diff --git a/protocol/xdg-shell.xml b/protocol/xdg-shell.xml
index 68cf469..50c81b5 100644
--- a/protocol/xdg-shell.xml
+++ b/protocol/xdg-shell.xml
@@ -368,6 +368,95 @@
       <arg name="height" type="int"/>
     </request>
 
+    <enum name="constraint">
+      <description summary="types">
+        These constaints allow the compositor to help position child surfaces 
+        without intreraction from the client application, and to notify the
+        client of any constraint issues.
+
+        Constraint issues may occur if the surface or another surface is moved
+        to clip either the edge of an output or another surface. 
+         
+        This can be useful for compositors implementing physics type window 
+        effects, non-overlaping windows or allowing the client to keep "popup"
+        windows open without having to rely on implicit grabs.
+
+        An application should use the weakest constraint possible for correct
+        functionality. 
+      </description>
+      <entry name="move" value="1">
+        The surface will be movable by the compositor.
+      </entry>
+      <entry name="mirror" value="2">
+        The surface can be mirrored by the compositor and window co-ordinates 
+        are guarenteed for this surface relative to its parent. 
+
+        Subsurfaces will not be mirrored and will be positioned as if mirrored 
+        first along the parent axis and then along their height mid point.
+
+        Decorations should be specified in this surface and then text and 
+        position dependent content as a subsurface.
+
+        Not all compositors will support this mode so the client should provide
+        an alternative should it fail.
+      </entry>
+      <entry name="resize" value="3">
+        The surface is resizable and window co-ordinates are guarenteed
+        for this surface relative to its parent. 
+
+        The compositor will suggest the maximum dimensions via configure events 
+        to fit the surface onto the output without clipping. The client is free 
+        to resize the surface or attempt to reposition the window if the surface
+        becomes too small.
+      </entry>
+      <entry name="rotate" value="4">
+        The surface is rotatable about the window co-ordinates which are 
+        guarenteed for this surface relative to its parent. 
+      </entry>
+      <entry name="scale_root_to_fit" value="5">
+        The root surface is scalable and window co-ordinates are 
+        guarenteed for this surface relative to its parent.
+
+        The parent and all child surfaces including this one will be scaled by
+        the compositor to fit onto the ouput. 
+
+        Not all compositors will support this mode so the client should provide
+        an alternative should it fail.
+      </entry>
+      <entry name="resize_root_to_fit" value="6">
+        The root surface is resizable and window co-ordinates are 
+        guarenteed for this surface relative to its parent.
+
+        The compositor will suggest the maximum dimensions via configure events 
+        to fit the root surface and all child surfaces onto the output without 
+        clipping. The client should then resize the root surface and all 
+        children or attempt to reposition the child or subsurface to fit inside
+        the maximum size.
+      </entry>
+    </enum>
+
+    <request name="set_window_constraints">
+      <description summary="set the new window constraints">
+        Advise the compositor a list of constraits for the surface.
+ 
+        If the compositor cannot guarentee the constaint on the surface then it
+        will proceed to the next constraint in the list provided.  
+
+        If the client provides a positive value for max_left, max_up, max_right 
+        or max_down then the movement for that axis will be limited to moving by
+        that amount that area.
+
+        If the compositor is unable to reach a satisfactory constraint based on 
+        the provided list then it will return to un-constrained functionality.
+      </description>
+      <arg name="x_constraints" type="array"/>
+      <arg name="y_constraints" type="array"/>
+      <arg name="max_left" type="int"/>
+      <arg name="max_up" type="int"/>
+      <arg name="max_right" type="int"/>
+      <arg name="max_down" type="int"/>
+    </request>
+
     <request name="set_maximized" />
     <request name="unset_maximized" />