Add more comments about ref counting and cow to

brush, pen, font and region.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@43567 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/latex/wx/region.tex

@@ -10,8 +10,14 @@
 
 \section{\class{wxRegion}}\label{wxregion}
 
-A wxRegion represents a simple or complex region on a device context or window. It uses
-reference counting, so copying and assignment operations are fast.
+A wxRegion represents a simple or complex region on a device context or window.
+
+This class uses \helpref{reference counting and copy-on-write}{trefcount}
+internally so that assignments between two instances of this class are very
+cheap. You can therefore use actual objects instead of pointers without
+efficiency problems. If an instance of this class is changed it will create
+its own data internally so that other instances, which previously shared the
+data using the reference counting, are not affected.
 
 \wxheading{Derived from}