Add some documentation about the workings of the attribute system.

(I hope I figured it out all correct)


git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@5574 dfc29bdd-3216-0410-991c-e03cc46cb475

source/Irrlicht/CAttributeImpl.h

@@ -13,7 +13,7 @@ namespace io
 {
 
 /*
-	basic types
+	Basic types, check documentation in IAttribute.h to see how they generally work.
 */
 
 // Attribute implemented for boolean values

source/Irrlicht/IAttribute.h

@@ -31,6 +31,15 @@ namespace irr
 namespace io
 {
 
+// All derived attribute types implement at least getter/setter for their own type (like CBoolAttribute will have setBool/getBool).
+// Simple types will also implement getStringW and setString, but don't expect it to work for all types.
+// String serialization makes no sense for some attribute-types (like stringw arrays or pointers), but is still useful for many types.
+// (Note: I do _not_ know yet why the default string serialization is asymmetric with char* in set and wchar_t* in get).
+// Additionally many attribute types will implement conversion functions like CBoolAttribute has p.E. getInt/setInt().
+// The reason for conversion functions is likely to make reading old formats easier which have changed in the meantime. For example
+// an old xml can contain a bool attribute which is an int in a newer format. You can still call getInt() even thought the attribute has the wrong type.
+// And please do _not_ confuse these attributes here with the ones used in the xml-reader (aka SAttribute which is just a key-value pair).
+
 class IAttribute : public virtual IReferenceCounted
 {
 public:

tests/tests-last-passed-at.txt

@@ -1,4 +1,4 @@
 Tests finished. 1 test of 1 passed.
 Compiled as DEBUG
-Test suite pass at GMT Tue Nov  7 00:00:50 2017
+Test suite pass at GMT Tue Nov  7 00:42:08 2017