This should get a test I think. Was center_baseline working at all with rotation_mode='anchor'?

@jklymak You are right. I added a test that makes sure settting rotation_mode doesn't change anything if rotation=0.

Do you know if rotation != 0 appears reasonable?

rotation != 0 seems to be reasonable:

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')

before:

after:

The rotation center is not at (0.5, 0.5) but at the edge of the "p". However, I'm unsure if that's supposed to happen, also it's the same before and after this PR. So if that's an issue it's a separate one.

Thanks, and congratulations on your first contribution to Matplotlib! Hoping to see you back some time.