Hi matplotlib developers,

While working with master, I discovered that the errorbar caps are sometimes missing when saving a figure to PDF. Here is a minimal working example:

import numpy as np
import matplotlib.pyplot as plt

N = 6

plt.figure()
# Caps are drawn
plt.errorbar(np.arange(N),
             np.ones(N),
             np.ones(N),
             )
# Caps are missing
plt.errorbar(np.arange(N+1),
             np.ones(N+1) + 4,
             np.ones(N+1),
             )
plt.xlim(-1,N+1)
plt.ylim(-1,7)
plt.savefig('bug.pdf')

Tested with python 2.7 in Linux with matplotlib master. The bug only shows up in master, version 1.4.3 is working correctly. Strangely, this bug does not show up in other vector backends, such as svg, eps, or ps. Stranger still, the appearance of the errorbar caps seems to depend on the number of points that are being drawn. In the above example, 6 points is the magic number to see caps, while the caps are missing if the arrays are extended to 7 points.

As always, thanks for the help.