Zoomer for yLeft and yRight (Curves applied to both y-axis) does not work

Since the QwtPlotZoomer can not handle multiple y-Axis I have tried to implement a single Zoomer class handling both axis and thus two zoomer instances at once (I extended the class from one zoomer to a second).

However what happens is that the zoomed region is wrong. I susspect that the left zoomer is called first, and then the right zoomer on an already zoomed region (because I sometimes see a second rectangle and then a second zoom).

Here is a debug output:

Quote:

--- Zoom Stack -----------------
0 *, QRectF(-10,3.72008e-44 19.98x1) , Y2: QRectF(-10,-0.172354 19.98x3.67272)

--- Zoom Stack -----------------
0 , QRectF(-10,3.72008e-44 19.98x1) , Y2: QRectF(-10,-0.172354 19.98x3.67272)

1 *, QRectF(-0.653651,3.72008e-44 1.23913x0.501961) , Y2: QRectF(-2.51714,-0.1
72354 4.97571x1.84356)

The actual zoom region was (X1Y1): (-2.5,0.5) - (2.5,0.0)

The code of the class is the following:

Code:

#include "Zoomer.h"
 
#include <qwt_plot.h>
#include <qwt_plot_panner.h>
#include <qwt_scale_widget.h>
#include <qwt_plot_layout.h>
 
#include <QDebug>
 
// TODO: add documentation
 
class PlotScale{
public:
    PlotScale() : enabled(false){}
    double min;
    double max;
    bool enabled;
};
 
class ZoomerPrivate{
public:
    ZoomerPrivate(QwtPlot * qwtplot)
        : zoomerY2(new QwtPlotZoomer(qwtplot->canvas()))
    {
        zoomerY2->setAxis(QwtPlot::xBottom, QwtPlot::yRight);
    }
    PlotScale plotScaleX;
    PlotScale plotScaleY;
    PlotScale plotScaleX2;
    PlotScale plotScaleY2;
 
    QScopedPointer<QwtPlotZoomer> zoomerY2;
 
};
 
Zoomer::Zoomer(QwtPlot * qwtplot)
    : QwtPlotZoomer(qwtplot->canvas())
    , plot(qwtplot)
    , d(new ZoomerPrivate(qwtplot))
{
    setAxis(QwtPlot::xBottom, QwtPlot::yLeft);
    setTrackerMode(QwtPicker::AlwaysOn);
    init();
    connect(this, SIGNAL(zoomed(const QwtDoubleRect &)), this, SLOT(OnZoomed()));
}
 
Zoomer::~Zoomer()
{
 
}
 
void Zoomer::initScale()
{
    d->zoomerY2->setZoomBase(true);
    this->setZoomBase(true);
    debugZoomerStack();
}
 
/*! \bug{setManualScaleX never used. Manual axis not applied} */
void Zoomer::setScaleX(double min, double max)
{
    d->plotScaleX.min = min;
    d->plotScaleX.max = max;
    d->plotScaleX.enabled = true;
}
 
void Zoomer::setScaleY(double min, double max)
{
    d->plotScaleY.min = min;
    d->plotScaleY.max = max;
    d->plotScaleY.enabled = true;
}
 
void Zoomer::init()
{
    // LeftButton for the zooming
    // MidButton for the panning
    // RightButton: zoom out by 1
    // Ctrl+RighButton: zoom out to full size
 
    this->setMousePattern(QwtEventPattern::MouseSelect2,
                          Qt::RightButton, Qt::ControlModifier);
//    d->zoomerY2->setMousePattern(QwtEventPattern::MouseSelect2,
//                                 Qt::RightButton, Qt::ControlModifier);
//    this->setMousePattern(QwtEventPattern::MouseSelect3,
//                          Qt::RightButton);
 
    // Mid Mouse. Panner moves whole plot area
    QwtPlotPanner *panner = new QwtPlotPanner(plot->canvas());
    panner->setAxisEnabled(QwtPlot::yRight, plot->axisEnabled(QwtPlot::yRight));
    panner->setMouseButton(Qt::MidButton);
 
    // Avoid jumping when labels with more/less digits
    // appear/disappear when scrolling vertically
 
    const QFontMetrics fm(plot->axisWidget(QwtPlot::yLeft)->font());
    QwtScaleDraw *sd = plot->axisScaleDraw(QwtPlot::yLeft);
    sd->setMinimumExtent( fm.width("100.00") );
 
    const QColor c(Qt::darkBlue);
    this->setRubberBandPen(c);
    this->setTrackerPen(c);
 
    // Reinitialized the zoom stack with scaleRect() as base.
    // Calls replot before initializing the zoomer with its scales.
    initScale();
}
 
/*!
 *  modify the visual appearance of tracker text.
 */
QwtText Zoomer::trackerText( const QwtDoublePoint& p ) const
{
    QwtText t( QwtPlotPicker::trackerText( p ));
 
    QColor c(Qt::white);
    c.setAlpha(180);
    t.setBackgroundBrush( QBrush(c) );
 
    return t;
}
 
/*!
 *  handle zoom events, especially reset zoom-base
 *  if back to initial zoom state
 */
void Zoomer::OnZoomed()
{
    static int previousIndex = 0;
 
    int index = this->zoomRectIndex();
 
    debugZoomerStack();
 
    // save startup scales
    // TODO: can not retrieve scales. Must be set externally
    if ((index  == 0) && (previousIndex == 0)) {
        d->plotScaleX.enabled = plot->axisAutoScale(xAxis());
        d->plotScaleY.enabled = plot->axisAutoScale(yAxis());
        initScale();
    }
 
    // only reset zoombase and replot if coming from
    // zoomed state and state is at the initual size
    if ((index  == 0) && (previousIndex > 0)) {
 
        if (!d->plotScaleX.enabled) {
            plot->setAxisAutoScale(xAxis());
        } else {
            plot->setAxisScale(xAxis(), d->plotScaleX.min, d->plotScaleX.max);
        }
 
        if (!d->plotScaleY.enabled) {
            plot->setAxisAutoScale(QwtPlot::yLeft);
            plot->setAxisAutoScale(QwtPlot::yRight);
        } else {
            plot->setAxisScale(yAxis(), d->plotScaleY.min, d->plotScaleY.max);
        }
 
        initScale();
    }
    previousIndex = index;
}
 
void Zoomer::zoomOut()
{
    this->zoom(-1);
    d->zoomerY2->zoom(-1);
}
 
void Zoomer::zoomIn()
{
    this->zoom(1);
    d->zoomerY2->zoom(1);
}
 
void Zoomer::zoomBase()
{
    this->zoom(0);
    d->zoomerY2->zoom(0);
}
 
 
void Zoomer::debugZoomerStack()
{
    int index = this->zoomRectIndex();
    QStack<QwtDoubleRect> stack = this->zoomStack();
    QStack<QwtDoubleRect> stackY2 = d->zoomerY2->zoomStack();
    qDebug() << "--- Zoom Stack -----------------";
    for(int i = 0; i < stack.size(); ++i) {
        if (i == index) {
            qDebug() << i << "*, " << stack.at(i) << ", Y2: " << stackY2.at(i);
        } else {
            qDebug() << i << ", " << stack.at(i) << ", Y2: " << stackY2.at(i);
        }
    }
}

Maybe my whole approach is wrong?
I do not know what really to debug.

Matthias