+char *x11_display(const char *display);
+/* Platform-dependent X11 functions */
+extern void platform_get_x11_auth(struct X11Display *display, Conf *);
+ /* examine a mostly-filled-in X11Display and fill in localauth* */
+extern const int platform_uses_x11_unix_by_default;
+ /* choose default X transport in the absence of a specified one */
+SockAddr platform_get_x11_unix_address(const char *path, int displaynum);
+ /* make up a SockAddr naming the address for displaynum */
+char *platform_get_x_display(void);
+ /* allocated local X display string, if any */
+/* Callbacks in x11.c usable _by_ platform X11 functions */
+/*
+ * This function does the job of platform_get_x11_auth, provided
+ * it is told where to find a normally formatted .Xauthority file:
+ * it opens that file, parses it to find an auth record which
+ * matches the display details in "display", and fills in the
+ * localauth fields.
+ *
+ * It is expected that most implementations of
+ * platform_get_x11_auth() will work by finding their system's
+ * .Xauthority file, adjusting the display details if necessary
+ * for local oddities like Unix-domain socket transport, and
+ * calling this function to do the rest of the work.
+ */
+void x11_get_auth_from_authfile(struct X11Display *display,
+ const char *authfilename);