clip_on vs clip_box

What is the difference between setting clip_on and clip_box? For
an annotation, there does not appear to be any difference. But if I give the
annotation a bbox, then only clip_box works to clip the box at the axes
boundary. The example below demonstrates:

from matplotlib.pyplot import figure, show

fig = figure()

ax = fig.add_subplot(111)

ax.annotate(‘This is a long annotation’,

xy=(1, 1),


bbox=dict(facecolor = ‘white’,


#clip_box = ax.bbox))

ax.set_xlim(-5, 2.8)

ax.set_ylim(-5, 5)


PS. I am using MPL 0.98.3.