+ 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 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
+ tialized, COLOR_PAIR(n) can be used to convert the pair to
+ a video attribute.
+
+ If a terminal is capable of redefining colors, the pro-
+ grammer can use the routine init_color to change the defi-
+ nition of a color. The routines has_colors and
+ can_change_color return TRUE or FALSE, depending on
+ whether the terminal has color capabilities and whether
+ the programmer can change the colors. The routine col-
+ or_content allows a programmer 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 foreground 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 containing video attributes including a color
+ pair value. Some functions such as wattr_set use a sepa-
+ rate parameter which is the color pair number.
+
+ 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 us-
+ es 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 at-
+ tribute.
+
+ 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 attribute next, and fi-
+ nally the background character.
+
+ Some curses functions such as wprintw call waddch. Those
+ do not combine its parameter with a color pair. Conse-
+ quently those calls use only the window attribute or the
+ background character.
+
+
+
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-
+ start_color does this:
+
+ o It initializes two global variables, COLORS and COL-
+ OR_PAIRS (respectively defining the maximum number of
+ colors and color-pairs the terminal can support).
+
+ 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_sat-
+ uration) capability is set). The table is initialized
+ first for eight basic colors (black, red, green, yel-
+ low, 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 appli-
+ cation may use init_color to alter the internal table
+ along with the terminal's color.
+
+ These limits apply to color values and color pairs. Val-
+ ues outside these limits are not legal, and may result in
+ a runtime error:
+
+ oCOLORS corresponds to the terminal database's max_col-
+ ors capability, which is typically a signed 16-bit in-
+ teger (see terminfo(5)).
+
+ o color values are expected to be in the range 0 to COL-
+ ORS-1, inclusive (including 0 and COLORS-1).
+
+ o a special color value -1 is used in certain extended
+ functions to denote the defaultcolor (see use_de-
+ fault_colors).
+
+ oCOLOR_PAIRS corresponds to the terminal database's
+ max_pairs capability, which is typically a signed
+ 16-bit integer (see terminfo(5)).
+
+ o legal color pair values are in the range 1 to COL-
+ OR_PAIRS-1, inclusive.
+
+ o color pair 0 is special; it denotes "no color".
+
+ 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 applica-
+ tion.
+
+ 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 applications:
+
+ o The first argument must be a legal color pair value.
+ If default colors are used (see use_default_colors)
+ the upper limit is adjusted to allow for extra pairs
+ which use a default color in foreground and/or back-
+ ground.
+
+ 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 definition.
+
+ As an extension, ncurses allows you to set color pair 0
+ via the assume_default_colors routine, or to specify the
+ use of default colors (color number -1) if you first in-
+ voke 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 first argument must
+ be a legal color value; default colors are not allowed
+ here. (See the section Colors for the default color in-
+ dex.) 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 has_colors routine requires no arguments. It returns
+ TRUE if the terminal can manipulate colors; otherwise, it
+ returns 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
+ tribute.
+
+ 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-independent programs.
+
+ 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 first argument must be a legal color
+ value, i.e., 0 through COLORS-1, inclusive. 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. The first argument must be a legal color
+ value, i.e., in the range 1 through COLOR_PAIRS-1, inclu-
+ sive. The values that are stored at the addresses pointed
+ to by the second and third arguments are in the range 0
+ through COLORS, inclusive.
+
+ PAIR_NUMBER(attrs) extracts the color value from its attrs
+ parameter and returns it as a color pair number. Its in-
+ verse COLOR_PAIR(n) converts a color pair number to an at-
+ tribute. 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 func-
+ tions such as attrset.
+
+
+
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.
+ the standard colors (ISO-6429). curses also assumes that
+ COLOR_BLACK is the default background color for all termi-
+ nals.
+
COLOR_BLACKCOLOR_REDCOLOR_GREEN
@@ -171,65 +301,66 @@
COLOR_WHITE
-
-
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.
+
+ 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
+ the range 0 to COLORS-1 (except for the default colors ex-
+ tension), or use color pairs outside the range 0 to COL-
+ OR_PAIRS-1. Color values used in init_color must be in
+ the range 0 to 1000. An error is returned from all func-
+ tions 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 sup-
- port this feature, e.g., if the initial-
- ize_color capability is absent from the termi-
- nal description.
+ init_color
+ returns an error if the terminal does not support
+ this feature, e.g., if the initialize_color capa-
+ bility is absent from the terminal description.
- start_color
- returns an error If the color table cannot be
- allocated.
+ start_color
+ returns an error if the color table cannot be al-
+ located.
-
-
NOTES
- In the ncurses implementation, there is a separate color
+
+ 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.
+ 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:
+ mind, and historical implementations may use a single
+ shared color palette.
- - COLOR_YELLOW is actually brown. To get yellow, use
- COLOR_YELLOW combined with the A_BOLD attribute.
+ Note that 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).
- - 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).
+ Several caveats apply on 386 and 486 machines with VGA-
+ compatible graphics:
- - Color RGB values are not settable.
+ 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 back-
+ ground 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).
-
This implementation satisfies XSI Curses's minimum maxi-
mums for COLORS and COLOR_PAIRS.
@@ -247,19 +378,31 @@
will treat those as optional parameters when null.
-