gtk2/docs/reference/gdk/gdk3-overrides.txt

# GdkAtom is an opaque typedef
<STRUCT>
<NAME>GdkAtom</NAME>
</STRUCT>

<MACRO>
<NAME>GDK_WINDOWING_X11</NAME>
#define GDK_WINDOWING_X11
</MACRO>

<MACRO>
<NAME>GDK_WINDOWING_WIN32</NAME>
#define GDK_WINDOWING_WIN32
</MACRO>