the minimized dialog can not change the geometry?

Below are the steps that create the bug:
1 create a dialog ;
2 minimize the dialog;
3 resize the dialog ;
4 show the dialog ;
the dialog’s size still unchanged .
Below are the code :
m_pDialog = new QDialog();
m_pDialog->resize(100,100);
m_pDialog->showMinimized();
QRect rect = m_pDialog->geometry() ;
m_pDialog->setGeometry(rect.x(),rect.y(),rect.width()*6,rect .height());
m_pDialog->showNormal();
so you can see the the dialog the size unchanged .