+ curses supports color attributes on terminals with that capability. To
+ use these routines start_color must be called, usually right after
+ initscr. Colors are always used in pairs (referred to as color-pairs).
+ A color-pair consists of a foreground color (for characters) and a
+ background color (for the blank field on which the characters are dis-
+ played). A programmer initializes a color-pair with the routine
+ init_pair. After it has been initialized, COLOR_PAIR(n) can be used to
+ convert the pair to a video attribute.
+
+ If a terminal is capable of redefining colors, the programmer can use
+ the routine init_color to change the definition of a color. The rou-
+ tines has_colors and can_change_color return TRUE or FALSE, depending
+ on whether the terminal has color capabilities and whether the program-
+ mer can change the colors. The routine color_content allows a program-
+ mer to extract the amounts of red, green, and blue components in an
+ initialized color. The routine pair_content allows a programmer to
+ find out how a given color-pair is currently defined.
+
+
+
+ The curses library combines these inputs to produce the actual fore-
+ ground and background colors shown on the screen:
+
+ o per-character video attributes (e.g., via waddch),
+
+ o the window attribute (e.g., by wattrset), and
+
+ o the background character (e.g., wbkgdset).
+
+ Per-character and window attributes are usually set by a parameter con-
+ taining video attributes including a color pair value. Some functions
+ such as wattr_set use a separate parameter which is the color pair num-
+ ber.
+
+ The background character is a special case: it includes a character
+ value, just as if it were passed to waddch.
+
+ The curses library does the actual work of combining these color pairs
+ in an internal function called from waddch:
+
+ o If the parameter passed to waddch is blank, and it uses the special
+ color pair 0,
+
+ ocurses next checks the window attribute.
+
+ o If the window attribute does not use color pair 0, curses uses
+ the color pair from the window attribute.
+
+ o Otherwise, curses uses the background character.
+
+ o If the parameter passed to waddch is notblank, or it does not use
+ the special color pair 0, curses prefers the color pair from the
+ parameter, if it is nonzero. Otherwise, it tries the window at-
+ tribute next, and finally the background character.
+
+ Some curses functions such as wprintw call waddch. Those do not com-
+ bine its parameter with a color pair. Consequently those calls use on-
+ ly the window attribute or the background character.
+
+
+
+ In <curses.h> the following macros are defined. These are the standard
+ colors (ISO-6429). curses also assumes that COLOR_BLACK is the default
+ background color for all terminals.
-
-
DESCRIPTION
- Overview
- curses support color attributes on terminals with that ca-
- pability. To use these routines start_color must be
- called, usually right after initscr. Colors are always
- used in pairs (referred to as color-pairs). A color-pair
- consists of a foreground color (for characters) and a
- background color (for the blank field on which the charac-
- ters are displayed). A programmer initializes a color-
- pair with the routine init_pair. After it has been ini-
- tialized, COLOR_PAIR(n), a macro defined in <curses.h>,
- can be used as a new video attribute. If a terminal is
- capable of redefining colors, the programmer can use the
- routine init_color to change the definition of a color.
- The routines has_colors and can_change_color return TRUE
- or FALSE, depending on whether the terminal has color ca-
- pabilities and whether the programmer can change the col-
- ors. The routine color_content allows a programmer to ex-
- tract the amounts of red, green, and blue components in an
- initialized color. The routine pair_content allows a pro-
- grammer to find out how a given color-pair is currently
- defined.
-
- RoutineDescriptions
- The start_color routine requires no arguments. It must be
- called if the programmer wants to use colors, and before
- any other color manipulation routine is called. It is
- good practice to call this routine right after initscr.
- start_color initializes eight basic colors (black, red,
- green, yellow, blue, magenta, cyan, and white), and two
- global variables, COLORS and COLOR_PAIRS (respectively
- defining the maximum number of colors and color-pairs the
- terminal can support). It also restores the colors on the
- terminal to the values they had when the terminal was just
- turned on. The init_pair routine changes the definition
- of a color-pair. It takes three arguments: the number of
- the color-pair to be changed, the foreground color number,
- and the background color number. For portable applica-
- tions:
-
- - The value of the first argument must be between 1 and
- COLOR_PAIRS-1.
-
- - The value of the second and third arguments must be
- between 0 and COLORS. Color pair 0 is assumed to be
- white on black, but is actually whatever the terminal
- implements before color is initialized. It cannot be
- modified by the application.
-
- If the color-pair was previously initialized, the screen
- is refreshed and all occurrences of that color-pair are
- changed to the new definition. As an extension, ncurses
- allows you to set color pair 0 via the assume_default_col-
- ors routine, or to specify the use of default colors (col-
- or number -1) if you first invoke the use_default_colors
- routine. The init_color routine changes the definition of
- a color. It takes four arguments: the number of the color
- to be changed followed by three RGB values (for the
- amounts of red, green, and blue components). The value of
- the first argument must be between 0 and COLORS. (See the
- section Colors for the default color index.) Each of the
- last three arguments must be a value between 0 and 1000.
- When init_color is used, all occurrences of that color on
- the screen immediately change to the new definition. The
- has_colors routine requires no arguments. It returns TRUE
- if the terminal can manipulate colors; otherwise, it re-
- turns FALSE. This routine facilitates writing terminal-
- independent programs. For example, a programmer can use
- it to decide whether to use color or some other video at-
- tribute. The can_change_color routine requires no argu-
- ments. It returns TRUE if the terminal supports colors
- and can change their definitions; other, it returns FALSE.
- This routine facilitates writing terminal-independent pro-
- grams. The color_content routine gives programmers a way
- to find the intensity of the red, green, and blue (RGB)
- components in a color. It requires four arguments: the
- color number, and three addresses of shorts for storing
- the information about the amounts of red, green, and blue
- components in the given color. The value of the first ar-
- gument must be between 0 and COLORS. The values that are
- stored at the addresses pointed to by the last three argu-
- ments are between 0 (no component) and 1000 (maximum
- amount of component). The pair_content routine allows
- programmers to find out what colors a given color-pair
- consists of. It requires three arguments: the color-pair
- number, and two addresses of shorts for storing the fore-
- ground and the background color numbers. The value of the
- first argument must be between 1 and COLOR_PAIRS-1. The
- values that are stored at the addresses pointed to by the
- second and third arguments are between 0 and COLORS.
-
- Colors
- In <curses.h> the following macros are defined. These are
- the default colors. curses also assumes that COLOR_BLACK
- is the default background color for all terminals.
COLOR_BLACKCOLOR_REDCOLOR_GREEN
@@ -170,96 +155,303 @@
COLOR_CYANCOLOR_WHITE
+ Some terminals support more than the eight (8) "ANSI" colors. There
+ are no standard names for those additional colors.
-
-
RETURN VALUE
- The routines can_change_color() and has_colors() return
- TRUE or FALSE. All other routines return the integer ERR
- upon failure and an OK (SVr4 specifies only "an integer
- value other than ERR") upon successful completion.
-
- X/Open defines no error conditions. This implementation
- will return ERR on attempts to use color values outside
- the range 0 to COLORS-1 (except for the default colors ex-
- tension), or use color pairs outside the range 0 to COL-
- OR_PAIR-1. Color values used in init_color must be in the
- range 0 to 1000. An error is returned from all functions
- if the terminal has not been initialized. An error is re-
- turned from secondary functions such as init_pair if
- start_color was not called.
-
- init_color
- returns an error if the terminal does not sup-
- port this feature, e.g., if the initial-
- ize_color capability is absent from the termi-
- nal description.
-
- start_color
- returns an error If the color table cannot be
- allocated.
+
- In the ncurses implementation, there is a separate color
- activation flag, color palette, color pairs table, and as-
- sociated COLORS and COLOR_PAIRS counts for each screen;
- the start_color function only affects the current screen.
- The SVr4/XSI interface is not really designed with this in
- mind, and historical implementations may use a single
- shared color palette. Note that setting an implicit back-
- ground color via a color pair affects only character cells
- that a character write operation explicitly touches. To
- change the background color used when parts of a window
- are blanked by erasing or scrolling operations, see
- curs_bkgd(3x). Several caveats apply on 386 and 486 ma-
- chines with VGA-compatible graphics:
-
- - COLOR_YELLOW is actually brown. To get yellow, use
- COLOR_YELLOW combined with the A_BOLD attribute.
-
- - The A_BLINK attribute should in theory cause the
- background to go bright. This often fails to work,
- and even some cards for which it mostly works (such
- as the Paradise and compatibles) do the wrong thing
- when you try to set a bright "yellow" background (you
- get a blinking yellow foreground instead).
-
- - Color RGB values are not settable.
+
+ is initialized by start_color to the maximum number of color pairs the
+ terminal can support.
- The init_pair routine accepts negative values of fore-
- ground and background color to support the use_de-
- fault_colors extension, but only if that routine has been
- first invoked.
- The assumption that COLOR_BLACK is the default background
- color for all terminals can be modified using the as-
- sume_default_colors extension.
+
- This implementation checks the pointers, e.g., for the
- values returned by color_content and pair_content, and
- will treat those as optional parameters when null.
+
+ The start_color routine requires no arguments. It must be called if
+ the programmer wants to use colors, and before any other color manipu-
+ lation routine is called. It is good practice to call this routine
+ right after initscr. start_color does this:
+ o It initializes two global variables, COLORS and COLOR_PAIRS (re-
+ spectively defining the maximum number of colors and color-pairs
+ the terminal can support).
-
-
SEE ALSO
- curses(3x), curs_initscr(3x), curs_attr(3x), default_col-
- ors(3x)
+ o It initializes the special color pair 0 to the default foreground
+ and background colors. No other color pairs are initialized.
+
+ o It restores the colors on the terminal to the values they had when
+ the terminal was just turned on.
+
+ o If the terminal supports the initc (initialize_color) capability,
+ start_color initializes its internal table representing the red,
+ green and blue components of the color palette.
+
+ The components depend on whether the terminal uses CGA (aka "ANSI")
+ or HLS (i.e., the hls (hue_lightness_saturation) capability is
+ set). The table is initialized first for eight basic colors
+ (black, red, green, yellow, blue, magenta, cyan, and white), and
+ after that (if the terminal supports more than eight colors) the
+ components are initialized to 1000.
+
+ start_color does not attempt to set the terminal's color palette to
+ match its built-in table. An application may use init_color to al-
+ ter the internal table along with the terminal's color.
+
+ These limits apply to color values and color pairs. Values outside
+ these limits are not legal, and may result in a runtime error:
+
+ oCOLORS corresponds to the terminal database's max_colors capabili-
+ ty, (see terminfo(5)).
+
+ o color values are expected to be in the range 0 to COLORS-1, inclu-
+ sive (including 0 and COLORS-1).
+
+ o a special color value -1 is used in certain extended functions to
+ denote the defaultcolor (see use_default_colors).
+
+ oCOLOR_PAIRS corresponds to the terminal database's max_pairs capa-
+ bility, (see terminfo(5)).
+
+ o legal color pair values are in the range 1 to COLOR_PAIRS-1, inclu-
+ sive.
+
+ o color pair 0 is special; it denotes "no color".
+
+ Color pair 0 is assumed to be white on black, but is actually what-
+ ever the terminal implements before color is initialized. It can-
+ not be modified by the application.
+
+
+
+ The has_colors routine requires no arguments. It returns TRUE if the
+ terminal can manipulate colors; otherwise, it returns FALSE. This rou-
+ tine facilitates writing terminal-independent programs. For example, a
+ programmer can use it to decide whether to use color or some other
+ video attribute.
+
+
+
+ The can_change_color routine requires no arguments. It returns TRUE if
+ the terminal supports colors and can change their definitions; other,
+ it returns FALSE. This routine facilitates writing terminal-indepen-
+ dent programs.
+
+
+
+ The init_pair routine changes the definition of a color-pair. It takes
+ three arguments: the number of the color-pair to be changed, the fore-
+ ground color number, and the background color number. For portable ap-
+ plications:
+
+ o The first argument must be a legal color pair value. If default
+ colors are used (see use_default_colors) the upper limit is adjust-
+ ed to allow for extra pairs which use a default color in foreground
+ and/or background.
+
+ o The second and third arguments must be legal color values.
+
+ If the color-pair was previously initialized, the screen is refreshed
+ and all occurrences of that color-pair are changed to the new defini-
+ tion.
+
+ As an extension, ncurses allows you to set color pair 0 via the as-
+ sume_default_colors(3x) routine, or to specify the use of default col-
+ ors (color number -1) if you first invoke the use_default_colors(3x)
+ routine.
+
+ The extension reset_color_pairs tells ncurses to discard all of the
+ color-pair information which was set with init_pair. It also touches
+ the current- and standard-screens, allowing an application to switch
+ color palettes rapidly.
+
+
+
+ The init_color routine changes the definition of a color. It takes
+ four arguments: the number of the color to be changed followed by three
+ RGB values (for the amounts of red, green, and blue components).
+
+ o The first argument must be a legal color value; default colors are
+ not allowed here. (See the section Colors for the default color
+ index.)
+
+ o Each of the last three arguments must be a value in the range 0
+ through 1000.
+
+ When init_color is used, all occurrences of that color on the screen
+ immediately change to the new definition.
+
+
+
+ The color_content routine gives programmers a way to find the intensity
+ of the red, green, and blue (RGB) components in a color. It requires
+ four arguments: the color number, and three addresses of shorts for
+ storing the information about the amounts of red, green, and blue com-
+ ponents in the given color.
+
+ o The first argument must be a legal color value, i.e., 0 through
+ COLORS-1, inclusive.
+
+ o The values that are stored at the addresses pointed to by the last
+ three arguments are in the range 0 (no component) through 1000
+ (maximum amount of component), inclusive.
+
+
+
+ The pair_content routine allows programmers to find out what colors a
+ given color-pair consists of. It requires three arguments: the color-
+ pair number, and two addresses of shorts for storing the foreground and
+ the background color numbers.
+
+ o The first argument must be a legal color value, i.e., in the range
+ 1 through COLOR_PAIRS-1, inclusive.
+
+ o The values that are stored at the addresses pointed to by the sec-
+ ond and third arguments are in the range 0 through COLORS, inclu-
+ sive.
+
+
+
+ Its inverse COLOR_PAIR(n) converts a color pair number to an attribute.
+ Attributes can hold color pairs in the range 0 to 255. If you need a
+ color pair larger than that, you must use functions such as attr_set
+ (which pass the color pair as a separate parameter) rather than the
+ legacy functions such as attrset.
+
+
+
+ The routines can_change_color and has_colors return TRUE or FALSE.
+
+ All other routines return the integer ERR upon failure and an OK (SVr4
+ specifies only "an integer value other than ERR") upon successful com-
+ pletion.
+
+ X/Open defines no error conditions. This implementation will return
+ ERR on attempts to use color values outside the range 0 to COLORS-1
+ (except for the default colors extension), or use color pairs outside
+ the range 0 to COLOR_PAIRS-1. Color values used in init_color must be
+ in the range 0 to 1000. An error is returned from all functions if the
+ terminal has not been initialized. An error is returned from secondary
+ functions such as init_pair if start_color was not called.
+
+ init_color
+ returns an error if the terminal does not support this feature,
+ e.g., if the initialize_color capability is absent from the
+ terminal description.
+
+ start_color
+ returns an error if the color table cannot be allocated.
+
+
+
+ In the ncurses implementation, there is a separate color activation
+ flag, color palette, color pairs table, and associated COLORS and COL-
+ OR_PAIRS counts for each screen; the start_color function only affects
+ the current screen. The SVr4/XSI interface is not really designed with
+ this in mind, and historical implementations may use a single shared
+ color palette.
+
+ Setting an implicit background color via a color pair affects only
+ character cells that a character write operation explicitly touches.
+ To change the background color used when parts of a window are blanked
+ by erasing or scrolling operations, see curs_bkgd(3x).
+
+ Several caveats apply on older x86 machines (e.g., i386, i486) with
+ VGA-compatible graphics:
+
+ o COLOR_YELLOW is actually brown. To get yellow, use COLOR_YELLOW
+ combined with the A_BOLD attribute.
+
+ o The A_BLINK attribute should in theory cause the background to go
+ bright. This often fails to work, and even some cards for which it
+ mostly works (such as the Paradise and compatibles) do the wrong
+ thing when you try to set a bright "yellow" background (you get a
+ blinking yellow foreground instead).
+
+ o Color RGB values are not settable.
+
+
+
+ This implementation satisfies XSI Curses's minimum maximums for COLORS
+ and COLOR_PAIRS.
+
+ The init_pair routine accepts negative values of foreground and back-
+ ground color to support the use_default_colors(3x) extension, but only
+ if that routine has been first invoked.
+
+ The assumption that COLOR_BLACK is the default background color for all
+ terminals can be modified using the assume_default_colors(3x) exten-
+ sion.
+
+ This implementation checks the pointers, e.g., for the values returned
+ by color_content and pair_content, and will treat those as optional pa-
+ rameters when null.
+
+ X/Open Curses does not specify a limit for the number of colors and
+ color pairs which a terminal can support. However, in its use of short
+ for the parameters, it carries over SVr4's implementation detail for
+ the compiled terminfo database, which uses signed 16-bit numbers. This
+ implementation provides extended versions of those functions which use
+ short parameters, allowing applications to use larger color- and pair-
+ numbers.
+
+ The reset_color_pairs function is an extension of ncurses.
+
+
+