QwtPlot + UI problem

[petromp]

Hello, I'm trying to learn how to use Qwt and I'm stucked with one problem.

When I create a custom application with just main function everything works fine. (the code is based on examples from qwt)

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
 
    QWidget w;
    double x[100];
    double y[100];
 
    for(int i=0;i<100;i++)
    {
        x[i] = i/20.0;
        y[i] = sin(x[i]);
    }
    QHBoxLayout *layout = new QHBoxLayout(&w);
    layout->setContentsMargins( 0, 0, 0, 0 );
    QwtPlot *myPlot = new QwtPlot(&w);
    myPlot->setMinimumSize(w.geometry().width()-20,w.geometry().height()-20);
    // add curve
    QwtPlotCurve *curve = new QwtPlotCurve();
    curve->setRawSamples(x, y, 100);
    curve->setSymbol(new QwtSymbol(QwtSymbol::Cross, Qt::NoBrush,
        QPen(Qt::black), QSize(5, 5) ) );
    curve->setPen(QColor(Qt::darkGreen));
    curve->setStyle(QwtPlotCurve::Lines);
    curve->setCurveAttribute(QwtPlotCurve::Fitted);
    curve->attach(myPlot);
    QPushButton *b = new QPushButton(&w);
    layout->addWidget(myPlot);
    layout->addWidget(b);
    w.setLayout(layout);
    w.show();
 
    return a.exec();
}

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QWidget w;
    double x[100];
    double y[100];

    for(int i=0;i<100;i++)
    {
        x[i] = i/20.0;
        y[i] = sin(x[i]);
    }
    QHBoxLayout *layout = new QHBoxLayout(&w);
    layout->setContentsMargins( 0, 0, 0, 0 );
    QwtPlot *myPlot = new QwtPlot(&w);
    myPlot->setMinimumSize(w.geometry().width()-20,w.geometry().height()-20);
    // add curve
    QwtPlotCurve *curve = new QwtPlotCurve();
    curve->setRawSamples(x, y, 100);
    curve->setSymbol(new QwtSymbol(QwtSymbol::Cross, Qt::NoBrush,
        QPen(Qt::black), QSize(5, 5) ) );
    curve->setPen(QColor(Qt::darkGreen));
    curve->setStyle(QwtPlotCurve::Lines);
    curve->setCurveAttribute(QwtPlotCurve::Fitted);
    curve->attach(myPlot);
    QPushButton *b = new QPushButton(&w);
    layout->addWidget(myPlot);
    layout->addWidget(b);
    w.setLayout(layout);
    w.show();

    return a.exec();
}

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The problem is when i try to copy this part of code and put it in MainWindow designed in QtCreator.

void MainWindow::initGraph()
{
    double x[100];
    double y[100];
 
    for(int i=0;i<100;i++)
    {
        x[i] = i/100.0;
        y[i] = sin(x[i]);
    }
    QHBoxLayout *layout = new QHBoxLayout(ui->widget);
    layout->setContentsMargins( 0, 0, 0, 0 );
    QwtPlot *myPlot = new QwtPlot(ui->widget);
    myPlot->setMinimumSize(ui->widget->geometry().width()-20,ui->widget->geometry().height()-20);
    myPlot->updateGeometry();
    // add curves
    QwtPlotCurve *curve = new QwtPlotCurve();
    curve->setRawSamples(x, y, 100);
    curve->setSymbol(new QwtSymbol(QwtSymbol::Cross, Qt::NoBrush,
        QPen(Qt::black), QSize(5, 5) ) );
    curve->setPen(QColor(Qt::darkGreen));
    curve->setStyle(QwtPlotCurve::Lines);
    curve->setCurveAttribute(QwtPlotCurve::Fitted);
    curve->attach(myPlot);
    myPlot->autoReplot();
    myPlot->replot();
    myPlot->autoRefresh();
    layout->addWidget(myPlot);
    ui->widget->setLayout(layout);
}
 
//and main 
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.initGraph();
    w.show();
 
    return a.exec();
}

void MainWindow::initGraph()
{
    double x[100];
    double y[100];

    for(int i=0;i<100;i++)
    {
        x[i] = i/100.0;
        y[i] = sin(x[i]);
    }
    QHBoxLayout *layout = new QHBoxLayout(ui->widget);
    layout->setContentsMargins( 0, 0, 0, 0 );
    QwtPlot *myPlot = new QwtPlot(ui->widget);
    myPlot->setMinimumSize(ui->widget->geometry().width()-20,ui->widget->geometry().height()-20);
    myPlot->updateGeometry();
    // add curves
    QwtPlotCurve *curve = new QwtPlotCurve();
    curve->setRawSamples(x, y, 100);
    curve->setSymbol(new QwtSymbol(QwtSymbol::Cross, Qt::NoBrush,
        QPen(Qt::black), QSize(5, 5) ) );
    curve->setPen(QColor(Qt::darkGreen));
    curve->setStyle(QwtPlotCurve::Lines);
    curve->setCurveAttribute(QwtPlotCurve::Fitted);
    curve->attach(myPlot);
    myPlot->autoReplot();
    myPlot->replot();
    myPlot->autoRefresh();
    layout->addWidget(myPlot);
    ui->widget->setLayout(layout);
}

//and main 

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.initGraph();
    w.show();

    return a.exec();
}

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After running code above I see my app, axis of the plot are scaled but curve is not painted properly (I think only first point is painted). I tried couple of functions from plot to fix it (as you can see in code above). I've created 2 or 3 gui apps using qtCreator's designer and even with just 1 main widget it doesn't work fine. Could anyone tell me where do I make a mistake and how to fix that problem?

Sorry if someone finds it hard to understand what I've written here but english is not my native language.

[alainstgt]

1. you must first define the constructor of your MainWindow class, and don't forget to derive it from QMainWindow.
2. The way your programm is structured, you do not need an Mainwindow::initGraph() method, you can put everything in your MainWindow() method.
3. I also recommend to split the code in 3 files, main.cpp, mainwindow.cpp and mainwindow.h

[petromp]

[EDIT] : hmn maybe I didn't say all of this correct (and coping just a fragments of bigger code is not a good thing) so this is simple new project with my problem...

mainwindow.h :

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QMainWindow>
 
namespace Ui {
    class MainWindow;
}
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
 
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
 
private:
    Ui::MainWindow *ui;
};
 
#endif // MAINWINDOW_H

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
    class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

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mainwindow.cpp

#include <qwt_plot_curve.h>
#include <qwt_plot.h>
#include <qapplication.h>
#include <qwt_symbol.h>
#include <qwt_math.h>
#include <qcolor.h>
#include <qlayout.h>
#include <qpainter.h>
#include "mainwindow.h"
#include "ui_mainwindow.h"
 
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    double x[100];
    double y[100];
 
    for(int i=0;i<100;i++)
    {
        x[i] = i/20.0;
        y[i] = 0;
    }
    QwtPlot *myPlot = new QwtPlot(this);
    // add curves
    QwtPlotCurve *curve = new QwtPlotCurve();
    curve->setRawSamples(x, y, 100);
    curve->setSymbol(new QwtSymbol(QwtSymbol::Cross, Qt::NoBrush,
        QPen(Qt::black), QSize(5, 5) ) );
    curve->setPen(QColor(Qt::darkGreen));
    curve->setStyle(QwtPlotCurve::Lines);
    curve->setCurveAttribute(QwtPlotCurve::Fitted);
    curve->attach(myPlot);
    this->setCentralWidget(myPlot);
    myPlot->autoReplot();
    myPlot->replot();
}
 
MainWindow::~MainWindow()
{
    delete ui;
}

#include <qwt_plot_curve.h>
#include <qwt_plot.h>
#include <qapplication.h>
#include <qwt_symbol.h>
#include <qwt_math.h>
#include <qcolor.h>
#include <qlayout.h>
#include <qpainter.h>
#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    double x[100];
    double y[100];

    for(int i=0;i<100;i++)
    {
        x[i] = i/20.0;
        y[i] = 0;
    }
    QwtPlot *myPlot = new QwtPlot(this);
    // add curves
    QwtPlotCurve *curve = new QwtPlotCurve();
    curve->setRawSamples(x, y, 100);
    curve->setSymbol(new QwtSymbol(QwtSymbol::Cross, Qt::NoBrush,
        QPen(Qt::black), QSize(5, 5) ) );
    curve->setPen(QColor(Qt::darkGreen));
    curve->setStyle(QwtPlotCurve::Lines);
    curve->setCurveAttribute(QwtPlotCurve::Fitted);
    curve->attach(myPlot);
    this->setCentralWidget(myPlot);
    myPlot->autoReplot();
    myPlot->replot();
}

MainWindow::~MainWindow()
{
    delete ui;
}

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main.cpp

#include <qwt_plot_curve.h>
#include <qwt_plot.h>
#include <QApplication>
#include <qwt_symbol.h>
#include <qwt_math.h>
#include <qcolor.h>
#include <QDebug>
#include <QPushButton>
#include <qlayout.h>
#include <qpainter.h>
#include "mainwindow.h"
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
/*
    QWidget w;
    double x[100];
    double y[100];
 
    for(int i=0;i<100;i++)
    {
        x[i] = i/20.0;
        y[i] = sin(x[i]);
    }
    QHBoxLayout *layout = new QHBoxLayout(&w);
    layout->setContentsMargins( 0, 0, 0, 0 );
    QwtPlot *myPlot = new QwtPlot(&w);
    myPlot->setMinimumSize(w.geometry().width()-20,w.geometry().height()-20);
    myPlot->updateGeometry();
    // add curves
    QwtPlotCurve *curve = new QwtPlotCurve();
    curve->setRawSamples(x, y, 100);
    curve->setSymbol(new QwtSymbol(QwtSymbol::Cross, Qt::NoBrush,
        QPen(Qt::black), QSize(5, 5) ) );
    curve->setPen(QColor(Qt::darkGreen));
    curve->setStyle(QwtPlotCurve::Lines);
    curve->setCurveAttribute(QwtPlotCurve::Fitted);
    curve->attach(myPlot);
    layout->addWidget(myPlot);
    w.update();
*/
    MainWindow w;
    w.show();
 
    return a.exec();
}

#include <qwt_plot_curve.h>
#include <qwt_plot.h>
#include <QApplication>
#include <qwt_symbol.h>
#include <qwt_math.h>
#include <qcolor.h>
#include <QDebug>
#include <QPushButton>
#include <qlayout.h>
#include <qpainter.h>
#include "mainwindow.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
/*
    QWidget w;
    double x[100];
    double y[100];

    for(int i=0;i<100;i++)
    {
        x[i] = i/20.0;
        y[i] = sin(x[i]);
    }
    QHBoxLayout *layout = new QHBoxLayout(&w);
    layout->setContentsMargins( 0, 0, 0, 0 );
    QwtPlot *myPlot = new QwtPlot(&w);
    myPlot->setMinimumSize(w.geometry().width()-20,w.geometry().height()-20);
    myPlot->updateGeometry();
    // add curves
    QwtPlotCurve *curve = new QwtPlotCurve();
    curve->setRawSamples(x, y, 100);
    curve->setSymbol(new QwtSymbol(QwtSymbol::Cross, Qt::NoBrush,
        QPen(Qt::black), QSize(5, 5) ) );
    curve->setPen(QColor(Qt::darkGreen));
    curve->setStyle(QwtPlotCurve::Lines);
    curve->setCurveAttribute(QwtPlotCurve::Fitted);
    curve->attach(myPlot);
    layout->addWidget(myPlot);
    w.update();
*/
    MainWindow w;
    w.show();

    return a.exec();
}

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mainwindow.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>400</width>
    <height>300</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralWidget"/>
 </widget>
 <layoutdefault spacing="6" margin="11"/>
 <resources/>
 <connections/>
</ui>

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>400</width>
    <height>300</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralWidget"/>
 </widget>
 <layoutdefault spacing="6" margin="11"/>
 <resources/>
 <connections/>
</ui>

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two outcomes (on screens you can see which part of main function was commented which not)



and second



the question is : why first outcome is like that ? it paints only first point where is the rest ?

[Uwe]

Your code uses QwtPlotCurve::setRawSamples(), but the passed arrays are from the stack and gone after leaving the constructor.

Uwe