make it possible to create wxWindowDC for a hidden window

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@41131 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/dfb/private.h

@@ -41,6 +41,14 @@ enum wxDfbCloneSurfaceMode
     wxDfbCloneSurface_CopyPixels
 };
 
+/**
+    Creates surface that is compatible with given @a surface (i.e. has same
+    capabilities, pixel format etc.) and has given @a size.
+ */
+wxIDirectFBSurfacePtr wxDfbCreateCompatibleSurface(
+                                    const wxIDirectFBSurfacePtr& surface,
+                                    const wxSize& size);
+
 /**
     Creates a new surface by cloning existing one. Depending on @a mode,
     either makes exact copy (wxDfbCloneSurface_CopyPixels) or only creates a