Add interface and simple docs doe wxOverlay and wxDCOverlay.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71493 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/overlay.h

@@ -0,0 +1,68 @@
+/////////////////////////////////////////////////////////////////////////////
+// Name:        overlay.h
+// Purpose:     interface of wxOverlay
+// Author:      wxWidgets team
+// RCS-ID:      $Id$
+// Licence:     wxWindows licence
+/////////////////////////////////////////////////////////////////////////////
+
+/**
+   @class wxOverlay
+
+   Creates an overlay over an existing window, allowing for manipulations like
+   rubberbanding, etc.  On wxOSX the overlay is implemented with native
+   platform APIs, on the other platforms it is simulated using wxMemoryDC.
+   
+   @library{wxcore}
+
+   @see wxDCOverlay, wxDC
+ */
+class wxOverlay
+{
+public:
+    wxOverlay();
+    ~wxOverlay();
+
+    /**
+       Clears the overlay without restoring the former state.  To be done, for
+       example, when the window content has been changed and repainted.
+    */
+    void Reset();
+};
+
+
+
+/**
+   @class wxDCOverlay
+
+   Connects an overlay with a drawing DC.
+   
+   @library{wxcore}
+
+   @see wxOverlay, wxDC
+   
+ */
+class wxDCOverlay
+{
+public:
+    /**
+       Connects this overlay to the corresponding drawing dc, if the overlay is
+       not initialized yet this call will do so.
+    */
+    wxDCOverlay(wxOverlay &overlay, wxDC *dc, int x , int y , int width , int height);
+
+    /**
+       Convenience wrapper that behaves the same using the entire area of the dc.
+    */
+    wxDCOverlay(wxOverlay &overlay, wxDC *dc);
+
+    /**
+       Removes the connection between the overlay and the dc.
+    */
+    virtual ~wxDCOverlay();
+
+    /**
+       Clears the layer, restoring the state at the last init.
+    */
+    void Clear();
+};