer = new qcpitemtracer(m_plot);
        m_tracer->setstyle(qcpitemtracer::tscircle);
        m_tracer->setpen(pendefault);
        m_tracer->setbrush(brushdefault);

        m_label = new qcpitemtext(m_plot);
        m_label->setlayer("overlay");
        m_label->setcliptoaxisrect(false);
        m_label->setpadding(qmargins(5, 5, 5, 5));
        m_label->setbrush(brushdefault);
        m_label->setpen(pendefault);
        m_label->position->setparentanchor(m_tracer->position);
//        m_label->setfont(qfont("宋体", 8));
        m_label->setfont(qfont("arial", 8));
        m_label->setcolor(clrdefault);
        m_label->settext("");

        m_arrow = new qcpitemline(m_plot);
        qpen  arrowpen(clrdefault, 1);
        m_arrow->setpen(pendefault);
        m_arrow->setlayer("overlay");
        m_arrow->setcliptoaxisrect(false);
        m_arrow->sethead(qcplineending::esspikearrow);//设置头部为箭头形状

        switch (m_type)
        {
        case xaxistracer:
        {
            m_tracer->position->settypex(qcpitemposition::ptplotcoords);
            m_tracer->position->settypey(qcpitemposition::ptaxisrectratio);
            m_tracer->setsize(7);
            m_label->setpositionalignment(qt::aligntop | qt::alignhcenter);

            m_arrow->end->setparentanchor(m_tracer->position);
            m_arrow->start->setparentanchor(m_arrow->end);
            m_arrow->start->setcoords(0, 20);//偏移量
            break;
        }
        case yaxistracer:
        {
            m_tracer->position->settypex(qcpitemposition::ptaxisrectratio);
            m_tracer->position->settypey(qcpitemposition::ptplotcoords);
            m_tracer->setsize(7);
            m_label->setpositionalignment(qt::alignright | qt::alignhcenter);

            m_arrow->end->setparentanchor(m_tracer->position);
            m_arrow->start->setparentanchor(m_label->position);
            m_arrow->start->setcoords(-20, 0);//偏移量
            break;
        }
        case datatracer:
        {
            m_tracer->position->settypex(qcpitemposition::ptplotcoords);
            m_tracer->position->settypey(qcpitemposition::ptplotcoords);
            m_tracer->setsize(5);

            m_label->setpositionalignment(qt::alignleft | qt::alignvcenter);

            m_arrow->end->setparentanchor(m_tracer->position);
            m_arrow->start->setparentanchor(m_arrow->end);
            m_arrow->start->setcoords(20, 0);
            break;
        }
        default:
            break;
        }
        setvisible(false);
    }
}

xxwtracer::~xxwtracer()
{
    if(m_plot)
    {
        if (m_tracer)
            m_plot->removeitem(m_tracer);
        if (m_label)
            m_plot->removeitem(m_label);
        if (m_arrow)
            m_plot->removeitem(m_arrow);
    }
}

void xxwtracer::setpen(const qpen &pen)
{
    if(m_tracer)
        m_tracer->setpen(pen);
    if(m_arrow)
        m_arrow->setpen(pen);
}

void xxwtracer::setbrush(const qbrush &brush)
{
    if(m_tracer)
        m_tracer->setbrush(brush);
}

void xxwtracer::setlabelpen(const qpen &pen)
{
    if(m_label)
    {
        m_label->setpen(pen);
        m_label->setbrush(qt::nobrush);
        m_label->setcolor(pen.color());
    }
}

void xxwtracer::settext(const qstring &text)
{
    if(m_label)
        m_label->settext(text);
}

void xxwtracer::setvisible(bool vis)
{
    m_visible = vis;
    if(m_tracer)
        m_tracer->setvisible(m_visible);
    if(m_label)
        m_label->setvisible(m_visible);
    if(m_arrow)
        m_arrow->setvisible(m_visible);
}

void xxwtracer::updateposition(double xvalue, double yvalue)
{
    if (!m_visible)
    {
        setvisible(true);
        m_visible = true;
    }

    if (yvalue > m_plot->yaxis->range().upper)
        yvalue = m_plot->yaxis->range().upper;

    switch (m_type)
    {
    case xaxistracer:
    {
        m_tracer->position->setcoords(xvalue, 1);
        m_label->position->setcoords(0, 15);
        m_arrow->start->setcoords(0, 15);
        m_arrow->end->setcoords(0, 0);
        settext(qstring::number(xvalue));
        break;
    }
    case yaxistracer:
    {
        m_tracer->position->setcoords(0, yvalue);
        m_label->position->setcoords(-20, 0);
//        m_arrow->start->setcoords(20, 0);
//        m_arrow->end->setcoords(0, 0);
        settext(qstring::number(yvalue));
        break;
    }
    case datatracer:
    {
        m_tracer->position->setcoords(xvalue, yvalue);
        m_label->position->setcoords(20, 0);
        settext(qstring("x:%1,y:%2").arg(xvalue).arg(yvalue));
        break;
    }
    default:
        break;
    }
}

xxwtraceline::xxwtraceline(qcustomplot *_plot, linetype _type, qobject *parent)
    : qobject(parent),
      m_type(_type),
      m_plot(_plot)
{
    m_linev = q_nullptr;
    m_lineh = q_nullptr;
    initline();
}

xxwtraceline::~xxwtraceline()
{
    if(m_plot)
    {
        if (m_linev)
            m_plot->removeitem(m_linev);
        if (m_lineh)
            m_plot->removeitem(m_lineh);
    }
}

void xxwtraceline::initline()
{
    if(m_plot)
    {
        qpen linespen(qt::red, 1, qt::dashline);

        if(verticalline == m_type || both == m_type)
        {
            m_linev = new qcpitemstraightline(m_plot);//垂直线
            m_linev->setlayer("overlay");
            m_linev->setpen(linespen);
            m_linev->setcliptoaxisrect(true);
            m_linev->point1->setcoords(0, 0);
            m_linev->point2->setcoords(0, 0);
        }

        if(horizonline == m_type || both == m_type)
        {
            m_lineh = new qcpitemstraightline(m_plot);//水平线
            m_lineh->setlayer("overlay");
            m_lineh->setpen(linespen);
            m_lineh->setcliptoaxisrect(true);
            m_lineh->point1->setcoords(0, 0);
            m_lineh->point2->setcoords(0, 0);
        }
    }
}

void xxwtraceline::updateposition(double xvalue, double yvalue)
{
    if(verticalline == m_type || both == m_type)
    {
        if(m_linev)
        {
            m_linev->point1->setcoords(xvalue, m_plot->yaxis->range().lower);
            m_linev->point2->setcoords(xvalue, m_plot->yaxis->range().upper);
        }
    }

    if(horizonline == m_type || both == m_type)
    {
        if(m_lineh)
        {
            m_lineh->point1->setcoords(m_plot->xaxis->range().lower, yvalue);
            m_lineh->point2->setcoords(m_plot->xaxis->range().upper, yvalue);
        }
    }
}

 

2 自定义的图表类xcustomplot

xcustomplot是基于qcustomplot二次开发的图表类，在鼠标移动过程中动态显示曲线上点的值。

头文件xcustomplot.h

#ifndef xcustomplot_h
#define xcustomplot_h

#include "xxwtracer.h"
#include "qcustomplot.h"
#include <qobject>
#include <qlist>

class xxwcustomplot:public qcustomplot
{
    q_object

public:
    xxwcustomplot(qwidget *parent = 0);

protected:
    virtual void mousemoveevent(qmouseevent *event);

public:
    ///
    /// \brief 设置是否显示鼠标追踪器
    /// \param show:是否显示
    ///
    void showtracer(bool show)
    {
        m_isshowtracer = show;
        if(m_xtracer)
            m_xtracer->setvisible(m_isshowtracer);
        foreach (xxwtracer *tracer, m_datatracers)
        {
            if(tracer)
                tracer->setvisible(m_isshowtracer);
        }
        if(m_linetracer)
            m_linetracer->setvisible(m_isshowtracer);
    }

    ///
    /// \brief 是否显示鼠标追踪器
    /// \return
    ///
    bool isshowtracer(){return m_isshowtracer;};

private:
    bool m_isshowtracer;//是否显示追踪器（鼠标在图中移动，显示对应的值）
    xxwtracer *m_xtracer;//x轴
    xxwtracer *m_ytracer;//y轴
    qlist<xxwtracer *> m_datatracers;//
    xxwtraceline  *m_linetracer;//直线
};

#endif // xcustomplot_h

源文件xcustomplot.h

#include "xxwcustomplot.h"

xxwcustomplot::xxwcustomplot(qwidget *parent)
    :qcustomplot(parent)
    ,m_isshowtracer(false)
    ,m_xtracer(q_nullptr)
    ,m_ytracer(q_nullptr)
    ,m_datatracers(qlist<xxwtracer *>())
    ,m_linetracer(q_nullptr)
{
}

void xxwcustomplot::mousemoveevent(qmouseevent *event)
{
    qcustomplot::mousemoveevent(event);

    if(m_isshowtracer)
    {
        //当前鼠标位置（像素坐标）
        int x_pos = event->pos().x();
        int y_pos = event->pos().y();

        //像素坐标转成实际的x,y轴的坐标
        float x_val = this->xaxis->pixeltocoord(x_pos);
        float y_val = this->yaxis->pixeltocoord(y_pos);

        if(q_nullptr == m_xtracer)
            m_xtracer = new xxwtracer(this, xxwtracer::xaxistracer);//x轴
        m_xtracer->updateposition(x_val, y_val);

        if(q_nullptr == m_ytracer)
            m_ytracer = new xxwtracer(this, xxwtracer::yaxistracer);//y轴
        m_ytracer->updateposition(x_val, y_val);

        int ntracercount = m_datatracers.count();
        int ngraphcount = graphcount();
        if(ntracercount < ngraphcount)
        {
            for(int i = ntracercount; i < ngraphcount; ++i)
            {
                xxwtracer *tracer = new xxwtracer(this, xxwtracer::datatracer);
                m_datatracers.append(tracer);
            }
        }
        else if(ntracercount > ngraphcount)
        {
            for(int i = ngraphcount; i < ntracercount; ++i)
            {
                xxwtracer *tracer = m_datatracers[i];
                if(tracer)
                {
                    tracer->setvisible(false);
                }
            }
        }
        for (int i = 0; i < ngraphcount; ++i)
        {
            xxwtracer *tracer = m_datatracers[i];
            if(!tracer)
                tracer = new xxwtracer(this, xxwtracer::datatracer);
            tracer->setvisible(true);
            tracer->setpen(this->graph(i)->pen());
            tracer->setbrush(qt::nobrush);
            tracer->setlabelpen(this->graph(i)->pen());
            auto iter = this->graph(i)->data()->findbegin(x_val);
            double value = iter->mainvalue();
//            double value = this->graph(i)->data()->findbegin(x_val)->value;
            tracer->updateposition(x_val, value);
        }

        if(q_nullptr == m_linetracer)
            m_linetracer = new xxwtraceline(this,xxwtraceline::both);//直线
        m_linetracer->updateposition(x_val, y_val);

        this->replot();//曲线重绘
    }
}

 

 

 

3 使用自定义图表类xcustomplot

在需要绘图的地方使用，代码如下：

 

  m_customplot = new xxwcustomplot();
    m_customplot->showtracer(true);

    // add title layout element:
    m_customplot->plotlayout()->insertrow(0);
    m_customplot->plotlayout()->addelement(0, 0, new qcptextelement(m_customplot, "标题", qfont("黑体", 12, qfont::bold)));

    m_customplot->legend->setvisible(true);
    qfont legendfont = font();  // start out with mainwindow's font..
    legendfont.setpointsize(9); // and make a bit smaller for legend
    m_customplot->legend->setfont(legendfont);
    m_customplot->legend->setbrush(qbrush(qcolor(255,255,255,230)));
    // by default, the legend is in the inset layout of the main axis rect. so this is how we access it to change legend placement:
    m_customplot->axisrect()->insetlayout()->setinsetalignment(0, qt::aligntop|qt::aligncenter);

    // make left and bottom axes always transfer their ranges to right and top axes:
    connect(m_customplot->xaxis, signal(rangechanged(qcprange)), m_customplot->xaxis2, slot(setrange(qcprange)));
    connect(m_customplot->yaxis, signal(rangechanged(qcprange)), m_customplot->yaxis2, slot(setrange(qcprange)));

    // allow user to drag axis ranges with mouse, zoom with mouse wheel and select graphs by clicking:
    m_customplot->setinteractions(qcp::irangedrag | qcp::irangezoom | qcp::iselectplottables);

    // generate some data:
    int ncount = 100;
    qvector<double> x(ncount), y0(ncount), y1(ncount); // initialize with entries 0..100
    for (int i = 0; i < ncount; ++i)
    {
        x[i] = i; // x goes from -1 to 1
        y0[i] = qsin(i * 10.0f / ncount); //sin
        y1[i] = qcos(i * 10.0f / ncount); //cos
    }
    // create graph and assign data to it:
    qpen pen;
    int i = 1;
    qcpgraph *pgraph = m_customplot->addgraph();
    //        m_customplot->graph(0)->setdata(x, y0);
    pgraph->setname("sin曲线");
    pgraph->setdata(x,y0);
    pgraph->setpen(qpen(qt::blue));

    pgraph = m_customplot->addgraph();
    //        m_customplot->graph(0)->setdata(x, y0);
    pgraph->setname("cos曲线");
    pgraph->setdata(x,y1);
    pgraph->setpen(qpen(qt::darkyellow));

    // give the axes some labels:
    m_customplot->xaxis->setlabel("x");
    m_customplot->yaxis->setlabel("y");

    // set axes ranges, so we see all data:
//    m_customplot->xaxis->setrange(-1, 1);
//    m_customplot->yaxis->setrange(0, 1);
    m_customplot->rescaleaxes(true);

    m_customplot->replot();

 

4 效果图

 
本程序的源码下载地址： https://github.com/xiongxw/xcustomplot.git

参考：