curs\_threads(3X) Library calls curs\_threads(3X)

# [NAME](#NAME)

*NCURSES\_WINDOW\_CB*, *NCURSES\_SCREEN\_CB*, **get\_escdelay**, **set\_escdelay**, **set\_tabsize**, **use\_screen**, **use\_window** - *curses* support for multi-threaded applications

# [SYNOPSIS](#SYNOPSIS)

```
#include <curses.h>
```

```
/* data types */
typedef int (*NCURSES_WINDOW_CB)(WINDOW *, void *);
typedef int (*NCURSES_SCREEN_CB)(SCREEN *, void *);
```

```
int get_escdelay(void);
int set_escdelay(int ms);
int set_tabsize(int cols);
```

```
int use_screen(SCREEN *scr, NCURSES_SCREEN_CB func, void *data);
int use_window(WINDOW *win, NCURSES_WINDOW_CB func, void *data);
```

# [DESCRIPTION](#DESCRIPTION)

The *ncurses* library can be configured to support multi-threaded applications in a rudimentary way. Such configuration produces a different set of libraries, named *libncursest*, for example, since doing so alters *ncurses*'s application binary interface (ABI).

Instead of modifying the programming interface (API) to make *ncurses* functions expect an additional argument specifying a thread, the library adds functions, usable in any configuration, that hide the *mutexes* (mutual exclusion locks) needed to prevent concurrent access to variables shared by multiple threads of execution.

*ncurses* threading support requires the use of functions to access members of the *WINDOW* structure (see [**curs\_opaque**(3X)](/man/os/ncurses/curs_opaque.3X)). It further makes functions of the common global variables **COLORS**, **COLOR\_PAIRS**, **COLS**, **ESCDELAY**, **LINES**, **TABSIZE**, **curscr**, **newscr**, and **ttytype**, maintaining them as read-only values in the *SCREEN* structure.

Even this is not enough to make an application using *curses* thread-safe. We would expect a multi-threaded application to have threads updating separate windows (on the same device), and separate screens (on different devices). Further, applications expect a few of the global variables to be writable. The functions described here address these special situations.

The **ESCDELAY** and **TABSIZE** global variables are modified by some applications. To modify them in any configuration, use the **set\_escdelay** or **set\_tabsize** functions. Other global variables are not modifiable. **get\_escdelay** retrieves **ESCDELAY**'s value.

The **use\_window** and **use\_screen** functions provide coarse-grained mutexes for their respective *WINDOW* and *SCREEN* parameters; they call a user-supplied function, pass it a *data* parameter, and return the value from the user-supplied function to the application.

## [Usage](#Usage)

All *ncurses* library functions assume that the locale is not altered during operation. In addition, they use data that is maintained within a hierarchy of scopes.

- global data used in the low-level *terminfo* or *termcap* interfaces
- terminal data associated with a call to [**set\_curterm**(3X)](/man/os/ncurses/set_curterm.3X)

Terminal data are initialized when screens are created.

- screen data associated with a call to [**newterm**(3X)](/man/os/ncurses/newterm.3X) or [**initscr**(3X)](/man/os/ncurses/initscr.3X)
- window data associated with a call to [**newwin**(3X)](/man/os/ncurses/newwin.3X) or [**subwin**(3X)](/man/os/ncurses/subwin.3X)

Windows are associated with screens. Pads are not necessarily associated with any particular screen.

Most *curses* applications operate on one or more windows within a single screen.

•

reentrant data associated with “pure” functions that alter no shared variables

The following table lists the scope of each symbol in the *ncurses* library when configured to support multi-threaded applications.

**Symbol** **Scope** **BC** global **COLORS** screen (read-only) **COLOR\_PAIR** reentrant **COLOR\_PAIRS** screen (read-only) **COLS** screen (read-only) **ESCDELAY** screen (read-only; see **set\_escdelay**) **LINES** screen (read-only) **PAIR\_NUMBER** reentrant **PC** global **SP** global **TABSIZE** screen (read-only; see **set\_tabsize**) **UP** global **acs\_map** screen (read-only) **add\_wch** window (**stdscr**) **add\_wchnstr** window (**stdscr**) **add\_wchstr** window (**stdscr**) **addch** window (**stdscr**) **addchnstr** window (**stdscr**) **addchstr** window (**stdscr**) **addnstr** window (**stdscr**) **addnwstr** window (**stdscr**) **addstr** window (**stdscr**) **addwstr** window (**stdscr**) **assume\_default\_colors** screen **attr\_get** window (**stdscr**) **attr\_off** window (**stdscr**) **attr\_on** window (**stdscr**) **attr\_set** window (**stdscr**) **attroff** window (**stdscr**) **attron** window (**stdscr**) **attrset** window (**stdscr**) **baudrate** screen **beep** screen **bkgd** window (**stdscr**) **bkgdset** window (**stdscr**) **bkgrnd** window (**stdscr**) **bkgrndset** window (**stdscr**) **boolcodes** global (read-only) **boolfnames** global (read-only) **boolnames** global (read-only) **border** window (**stdscr**) **border\_set** window (**stdscr**) **box** window (**stdscr**) **box\_set** window (**stdscr**) **can\_change\_color** terminal **cbreak** screen **chgat** window (**stdscr**) **clear** window (**stdscr**) **clearok** window **clrtobot** window (**stdscr**) **clrtoeol** window (**stdscr**) **color\_content** screen **color\_set** window (**stdscr**) **copywin** window (locks source, target) **cur\_term** terminal **curs\_set** screen **curscr** screen (read-only) **curses\_version** global (read-only) **def\_prog\_mode** terminal **def\_shell\_mode** terminal **define\_key** screen **del\_curterm** screen **delay\_output** screen **delch** window (**stdscr**) **deleteln** window (**stdscr**) **delscreen** global (locks screen list, screen) **delwin** global (locks window list) **derwin** screen **doupdate** screen **dupwin** screen (locks window) **echo** screen **echo\_wchar** window (**stdscr**) **echochar** window (**stdscr**) **endwin** screen **erase** window (**stdscr**) **erasechar** window (**stdscr**) **erasewchar** window (**stdscr**) **filter** global **flash** terminal **flushinp** screen **get\_wch** screen (input operation) **get\_wstr** screen (input operation) **getattrs** window **getbegx** window **getbegy** window **getbkgd** window **getbkgrnd** window **getcchar** reentrant **getch** screen (input operation) **getcurx** window **getcury** window **getmaxx** window **getmaxy** window **getmouse** screen (input operation) **getn\_wstr** screen (input operation) **getnstr** screen (input operation) **getparx** window **getpary** window **getstr** screen (input operation) **getwin** screen (input operation) **halfdelay** screen **has\_colors** terminal **has\_ic** terminal **has\_il** terminal **has\_key** screen **hline** window (**stdscr**) **hline\_set** window (**stdscr**) **idcok** window **idlok** window **immedok** window **in\_wch** window (**stdscr**) **in\_wchnstr** window (**stdscr**) **in\_wchstr** window (**stdscr**) **inch** window (**stdscr**) **inchnstr** window (**stdscr**) **inchstr** window (**stdscr**) **init\_color** screen **init\_pair** screen **initscr** global (locks screen list) **innstr** window (**stdscr**) **innwstr** window (**stdscr**) **ins\_nwstr** window (**stdscr**) **ins\_wch** window (**stdscr**) **ins\_wstr** window (**stdscr**) **insch** window (**stdscr**) **insdelln** window (**stdscr**) **insertln** window (**stdscr**) **insnstr** window (**stdscr**) **insstr** window (**stdscr**) **instr** window (**stdscr**) **intrflush** terminal **inwstr** window (**stdscr**) **is\_cleared** window **is\_idcok** window **is\_idlok** window **is\_immedok** window **is\_keypad** window **is\_leaveok** window **is\_linetouched** window **is\_nodelay** window **is\_notimeout** window **is\_scrollok** window **is\_syncok** window **is\_term\_resized** terminal **is\_wintouched** window **isendwin** screen **key\_defined** screen **key\_name** global (static data) **keybound** screen **keyname** global (static data) **keyok** screen **keypad** window **killchar** terminal **killwchar** terminal **leaveok** window **longname** screen **mcprint** terminal **meta** screen **mouse\_trafo** window (**stdscr**) **mouseinterval** screen **mousemask** screen **move** window (**stdscr**) **mvadd\_wch** window (**stdscr**) **mvadd\_wchnstr** window (**stdscr**) **mvadd\_wchstr** window (**stdscr**) **mvaddch** window (**stdscr**) **mvaddchnstr** window (**stdscr**) **mvaddchstr** window (**stdscr**) **mvaddnstr** window (**stdscr**) **mvaddnwstr** window (**stdscr**) **mvaddstr** window (**stdscr**) **mvaddwstr** window (**stdscr**) **mvchgat** window (**stdscr**) **mvcur** screen **mvdelch** window (**stdscr**) **mvderwin** window (**stdscr**) **mvget\_wch** screen (input operation) **mvget\_wstr** screen (input operation) **mvgetch** screen (input operation) **mvgetn\_wstr** screen (input operation) **mvgetnstr** screen (input operation) **mvgetstr** screen (input operation) **mvhline** window (**stdscr**) **mvhline\_set** window (**stdscr**) **mvin\_wch** window (**stdscr**) **mvin\_wchnstr** window (**stdscr**) **mvin\_wchstr** window (**stdscr**) **mvinch** window (**stdscr**) **mvinchnstr** window (**stdscr**) **mvinchstr** window (**stdscr**) **mvinnstr** window (**stdscr**) **mvinnwstr** window (**stdscr**) **mvins\_nwstr** window (**stdscr**) **mvins\_wch** window (**stdscr**) **mvins\_wstr** window (**stdscr**) **mvinsch** window (**stdscr**) **mvinsnstr** window (**stdscr**) **mvinsstr** window (**stdscr**) **mvinstr** window (**stdscr**) **mvinwstr** window (**stdscr**) **mvprintw** window (**stdscr**) **mvscanw** screen **mvvline** window (**stdscr**) **mvvline\_set** window (**stdscr**) **mvwadd\_wch** window **mvwadd\_wchnstr** window **mvwadd\_wchstr** window **mvwaddch** window **mvwaddchnstr** window **mvwaddchstr** window **mvwaddnstr** window **mvwaddnwstr** window **mvwaddstr** window **mvwaddwstr** window **mvwchgat** window **mvwdelch** window **mvwget\_wch** screen (input operation) **mvwget\_wstr** screen (input operation) **mvwgetch** screen (input operation) **mvwgetn\_wstr** screen (input operation) **mvwgetnstr** screen (input operation) **mvwgetstr** screen (input operation) **mvwhline** window **mvwhline\_set** window **mvwin** window **mvwin\_wch** window **mvwin\_wchnstr** window **mvwin\_wchstr** window **mvwinch** window **mvwinchnstr** window **mvwinchstr** window **mvwinnstr** window **mvwinnwstr** window **mvwins\_nwstr** window **mvwins\_wch** window **mvwins\_wstr** window **mvwinsch** window **mvwinsnstr** window **mvwinsstr** window **mvwinstr** window **mvwinwstr** window **mvwprintw** window **mvwscanw** screen **mvwvline** window **mvwvline\_set** window **napms** reentrant **newpad** global (locks window list) **newscr** screen (read-only) **newterm** global (locks screen list) **newwin** global (locks window list) **nl** screen **nocbreak** screen **nodelay** window **noecho** screen **nofilter** global **nonl** screen **noqiflush** terminal **noraw** screen **notimeout** window **numcodes** global (read-only) **numfnames** global (read-only) **numnames** global (read-only) **ospeed** global **overlay** window (locks source, target) **overwrite** window (locks source, target) **pair\_content** screen **pecho\_wchar** screen **pechochar** screen **pnoutrefresh** screen **prefresh** screen **printw** window **putp** global **putwin** window **qiflush** terminal **raw** screen **redrawwin** window **refresh** screen **reset\_prog\_mode** screen **reset\_shell\_mode** screen **resetty** terminal **resize\_term** screen (locks window list) **resizeterm** screen **restartterm** screen **ripoffline** global (static data) **savetty** terminal **scanw** screen **scr\_dump** screen **scr\_init** screen **scr\_restore** screen **scr\_set** screen **scrl** window (**stdscr**) **scroll** window **scrollok** window **set\_curterm** screen **set\_escdelay** screen **set\_tabsize** screen **set\_term** global (locks screen list, screen) **setcchar** reentrant **setscrreg** window (**stdscr**) **setupterm** global **slk\_attr** screen **slk\_attr\_off** screen **slk\_attr\_on** screen **slk\_attr\_set** screen **slk\_attroff** screen **slk\_attron** screen **slk\_attrset** screen **slk\_clear** screen **slk\_color** screen **slk\_init** screen **slk\_label** screen **slk\_noutrefresh** screen **slk\_refresh** screen **slk\_restore** screen **slk\_set** screen **slk\_touch** screen **slk\_wset** screen **standend** window **standout** window **start\_color** screen **stdscr** screen (read-only) **strcodes** global (read-only) **strfnames** global (read-only) **strnames** global (read-only) **subpad** window **subwin** window **syncok** window **term\_attrs** screen **termattrs** screen **termname** terminal **tgetent** global **tgetflag** global **tgetnum** global **tgetstr** global **tgoto** global **tigetflag** terminal **tigetnum** terminal **tigetstr** terminal **timeout** window (**stdscr**) **touchline** window **touchwin** window **tparm** global (static data) **tputs** screen **trace** global (static data) **ttytype** screen (read-only) **typeahead** screen **unctrl** screen **unget\_wch** screen (input operation) **ungetch** screen (input operation) **ungetmouse** screen (input operation) **untouchwin** window **use\_default\_colors** screen **use\_env** global (static data) **use\_extended\_names** global (static data) **use\_legacy\_coding** screen **use\_screen** global (locks screen list, screen) **use\_window** global (locks window list, window) **vid\_attr** screen **vid\_puts** screen **vidattr** screen **vidputs** screen **vline** window (**stdscr**) **vline\_set** window (**stdscr**) **vw\_printw** window **vw\_scanw** screen **vwprintw** window **vwscanw** screen **wadd\_wch** window **wadd\_wchnstr** window **wadd\_wchstr** window **waddch** window **waddchnstr** window **waddchstr** window **waddnstr** window **waddnwstr** window **waddstr** window **waddwstr** window **wattr\_get** window **wattr\_off** window **wattr\_on** window **wattr\_set** window **wattroff** window **wattron** window **wattrset** window **wbkgd** window **wbkgdset** window **wbkgrnd** window **wbkgrndset** window **wborder** window **wborder\_set** window **wchgat** window **wclear** window **wclrtobot** window **wclrtoeol** window **wcolor\_set** window **wcursyncup** screen (affects window plus parents) **wdelch** window **wdeleteln** window **wecho\_wchar** window **wechochar** window **wenclose** window **werase** window **wget\_wch** screen (input operation) **wget\_wstr** screen (input operation) **wgetbkgrnd** window **wgetch** screen (input operation) **wgetdelay** window **wgetn\_wstr** screen (input operation) **wgetnstr** screen (input operation) **wgetparent** window **wgetscrreg** window **wgetstr** screen (input operation) **whline** window **whline\_set** window **win\_wch** window **win\_wchnstr** window **win\_wchstr** window **winch** window **winchnstr** window **winchstr** window **winnstr** window **winnwstr** window **wins\_nwstr** window **wins\_wch** window **wins\_wstr** window **winsch** window **winsdelln** window **winsertln** window **winsnstr** window **winsstr** window **winstr** window **winwstr** window **wmouse\_trafo** window **wmove** window **wnoutrefresh** screen **wprintw** window **wredrawln** window **wrefresh** screen **wresize** window (locks window list) **wscanw** screen **wscrl** window **wsetscrreg** window **wstandend** window **wstandout** window **wsyncdown** screen (affects window plus parents) **wsyncup** screen (affects window plus parents) **wtimeout** window **wtouchln** window **wunctrl** global (static data) **wvline** window **wvline\_set** window

# [RETURN VALUE](#RETURN_VALUE)

**get\_escdelay** returns the value of **ESCDELAY**. **set\_escdelay** and **set\_tabsize** return **ERR** upon failure and **OK** upon successful completion. **use\_screen** and **use\_window** return the *int* returned by the user-supplied function they are called with.

# [NOTES](#NOTES)

*ncurses* provides both a C function and a preprocessor macro for each function documented in this page.

# [PORTABILITY](#PORTABILITY)

Applications employing *ncurses* extensions should condition their use on the visibility of the **NCURSES\_VERSION** preprocessor macro.

# [SEE ALSO](#SEE_ALSO)

[**curses**(3X)](/man/os/ncurses/curses.3X), [**curs\_opaque**(3X)](/man/os/ncurses/curs_opaque.3X), [**curs\_variables**(3X)](/man/os/ncurses/curs_variables.3X)

2026-09-19 ncurses 6.6

---

Document: set_escdelay(3x) from ncurses 6.6.20261017-r0 (Chainguard OS)
Source: https://github.com/ThomasDickey/ncurses-snapshots