Windows 7: QWizard resizes vertically when moving the window and using CustomizeWindowHint

A QWizard with no window title buttons (using the Qt::CustomizeWindowHint flag) will resize vertically when the window is moved and the wizard's frame is not rendered/positioned correctly.

This issue was not present on Windows XP, and it appears to be caused by QVistaHelper::resizeEvent() using some wrong offset/height if no window title button is present.

The attached screenshot shows both the vertically resized dialog and the frame not showing in the top part of the wizard page.

To reproduce it use one of the QWizard examples shipped with Qt, like the ClassWizard, and customize the window flags:

// #1
  ClassWizard::ClassWizard(QWidget *parent) 
    : QWizard(parent, Qt::Dialog|Qt::CustomizeWindowHint)
// #2
  ClassWizard::ClassWizard(QWidget *parent) 
    : QWizard(parent, Qt::Dialog|Qt::CustomizeWindowHint|Qt::WindowCloseButtonHint)

#1 will reproduce the problem, and #2 will work as expected.