Using facecolors='none' with a scatter plot results in off-centered symbols #17790

Bug report

Bug summary

Using facecolors='none' with matplotlib.pyplot.scatter(x,y) displays symbols that are offset from their input (x,y) positions. This is a different behavior compared to using, e.g., facecolors='white', in which case the symbols are centered properly on the input (x,y) values.

Code for reproduction

import numpy as np
import matplotlib.pyplot as plt

x = np.arange(8)
y = np.random.rand(8)

fig = plt.figure(figsize=(10,3))
plt.scatter(x,y,marker="o",s=80,facecolors='white',edgecolors='blue')
plt.scatter(x,y,s=2)
plt.scatter(x,y,marker="o",s=140,facecolors='none',edgecolors='red')

Actual outcome

Expected outcome

I would expect that the symbols should be properly centered and not offset when using facecolors='none' (red edge color in the example above). We can see on the figure that using facecolors='white' produces properly centered symbols (blue edge color). The red symbols should have the same centers.

Matplotlib version

• Operating system: Scientific Linux release 6.10
• Matplotlib version: 3.1.1
• Matplotlib backend (print(matplotlib.get_backend())): module://ipykernel.pylab.backend_inline
• Python version: 3.7.4
• Jupyter version (if applicable): 4.3.0
• Other libraries: numpy 1.17.2