Center of rotation for text with rotation_mode='anchor' #13044

Bug report

After fixing an obvious vertical offset bug in #13029 the rotation

import matplotlib.pyplot as plt
plt.plot([0, 1], lw=0)
plt.axvline(.5, linewidth=.5, color='.5')
plt.axhline(.5, linewidth=.5, color='.5')

N = 4
for r in range(N):
    plt.text(.5, .5, 'pP', color=plt.get_cmap('jet')(r/N), size=100, rotation=r/N*360, va='center_baseline', rotation_mode='anchor')

looks like this:

I'm not sure if this is now 100% as desired:

• The vertical position of the rotation point is not exactly at y=0.5 (slightly shifted down).
• The horizontal position of the rotation point is not at x=0.5 but at the left edge of the first letter.

Is this intended or are there still other bugs in the position calculation?