update docstrings and faq for modified config directory strategy

efiring · efiring · commit be72e1b63f34 · 2012-08-25T09:54:37.000-10:00
diff --git a/doc/faq/environment_variables_faq.rst b/doc/faq/environment_variables_faq.rst
@@ -25,7 +25,10 @@ Environment Variables
 
   This is the directory used to store user customizations to matplotlib, as
   well as some caches to improve performance. If :envvar:`MPLCONFIGDIR` is not
-  defined, :file:`{HOME}/.matplotlib` is used by default.
+  defined, :file:`{HOME}/.matplotlib` is used if it is writable.
+  Otherwise, the python standard library :func:`tempfile.gettmpdir` is
+  used to find a base directory in which the :file:`matplotlib`
+  subdirectory is created.
 
 .. _setting-linux-osx-environment-variables:
 
diff --git a/lib/matplotlib/__init__.py b/lib/matplotlib/__init__.py
@@ -483,10 +483,14 @@ def _create_tmp_config_dir():
 
 def _get_configdir():
     """
-    Return the string representing the configuration dir.
+    Return the string representing the configuration directory.
 
-    default is HOME/.matplotlib.  you can override this with the
-    MPLCONFIGDIR environment variable
+    Default is HOME/.matplotlib.  You can override this with the
+    MPLCONFIGDIR environment variable.  If the default is not
+    writable, and MPLCONFIGDIR is not set, then
+    tempfile.gettempdir() is used to provide a directory in
+    which a matplotlib subdirectory is created as the configuration
+    directory.
     """
 
     configdir = os.environ.get('MPLCONFIGDIR')
