The slk* functions manipulate the set of soft function-key labels that exist on many terminals. For those terminals that do not have soft labels, curses takes over the bottom line of stdscr, reducing the size of stdscr and the variable LINES. curses standardizes on eight labels of up to eight characters each. In addition to this, the ncurses implementation supports a mode where it simulates 12 labels of up to five characters each. This is most common for todays PC like enduser devices. Please note that ncurses simulates this mode by taking over up to two lines at the bottom of the screen, it doesnt try to use any hardware support for this mode.
The slk_init routine must be called before initscr or newterm is called. If initscr eventually uses a line from stdscr to emulate the soft labels, then fmt determines how the labels are arranged on the screen. Setting fmt to 0 indicates a 3-2-3 arrangement of the labels, 1 indicates a 4-4 arrangement and 2 indicates the PC like 4-4-4 mode. If fmt is set to 3, it is again the PC like 4-4-4 mode, but in addition an index line is generated, helping the user to identify the key numbers easily.
The slk_set routine requires labnum to be a label number, from 1 to 8 (resp. 12); label must be the string to be put on the label, up to eight (resp. five) characters in length. A null string or a null pointer sets up a blank label. fmt is either 0, 1, or 2, indicating whether the label is to be left-justified, centered, or right-justified, respectively, within the label.
The slk_refresh and slk_noutrefresh routines correspond to the wrefresh and wnoutrefresh routines.
The slk_label routine returns the current label for label number labnum, with leading and trailing blanks stripped.
The slk_clear routine clears the soft labels from the screen.
The slk_restore routine, restores the soft labels to the screen after a slk_clear has been performed.
The slk_touch routine forces all the soft labels to be output the next time a slk_noutrefresh is performed.
The slk_attron, slk_attrset, slk_attroff and slk_attr routines correspond to attron, attrset, attroff and attr_get. They have an effect only if soft labels are simulated on the bottom line of the screen. The default highlight for soft keys is A_STANDOUT (as in System V curses, which does not document this fact).
The slk_color routine corresponds to color_set. It has an effect only if soft labels are simulated on the bottom line of the screen.
These routines return ERR upon failure and OK (SVr4 specifies only "an integer value other than ERR") upon successful completion. slk_attr returns the attribute used for the soft keys.
slk_label returns NULL on error.
Most applications would use slk_noutrefresh because a wrefresh is likely to follow soon.
The XSI Curses standard, Issue 4, describes these functions. It changes the argument type of the attribute-manipulation functions slk_attron, slk_attroff, slk_attrset to be attr_t, and adds const qualifiers. The format codes 2 and 3 for slk_init() and the function slk_attr are specific to ncurses.
curses(3), curs_attr(3), curs_initscr(3), curs_refresh(3)