QT project QThread and C++ Thread limitations

Question

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QFileSystemModel>
#include <QThread>

#include <statusdialog.h>
#include <pbt.h>
#include <stdint.h>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private slots:
    //void on_treeView_clicked(const QModelIndex &index);

    void onCustomContextMenuTV(const QPoint &point);

    void dirSize();

    void getSelectedTreeItemSize();
    void resultHandle(uint64_t);

signals:
    void sizeCalculation(uint64_t);

private:
    Ui::MainWindow *ui;
    QString sPath;
    QFileSystemModel *dirmodel;
    QFileSystemModel *filemodel;
    QAction *dirSizeAct;
    statusDialog statusdialog;
};

#endif // MAINWINDOW_H

pbt.h

   #ifndef STATUSDIALOG_H
#define STATUSDIALOG_H

#include <QDialog>

#include <stdint.h>

namespace Ui {
class statusDialog;
}

class statusDialog : public QDialog
{
    Q_OBJECT

public:
    explicit statusDialog(QWidget *parent = 0);
    ~statusDialog();
    void setProgressbarMax(uint64_t);

private slots:
    void on_pushButton_clicked();

private:
    Ui::statusDialog *ui;
};

#endif // STATUSDIALOG_H

statusdialog.h

#ifndef STATUSDIALOG_H
#define STATUSDIALOG_H

#include <QDialog>

#include <stdint.h>

namespace Ui {
class statusDialog;
}

class statusDialog : public QDialog
{
    Q_OBJECT

public:
    explicit statusDialog(QWidget *parent = 0);
    ~statusDialog();
    void setProgressbarMax(uint64_t);

private slots:
    void on_pushButton_clicked();

private:
    Ui::statusDialog *ui;
};

#endif // STATUSDIALOG_H

mainwindow.cpp

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

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

    sPath = "C:/";
    dirmodel = new QFileSystemModel(this);
    dirmodel->setFilter(QDir::NoDotAndDotDot | QDir::AllDirs);
    dirmodel->setRootPath(sPath);
    ui->treeView->setModel(dirmodel);

    ui->treeView->setContextMenuPolicy(Qt::CustomContextMenu);
    connect(ui->treeView, SIGNAL(customContextMenuRequested(const QPoint &)), this, SLOT(onCustomContextMenuTV(const QPoint &)));

    connect(this,SIGNAL(sizeCalculation(uint64_t)),this,SLOT(resultHandle(uint64_t)));

}

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

void MainWindow::resultHandle(uint64_t t_size)
{
    statusdialog.setProgressbarMax(t_size);
}



void MainWindow::onCustomContextMenuTV(const QPoint &point)
{
    dirSizeAct = new QAction(tr("Size"), this);

    connect(dirSizeAct, SIGNAL(triggered()), this, SLOT(dirSize()));

    QMenu contextMenu(this);

    contextMenu.addAction(dirSizeAct);

    QModelIndex index = ui->treeView->indexAt(point);
    if (index.isValid()){
        contextMenu.exec(ui->treeView->mapToGlobal(point));
    }
}

void MainWindow::dirSize()
{
    pBT pbt;
    pbt.setFP(this->getSelectedTreeItemSize);
    QThread thread1;

    connect(&thread1,SIGNAL(started()),&pbt,SLOT(startThreadAction()));//Clone the object and it will not work, becouse it is QWidget

    pbt.moveToThread(&thread1);


    thread1.start();//Starts in the same thread

    statusdialog.setModal(true);
    statusdialog.exec();
}

void MainWindow::getSelectedTreeItemSize()
{
    QModelIndex index = ui->treeView->selectionModel()->selectedIndexes().takeFirst();
    QString dirPath = dirmodel->filePath(index);

    QDirIterator it(dirPath, QStringList() << "*.*", QDir::Files, QDirIterator::Subdirectories);
    uint64_t t_size = 0;

    while (it.hasNext()) {
        QFile myFile(it.next());
        if (myFile.open(QIODevice::ReadOnly)){
            t_size += myFile.size();
            myFile.close();
        }
    }

    emit sizeCalculation(t_size);
}

pbt.cpp

#include "pbt.h"

pBT::pBT(QObject *parent) : QObject(parent)
{

}

void pBT::startThreadAction()
{
      this->fp1();
}

void pBT::setFP(void (*fp1)())
{
    this->fp1 = fp1;
}

statusdialog.cpp

#include "statusdialog.h"
#include "ui_statusdialog.h"

statusDialog::statusDialog(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::statusDialog)
{
    ui->setupUi(this);
}

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

void statusDialog::on_pushButton_clicked()
{
    this->close();
}

void statusDialog::setProgressbarMax(uint64_t size)
{
    ui->progressBar->setMaximum(size);
}

main.cpp

#include "mainwindow.h"
#include <QApplication>

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

    return a.exec();
}

To see more info of what I am doing you can look this topic(It is all about prograssbar and threaded execution of job). Theoretically I whant to run a member function of mainwindow(which use member variables of mainwindow) into new thread(the function is not static) inside slot dirSize()(also member slot of the same class mainwindow), but it seems with QThread it is necessary to create new class(no matter if I will inherit QThread class or use moveToThread function of QObject) and run that class in new thread. If I use C++ thread.h the function I run must be static, nevermind I have tried to create pBT class in which I have function pointer fp1 and public slot startThreadedAction, but when try to buil this error occures:

C:\Users\niki\Documents\EPsimple\mainwindow.cpp:54: error: C3867: 'MainWindow::getSelectedTreeItemSize': function call missing argument list; use '&MainWindow::getSelectedTreeItemSize' to create a pointer to member

I don`t want to create function pointer to static function! How can I fix this?