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latex textrm does not work in Cairo backend #17932

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esheldon opened this issue Jul 15, 2020 · 7 comments · Fixed by #17948
Closed

latex textrm does not work in Cairo backend #17932

esheldon opened this issue Jul 15, 2020 · 7 comments · Fixed by #17948
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@QuLogic
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backend: cairo topic: text/usetex
Milestone
v3.4.0

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@esheldon
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Bug report

Bug summary

Use of \textrm latex in Cairo backend raises an exception

Code for reproduction

import matplotlib as mpl
import matplotlib.pyplot as plt

mpl.use('Cairo')
mpl.rc('text', usetex=True)

fig, ax = plt.subplots()

ax.set_xlabel(r'$x [\textrm{cm}]$')
ax.scatter([1, 2], [1, 2], marker='o')
fig.savefig('test-cairo.png')

Raises an exception

ValueError:
x [\textrm{cm}]
^ 
Unknown symbol: \textrm, found '\'  (at char 3), (line:1, col:4)

Expected outcome

The textrm should work to produce rm text. For reference, this works fine in the Agg backend.

Matplotlib version

  • Operating system: linux ubuntu
  • Matplotlib version: 3.2.2
  • Matplotlib backend: Cairo
  • Python version: 3.7.6

Installed with conda
@QuLogic QuLogic self-assigned this Jul 15, 2020
@anntzer
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anntzer commented Jul 16, 2020

The cairo backend does not support usetex at all; at least as a quick improvement one could at least log a warning, e.g.

diff --git i/lib/matplotlib/backends/backend_cairo.py w/lib/matplotlib/backends/backend_cairo.py
index 773886e56..e4fa01b6c 100644
--- i/lib/matplotlib/backends/backend_cairo.py
+++ w/lib/matplotlib/backends/backend_cairo.py
@@ -7,6 +7,7 @@ This backend depends on cairocffi or pycairo.
 """
 
 import gzip
+import logging
 import math
 
 import numpy as np
@@ -35,6 +36,7 @@ from matplotlib.transforms import Affine2D
 
 
 backend_version = cairo.version
+_log = logging.getLogger(__name__)
 
 
 if cairo.__name__ == "cairocffi":
@@ -236,14 +238,15 @@ class RendererCairo(RendererBase):
 
         # Note: (x, y) are device/display coords, not user-coords, unlike other
         # draw_* methods
+        if ismath == "TeX":
+            _log.warning("The cairo backend does not support usetex and this "
+                         "setting will be ignored.")
         if ismath:
             self._draw_mathtext(gc, x, y, s, prop, angle)
-
         else:
             ctx = gc.ctx
             ctx.new_path()
             ctx.move_to(x, y)
-
             ctx.select_font_face(*_cairo_font_args_from_font_prop(prop))
             ctx.save()
             ctx.set_font_size(prop.get_size_in_points() * self.dpi / 72)
@@ -286,6 +289,9 @@ class RendererCairo(RendererBase):
     def get_text_width_height_descent(self, s, prop, ismath):
         # docstring inherited
 
+        if ismath == "TeX":
+            _log.warning("The cairo backend does not support usetex and this "
+                         "setting will be ignored.")
         if ismath:
             width, height, descent, fonts, used_characters = \
                 self.mathtext_parser.parse(s, self.dpi, prop)

@esheldon
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I use the Cairo backend with tex. This figure was generated using it, and all text was run through latex

test

@esheldon
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Please do not remove the ability to use tex with cairo, or add any additional warnings

@anntzer
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anntzer commented Jul 16, 2020 •
edited
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Why, exactly, do you want to use the cairo backend for this purpose?
However you are right, things actually work; it's just a matter of falling back to the base class implementation:

diff --git i/lib/matplotlib/backends/backend_cairo.py w/lib/matplotlib/backends/backend_cairo.py
index 773886e56..244f7103d 100644
--- i/lib/matplotlib/backends/backend_cairo.py
+++ w/lib/matplotlib/backends/backend_cairo.py
@@ -286,6 +286,8 @@ class RendererCairo(RendererBase):
     def get_text_width_height_descent(self, s, prop, ismath):
         # docstring inherited
 
+        if ismath == "TeX":
+            return super().get_text_width_height_descent(s, prop, ismath)
         if ismath:
             width, height, descent, fonts, used_characters = \
                 self.mathtext_parser.parse(s, self.dpi, prop)

@esheldon
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In my work I have only ever seen the \textrm command fail with Cairo, nothing else. E.g. substituting \mathrm for \textrm works fine, it is something particular to that latex command.

@jklymak
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jklymak commented Jul 16, 2020

Also have you tried mplcairo? It's not part of core matplotlib yet because it's a bit harder to build but it seems more robust and is actively maintained.

@esheldon
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Cairo works fine except for this one issue, and has the advantage over Agg which, for example, has alignment problems #3400

@QuLogic QuLogic mentioned this issue Jul 17, 2020
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@QuLogic QuLogic added this to the v3.4.0 milestone Jul 18, 2020
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@QuLogic QuLogic

Labels
backend: cairo topic: text/usetex
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v3.4.0
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Sync Cairo's usetex measurement with base class. QuLogic/matplotlib
4 participants
@QuLogic @esheldon @anntzer @jklymak