sub/superscripts should be moved further from the baseline following large delimiters #18086

Bug report

Bug summary

Matplotlib's mathtext appears not to take the size of the preceding glyph into account when positioning sub/superscripts.

Code for reproduction

from pylab import *
figtext(.4, .5, r"$\left[\frac{x}{y}\right]^2_n$")
figtext(.5, .5, r"$\left[\frac{x}{y}\right]^2_n$", usetex=True)

Actual outcome

Note that the baseline of the 2 is even lower than the baseline of the x in the mathtext case.

Expected outcome

Something approaching the usetex case.

Matplotlib version

• Operating system: linux
• Matplotlib version: master
• Matplotlib backend (print(matplotlib.get_backend())): qt5agg
• Python version: 38
• Jupyter version (if applicable):
• Other libraries: