Fix support for empty usetex strings.

anntzer · anntzer · commit 3ee33f42ce23 · 2020-04-06T11:18:57.000+02:00
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/dviread.py b/lib/matplotlib/dviread.py
@@ -275,6 +275,9 @@ def _output(self):
             maxy = max(maxy, y + e)
             maxy_pure = max(maxy_pure, y)
 
+        if not self.text and not self.boxes:  # Avoid infs/nans from inf+/-inf.
+            return Page(text=[], boxes=[], width=0, height=0, descent=0)
+
         if self.dpi is None:
             # special case for ease of debugging: output raw dvi coordinates
             return Page(text=self.text, boxes=self.boxes,
diff --git a/lib/matplotlib/tests/test_usetex.py b/lib/matplotlib/tests/test_usetex.py
@@ -32,6 +32,12 @@ 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
@@ -207,7 +207,8 @@ 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')
