Manual Pages  — curs_variables

 bool,  chtype,  cchar_t,  attr_t,  SCREEN,  WINDOW,  TRUE,  FALSE,  ERR,  OK,  curscr,  newscr,  stdscr,  COLORS,  COLOR_PAIRS,  COLS,  LINES,  ESCDELAY,  TABSIZE - curses data types, constants, and global variables

SYNOPSIS DESCRIPTION CONSTANTS TRUE, FALSE ERR, OK PREDEFINED TYPES bool chtype cchar_t, attr_t SCREEN WINDOW VARIABLES curscr, stdscr, newscr COLORS COLOR_PAIRS COLS, LINES ESCDELAY TABSIZE NOTES PORTABILITY SEE ALSO

#include <curses.h>

/* data types */
typedef /* ... */ bool;
typedef /* ... */ chtype;
typedef /* ... */ cchar_t;
typedef /* ... */ attr_t;
typedef /* ... */ SCREEN;
typedef /* ... */ WINDOW;

/* constants */
const bool TRUE;
const bool FALSE;

const /* ... */ ERR;
const /* ... */ OK;

/* variables */
int COLORS;
int COLOR_PAIRS;
int COLS;
int LINES;
WINDOW * curscr;
WINDOW * stdscr;

/* extensions */
int ESCDELAY;
int TABSIZE;
WINDOW * newscr;

This page summarizes data types, constants, and variables provided by the curses library. Locate further discussion in  curses(3X).

Depending on  ncurses's build-time configuration, the variables may instead be macros (see  curs_threads(3X) and  curs_opaque(3X)) that provide read-only access to the library's state. In either case, applications should treat them as read-only to avoid confusing the library.

The curses library defines TRUE and FALSE to represent the values of the Boolean data type.

curses and terminfo routines frequently return these constant integral values indicating failure and success, respectively.

The library records updates to the terminal screen in a window named  curscr. This object is referred to as the physical screen in  curs_refresh(3X) and  curs_outopts(3X).

 ncurses collects pending updates to the terminal screen in a window named  newscr. This object is referred to as the virtual screen in the  curs_kernel(3X),  curs_refresh(3X), and  curs_outopts(3X). When the screen is refreshed, curses determines a minimal set of updates using the terminal's capabilities to make  curscr look like  newscr.

Once curses is initialized, it creates a window named  stdscr. It is the same size as the terminal screen and is the default window used by routines that do not take a parameter identifying one. Many curses functions use this window.

Once curses is initialized,  COLORS contains the number of colors supported by the terminal; see  curs_color(3X).

Once curses is initialized,  COLOR_PAIRS contains the number of color pairs supported by the terminal; see  curs_color(3X).

Once curses is initialized,  COLS and LINES contain the screen's width and height in character cells, respectively; that is, the number of columns and lines.

For curses to distinguish the ESC character resulting from a user's press of the Escape key on the input device from one beginning an escape sequence (as commonly produced by function keys), it waits after the escape character to see if further characters are available on the input stream within a short interval.  ESCDELAY stores this interval in milliseconds.

If  keypad(3X) is disabled for the curses window receiving input, a program must disambiguate escape sequences itself.

The curses library converts a tab character to this number of spaces as it adds a tab to a window; see  curs_addch(3X).

Either  initscr(3X) or  newterm(3X) initializes curses.

If  ncurses is configured to provide separate curses and  tinfo libraries, most of these variables reside in the former.

The X/Open Curses standard documents all of the foregoing types and symbols except for  newscr,  TABSIZE, and  ESCDELAY.

X/Open Curses describes  curscr only as an internal data structure; SVr4 gave more details, noting its use for certain low-level operations like clearing and redrawing a screen containing garbage. Neither specified its interaction with the rest of the interface beyond use as an argument to  clearok(3X) and  wrefresh(3X).

 newscr is a feature of SVr4 curses. When refreshing the screen, it is used as a working area for combining the standard window  stdscr with any others the application may have created with  newwin(3X). When the update of  newscr is complete, curses modifies  curscr to match  newscr.

 TABSIZE is a feature of SVr4 curses.

»	SVr4 initially sets  TABSIZE from the terminal description's  init_tabs capability. After that, it can be altered by applications using SVr4 curses.
»	SVr4 curses uses the value of  TABSIZE to compute the position of tab stops when updating both the virtual screen with  addch(3X) and the physical screen with  mvcur(3X).
»	ncurses uses the value of  TABSIZE only to update the virtual screen. It uses the terminal description's it ( init_tabs) capability for computing hardware tabs (that is, tab stops on the physical screen).
»	Other implementations differ. For instance, NetBSD curses allows  TABSIZE to be set through an environment variable.  ncurses does not.
	NetBSD curses does not support hardware tabs; it uses the  init_tabs capability and the  TABSIZE variable only for updating the virtual screen.

 ESCDELAY is a feature of AIX curses.

»	In AIX, the units for  ESCDELAY are fifths of milliseconds.
»	The default value for AIX's  ESCDELAY equals 0.1 seconds.
»	AIX also enforces a limit of 10,000 seconds for  ESCDELAY;  ncurses does not enforce any upper limit.

 ncurses has long used  ESCDELAY with units of milliseconds, making it impossible to be completely compatible with AIX. Consequently, most users have decided either to override the value, or to rely upon its default.