+DEFUN ("tty-top-frame", Ftty_top_frame, Stty_top_frame, 0, 1, 0,
+ doc: /* Return the topmost terminal frame on TERMINAL.
+TERMINAL can be a terminal object, a frame or nil (meaning the
+selected frame's terminal). This function returns nil if TERMINAL
+does not refer to a text terminal. Otherwise, it returns the
+top-most frame on the text terminal. */)
+ (Lisp_Object terminal)
+{
+ struct terminal *t = get_terminal (terminal, 1);
+
+ if (t->type == output_termcap)
+ return t->display_info.tty->top_frame;
+ return Qnil;
+}
+