Support marking a single artist as not-usetex.

anntzer · anntzer · commit e919969fc2e3 · 2020-05-22T23:54:12.000+02:00
... even when `rcParams["text.usetex"] = True`.  See
test_single_artist_no_usetex for an example.
diff --git a/doc/api/api_changes_3.3/behaviour.rst b/doc/api/api_changes_3.3/behaviour.rst
@@ -301,3 +301,9 @@ When `.cbook.get_sample_data` is used to load a npy or npz file and the
 keyword-only parameter ``np_load`` is True, the file is automatically loaded
 using `numpy.load`.  ``np_load`` defaults to False for backwards compatibility,
 but will become True in a later release.
+
+``get_text_width_height_descent`` now checks ``ismath`` rather than :rc:`text.usetex`
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+... to determine whether a string should be passed to the usetex machinery or
+not.  This allows single strings to be marked as not-usetex even when the
+rcParam is True.
diff --git a/lib/matplotlib/backends/_backend_pdf_ps.py b/lib/matplotlib/backends/_backend_pdf_ps.py
@@ -80,7 +80,7 @@ def get_canvas_width_height(self):
 
     def get_text_width_height_descent(self, s, prop, ismath):
         # docstring inherited
-        if mpl.rcParams["text.usetex"]:
+        if ismath == "TeX":
             texmanager = self.get_texmanager()
             fontsize = prop.get_size_in_points()
             w, h, d = texmanager.get_text_width_height_descent(
diff --git a/lib/matplotlib/tests/test_text.py b/lib/matplotlib/tests/test_text.py
@@ -558,11 +558,23 @@ def test_single_artist_usetex():
     # Check that a single artist marked with usetex does not get passed through
     # the mathtext parser at all (for the Agg backend) (the mathtext parser
     # currently fails to parse \frac12, requiring \frac{1}{2} instead).
-    fig, ax = plt.subplots()
-    ax.text(.5, .5, r"$\frac12$", usetex=True)
+    fig = plt.figure()
+    fig.text(.5, .5, r"$\frac12$", usetex=True)
     fig.canvas.draw()
 
 
+@pytest.mark.parametrize("fmt", ["png", "pdf", "svg"])
+def test_single_artist_usenotex(fmt):
+    # Check that a single artist can be marked as not-usetex even though the
+    # rcParam is on ("2_2_2" fails if passed to TeX).  This currently skips
+    # postscript output as the ps renderer doesn't support mixing usetex and
+    # non-usetex.
+    plt.rcParams["text.usetex"] = True
+    fig = plt.figure()
+    fig.text(.5, .5, "2_2_2", usetex=False)
+    fig.savefig(io.BytesIO(), format=fmt)
+
+
 @image_comparison(['text_as_path_opacity.svg'])
 def test_text_as_path_opacity():
     plt.figure()
diff --git a/lib/matplotlib/textpath.py b/lib/matplotlib/textpath.py
@@ -52,7 +52,7 @@ def _get_char_id_ps(self, font, ccode):
         return char_id
 
     def get_text_width_height_descent(self, s, prop, ismath):
-        if rcParams['text.usetex']:
+        if ismath == "TeX":
             texmanager = self.get_texmanager()
             fontsize = prop.get_size_in_points()
             w, h, d = texmanager.get_text_width_height_descent(s, fontsize,
