docs: Improve wl_callback protocol docs

Add some information about wl_callback and its done event.

diff --git a/protocol/wayland.xml b/protocol/wayland.xml
index ad72fd1..cc009eb 100644 (file)
--- a/protocol/wayland.xml
+++ b/protocol/wayland.xml
@@ -157,8 +157,15 @@
   </interface>
 
   <interface name="wl_callback" version="1">
+    <description summary="callback object">
+      Clients can handle the 'done' event to get notified when
+      the related request is done.
+    </description>
     <event name="done">
-      <arg name="serial" type="uint"/>
+      <description summary="done event">
+       Notify the client when the related request is done.
+      </description>
+      <arg name="serial" type="uint" summary="serial of the event"/>
     </event>
   </interface>