Fix support for empty usetex strings.

anntzer · anntzer · commit ac6cc5076e0c · 2020-02-21T11:21:52.000+01:00
Currently, `figtext(.5, .5, "%foo", usetex=True)` results in an obscure
exception (`FileNotFoundError: No such file or directory: blah.dvi`).

Fix that by forcing tex to always generate a page, by inserting at least
an empty \hbox{}.
diff --git a/lib/matplotlib/tests/test_usetex.py b/lib/matplotlib/tests/test_usetex.py
@@ -30,6 +30,12 @@ def test_usetex():
     ax.set_yticks([])
 
 
+@check_figures_equal()
+def test_empty(fig_test, fig_ref):
+    mpl.rcParams['text.usetex'] = True
+    fig_test.text(.5, .5, "% a comment")
+
+
 @check_figures_equal()
 def test_unicode_minus(fig_test, fig_ref):
     mpl.rcParams['text.usetex'] = True
diff --git a/lib/matplotlib/texmanager.py b/lib/matplotlib/texmanager.py
@@ -214,7 +214,8 @@ def make_tex(self, tex, fontsize):
 \usepackage[papersize={72in,72in},body={70in,70in},margin={1in,1in}]{geometry}
 \pagestyle{empty}
 \begin{document}
-\fontsize{%f}{%f}%s
+%% The empty hbox ensures that a page is printed even for empty inputs.
+\fontsize{%f}{%f}\hbox{}%s
 \end{document}
 """ % (self._get_preamble(), fontsize, fontsize * 1.25, fontcmd % tex),
             encoding='utf-8')
