code: def _adjust_scrollbar(self, f):
          
          # Adjust horizontal scrollbar :
          hb = self.horizontalScrollBar()
          hb.setValue(int(f * hb.value() + ((f - 1) * hb.pageStep()/2)))
  
          # Adjust the vertical scrollbar :
          vb = self.verticalScrollBar()
          vb.setValue(int(f * vb.value() + ((f - 1) * vb.pageStep()/2)))
docs: Adjust the scrollbar position to take into account the zooming of
          the figure.