//mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <thread>
#include <mutex>
#include <QMainWindow>

namespace Ui { class MainWindow; }

struct Observer
{
    virtual void notify() = 0;
};

class Core
{
public:
    void *run()
        {
            std::thread thread(&Core::runP, this);
            thread.detach();
        }

    void setObserver(Observer *observer) { _observer = observer; }
    int ii() const { return _ii; }
    void nextIi() { _ii++; }

    void lock()    { _mutex.lock(); }
    bool tryLock() { return _mutex.try_lock(); }
    void unlock()  { _mutex.unlock(); }

private:
    void runP()
        {
            for (int i = 1; i <= 1000; i++) {
                if (i % 10 == 0) {
                    lock();
                    nextIi();
                    unlock();
                    notify();
                }
            }
        }

    void notify() { _observer->notify(); }
    Observer *_observer;
    int _ii;
    std::mutex _mutex;
};

struct MwObserver : public QObject, public Observer
{
    Q_OBJECT

public:
    explicit MwObserver(struct MainWindow *mainWindow) { _mainWindow = mainWindow; }
    virtual void notify() { emit SomeEvent(); }

signals:
    void SomeEvent();

public:
    MainWindow *_mainWindow;
};


class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow() { delete _ui; }

public slots:
    void run() { _core.run(); }
    void upd();

private:
    Ui::MainWindow *_ui;
    MwObserver _observer;
    Core _core;
};

#endif


//mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    _ui(new Ui::MainWindow),
    _observer(this)
{
    _ui->setupUi(this);
    connect(_ui->pushButtonRun, SIGNAL(clicked(bool)), this, SLOT(run()));
    connect(&_observer, SIGNAL(SomeEvent()), this, SLOT(upd()));
}

void MainWindow::upd()
{
    _core.lock();
    setWindowTitle(QString::number(_core.ii()));
    _core.unlock();
}