self.documento.clear()
self.documento.setHtml(html)
left=20; top=10; right=10; bottom=10
self.dialogo=QtGui.QPrintPreviewDialog(self)
self.dialogo.printer().setPageMargins(left,top,right,bottom,QtGui.QPrinter.Millimeter)
self.dialogo.paintRequested.connect(self.documento.print_)
self.dialogo.showMaximized()