qt5 在有数据读取绘图的时候，使用鼠标绘图会有延迟

GUIWidget::GUIWidget(QWidget *parent) :

    QWidget(parent),

    ui(new Ui::GUIWidget)

{

   image = QImage(592,550,QImage::Format_RGB32);

   pix = QPixmap(592,550);

   QColor backColor=qRgb(255,255,255);

   image.fill(backColor);

   pix.fill(Qt::transparent);

   Paint();//绘制坐标

    timer = new QTimer(this);

    connect(timer,&QTimer::timeout,this,[=]{

        if(wid_ptr!=NULL)

       {

            buff=wid_ptr->buffer;

        arrayCut(wid_ptr->buffer,newbuf);

        }

        paint(newbuf);            //绘图

        update();         //刷新

    });

    timer->start(0); //300毫秒后发送timeout信号

/**************/

    ui->setupUi(this);

/*******************/

}

GUIWidget::~GUIWidget()

{

    delete ui;

}

/***************绘图函数*******************/

void GUIWidget::paint(float newbuf[][6])

{

    QPainter p(&image);//指定当前绘画对象p

/************设置画笔参数***************/

    QColor color(255,0,0);

    QPen pen(color);

    pen.setWidth(3);

    p.setRenderHint(QPainter::Antialiasing);

/******************************************/

    p.setPen(pen);

    int xx=0;   //记录多少个需要绘制的线段

    int i=0,j=0;

    for(i=0;i<64;i++)

    {

        if(0 != newbuf[i][0])

        {

            for(j=0;j<64;j++)

            {

                if( 0 !=oldbuf[j][0])

                {

                    if(newbuf[i][0]==oldbuf[j][0])

                        if(newbuf[i][2]!=oldbuf[j][1]||newbuf[i][3]!=oldbuf[j][2])

                        {

                          {

                            linef[i]= QLine(296+(oldbuf[j][2]*20),550-(oldbuf[j][1]*1.5),296+(newbuf[i][3]*20),550-(newbuf[i][2]*1.5));

                            qDebug()<<oldbuf[j][0]<<"oldbuf"<<j<<"[1],oldbuf[j][2]"<<oldbuf[j][1]<<","<<oldbuf[j][2]<<endl;

                            qDebug()<<newbuf[i][0]<<"newbuf"<<i<<"[2],newbuf[i][3]"<<newbuf[i][2]<<","<<newbuf[i][3]<<endl;

                            qDebug()<<"*********************"<<endl;

                            xx++;

                            break;

                          }

                        }

                 }

                else

                    break;

            }

        }

        else

            break;

    }

    p.drawLines(linef,xx);

    for(i=0;i<64;i++)

    {

        oldbuf[i][0]=newbuf[i][0];

        oldbuf[i][1]=newbuf[i][2];

        oldbuf[i][2]=newbuf[i][3];

    }

}

void GUIWidget::paintEvent(QPaintEvent *)

{

    QPainter painter(this);

    painter.drawImage(0,0,image);

    QColor color(0,255,0);

    QPen pen(color);

    pen.setWidth(6);

    painter.setPen(pen);

    for(int i=0;i<64;i++)

    {

        if(0!=newbuf[i][0])

          painter.drawPoint(296+newbuf[i][3]*20,550-newbuf[i][2]*1.5);

    }

    QPainter p(&image);

    p.drawPixmap(0,0,pix);

    QPainter pp(&pix);

    for(int i=0; i<_lines.size(); i++)

    {

        //第i条线

        const QVector<QPoint> &line = _lines.at(i);

        //每一条线中所有的点，两两连起来，就是一条线

        for(int j=0; j<line.size()-1; j++)

        {

            pp.drawLine(line.at(j), line.at(j+1));

        }

    }

}

void GUIWidget::Paint()//绘制坐标系

{

    QPainter painter(&image);

        painter.setRenderHint(QPainter::Antialiasing, true);//设置反锯齿模式，好看一点

        int pointx=296,pointy=550;

        int height=550;

        painter.drawLine(0,pointy,592,pointy);//坐标轴x宽度为width

        painter.drawLine(pointx,pointy-height,pointx,pointy);//坐标轴y高度为height

        QPen penDegree;

           penDegree.setColor(Qt::black);

           penDegree.setWidth(2);

           painter.setPen(penDegree);

          //  double n=3.7;

           //画上x轴刻度线

           for(int i=0;i<8;i++)//分成8份

           {

               //选取合适的坐标，绘制一段长度为4的直线，用于表示刻度

               painter.drawLine(i*3.7*20,pointy,i*3.7*20,pointy-4);

               painter.drawText((i+0.65)*3.7*20,pointy-10,QString::number((int)(i+1)));

           }

           //y轴刻度线

           double _maStep=30;//y轴刻度间隔需根据最大值来表示

           for(int i=0;i<10;i++)

           {

               //主要就是确定一个位置，然后画一条短短的直线表示刻度。

               painter.drawLine(pointx,pointy-(i+1)*height/10,

                                pointx-4,pointy-(i+1)*height/10);

               painter.drawText(pointx-20,pointy-(i+0.85)*height/10,

                                QString::number((int)(_maStep*(i+1))));

           }

}