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Special-case usetex minus to zero depth. #16366

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Merged
tacaswell merged 1 commit into from
Jan 30, 2020
Merged

Special-case usetex minus to zero depth. #16366

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6 changes: 6 additions & 0 deletions lib/matplotlib/dviread.py
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Original file line number Diff line number Diff line change
Expand Up @@ -566,6 +566,12 @@ def _height_depth_of(self, char):
result.append(0)
else:
result.append(_mul2012(value, self._scale))
# cmsy10 glyph 0 ("minus") has a nonzero descent so that TeX aligns
# equations properly (https://tex.stackexchange.com/questions/526103/),
# but we actually care about the rasterization depth to align the
# dvipng-generated images.
if self.texname == b"cmsy10" and char == 0:
result[-1] = 0
return result


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22 changes: 21 additions & 1 deletion lib/matplotlib/tests/test_usetex.py
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Original file line number Diff line number Diff line change
@@ -1,6 +1,8 @@
import pytest
import platform

import numpy as np
import pytest

import matplotlib as mpl
from matplotlib.testing.decorators import check_figures_equal, image_comparison
import matplotlib.pyplot as plt
Expand Down Expand Up @@ -43,3 +45,21 @@ def test_mathdefault():
# problems when later switching usetex on.
mpl.rcParams['text.usetex'] = True
fig.canvas.draw()


def test_minus_no_descent():
# Test special-casing of minus descent in DviFont._height_depth_of, by
# checking that overdrawing a 1 and a -1 results in an overall height
# equivalent to drawing either of them separately.
mpl.style.use("mpl20")
heights = {}
fig = plt.figure()
for vals in [(1,), (-1,), (-1, 1)]:
fig.clf()
for x in vals:
fig.text(.5, .5, f"${x}$", usetex=True)
fig.canvas.draw()
# The following counts the number of non-fully-blank pixel rows.
heights[vals] = ((np.array(fig.canvas.buffer_rgba())[..., 0] != 255)
.any(axis=1).sum())
assert len({*heights.values()}) == 1