Update send_file() docs to clarify encoding requirement #1286

flask/helpers.py

@@ -445,14 +445,14 @@ def send_file(filename_or_fp, mimetype=None, as_attachment=False,
     .. versionchanged:: 0.9
        cache_timeout pulls its default from application config, when None.
 
-    :param filename_or_fp: the filename of the file to send.  This is
+    :param filename_or_fp: the filename of the file to send in `latin-1`.
-                           relative to the :attr:`~Flask.root_path` if a
+                           This is relative to the :attr:`~Flask.root_path`
-                           relative path is specified.
+                           if a relative path is specified.
-                           Alternatively a file object might be provided
+                           Alternatively a file object might be provided in
-                           in which case ``X-Sendfile`` might not work and
+                           which case ``X-Sendfile`` might not work and fall
-                           fall back to the traditional method.  Make sure
+                           back to the traditional method.  Make sure that the
-                           that the file pointer is positioned at the start
+                           file pointer is positioned at the start of data to
-                           of data to send before calling :func:`send_file`.
+                           send before calling :func:`send_file`.
     :param mimetype: the mimetype of the file if provided, otherwise
                      auto detection happens.
     :param as_attachment: set to ``True`` if you want to send this file with