code: def detailxy(self, canvas, button, data_x, data_y):
          
          if button == 0:
              # TODO: we could track the focus changes to make this check
              # more efficient
              chviewer = self.fv.getfocus_viewer()
              # Don't update global information if our chviewer isn't focused
              if chviewer != self.fitsimage:
                  return True
  
              # Add offsets from cutout
              data_x = data_x + self.pick_x1
              data_y = data_y + self.pick_y1
  
              return self.fv.showxy(chviewer, data_x, data_y)
docs: Motion event in the pick fits window.  Show the pointing
          information under the cursor.