def add_btn_ok(self,label_ok):
        """
        Adds an OK button to allow the user to exit the dialog.
        
        This widget can be triggered by setting the label ``label_ok`` to a string.
        
        This widget will be mostly centered on the screen, but below the main label
        by the double of its height.
        """
        # OK Button
        self.wbtn_ok = button.Button("btn_ok",self,self.window,self.peng,
                        pos=lambda sw,sh, bw,bh: (sw/2-bw/2,sh/2-bh/2-bh*2),
                        size=[0,0],
                        label=label_ok,
                        borderstyle=self.borderstyle
                        )
        self.wbtn_ok.size = lambda sw,sh: (self.wbtn_ok._label.font_size*8,self.wbtn_ok._label.font_size*2)
        self.addWidget(self.wbtn_ok)
        
        def f():
            self.doAction("click_ok")
            self.exitDialog()
        self.wbtn_ok.addAction("click",f)
Adds an OK button to allow the user to exit the dialog.
        
        This widget can be triggered by setting the label ``label_ok`` to a string.
        
        This widget will be mostly centered on the screen, but below the main label
        by the double of its height.