Zoom in real time

Hello. I have a plot, which is updated on a timer. New points are taken from the database.
New points are added to the chart every 3 seconds and the plot is redrawn.

Code:

---

curv1 = new QwtPlotCurve();
    curv1->setPen(QPen(Qt::red));
    curv1->setAxes(xb,yl);
    myPlot->enableAxis(yl);
    curv1->attach(myPlot);
 
    timerUpdPlot = new QTimer;
    connect (timerUpdPlot, SIGNAL(timeout()), SLOT(realTimePoints()));
    timerUpdPlot->start(3000);
    realTimePoints();

---

Curve is connected to zoomer

Code:

---

d_zoomer[0] = new Zoomer( xb, yl, myPlot->canvas());
    d_zoomer[0]->setRubberBand(QwtPicker::RectRubberBand);
    d_zoomer[0]->setRubberBandPen(QColor(Qt::white));
    d_zoomer[0]->setTrackerPen(QColor(Qt::white));

---

Code:

---

void TrendTop::realTimePoints()
{
    if (!db.open()) {
    CreateConnection();
    }
 
    if (db.isOpen())
    {
        QSqlQuery query(db);
        query.exec("SELECT tm, val  FROM currstamp where id = 1136");
 
        if (query.next())
        {
          osX = query.value(0).toUInt();
          osY = query.value(1).toDouble();
        }
 
        X++;
        vectX.append(X);
        vectY.append(osY);
 
        curv1->setSamples(vectX,vectY);
        myPlot->replot();
 
    }
}

---

Attachment 7367

But when I click zoom, plot itself is scaled to the very first point on the graph.
Attachment 7368

Although, I must first select the area that I want to scale.

Slot is invoked by pressing the zoom:

Code:

---

void TrendTop::enableZoomMode(bool on)
{
    d_panner->setEnabled(on);
 
    d_zoomer[0]->setEnabled(on);
    d_zoomer[0]->zoom(0);
 
    d_zoomer1[0]->setEnabled(on);
    d_zoomer1[0]->zoom(0);
 
}

---

What am I doing wrong?

you have to call "setZoomBase" after adding new points

Thanks. I added:

Code:

---

void TrendTop::enableZoomMode(bool on)
{
    d_panner->setEnabled(on);
 
    d_zoomer[0]->setEnabled(on);
    d_zoomer[0]->setZoomBase(on);
    d_zoomer[0]->zoom(0);
 
    d_zoomer1[0]->setEnabled(on);
    d_zoomer1[0]->zoom(0);
 
}

---

The zoom works fine.

But there is another question.
On the plot continues to add new points.
But when I turn off the zoom, plot is redrawn back. But while the plot has been zoomed, to plot new points added. A zoomer returns to the state when the points did not exist. And I have to manually scroll right to the new points.
How to make the graph is redrawn with the newly added points?

Code:

---

plot->setAxisAutoScale( QwtPlot::xBottom );
    plot->setAxisAutoScale( QwtPlot::yLeft );
    plot->updateAxes();
 
    zoomer->setZoomBase( true );

---

this will update axes to include new points and update zoomer base (zoom out).

Big Thanks!