use SS_CENTERIMAGE to prevent wxStaticBitmap from stretching its bitmap; also a face lift for control creation code

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@18388 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/statbmp.h

@@ -36,6 +36,8 @@ public:
                    long style = 0,
                    const wxString& name = wxStaticBitmapNameStr)
     {
+        Init();
+
         Create(parent, id, label, pos, size, style, name);
     }
 
@@ -55,11 +57,23 @@ public:
     // assert failure is provoked by an attempt to get an icon from bitmap or
     // vice versa
     wxIcon GetIcon() const
-        { wxASSERT( m_isIcon ); return *(wxIcon *)m_image; }
-    wxBitmap GetBitmap() const
-        { wxASSERT( !m_isIcon ); return *(wxBitmap *)m_image; }
+    {
+        wxASSERT_MSG( m_isIcon, _T("no icon in this wxStaticBitmap") );
 
-    // IMPLEMENTATION
+        return *(wxIcon *)m_image;
+    }
+
+    wxBitmap GetBitmap() const
+    {
+        wxASSERT_MSG( !m_isIcon, _T("no bitmap in this wxStaticBitmap") );
+
+        return *(wxBitmap *)m_image;
+    }
+
+    // implementation only from now on
+    // -------------------------------
+
+    // implement base class virtuals
 #ifdef __WIN16__
     virtual bool MSWOnDraw(WXDRAWITEMSTRUCT *item);
 #endif // __WIN16__
@@ -67,7 +81,9 @@ public:
 
 protected:
     virtual wxSize DoGetBestSize() const;
+    virtual WXDWORD MSWGetStyle(long style, WXDWORD *exstyle) const;
 
+    // ctor/dtor helpers
     void Init() { m_isIcon = TRUE; m_image = NULL; }
     void Free();