Search for minus of any font size to get height of tex result - #17578

PR Summary

When searching for minus symbols in tex output, to treat them as a special case, do so for any font size not just font size 10. Minus is glyph zero of the font cmsyXX (XX being the font size).

This ensures that negative numbers have correct alignment when using tex, whatever the font size being used. This closes #17574.

The same example in the issue now gives the correct output:

from matplotlib import pyplot as plt
fig = plt.figure(dpi=300)
plt.rc('text', usetex=True)
ax = fig.add_subplot(1,2,1)
plt.plot((-7.,0.,7.), (-1.,0.,1.), 'r-')
plt.rc('text', usetex=True)
ax = fig.add_subplot(1,2,2)
plt.plot((-7.,0.,7.), (-1.,0.,1.), 'r-')
plt.xticks(fontsize=8)
plt.yticks(fontsize=8)
plt.show()

PR Checklist

• Has Pytest style unit tests
• Code is Flake 8 compliant
• New features are documented, with examples if plot related
• Documentation is sphinx and numpydoc compliant
• Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
• Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way