Refactor code finding the name of the windows class to use in wxMSW

Determine which class name to use in MSWCreate() caller instead of doing it
partly there and partly in MSWCreate() itself, which used to add the "NR"
suffix if necessary -- now it doesn't do this any more and just really created
the window using the given class.

No real changes, just prepare for future enhancements.

src/msw/window.cpp

@@ -468,10 +468,16 @@ wxWindowMSW::~wxWindowMSW()
 
 }
 
-/* static */
-const wxChar *wxWindowMSW::MSWGetRegisteredClassName()
+const wxChar *wxWindowMSW::GetMSWClassName() const
 {
-    return wxApp::GetRegisteredClassName(wxT("wxWindow"), COLOR_BTNFACE);
+    return wxApp::GetRegisteredClassName
+                  (
+                    wxT("wxWindow"),
+                    COLOR_BTNFACE,
+                    0, // no special extra style
+                    HasFlag(wxFULL_REPAINT_ON_RESIZE) ? wxApp::RegClass_Default
+                                                      : wxApp::RegClass_ReturnNR
+                  );
 }
 
 // real construction (Init() must have been called before!)
@@ -506,8 +512,7 @@ bool wxWindowMSW::Create(wxWindow *parent,
         msflags |= WS_VISIBLE;
     }
 
-    if ( !MSWCreate(MSWGetRegisteredClassName(),
-                    NULL, pos, size, msflags, exstyle) )
+    if ( !MSWCreate(GetMSWClassName(), NULL, pos, size, msflags, exstyle) )
         return false;
 
     InheritAttributes();
@@ -3695,22 +3700,13 @@ bool wxWindowMSW::MSWCreate(const wxChar *wclass,
     // unless we're creating a child window
     int controlId = style & WS_CHILD ? GetId() : 0;
 
-    // for each class "Foo" we have we also have "FooNR" ("no repaint") class
-    // which is the same but without CS_[HV]REDRAW class styles so using it
-    // ensures that the window is not fully repainted on each resize
-    wxString className(wclass);
-    if ( !HasFlag(wxFULL_REPAINT_ON_RESIZE) )
-    {
-        className += wxApp::GetNoRedrawClassSuffix();
-    }
-
     // do create the window
     wxWindowCreationHook hook(this);
 
     m_hWnd = (WXHWND)::CreateWindowEx
                        (
                         extendedStyle,
-                        className.t_str(),
+                        wclass,
                         title ? title : m_windowName.t_str(),
                         style,
                         x, y, w, h,
@@ -3722,7 +3718,7 @@ bool wxWindowMSW::MSWCreate(const wxChar *wclass,
 
     if ( !m_hWnd )
     {
-        wxLogSysError(_("Can't create window of class %s"), className.c_str());
+        wxLogSysError(_("Can't create window of class %s"), wclass);
 
         return false;
     }