Slot in main thread (gui), signal from background thread - how?

[giaur]

Hello,

I have simple gui application. This application creates new background thread. There are some operations to execute in the thread with progress reporting to gui thread.

Some code:
backthread.h:

#ifndef BACKTHREAD_H
#define BACKTHREAD_H
 
#include <QThread>
#include "Counter.h"
 
 
class BackThread : public QThread
{
    public:
        virtual void run();
 
    private:
        Counter counter;
 
 
};
 
#endif // BACKTHREAD_H

#ifndef BACKTHREAD_H
#define BACKTHREAD_H

#include <QThread>
#include "Counter.h"


class BackThread : public QThread
{
    public:
        virtual void run();

    private:
        Counter counter;


};

#endif // BACKTHREAD_H

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backthread.cpp:

#include "backthread.h"
 
void BackThread::run()
{
    int i=0;
    while(1)
    {
        counter.setValue(i);
        sleep( 1 );
        qDebug( "Ping!" );
        i+=10;
        if(i==100) i=0;
    }
}

#include "backthread.h"

void BackThread::run()
{
    int i=0;
    while(1)
    {
        counter.setValue(i);
        sleep( 1 );
        qDebug( "Ping!" );
        i+=10;
        if(i==100) i=0;
    }
}

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Counter.h:

#ifndef COUNTER_H
#define COUNTER_H
 
 
#include <QObject>
 
    class Counter : public QObject
    {
        Q_OBJECT
 
    public:
        Counter() { m_value = 0; }
 
        int value() const { return m_value; }
 
    public slots:
        void setValue(int value);
 
    signals:
        void valueChanged(int newValue);
 
    private:
        int m_value;
    };
 
#endif

#ifndef COUNTER_H
#define COUNTER_H


#include <QObject>

    class Counter : public QObject
    {
        Q_OBJECT

    public:
        Counter() { m_value = 0; }

        int value() const { return m_value; }

    public slots:
        void setValue(int value);

    signals:
        void valueChanged(int newValue);

    private:
        int m_value;
    };

#endif

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Counter.cpp:

#include "Counter.h"
 
void Counter::setValue(int value)
    {
        if (value != m_value) {
            m_value = value;
            emit valueChanged(value);
        }
    }

#include "Counter.h"

void Counter::setValue(int value)
    {
        if (value != m_value) {
            m_value = value;
            emit valueChanged(value);
        }
    }

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And in main windows class:

#include "mainwindow.h"
#include "ui_mainwindow.h"
 
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindow)
{
    ui->setupUi(this);
 
    BackThread th;
    th.start();
}
 
MainWindow::~MainWindow()
{
    delete ui;
}

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    BackThread th;
    th.start();
}

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

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There is Progress Bar widget in main window, and its value should be updated when Counter::m_progress changes. But I have no idea how to define slot for main window class to receive notifications from thread.

Can you help me?