Problems with replot() and dynamical plotting

Hi there,

I have a problem with dynamically updating a QwtPlot. I based my code on the example "data_plot" but instead of having a timer inside of my data_plot-object I created a slot which gives me new values to add. Here is the code:

Code:

---

#ifndef _DATA_PLOT_H
#define _DATA_PLOT_H 1
 
#include <qwt_plot.h>
 
const int PLOT_SIZE = 201;      // 0 to 200
 
class DataPlot : public QwtPlot
{
    Q_OBJECT
 
public:
    DataPlot(QWidget* = NULL);
 
public slots:
    void refreshP(double val);
 
private:
 
    double d_x[PLOT_SIZE]; 
    double d_y[PLOT_SIZE]; 
    double d_z[PLOT_SIZE];
};
 
#endif

---

Code:

---

#include <stdlib.h>
#include <qwt_painter.h>
#include <qwt_plot_canvas.h>
#include <qwt_plot_marker.h>
#include <qwt_plot_curve.h>
#include <qwt_scale_widget.h>
#include <qwt_legend.h>
#include <qwt_scale_draw.h>
#include <qwt_math.h>
#include "data_plot.h"
#include <iostream>
 
DataPlot::DataPlot(QWidget *parent): QwtPlot(parent)
{
 
    // Disable polygon clipping
    QwtPainter::setDeviceClipping(false);
 
    // We don't need the cache here
    canvas()->setPaintAttribute(QwtPlotCanvas::PaintCached, false);
    canvas()->setPaintAttribute(QwtPlotCanvas::PaintPacked, false);
 
 
    //  Initialize data
    for (int i = 0; i< PLOT_SIZE; i++)
    {
        d_x[i] = 0.5 * i;     // time axis
        d_y[i] = 0;
    }
 
    // Insert new curves
    QwtPlotCurve *cRight = new QwtPlotCurve("Data Moving Right");
    cRight->attach(this);
 
    // Set curve styles
    cRight->setPen(QPen(Qt::red));
 
    // Attach (don't copy) data. Both curves use the same x array.
    cRight->setRawData(d_x, d_y, PLOT_SIZE);
 
}
 
//  Generate new values 
void DataPlot::refreshP(double val)
{
    for ( int j = 0; j < PLOT_SIZE - 1; j++ )
        d_y[j] = d_y[j+1];
 
    d_y[PLOT_SIZE - 1] = val;
    // update the display
    replot();
 
}

---

Then here is how it is used:

Code:

---

#include "window.h"
 
Window::Window(QWidget *parent) : QWidget(parent)
{
.
.
.
Widget2D *evolving_obj = new Widget2D;
DataPlot *dynamics = new DataPlot(this);
connect(evolving_obj, SIGNAL(newSignal(double)), dynamics, SLOT(replot())); // this does not work
connect(someButton , SIGNAL(clicked()), dynamics, SLOT(replot()));  //this works!
 
.
.
.
}

---

Widget2D has a timer and produces data and of course Widget2D has a signal "void newSignal(double nS);" with the corresponding body. The new data is correctly stores in the array d_Y but the plot is not updated.

If I however click on the someButton, the plot is updated.

I have no clue how to solve this problem. Thanks for your help.

Hi gi0rgi0ne,
Your slot is wrong in the connection:

Code:

---

connect(evolving_obj, SIGNAL(newSignal(double)), dynamics, SLOT(replot()));

---

use this:

Code:

---

connect(evolving_obj, SIGNAL(newSignal(double)), dynamics, SLOT(refreshP(double)));

---

Hüseyin

Thanks for your help Hüseyin,
unfortunaltely this does not help. I mixed up some code while posting, sorry.

Code:

---

connect(evolving_obj, SIGNAL(newSignal(double)), dynamics, SLOT(refreshP(double)));

---

is the way I implemented it, and it did not work.

My alternative was to overwrite replot()

Code:

---

void DataPlot::replot()
{
   refreshP(1.0); //this just to give it some value
   QwtPlot::replot();
}

---

then I commented the "replot()" statement out of refreshP() and use the following connect:

Code:

---

connect(evolving_obj, SIGNAL(newSignal(double)), dynamics, SLOT(replot()));

---

This did not help either.
Any idea?

Hmm, it seems you override the original replot.
Maybe closing the auto replot works:

Code:

---

DataPlot::DataPlot(QWidget *parent): QwtPlot(parent)
{
setAutoReplot(false);

---

or try to not override replot.


Hüseyin

That did not help either.

What is funny is that

Code:

---

connect(evolving_obj, SIGNAL(newSignal(double)), dynamics, SLOT(refreshP(double)));

---

does not work.

Code:

---

connect(evolving_obj, SIGNAL(newSignal(double)), dynamics, SLOT(replot()));

---

does not have any effect, HOWEVER

Code:

---

connect(someButton, SIGNAL(clicked()), dynamics, SLOT(replot()));

---

works!! I do not understand that.

Why does one SIGNAL work and the other one does not??

Can you give the "Window.h". I want to see that your signal definition in the header. And also want to see the timer configuration (timer->start(), connect(timer,...) ...etc.) if it is possible.

Sometimes different function names doesn't give any error but it also doesn't work.


Hüseyin

my window.h

Code:

---

#ifndef WINDOW_H
#define WINDOW_H
 
#include <QWidget>
#include <QLabel>
#include <QApplication>
#include <QFont>
#include <QGridLayout>
#include <QHBoxLayout>
#include <QPushButton>
#include <QVBoxLayout>
#include <QtGui>
 
#include <iostream>
 
#include "widget2d.h"
#include "lcdrange.h"
 
 
#include <qapplication.h>
#include <qmainwindow.h>
#include <qwt_counter.h>
#include <qtoolbar.h>
#include <qlabel.h>
#include <qlayout.h>
#include "data_plot.h"
 
 
 
QT_BEGIN_NAMESPACE
class QLabel;
QT_END_NAMESPACE
 
class Window : public QWidget
{
 
public:
    Window(QWidget *parent = 0);
 
 
 
};
 
#endif

---

and here the code of the widget2d.h, where the signals and the timer are:

Code:

---

#ifndef WIDGET2D_H
#define WIDGET2D_H
 
#include <QWidget>
#include <QImage>
#include <QRgb>
#include <iostream>
//#include <cstdlib>
#include <QtGui>
//#include <dranxor.h>
#include "ExVolWid.h"
 
class Widget2D : public QWidget
{
    Q_OBJECT
 
public:
    Widget2D(QWidget *parent = 0);
 
    QSize minimumSizeHint() const;
 
public slots:
    void nextAnimationFrame();
    void setGridScale(int value);
    void ScaleGrid();
    void changeStatus(bool s);
    void changeRes(int value);
 
signals:
    void scaleChanged(int newValue);
    void newSignal(double nS);
 
protected:
    void paintEvent(QPaintEvent *event);
    void timerEvent(QTimerEvent *event);
 
private:
    int ll;
    bool isStarted;
    bool isPaused;
    bool changed;
    int gridScale;
    ExVolWid* my_system;
    QBasicTimer timer;
};
 
#endif

---

and widget2d.cpp code :

Code:

---

#include "widget2d.h"
#define min(a, b) a < b ? a : b
 
Widget2D::Widget2D(QWidget *parent) : QWidget(parent)
{
 
    ll = 50;
    gridScale = 400;
    setBackgroundRole(QPalette::Base);
    setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    changed = true;
    my_system = new ExVolWid(ll,1.0);
 
}
////////////
QSize Widget2D::minimumSizeHint() const
{
    return QSize(400, 400);
}
////////////
void Widget2D::setGridScale(int value)
{
     gridScale = value;
     emit scaleChanged(gridScale);
}
////////////
void Widget2D::ScaleGrid()
{
     gridScale = min(size().height(),size().width());
     update();
     emit scaleChanged(gridScale);
}
//////////////
void Widget2D::changeStatus(bool s)
{
    if (s){
        if (changed){
             delete my_system;
             my_system = new ExVolWid(ll,1.0);
             changed = false;
        }
        timer.start(50,this);
    }
    else {
        if (timer.isActive())
             timer.stop();
    }
}
//////////////////
void Widget2D::timerEvent(QTimerEvent *){
    update(); 
}
//////////////////
void Widget2D::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    painter.drawImage(0,0,my_system->get_pic().scaled(gridScale,gridScale));
    emit newSignal(my_system->getSignal());
    my_system->evolve();
}
///////////////////
void Widget2D::changeRes(int value)
{
   ll = value;
   changed = true;
}
///////////////////

---

thanks for your help.

Sorry, I am not good at paintEvent related subjects. But it seems the problem is your style when using the timer event.
Try to get data in timer event, and replot it in the timer.
Maybe calling the replot in the paintEvent is confusing.


Hüseyin

I do not use paintEvent with the data_plot class. I just use it to let my Widget2d evolve, this is unrelated to the data_plot. My Widget2d-object (evolving_obj) then sends a new value via newSignal(double nS) to the data_plot object.

So data_plot does not need a timer, it should update when ever it gets a new value.

Quote:

---

Maybe calling the replot in the paintEvent is confusing.

---

The methods "void Widget2D::timerEvent(QTimerEvent *)" and "void Widget2D::paintEvent(QPaintEvent *)" are only talking to the Widget2D object and should be (at least I hope, tell me if I am wrong) completely unrelated to the data_plot-object.