Improve three-state read-only logic.

IPython/frontend/html/notebook/handlers.py

@@ -137,17 +137,25 b' class AuthenticatedHandler(RequestHandler):'
             if not self.application.password and not self.application.read_only:
                 user_id = 'anonymous'
         return user_id
-    
+
     @property
     def read_only(self):
-        if self.application.read_only:
+        """Is the notebook read-only?
+
+        None -- notebook is read-only, but the user can log-in to edit
+        True -- notebook is read-only, no log-in available
+        False -- no read-only mode available, user must log in
+
+        """
+        user = self.get_current_user()
+        if user and user != 'anonymous':
+            return False
+        elif self.application.read_only:
             if self.application.password:
-                return self.get_current_user() is None
+                return None
             else:
                 return True
-        else:
-            return False
-    
+
     @property
     def ws_url(self):
         """websocket url matching the current request

IPython/frontend/html/notebook/templates/layout.html

@@ -25,7 +25,7 b''
     <span id="login_widget">
       {% if current_user and current_user != 'anonymous' %}
         <button id="logout">Logout</button>
-      {% else %}
+      {% elif read_only is None %}
         <button id="login">Login</button>
       {% end %}
     </span>

IPython/frontend/html/notebook/templates/notebook.html

@@ -54,7 +54,7 b''
       {% comment  when appropriate until notebook.html is templated %}
       {% if current_user and current_user != 'anonymous' %}
         <button id="logout">Logout</button>
-      {% else %}
+      {% elif read_only is None %}
         <button id="login">Login</button>
       {% end %}
     </span>

IPython/frontend/html/notebook/templates/projectdashboard.html

@@ -20,10 +20,15 b' data-base-kernel-url={{base_kernel_url}}'
 
 {% block content_panel %}
     <div id="content_toolbar">
-        <span id="drag_info" class="hidden">Drag files onto the list to import notebooks.</span>
-        <span id="notebooks_buttons">
-            <button id="new_notebook" class="hidden">New Notebook</button>
-        </span>
+        <span id="drag_info" class="hidden">Drag files onto the list to import
+        notebooks.</span>
+
+        {% if read_only == False %}
+          <span id="notebooks_buttons">
+              <button id="new_notebook" class="hidden">New Notebook</button>
+          </span>
+        {% end %}
+
     </div>
     <div id="notebook_list">
         <div id="project_name"><h2>{{project}}</h2></div>