Add test and expand comment

zblz · zblz · commit 26c0c63d41f6 · 2015-08-10T21:39:45.000+01:00
A test comparing images is difficult because the metrics are taken from the tex
(which is correctly selected) so that even when the incorrect png is selected,
it will be shifted so an image comparison will always fail.
diff --git a/lib/matplotlib/tests/test_texmanager.py b/lib/matplotlib/tests/test_texmanager.py
@@ -0,0 +1,21 @@
+from __future__ import (absolute_import, division, print_function,
+                        unicode_literals)
+
+import matplotlib.pyplot as plt
+
+from matplotlib.texmanager import TexManager
+
+def test_fontconfig_preamble():
+    """
+    Test that the preamble is included in _fontconfig
+    """
+    plt.rcParams['text.usetex'] = True
+
+    tm1 = TexManager()
+    font_config1 = tm1.get_font_config()
+
+    plt.rcParams['text.latex.preamble'] = [r'\usepackage{txfonts}']
+    tm2 = TexManager()
+    font_config2 = tm2.get_font_config()
+
+    assert font_config1 != font_config2
diff --git a/lib/matplotlib/texmanager.py b/lib/matplotlib/texmanager.py
@@ -203,7 +203,9 @@ def __init__(self):
                                    'default.' % ff, 'helpful')
                 setattr(self, font_family_attr, self.font_info[font_family])
             fontconfig.append(getattr(self, font_family_attr)[0])
-        # Add a hash of the latex preamble to fontconfig
+        # Add a hash of the latex preamble to self._fontconfig so that the
+        # correct png is selected for strings rendered with same font and dpi
+        # even if the latex preamble changes within the session
         preamble_bytes = six.text_type(self.get_custom_preamble()).encode('utf-8')
         fontconfig.append(md5(preamble_bytes).hexdigest())
         self._fontconfig = ''.join(fontconfig)
