title: Where does the function call occur?
body: <p>In the following code from the <em>C++ GUI Programming with Qt 4</em>, where is the call for the <code>on_lineEdit_textchanged()</code> function occuring, as it is not explicitly shown in the code?</p>
  
  <pre><code>#include &lt;QtGui&gt;
  #include "gotocelldialog.h"
  GoToCellDialog::GoToCellDialog(QWidget *parent): QDialog(parent)
  {
  setupUi(this); 
  QRegExp regExp("[A-Za-z][1-9][0-9]{0,2}");
  QValidator *validator = new QRegExpValidator(regExp, this);
  lineEdit-&gt;setValidator(validator);
  connect(okButton, SIGNAL(clicked()),this, SLOT(accept()));
  connect(cancelButton, SIGNAL(clicked()), this, SLOT(reject()));
  }
  void GoToCellDialog::on_lineEdit_textChanged()
  {
  okButton-&gt;setEnabled(lineEdit-&gt;hasAcceptableInput());
  }
  </code></pre>
  
  <p>Thanks.</p>