- This page summarizes variables provided by the curses li-
- brary. A more complete description is given in the curs-
- es(3x) manual page.
-
- Depending on the configuration, these may be actual vari-
- ables, or macros (see curs_threads(3x)) which provide
- read-only access to curses's state. In either case, ap-
- plications should treat them as read-only to avoid confus-
- ing the library.
-
- COLOR_PAIRS
- After initializing curses, this variable contains the num-
- ber of color pairs which the terminal can support. Usual-
- ly the number of color pairs will be the product COL-
- ORS*COLORS, however this is not always true:
-
- o a few terminals use HLS colors, which do not follow
- this rule
-
- o terminals supporting a large number of colors are lim-
- ited by the number of color pairs that can be repre-
- sented in a signedshort value.
-
- COLORS
- After initializing curses, this variable contains the num-
- ber of colors which the terminal can support.
-
- COLS
- After initializing curses, this variable contains the
- width of the screen, i.e., the number of columns.
-
- ESCDELAY
- This variable holds the number of milliseconds to wait af-
- ter reading an escape character, to distinguish between an
- individual escape character entered on the keyboard from
- escape sequences sent by cursor- and function-keys (see
- curses(3x).
-
- LINES
- After initializing curses, this variable contains the
- height of the screen, i.e., the number of lines.
-
- TABSIZE
- This variable holds the number of columns used by the
- curses library when converting a tab character to spaces
- as it adds the tab to a window (see curs_addch(3x).
-
- TheCurrentScreen
- This implementation of curses uses a special window curscr
- to record its updates to the terminal screen.
-
- TheNewScreen
- This implementation of curses uses a special window newscr
- to hold updates to the terminal screen before applying
- them to curscr.
-
- TheStandardScreen
- Upon initializing curses, a default window called stdscr,
- which is the size of the terminal screen, is created.
- Many curses functions use this window.
+ /*extensions*/
+ intESCDELAY;
+ intTABSIZE;
+ WINDOW*newscr;
-
+ This page summarizes data types, constants, and variables provided by
+ the curses library. Locate further discussion in curses(3x).
- If curses is configured to use separate curses/terminfo
- libraries, most of these variables reside in the curses
+ 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.
-
-
PORTABILITY
- ESCDELAY and TABSIZE are extensions, not provided in most
- other implementations of curses.
+
+ X/Open Issue 4 curses (1996) preceded the ISO C99 and ISO C++98
+ standards, each of which also defined a Boolean data type. The curses
+ library requires an integral type bool.
+
+ ncurses' configure script attempts to discover the data type used by
+ the system's C and C++ compilers, to reuse for the cursesbool.
+
+
+
+ The chtype integral type combines a ("narrow", 8-bit) character with
+ attributes encoding the character's rendition, such as the styling of
+ its typeface and/or foreground and background colors. See, for
+ example, addch(3x), attron(3x), and inch(3x).
+
+
+
+ chtype is too small for the standard C library's wide-character type,
+ wchar_t. cchar_t is a type that can accommodate an attr_t and enough
+ wide characters to store what Unicode terms a graphemecluster (a
+ "user-perceived character" [UAX #29], which may nevertheless require
+ several character encoding units to represent). attr_t is an integral
+ type storing "wide" attributes that apply to cchar_ts. See, for
+ example, add_wch(3x), attr_on(3x), and in_wch(3x).
+
+
+
+ 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, 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
+ escapesequence (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.
+
+
+
+ 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.
+
+ o SVr4 initially sets TABSIZE from the terminal description's
+ init_tabs capability. After that, it can be altered by
+ applications using SVr4 curses.
+
+ o 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).
+
+ oncurses 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).
+
+ o 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.
+
+ o In AIX, the units for ESCDELAY are fifths of milliseconds.
+
+ o The default value for AIX's ESCDELAY equals 0.1 seconds.
+
+ o 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.
+
+
+