Showing annotation-arrows when I zoom

Hi,
How can I show annotation-arrows when I zoom ?
I tried:
(But none of the arrows are seen)
‘’’
def callback(attr, old, new):
xmin=p.x_range.start
xmax=p.x_range.end
ymin=p.y_range.start
ymax=p.y_range.end

      if ( ((xmax-xmin) < 100000) | ((ymax-ymin) < 100000 ) ):,
            for arrow in arrow_arr: 
                   p.add_layout(arrow)   ## arrow_arr contains arrow objects 
                                                      ## ie   Arrow(end=VeeHead( .... 

p.x_range.on_change(‘start’, callback)
p.x_range.on_change(‘end’, callback)
p.y_range.on_change(‘start’, callback)
p.y_range.on_change(‘end’, callback)
‘’’
I will appreciate any insight.
Regards