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Support units for the third \genfrac argument #22171

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Support units for the third \genfrac argument #22171

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11 changes: 11 additions & 0 deletions doc/users/next_whats_new/mathtext_genfrac_supports_unit.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
``mathtext`` now supports units for the bar thickness ``\genfrac`` argument
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This follows the standard LaTeX version where units are required.

.. code-block:: python

import matplotlib.pyplot as plt

plt.text(0.5, 0.5, r'$\genfrac{(}{)}{0.5cm}{0}{foo}{bar}$')
plt.draw()
43 changes: 38 additions & 5 deletions lib/matplotlib/_mathtext.py
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Expand Up @@ -1958,6 +1958,7 @@ def __init__(self):
p.customspace = Forward()
p.end_group = Forward()
p.float_literal = Forward()
p.float_with_wo_unit = Forward()
p.font = Forward()
p.frac = Forward()
p.dfrac = Forward()
Expand Down Expand Up @@ -1995,6 +1996,7 @@ def __init__(self):
p.symbol_name = Forward()
p.token = Forward()
p.underset = Forward()
p.unit = Forward()
p.unknown_symbol = Forward()

# Set names on everything -- very useful for debugging
Expand All @@ -2004,6 +2006,10 @@ def __init__(self):

p.float_literal <<= Regex(r"[-+]?([0-9]+\.?[0-9]*|\.[0-9]+)")
p.int_literal <<= Regex("[-+]?[0-9]+")
p.unit <<= Regex("(pt|mm|cm|in|em|mu|"
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I think you can get rid of the grouping parentheses, which should be marginally more efficient.

"sp|bp|dd|pc|nc|nd|cc)")
p.float_with_wo_unit <<= Group((p.float_literal + p.unit) |
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what's "wo"?

p.float_literal)

p.lbrace <<= Literal('{').suppress()
p.rbrace <<= Literal('}').suppress()
Expand Down Expand Up @@ -2093,7 +2099,7 @@ def __init__(self):
+ (p.lbrace
+ Optional(p.ambi_delim | p.right_delim_safe, default='')
+ p.rbrace)
+ (p.lbrace + p.float_literal + p.rbrace)
+ (p.lbrace + p.float_with_wo_unit + p.rbrace)
+ p.simple_group + p.required_group + p.required_group)
| Error("Expected "
r"\genfrac{ldelim}{rdelim}{rulesize}{style}{num}{den}"))
Expand Down Expand Up @@ -2322,6 +2328,22 @@ def _make_space(self, percentage):
r'\!': -0.16667, # -3/18 em = -3 mu
}

_unit_multipliers = {
# pt|mm|cm|in|mu|sp|bp|dd|pc|nc|nd|cc
"pt": 1,
'mm': 7227/2540,
'cm': 7227/254,
'in': 7227/100,
'mu': 7227/2540000,
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I can't find a ref for mu, nc, nd as standard tex units, perhaps you can link their definition? (as a comment here at least, not in the code)

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I used some stack exchange thread combined with other sources, but cannot seem to find where I got ex and em from now. I agree with that they shouldn't be there though (just added what was there without really thinking about the meaning).

Here are some better sources:
https://en.wikibooks.org/wiki/LaTeX/Lengths
https://latexref.xyz/Units-of-length.html

(And here is a good discussion why ex and em are bad choices: https://tex.stackexchange.com/questions/4239/which-measurement-units-should-one-use-in-latex
)

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And here is for mu: https://sv.overleaf.com/learn/latex/Lengths_in_LaTeX

'sp': 1/65536,
'bp': 803/800,
'dd': 1238/1157,
'pc': 12,
'nc': 1370/107,
'nd': 685/642,
'cc': 14856/1157
}

def space(self, s, loc, toks):
tok, = toks
num = self._space_widths[tok]
Expand Down Expand Up @@ -2741,7 +2763,7 @@ def _genfrac(self, ldelim, rdelim, rule, style, num, den):
thickness = state.font_output.get_underline_thickness(
state.font, state.fontsize, state.dpi)

rule = float(rule)
rule = self._get_float_with_unit(rule, state.fontsize)

if style is not self._MathStyle.DISPLAYSTYLE:
num.shrink()
Expand Down Expand Up @@ -2786,22 +2808,33 @@ def frac(self, s, loc, toks):
thickness = state.font_output.get_underline_thickness(
state.font, state.fontsize, state.dpi)
(num, den), = toks
return self._genfrac('', '', thickness, self._MathStyle.TEXTSTYLE,
return self._genfrac('', '', [thickness], self._MathStyle.TEXTSTYLE,
num, den)

def dfrac(self, s, loc, toks):
state = self.get_state()
thickness = state.font_output.get_underline_thickness(
state.font, state.fontsize, state.dpi)
(num, den), = toks
return self._genfrac('', '', thickness, self._MathStyle.DISPLAYSTYLE,
return self._genfrac('', '', [thickness], self._MathStyle.DISPLAYSTYLE,
num, den)

def binom(self, s, loc, toks):
(num, den), = toks
return self._genfrac('(', ')', 0.0, self._MathStyle.TEXTSTYLE,
return self._genfrac('(', ')', [0.0], self._MathStyle.TEXTSTYLE,
num, den)

def _get_float_with_unit(self, val, fontsize):
ret = float(val[0])
if len(val) == 2:
if val[1].lower() == 'em':
# "1 em is a distance equal to the type size"
ret = ret*fontsize
else:
# Remaining units
ret = ret*self._unit_multipliers[val[1]]
return ret

def _genset(self, s, loc, toks):
(annotation, body), = toks
state = self.get_state()
Expand Down