'The forward kwarg is passed on to set_size_inches'

def _set_dpi(self, dpi, forward=True):

    self._dpi = dpi
    self.dpi_scale_trans.clear().scale(dpi, dpi)
    (w, h) = self.get_size_inches()
    self.set_size_inches(w, h, forward=forward)
    self.callbacks.process(u'dpi_changed', self)
