curses(3XCURSES) X/Open Curses Library Functions curses(3XCURSES)NAMEcurses - introduction and overview of X/Open Curses
DESCRIPTION
The Curses screen management package conforms fully with Issue 4, Ver‐
sion 2 of the X/Open Curses specification. It provides a set of
internationalized functions and macros for creating and modifying
input and output to a terminal screen. This includes functions for
creating windows, highlighting text, writing to the screen, reading
from user input, and moving the cursor.
X/Open Curses is a terminal-independent package, providing a common
user interface to a variety of terminal types. Its portability is
facilitated by the Terminfo database which contains a compiled defini‐
tion of each terminal type. By referring to the database information
X/Open Curses gains access to low-level details about individual termi‐
nals.
X/Open Curses tailors its activities to the terminal type specified by
the TERM environment variable. The TERM environment variable may be
set in the Korn Shell (see ksh(1)) by typing:
export TERM=terminal_name
To set environment variables using other command line interfaces or
shells, see the environ(5) manual page.
Three additional environment variables are useful, and can be set in
the Korn Shell:
1. If you have an alternate Terminfo database containing terminal
types that are not available in the system default database
/usr/share/lib/terminfo, you can specify the TERMINFO environment
variable to point to this alternate database:
export TERMINFO=path
This path specifies the location of the alternate compiled Terminfo
database whose structure consists of directory names 0 to 9 and a
to z (which represent the first letter of the compiled terminal
definition file name).
The alternate database specified by TERMINFO is examined before
the system default database. If the terminal type specified by
TERM cannot be found in either database, the default terminal type
dumb is assumed.
2. To specify a window width smaller than your screen width (for exam‐
ple, in situations where your communications line is slow), set the
COLUMNS environment variable to the number of vertical columns
you want between the left and right margins:
export COLUMNS=number
The number of columns may be set to a number smaller than the
screen size; however, if set larger than the screen or window
width, the results are undefined.
The value set using this environment variable takes precedence over
the value normally used for the terminal.
3. To specify a window height smaller than your current screen height
(for example, in situations where your communications line is
slow), override the LINES environment variable by setting it to a
smaller number of horizontal lines:
export LINES=number
The number of lines may be set to a number smaller than the screen
height; however, if set larger than the screen or window height,
the results are undefined.
The value set using this environment variable takes precedence over
the value normally used for the terminal.
Data Types
X/Open Curses defines the following data types:
attr_t An integral type that holds an OR-ed set of attributes.
The attributes acceptable are those which begin with
the WA_ prefix .
bool Boolean data type.
cchar_t A type that refers to a string consisting of a spacing
wide character, up to 5 non-spacing wide characters,
and zero or more attributes of any type. See
Attributes, Color Pairs, and Renditions. A null cchar_t
object terminates arrays of cchar_t objects.
chtype An integral type whose values are formed by OR-ing an
"unsigned char" with a color pair. and with zero or
more attributes. The attributes acceptable are those
which begin with the A_ prefix and COLOR_PAIR(3XCURSES)
SCREEN An opaque data type associated with a terminal's dis‐
play screen.
TERMINAL An opaque data type associated with a terminal. It con‐
tains information about the terminal's capabilities (as
defined by terminfo), the terminal modes, and current
state of input/output operations.
wchar_t An integral data type whose values represent wide char‐
acters.
WINDOW An opaque data type associated with a window.
Screens, Windows, and Terminals
The X/Open Curses manual pages refer at various points to screens, win‐
dows (also subwindows, derived windows, and pads), and terminals. The
following list defines each of these terms.
Screen A screen is a terminal's physical output device. The
SCREEN data type is associated with a terminal.
Window Window objects are two-dimensional arrays of characters
and their renditions. X/Open Curses provides stdscr, a
default window which is the size of of the terminal
screen. You can use the newwin(3XCURSES) function to
create others.
To refer to a window, use a variable declared as WINDOW *. X/Open
Curses includes both functions that modify stdscr, and more general
versions that let you specify a window.
There are three sub-types of windows:
Subwindow A window which has been created within another
window (the parent window) and whose position
has been specified with absolute screen coordi‐
nates. The derwin(3XCURSES) and sub‐
win(3XCURSES) functions can be used to create
subwindows.
Derived Window A subwindow whose position is defined relative
to the parent window's coordinates rather than
in absolute terms.
Pad A special type of window that can be larger
than the screen. For more information, see the
newpad(3XCURSES) man page.
Terminal A terminal is the input and output device which
character-based applications use to interact
with the user. The TERMINAL data type is asso‐
ciated with such a device.
Attributes, Color Pairs, and Renditions
A character's rendition consists of its attributes (such as underlining
or reverse video) and its color pair (the foreground and background
colors). When using waddstr(3XCURSES), waddchstr(3XCURSES),
wprintw(3XCURSES), winsch(3XCURSES), and so on, the window's rendition
is combined with that character's renditions. The window rendition is
the attributes and color set using the attroff(3XCURSES) and
attr_off(3XCURSES) sets of functions. The window's background character
and rendition are set with the bkgdset(3XCURSES) and bkgrnd‐
set(3XCURSES) sets of functions.
When spaces are written to the screen, the background character and
window rendition replace the space. For example, if the background
rendition and character is A_UNDERLINE|'*', text written to the window
appears underlined and the spaces appear as underlined asterisks.
Each character written retains the rendition that it has obtained. This
allows the character to be copied "as is" to or from a window with the
addchstr(3XCURSES) or inch(3XCURSES) functions.
A_ Constant Values for Attributes
You can specify Attributes, Color Pairs, and Renditions attributes
using the constants listed in the tables below. The following constants
modify objects of type chtype:
┌──────────────────────────────────────────────────────────────┐
│Constant Description │
│A_ALTCHARSET Alternate character set │
│A_ATTRIBUTES Bit-mask to extract attributes │
│A_BLINK Blinking │
│A_BOLD Bold │
│A_CHARTEXT Bit-mask to extract a character │
│A_COLOR Bit-mask to extract color-pair │
│ information │
│A_DIM Half-bright │
│A_INVIS Invisible │
│A_PROTECT Protected │
│A_REVERSE Reverse video │
│A_STANDOUT Highlights specific to terminal │
│A_UNDERLINE Underline │
└──────────────────────────────────────────────────────────────┘
WA_ Constant Values for Attributes
The following constants modify objects of type attr_t:
┌──────────────────────────────────────────────────────────────┐
│Constant Description │
│WA_ALTCHARSET Alternate character set │
│WA_ATTRIBUTES Attribute mask │
│WA_BLINK Blinking │
│WA_BOLD Bold │
│WA_DIM Half-bright │
│WA_HORIZONTAL Horizontal highlight │
│WA_INVIS Invisible │
│WA_LEFT Left highlist │
│WA_LOW Low highlist │
│WA_PROTECT Protected │
│WA_REVERSE Reverse video │
│WA_RIGHT Right highlight │
│WA_STANDOUT Highlights specific to terminal │
│WA_TOP Top highlight │
│WA_UNDERLINE Underline │
│WA_VERTICAL Vertical highlight │
└──────────────────────────────────────────────────────────────┘
Color Macros
Colors always appear in pairs; the foreground color of the character
itself and the background color of the field on which it is displayed.
The following color macros are defined:
┌───────────────────────────────────────────────────────────┐
│Macro Description │
│COLOR_BLACK Black │
│COLOR_BLUE Blue │
│COLOR_GREEN Green │
│COLOR_CYAN Cyan │
│COLOR_RED Red │
│COLOR_MAGENTA Magenta │
│COLOR_YELLOW Yellow │
│COLOR_WHITE White │
└───────────────────────────────────────────────────────────┘
Together, a character's attributes and its color pair form the charac‐
ter's rendition. A character's rendition moves with the character dur‐
ing any scrolling or insert/delete operations. If your terminal lacks
support for the specified rendition, X/Open Curses may substitute a
different rendition.
The COLOR_PAIR(3XCURSES) function modifies a chtype object. The
PAIR_NUMBER(3XCURSES) function extracts the color pair from a chtype
object.
Functions for Modifying a Window's Color
The following functions modify a window's color:
┌─────────────────────────────────────────────────────────────┐
│Function Description │
│attr_set(), wattr_set() Change the window's rendition. │
│color_set(), wcolor_set() Set the window's color │
└─────────────────────────────────────────────────────────────┘
Non-Spacing Characters
When the wcwidth(3C) function returns a width of zero for a character,
that character is called a non-spacing character. Non-spacing charac‐
ters can be written to a window. Each non-spacing character is associ‐
ated with a spacing character (that is, one which does not have a width
of zero) and modifies that character. You cannot address a non-spacing
character directly. Whenever you perform an X/Open Curses operation on
the associated character, you are implicitly addressing the non-spac‐
ing character.
Non-spacing characters do not have a rendition. For functions that use
wide characters and a rendition, X/Open Curses ignores any rendition
specified for non-spacing characters. Multi-column characters have one
rendition that applies to all columns spanned.
Complex Characters
The cchar_t date type represents a complex character. A complex charac‐
ter may contain a spacing character, its associated non-spacing charac‐
ters, and its rendition. This implementation of complex characters sup‐
ports up to 5 non-spacing characters for each spacing character.
When a cchar_t object representing a non-spacing complex character is
written to the screen, its rendition is not used, but rather it becomes
associated with the rendition of the existing character at that loca‐
tion. The setcchar(3XCURSES) function initializes an object of type
cchar_t. The getcchar(3XCURSES) function extracts the contents of a
cchar_t object.
Display Operations
In adding internationalization support to X/Open Curses, every attempt
was made to minimize the number of changes to the historical CURSES
package. This enables programs written to use the historical implemen‐
tation of CURSES to use the internationalized version with little or no
modification. The following rules apply to the internationalized X/Open
Curses package:
· The cursor can be placed anywhere in the window. Window and
screen origins are (0,0).
· A multi-column character cannot be displayed in the last column,
because the character would appear truncated. Instead, the back‐
ground character is displayed in the last column and the multi-
column character appears at the beginning of the next line. This
is called wrapping.
If the original line is the last line in the scroll region and
scrolling is enabled, X/Open Curses moves the contents of each
line in the region to the previous line. The first line of the
region is lost. The last line of the scrolling region contains any
wrapped characters. The remainder of that line is filled with
the background character. If scrolling is disabled, X/Open Curses
truncates any character that would extend past the last column of
the screen.
· Overwrites operate on screen columns. If displaying a single-col‐
umn or multi-column character results in overwriting only a por‐
tion of a multi-column character or characters, background charac‐
ters are displayed in place of the non-overwritten portions.
· Insertions and deletions operate on whole characters. The cursor
is moved to the first column of the character prior to performing
the operation.
Overlapping Windows
When windows overlap, it may be necessary to overwrite only part of a
multi-column character. As mentioned earlier, the non-overwritten
portions are replaced with the background character. This results in
issues concerning the overwrite(3XCURSES), overlay(3XCURSES), copy‐
win(3XCURSES), wnoutrefresh(3XCURSES), and wrefresh(3XCURSES) func‐
tions.
Special Characters
Some functions assign special meanings to certain special characters:
Backspace Moves the cursor one column towards the begin‐
ning of the line. If the cursor was already
at the beginning of the line, it remains there.
All subsequent characters are added or inserted
at this point.
Carriage Return Moves the cursor to the beginning of the cur‐
rent line. If the cursor was already at the
beginning of the line, it remains there. All
subsequent characters are added or inserted at
this point.
Newline When adding characters, X/Open Curses fills the
remainder of the line with the background char‐
acter (effectively truncating the newline) and
scrolls the window as described earlier. All
subsequent characters are inserted at the start
of the new line.
When inserting characters, X/Open Curses fills
the remainder of the line with the background
character (effectively truncating the line),
moves the cursor to the beginning of a new
line, and scrolls the window as described ear‐
lier. All subsequent characters are placed at
the start of the new line.
Tab moves subsequent characters to next horizontal
tab strop. Default tab stops are set at 0, 8,
16, and so on.
When adding or inserting characters, X/Open
Curses inserts or adds the background charac‐
ter into each column until the next tab stop is
reached. If there are no remaining tab stops on
the current line, wrapping and scrolling occur
as described earlier.
Control Characters When X/Open Curses functions perform special
character processing, they convert control
characters to the ^X notation, where X is a
single-column character (uppercase, if it is a
letter) and writes that notation to the win‐
dow. Functions that retrieve text from the win‐
dow will retrieve the converted notation not
the original.
X/Open Curses displays non-printable bytes, that have their high bit
set, using the M-X meta notation where X is the non-printable byte with
its high bit turned off.
Input Processing
There are four input modes possible with X/Open Curses that affect the
behavior of input functions like getch(3XCURSES) and getnstr(3XCURSES).
Line Canonical (Cooked) In line input mode, the terminal driver handles
the input of line units as well as SIGERASE
and SIGKILL character processing. See
termio(7I) for more information.
In this mode, the getch() and getnstr() func‐
tions will not return until a complete line has
been read by the terminal driver, at which
point only the requested number of bytes/char‐
acters are returned. The rest of the line unit
remains unread until subsequent call to the
getch() or getnstr() functions.
The functions nocbreak(3XCURSES) and
noraw(3XCURSES) are used to enter this mode.
These functions are described on the
cbreak(3XCURSES) man page which also details
which termios flags are enabled.
Of the modes available, this one gives applica‐
tions the least amount of control over input.
However, it is the only input mode possible on
a block mode terminal.
cbreak Mode Byte/character input provides a finer degree of
control. The terminal driver passes each byte
read to the application without interpreting
erase and kill characters. It is the applica‐
tion's responsibility to handle line editing.
It is unknown whether the signal characters
(SIGINTR, SIGQUIT, SIGSUSP) and flow control
characters (SIGSTART, SIGSTOP) are enabled.
To ensure that they are, call the noraw() func‐
tion first, then call the cbreak() function.
halfdelay Mode This is the same as the cbreak() mode with a
timeout. The terminal driver waits for a byte
to be received or for a timer to expire, in
which case the getch() function either returns
a byte or ERR respectively. This mode over‐
rides timeouts set for an individual window
with the wtimeout() function.
raw Mode This mode provides byte/character input with
the most control for an application. It is
similar to cbreak() mode, but also disables
signal character processing (SIGINTR, SIGSUSP,
SIGQUIT) and flow control processing
(SIGSTART, SIGSTOP) so that the application can
process them as it wants.
These modes affect all X/Open Curses input. The default input mode is
inherited from the parent process when the application starts up.
A timeout similar to halfdelay(3XCURSES) can be applied to individual
windows (see timeout(3XCURSES)). The nodelay(3XCURSES) function is
equivalent to setting wtimeout(3XCURSES) for a window with a zero time‐
out (non-blocking) or infinite delay (blocking).
To handle function keys, keypad(3XCURSES) must be enabled. When it is
enabled, the getch() function returns a KEY_ constant for a uniquely
encoded key defined for that terminal. When keypad() is disabled, the
getch() function returns the individual bytes composing the function
key (see getch(3XCURSES) and wget_wch(3XCURSES)). By default, key‐
pad() is disabled.
When processing function keys, once the first byte is recognized, a
timer is set for each subsequent byte in the sequence. If any byte in
the function key sequence is not received before the timer expires,
the bytes already received are pushed into a buffer and the original
first byte is returned.
Subsequent X/Open Curses input would take bytes from the buffer until
exhausted, after which new input from the terminal will be requested.
Enabling and disabling of the function key interbyte timer is handled
by the notimeout(3XCURSES) function. By default, notimeout() is dis‐
abled (that is, the timer is used).
X/Open Curses always disables the terminal driver's echo processing.
The echo(3XCURSES) and noecho(3XCURSES) functions control X/Open Curses
software echoing. When software echoing is enabled, X/Open Curses
input functions echo printable characters, control keys, and meta keys
in the input window at the last cursor position. Functions keys are
never echoed. When software echoing is disabled, it is the applica‐
tion's responsibility to handle echoing.
EXAMPLES
Example 1: Copying Single-Column Characters Over Single-Column Charac‐
ters
In the upcoming examples, some characters have special meanings:
· {, [, and ( represent the left halves of multi-column characters.
}, ], and ) represent the corresponding right halves of the same
multi-column characters.
· Alphanumeric characters and periods (.) represent single-column
characters.
· The number sign (#) represents the background character.
copywin(s, t, 0, 1, 0, 1, 1, 3, 0)
s t → t
abcdef ...... .bcd..
ghijkl ...... .hij..
There are no special problems with this situation.
Example 2: Copying Multi-column Characters Over Single-Column Charac‐
ters
copywin(s, t, 0, 1, 0, 1, 1, 3, 0)
s t → t
a[]def ...... .[]d..
gh()kl ...... .h()..
There are no special problems with this situation.
Example 3: Copying Single-Column Characters From Source Overlaps Multi-
column Characters In Target
copywin(s, t, 0, 1, 0, 1, 1, 3, 0)
s t → t
abcdef [].... #bcd..
ghijk tol ...(). .hij#.
Overwriting multi-column characters in t has resulted in the # back‐
ground characters being required to erase the remaining halves of the
target's multi-column characters.
Example 4: Copy Incomplete Multi-column Characters From Source To Tar‐
get.
copywin(s, t, 0, 1, 0, 1, 1, 3, 0)
s t → t
[]cdef 123456 []cd56
ghi()l 789012 7hi()2
The ] and ( halves of the multi-column characters have been copied from
the source and expanded in the target outside of the specified target
region.
Consider a pop-up dialog box that contains single-column characters and
a base window that contains multi-column characters and you do the fol‐
lowing:
save=dupwin(dialog); /* create backing store */
overwrite(cursor, save); /* save region to be overlayed */
wrefresh(dialog); /* display dialog */
wrefresh(save); /* restore screen image */
delwin(save); /* release backing store */
You can use code similar to this to implement generic popup() and pop‐
down() routines in a variety of CURSES implementations (including BSD
UNIX, and UNIX System V). In the simple case where the base window con‐
tains single-column characters only, it would correctly restore the
image that appeared on the screen before the dialog box was displayed.
However, with multi-column characters, the overwrite() function might
save a region with incomplete multi-column characters. The wre‐
fresh(dialog) statement results in the behavior described in example 3
above. The behavior described in this example (that is, example 4)
allows the wrefresh(save) statement to restore the window correctly.
Example 5: Copying An Incomplete Multi-column Character To Region Next
To Screen Margin (Not A Window Edge)
Two cases of copying an incomplete multi-column character to a region
next to a screen margin follow:
copywin(s, t, 0, 1, 0, 0, 1, 2, 0)
s t → t
[]cdef 123456 #cd456
ghijkl 789012 hij012
The background character (#) replaces the ] character that would have
been copied from the source, because it is not possible to expand the
multi-column character to its complete form.
copywin(s, t, 0, 1, 0, 3, 1, 5, 0)
s t → t
abcdef 123456 123bcd
ghi()l 789012 789hi#
This second example is the same as the first, but with the right mar‐
gin.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Standard │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │Unsafe │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOksh(1), COLOR_PAIR(3XCURSES), PAIR_NUMBER(3XCURSES), addch‐
str(3XCURSES), attr_off(3XCURSES), attroff(3XCURSES),
bkgdset(3XCURSES), bkgrndset(3XCURSES), cbreak(3XCURSES), copy‐
win(3XCURSES), derwin(3XCURSES), echo(3XCURSES), getcchar(3XCURSES),
getch(3XCURSES), getnstr(3XCURSES), halfdelay(3XCURSES),
inch(3XCURSES), keypad(3XCURSES), libcurses(3XCURSES), new‐
pad(3XCURSES), newwin(3XCURSES), nocbreak(3XCURSES), nodelay(3XCURSES),
noecho(3XCURSES), noraw(3XCURSES), notimeout(3XCURSES), over‐
lay(3XCURSES), overwrite(3XCURSES), setcchar(3XCURSES), sub‐
win(3XCURSES), timeout(3XCURSES), waddchstr(3XCURSES),
waddstr(3XCURSES), wcwidth(3C), wget_wch(3XCURSES), winsch(3XCURSES),
wnoutrefresh(3XCURSES), wprintw(3XCURSES), wrefresh(3XCURSES), wtime‐
out(3XCURSES), attributes(5), environ(5), standards(5), termio(7I)SunOS 5.10 5 Jun 2002 curses(3XCURSES)
