Cleaned up wxArtProvider:

1. Move platform-specific code for both GetSizeHint() and GetBitmap()
   into platform-specific files.
2. Introduced GetNativeSizeHint() to make native sizes better accessible,
   without having to understand weird GetSizeHint() semantics.
3. Fixed GetNativeSizeHint() to return sensible values in non-GTK ports;
   it returns wxDefaultSize if it can't make a good guess instead of
   returning arbitrary value.
4. Use 16x16 icons on MSW instead of 16x15: it works and is more
   'natural' size.



git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@56372 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/artprov.h

@@ -165,6 +165,10 @@ public:
     static wxIconBundle GetIconBundle(const wxArtID& id,
                                       const wxArtClient& client = wxART_OTHER);
 
+    // Gets native size for given 'client' or wxDefaultSize if it doesn't
+    // have native equivalent
+    static wxSize GetNativeSizeHint(const wxArtClient& client);
+
     // Get the size hint of an icon from a specific wxArtClient, queries
     // the topmost provider if platform_dependent = false
     static wxSize GetSizeHint(const wxArtClient& client, bool platform_dependent = false);
@@ -222,4 +226,12 @@ private:
 };
 
 
+#if !defined(__WXUNIVERSAL__) && \
+    (defined(__WXGTK__) || defined(__WXMSW__) || \
+     (defined(__WXMAC__) && wxOSX_USE_CARBON))
+  // *some* (partial) native implementation of wxArtProvider exists; this is
+  // not the same as wxArtProvider::HasNativeProvider()!
+  #define wxHAS_NATIVE_ART_PROVIDER_IMPL
+#endif
+
 #endif // _WX_ARTPROV_H_