[gtk/render-node-types: 1/3] Add macro for exported variables

[Emmanuele Bassi <ebassi src gnome org>]

commit 1d8143e091068ed39a4631d6707979f61b8cd291
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Tue Apr 7 23:32:22 2020 +0100

    Add macro for exported variables
    
    The logic is based on the similar macro in GLib, but with the
    appropriate GDK symbols.

 gdk/gdktypes.h | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)
---
diff --git a/gdk/gdktypes.h b/gdk/gdktypes.h
index 39f38788a0..eada3e43d3 100644
--- a/gdk/gdktypes.h
+++ b/gdk/gdktypes.h
@@ -624,4 +624,30 @@ typedef enum
 
 G_END_DECLS
 
+/*< private >
+ * GDK_EXTERN_VAR:
+ *
+ * A macro to annotate extern variables so that they show up properly in
+ * Windows DLLs.
+ */
+#ifndef GDK_EXTERN_VAR
+#  ifdef G_PLATFORM_WIN32
+#    ifdef GDK_STATIC_COMPILATION
+#      define GDK_EXTERN_VAR extern
+#    else /* !GDK_STATIC_COMPILATION */
+#      ifdef GDK_COMPILATION
+#        ifdef DLL_EXPORT
+#          define GDK_EXTERN_VAR __declspec(dllexport)
+#        else /* !DLL_EXPORT */
+#          define GDK_EXTERN_VAR extern
+#        endif /* !DLL_EXPORT */
+#      else /* !GDK_COMPILATION */
+#        define GDK_EXTERN_VAR extern __declspec(dllimport)
+#      endif /* !GDK_COMPILATION */
+#    endif /* !GDK_STATIC_COMPILATION */
+#  else /* !G_PLATFORM_WIN32 */
+#    define GDK_EXTERN_VAR _GDK_EXTERN
+#  endif /* !G_PLATFORM_WIN32 */
+#endif /* GLIB_VAR */
+
 #endif /* __GDK_TYPES_H__ */