Freeze_drawing

in my application i am drawing sine-wave using qpainter widget.now i have to implement such functionality that on button pressed wave drawing should be stopped at that instant. and when i pressed same button again it should resume wave drawing from last instant.how to implement freeze functionalit
drawthread.cpp

Code:

#include "drawthread.h"
#include <QtCore>
#include <QtGui>
 
DrawThread::DrawThread(QObject *parent):QThread(parent)
{
    X1=XStartpoint=50;
    Y1=YStartpoint=150;
    amplitude = 10;
    Ttime = 5;
}
 
void DrawThread::run()
{
    while(1)
    {
        qreal tempAmp;
 
 
        tempAmp=amplitude;
 
        for(int a=1;a<amplitude;a++)
        {
            XStartpoint = X1;
            YStartpoint = Y1;
 
            X1+=Ttime/tempAmp;
            tempAmp--;
            Y1-=1;
 
            emit DrawLine(XStartpoint,YStartpoint,X1,Y1);
        }
 
        tempAmp=1;
        for(int g=amplitude;g>0;g--)
        {
            XStartpoint = X1;
            YStartpoint = Y1;
 
            X1+=Ttime/tempAmp;
            tempAmp++;
            Y1+=1;
 
            emit DrawLine(XStartpoint,YStartpoint,X1,Y1);
        }
 
        // second
 
        tempAmp=amplitude;
 
        for(int a=1;a<amplitude;a++)
        {
            XStartpoint = X1;
            YStartpoint = Y1;
 
            X1+=Ttime/tempAmp;
            tempAmp--;
            Y1+=1;
 
            emit DrawLine(XStartpoint,YStartpoint,X1,Y1);
        }
 
        tempAmp=1;
        for(int g=amplitude;g>0;g--)
        {
            XStartpoint = X1;
            YStartpoint = Y1;
 
            X1+=Ttime/tempAmp;
            tempAmp++;
            Y1-=1;
 
            emit DrawLine(XStartpoint,YStartpoint,X1,Y1);
        }
        if(X1 > 300)
        {
            X1=XStartpoint=50;
            Y1=YStartpoint=150;
 
            emit DrawLine(XStartpoint,YStartpoint,X1,Y1);
        }
        msleep(250);
    }
}

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pixmap.cpp

Code:

#include "pixmap.h"
#include "ui_pixmap.h"
#include "drawthread.h"
 
DrawThread thread1;
 
pixmap::pixmap(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::pixmap)
{
    ui->setupUi(this);
    X1=XStartpoint=50;
    Y1=YStartpoint=150;
 
    amplitude = 10;
    Ttime = 5;
 
    drawpath=new QPainterPath(QPointF(50,150));
 
    drawpixmap = new QPixmap(size());
    drawpixmap->fill(Qt::transparent);
 
    connect(&thread1,SIGNAL(DrawLine(int ,int ,qreal ,qreal )),this,SLOT(display(int ,int ,qreal ,qreal)));
    thread1.start();
}
 
pixmap::~pixmap()
{
    delete ui;
}
 
void pixmap::paintEvent(QPaintEvent *pEvent)
{
 
    QWidget::paintEvent(pEvent);
    QPainter painter(this) ;
 
    painter.begin(drawpixmap);
    QPen pen1(Qt::red, 2);
    QPen pen2(Qt::magenta, 2);
    QPen pen3(Qt::green, 1);
 
 
    painter.setRenderHint(QPainter::SmoothPixmapTransform,true);
    painter.setPen(pen1);
 
    painter.drawLine(50,100,50,250);            //Y-AXIS
    painter.drawLine(50,150,350,150);           //X-AXIS
 
 
    painter.drawText(360,150,"Time ");
    painter.drawText(50,80,"Amplitude");
 
    //y-arrow
    painter.drawLine(50,100,40,110);
    painter.drawLine(50,100,60,110);
 
    //    //x-arrows
 
    painter.setPen(pen2);
 
    painter.drawLine(XStartpoint,YStartpoint,XStartpoint-5,YStartpoint-5);
    painter.drawLine(XStartpoint,YStartpoint,XStartpoint-5,YStartpoint+5);
 
    painter.setPen(pen3);
 
    if(!drawpath->isEmpty())
    {
        painter.drawPath(*drawpath);
        painter.drawPixmap(0,0,*drawpixmap);
    }
}
 
void pixmap::display(int lastx,int lasty,qreal currx,qreal curry)
{
    X1=currx;
    Y1=curry;
    XStartpoint=lastx;
    YStartpoint=lasty;
 
    if(X1==XStartpoint)
    {
        *drawpath=drawpath->subtracted(*drawpath);
    }
 
    drawpath->moveTo(XStartpoint,YStartpoint);
    drawpath->lineTo(X1,Y1);
    repaint();
}