Bug report

Hello, as discussed on matplotlib-devel, there is a unexpected change in Matplotlib 2.2 when plotting lines and markers (e.g. style 'D-') combined with drawstyle='steps-post' (steps-pre' and 'steps-mid' as well).

Code for reproduction

import matplotlib.pyplot as plt
import numpy as np
x = np.linspace(0, 6, 7)
y = np.sin(x)
plt.plot(x, y, 'D-', drawstyle='steps-post')

Actual outcome

In Matplotlib 2.2.2, markers are drawn at each "line break".

Running the same script with drawstyle='steps-mid' yields markers at half-integer positions (except for those at the end)

Expected outcome

In all previous Matplotlib versions, the marker was placed at the exact x-position of the input data (which is the left of each segment for drawstyle='steps-post'). I didn't do the bissection to know when the changed happen, but I suspect it's quite new (2.1 → 2.2 ?).

Matplotlib version

• Matplotlib version: 2.2.2
• Python version: 3.6