extern Lisp_Object help_echo_string, help_echo_window;
extern Lisp_Object help_echo_object, previous_help_echo_string;
extern ptrdiff_t help_echo_pos;
-extern int last_tool_bar_item;
extern void reseat_at_previous_visible_line_start (struct it *);
extern Lisp_Object lookup_glyphless_char_display (int, struct it *);
extern ptrdiff_t compute_display_string_pos (struct text_pos *,