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
@@ -91,54 +93,106 @@
The routine pair_content allows a programmer 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.
+ 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 value of the first argument must be between 1 and
- COLOR_PAIRS-1, except that 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 background.
+ 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 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.
+ 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
+ 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-
+ 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 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 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
@@ -157,24 +211,27 @@
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 argument must be
- between 0 and COLORS. The values that are stored at the
- addresses pointed to by the last three arguments are be-
- tween 0 (no component) and 1000 (maximum amount of compo-
- nent).
+ 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 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 argu-
- ments are between 0 and COLORS.
+ 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.
- Colors
+
+
In <curses.h> the following macros are defined. These are
- the default colors. curses also assumes that COLOR_BLACK
+ the default colors. curses also assumes that COLOR_BLACK
is the default background color for all terminals.
COLOR_BLACK
@@ -188,87 +245,87 @@
-
RETURN VALUE
- The routines can_change_color() and has_colors() return
+
+ 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
+ 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_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
+ 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_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 support
- this feature, e.g., if the initialize_color capa-
+ 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 al-
+ 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
+ mind, and historical implementations may use a single
shared color palette.
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
+ 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 machines with VGA-
+ Several caveats apply on 386 and 486 machines with VGA-
compatible graphics:
- o COLOR_YELLOW is actually brown. To get yellow, use
+ 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
+ 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
+ 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.
-
PORTABILITY
- This implementation satisfies XSI Curses's minimum maxi-
+
+ This implementation satisfies XSI Curses's minimum maxi-
mums for COLORS and COLOR_PAIRS.
- 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
+ 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-
+ 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
+ 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.