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Public API to modify mathtext font constants #9165
Description
Hi matplotlib developers,
I recently needed to modify the mathtext font constants (the superscript height) of a non-standard font (Arial) and found that there is no public API to accomplish this. I did, however, find that I could do what I wanted by accessing the private mathtext._font_constant_mapping dictionary. A minimal working example is below:
import matplotlib.pyplot as plt
from matplotlib import mathtext
plt.rcParams.update({
'text.usetex':False,
'font.family':'sans-serif',
'font.sans-serif':['Arial'],
'mathtext.default':'regular',
})
class ArialFontConstants(mathtext.FontConstantsBase):
# Percentage of x-height that superscripts are raised from the baseline
sup1 = 0.4
# Register font constants for Arial
mathtext._font_constant_mapping['Arial'] = ArialFontConstants
text = r'$h = 6.62607004 \times 10^{-34}\; m^2\, kg\,/\,s$'
plt.figure(figsize=(3, 2))
plt.axis('off')
plt.text(0, 0.5, text)
plt.show()This works great, but I think there should be a public and documented method to customize mathtext font constants. Perhaps we should just remove the leading underscore of _font_constant_mapping to make it permanent and public? Also, I think that an example of the new public API should be added to the mathtext tutorial documentation.
Thanks,
Tested with matplotlib 2.0.2 and python 3.6.2 running on Arch Linux.
Activity
u55 commentedon Sep 9, 2017
@mdboom Michael, git blame tells me that you changed the API back in baa2b6e. Did you have a particular reason in mind for keeping
_font_constant_mappingprivate?anntzer commentedon Sep 10, 2017
It's probably private because no one asked for it to be public, and we are actively trying to keep the public API as small as possible (and if it goes public it should be properly documented). Of course the funny thing is that the various constant classes are themselves public.
FWIW having spent ~10s looking at it I'd guess the various classes should just be namedtuples (using
._replaceif we want to be able to inherit from another font constant), but otherwise have no strong opinion as to making the dictionary public (if documented).github-actions commentedon Apr 18, 2023
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