Document "base" and "outer".

Change-Id: I2879c41fccdf4f3c6dfa4321d506c0ab9b84f541
Reviewed-by: Jake Petroules <jake.petroules@petroules.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/doc/reference/items/module.qdoc b/doc/reference/items/module.qdoc
index c91fd08fd..4a6e38678 100644
--- a/doc/reference/items/module.qdoc
+++ b/doc/reference/items/module.qdoc
@@ -101,6 +101,38 @@
     How you make your own modules available to \QBS is explained
     \l{Custom Modules and Items}{here}.
 
+    \section1 Special Property Values
+
+    For every property defined in a module, \QBS provides the following special built-in values:
+    \section2 \c base
+    This value is useful when making use of inheritance. It stands for the value of the respective
+    property in the item one level up in the inheritance chain. For instance:
+    \code
+    Product { // defined in MyProduct.qbs
+        Depends { name: "mymodule" }
+        mymodule.someProperty: ["value1"]
+    }
+    ------ some other file ------
+    MyProduct {
+        mymodule.someProperty: base.concat(["value2"]) // => ["value1", "value2"]
+    }
+    \endcode
+
+    \section2 \c outer
+    This value is used in nested items, where it refers to the value of the respective property
+    in the surrounding item. It is often encountered in \l{Group Item}{groups}:
+    \code
+    Product {
+        Depends { name: "mymodule" }
+        mymodule.someProperty: ["value1"]
+        Group {
+            name: "special files"
+            files: ["somefile1", "somefile2"]
+            mymodule.someProperty: outer.concat(["value"]) // => ["value1", "value2"]
+        }
+    }
+    \endcode
+
     \section1 Module Properties
 
     \table