Changes and docs are modified.

CHANGES

@@ -8,6 +8,7 @@ Version 1.0
 
 (release date to be announced, codename to be selected)
 
+- Added before_render_template signal.
 - Added `**kwargs` to :meth:`flask.Test.test_client` to support passing
   additional keyword arguments to the constructor of
   :attr:`flask.Flask.test_client_class`.

docs/api.rst

@@ -538,6 +538,23 @@ The following signals exist in Flask:
         from flask import template_rendered
         template_rendered.connect(log_template_renders, app)
 
+.. data:: flask.before_render_template
+   :noindex:
+
+   This signal is sent before template rendering process. The
+   signal is invoked with the instance of the template as `template`
+   and the context as dictionary (named `context`).
+
+   Example subscriber::
+
+        def log_template_renders(sender, template, context, **extra):
+            sender.logger.debug('Rendering template "%s" with context %s',
+                                template.name or 'string template',
+                                context)
+
+        from flask import before_render_template
+        before_render_template.connect(log_template_renders, app)
+
 .. data:: request_started
 
    This signal is sent when the request context is set up, before