- Overview
- curses support color attributes on terminals with that
- capability. To use these routines start_color must be
- called, usually right after initscr. Colors are always
+ 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>,
+ 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 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
+ 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
- color_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.
-
- RoutineDescriptions
- The start_color routine requires no arguments. It must be
+ 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.
+
+ 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,
+ 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
+ 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-
+ 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:
- - The value of the first argument must be between 1 and
- COLOR_PAIRS-1.
+ - 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 (the 0 color pair is wired to
- white on black and cannot be changed).
+ 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 is
+ 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
- invoke the use_default_colors routine.
+ 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.
+ 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
+ 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
+ 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-
+ 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
- attribute.
+ it to decide whether to use color or some other video at-
+ 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
+ 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 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
+ 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
- between 0 (no component) and 1000 (maximum amount of com-
- ponent).
+ 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 pair_content routine allows programmers to find out
+ 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
+ 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
+ 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.
+ ments 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
+ 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_BLACK
- COLOR_RED
- COLOR_GREEN
- COLOR_YELLOW
- COLOR_BLUE
- COLOR_MAGENTA
- COLOR_CYAN
- COLOR_WHITE
+ COLOR_BLACK
+ COLOR_RED
+ COLOR_GREEN
+ COLOR_YELLOW
+ COLOR_BLUE
+ COLOR_MAGENTA
+ COLOR_CYAN
+ 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
+ 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.
NOTES
- In the ncurses implementation, there is a separate color
- activation flag, color palette, color pairs table, and
- associated COLORS and COLOR_PAIRS counts for each screen;
- the start_color function only affects the current screen.
+ 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.
@@ -163,13 +227,13 @@
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).
+ or scrolling operations, see curs_bkgd(3x).
Several caveats apply on 386 and 486 machines with VGA-
compatible graphics:
- COLOR_YELLOW is actually brown. To get yellow, use
- COLOR_YELLOW combined with the A_BOLD attribute.
+ 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,
@@ -184,54 +248,30 @@
PORTABILITY
This implementation satisfies XSI Curses's minimum maxi-
- mums for COLORS and COLOR_PAIRS.
+ mums for COLORS and COLOR_PAIRS.
- The init_pair routine accepts negative values of fore-
- ground and background color to support the
- use_default_colors extension, but only if that routine has
- been first invoked.
+ 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
- assume_default_colors extension,
+ 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.