main window close not working

new on forum, be gentle, thx for help.
qt version 4.6.2

This is code:

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent)
{

closeButton = new QPushButton("close");
connect(closeButton, SIGNAL(clicked()), this, SLOT(close()));
setCentralWidget(closeButton);

bool x = false;
// here is problem
if ( !x )
close();
}

Q: why doesn't MainWindow closes?

Very simple.
In the doc it says:

Quote:

---

Closes this widget. Returns true if the widget was closed; otherwise returns false.

First it sends the widget a QCloseEvent.

---

And a close event will be accepted by a visible widget.
A widget gets to be visible after it got a QShowEvent, and since you are still in the constructor, no such event has been received, hence the widget is not yet visible, hence, no effect of close().

Code:

---

#include<qapplication.h>
 
connect(closeButton, SIGNAL(clicked()), qApp, SLOT(quit()));

---

this works