Access class from function - c++

Question

Is there another way besides declaring a static method inside a class to call it from outside the class ?
Here is my code (See the question marked as comment )
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
_stdcall BOOL EnumWindowsProc(HWND hw,LPARAM lp)
{
char title[255];
memset(title,0,255);
GetWindowTextA(hw,title,255);
qDebug() << title << endl;
// How can I access class MainWindow from this function ?
return true;
}
void MainWindow::on_pushButton_clicked()
{
EnumWindows(&EnumWindowsProc,0);
}

Answer 1

The typical way of doing this in the Windows world is to pass a pointer to the Enum function, like this:
void MainWindow::on_pushButton_clicked()
{
EnumWindows(&EnumWindowsProc,reinterpret_cast<void*>(this));
}
...and then cast it back in the callback:
_stdcall BOOL EnumWindowsProc(HWND hw,LPARAM lp)
{
char title[255];
memset(title,0,255);
GetWindowTextA(hw,title,255);
qDebug() << title << endl;
// How can I access class MainWindow from this function ?
MainWindow* that = reinterpret_cast<MainWindow*>(lp);
return true;
}