8000 Fix baseline alignment when using usetex. · matplotlib/matplotlib@a494553 · GitHub
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Fix baseline alignment when using usetex.
Previously we inferred the baseline of usetex strings with the baseline of the character with the lowest baseline, which is wrong in the presence of indices (see usetex_baseline_test.py). There was an option to use the "preview" latex package to fix that, but that was never made the default and likely cannot as the package is GPL. Instead I can infer the baseline position by "reverse-engineering" the starting instructions of the dvi stream (this was done without consulting the approach in "preview"). The results can be checked using usetex_baseline_test.py (preview=False now looks the same as preview=True; likewise, the output of test_usetex was changed. The text.latex.preview rc can now be deprecated (in a future PR). The test was also updated to include the strings of the usetex_baseline_test example (which may go away once text.latex.preview is removed).
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6 files changed

+38
-12
lines changed

6 files changed

+38
-12
lines changed

‎lib/matplotlib/backends/backend_ps.py

Lines changed: 1 addition & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -484,8 +484,7 @@ def draw_tex(self, gc, x, y, s, prop, angle, ismath='TeX!', mtext=None):
484484
r'\psfrag{%s}[Bl][Bl][1][%f]{\fontsize{%f}{%f}%s}' % (
485485
thetext, angle, fontsize, fontsize*1.25, tex))
486486
else:
487-
# Stick to the bottom alignment, but this may give incorrect
488-
# baseline some times.
487+
# Stick to the bottom alignment.
489488
pos = _nums_to_str(x-corr, y-bl)
490489
self.psfrag.append(
491490
r'\psfrag{%s}[bl][bl][1][%f]{\fontsize{%f}{%f}%s}' % (

‎lib/matplotlib/dviread.py

Lines changed: 18 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -263,6 +263,9 @@ def _output(self):
263263
maxx = max(maxx, x + w)
264264
maxy = max(maxy, y + e)
265265
maxy_pure = max(maxy_pure, y)
266+
if self._baseline_v is not None:
267+
maxy_pure = self._baseline_v # This should normally be the case.
268+
self._baseline_v = None
266269

267270
if self.dpi is None:
268271
# special case for ease of debugging: output raw dvi coordinates
@@ -290,9 +293,24 @@ def _read(self):
290293
Read one page from the file. Return True if successful,
291294
False if there were no more pages.
292295
"""
296+
# Pages appear to start with the sequence
297+
# bop (begin of page)
298+
# xxx comment
299+
# down
300+
# push
301+
# down, down
302+
# push
303+
# down (possibly multiple)
304+
# push <= here, v is the baseline position.
305+
# etc.
306+
# (dviasm is useful to explore this structure.)
307+
self._baseline_v = None
293308
while True:
294309
byte = self.file.read(1)[0]
295310
self._dtable[byte](self, byte)
311+
if (self._baseline_v is None
312+
and len(getattr(self, "stack", [])) == 3):
313+
self._baseline_v = self.v
296314
if byte == 140: # end of page
297315
return True
298316
if self.state is _dvistate.post_post: # end of file

‎lib/matplotlib/tests/baseline_images/test_usetex/test_usetex.pdf

-47.9 KB
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‎lib/matplotlib/tests/baseline_images/test_usetex/test_usetex.png

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‎lib/matplotlib/tests/test_usetex.py

Lines changed: 18 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -12,24 +12,33 @@
1212
pytestmark = pytest.mark.skip('Missing TeX of Ghostscript or dvipng')
1313

1414

15-
@image_comparison(baseline_images=['test_usetex'],
16-
extensions=['pdf', 'png'],
17-
tol={'aarch64': 2.868, 'x86_64': 2.868}.get(
18-
platform.machine(), 0.3
19-
))
15+
@image_comparison(
16+
baseline_images=['test_usetex'],
17+
extensions=['pdf', 'png'],
18+
tol={'aarch64': 2.868, 'x86_64': 2.868}.get(platform.machine(), 0.3),
19+
style="mpl20")
2020
def test_usetex():
2121
mpl.rcParams['text.usetex'] = True
2222
fig = plt.figure()
2323
ax = fig.add_subplot(111)
24-
ax.text(0.1, 0.2,
24+
kwargs = {"verticalalignment": "baseline", "size": 24,
25+
"bbox": dict(pad=0, edgecolor="k", facecolor="none")}
26+
ax.text(0.2, 0.7,
2527
# the \LaTeX macro exercises character sizing and placement,
2628
# \left[ ... \right\} draw some variable-height characters,
2729
# \sqrt and \frac draw horizontal rules, \mathrm changes the font
2830
r'\LaTeX\ $\left[\int\limits_e^{2e}'
2931
r'\sqrt\frac{\log^3 x}{x}\,\mathrm{d}x \right\}$',
30-
fontsize=24)
31-
ax.set_xticks([])
32-
ax.set_yticks([])
32+
**kwargs)
33+
ax.text(0.2, 0.3, "lg", **kwargs)
34+
ax.text(0.4, 0.3, r"$\frac{1}{2}\pi$", **kwargs)
35+
ax.text(0.6, 0.3, "$p^{3^A}$", **kwargs)
36+
ax.text(0.8, 0.3, "$p_{3_2}$", **kwargs)
37+
for x in {t.get_position()[0] for t in ax.texts}:
38+
ax.axvline(x)
39+
for y in {t.get_position()[1] for t in ax.texts}:
40+
ax.axhline(y)
41+
ax.set_axis_off()
3342

3443

3544
@check_figures_equal()

‎lib/matplotlib/texmanager.py

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -411,7 +411,7 @@ def get_text_width_height_descent(self, tex, fontsize, renderer=None):
411411
return width, height + depth, depth
412412

413413
else:
414-
# use dviread. It sometimes returns a wrong descent.
414+
# use dviread.
415415
dvifile = self.make_dvi(tex, fontsize)
416416
with dviread.Dvi(dvifile, 72 * dpi_fraction) as dvi:
417417
page, = dvi

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