[Xcb] [PATCH proto 2/7] xml-doc: add sumof with nested expression

[Christian Linhart]

---
 doc/xml-xcb.txt | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/doc/xml-xcb.txt b/doc/xml-xcb.txt
index 235958d..d47b12c 100644
--- a/doc/xml-xcb.txt
+++ b/doc/xml-xcb.txt
@@ -318,14 +318,25 @@ Expressions
   which operator. The only supported operation so far is ~, and its semantic
   is identical to the corresponding operator in C.
 
 <sumof ref="identifier" />
 
   This element represents a sumation of the elements of the referenced list.
 
+<sumof ref="identifier" >expression</sumof>
+
+  The expression is evaluated for each element of the referenced list,
+  in the context of this element.
+  This sumof element then represents a sumation of the results of these
+  evaluations.
+
+  expression will usually be a fieldref which references a field of
+  a list-element or an expression containing a fieldref,
+  such as popcount of a fieldref.
+
 <popcount>expression</popcount>
 
   This element represents the number of bits set in the expression.
 
 Documentation
 -------------
 
-- 
2.0.1