--- a/src/gui.h
+++ b/src/gui.h
@@ -504,3 +504,46 @@ typedef enum
 # define FRD_WHOLE_WORD	0x08	/* match whole word only */
 # define FRD_MATCH_CASE	0x10	/* match case */
 #endif
+
+#ifdef HAVE_GTK2
+/*
+ * Convenience macros to convert from 'encoding' to 'termencoding' and
+ * vice versa.	If no conversion is necessary the passed-in pointer is
+ * returned as is, without allocating any memory.  Thus additional _FREE()
+ * macros are provided.  The _FREE() macros also set the pointer to NULL,
+ * in order to avoid bugs due to illegal memory access only happening if
+ * 'encoding' != utf-8...
+ *
+ * Defining these macros as pure expressions looks a bit tricky but
+ * avoids depending on the context of the macro expansion.  One of the
+ * rare occasions where the comma operator comes in handy :)
+ *
+ * Note: Do NOT keep the result around when handling control back to
+ * the main Vim!  The user could change 'encoding' at any time.
+ */
+# define CONVERT_TO_UTF8(String)				\
+    ((output_conv.vc_type == CONV_NONE || (String) == NULL)	\
+	    ? (String)						\
+	    : string_convert(&output_conv, (String), NULL))
+
+# define CONVERT_TO_UTF8_FREE(String)				\
+    ((String) = ((output_conv.vc_type == CONV_NONE)		\
+			? (char_u *)NULL			\
+			: (vim_free(String), (char_u *)NULL)))
+
+# define CONVERT_FROM_UTF8(String)				\
+    ((input_conv.vc_type == CONV_NONE || (String) == NULL)	\
+	    ? (String)						\
+	    : string_convert(&input_conv, (String), NULL))
+
+# define CONVERT_FROM_UTF8_FREE(String)				\
+    ((String) = ((input_conv.vc_type == CONV_NONE)		\
+			? (char_u *)NULL			\
+			: (vim_free(String), (char_u *)NULL)))
+
+#else
+# define CONVERT_TO_UTF8(String) (String)
+# define CONVERT_TO_UTF8_FREE(String) ((String) = (char_u *)NULL)
+# define CONVERT_FROM_UTF8(String) (String)
+# define CONVERT_FROM_UTF8_FREE(String) ((String) = (char_u *)NULL)
+#endif /* HAVE_GTK2 */