curses supports color attributes on terminals with that capability. To
- use these routines start_color must be called, usually right after
+ 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
+ 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
+ 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
+ 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-
+ 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),
@@ -111,14 +112,14 @@
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
+ 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
+ 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
+ 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
@@ -126,17 +127,17 @@
ocurses next checks the window attribute.
- o If the window attribute does not use color pair 0, curses uses
+ 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-
+ 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-
+ 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.
@@ -155,68 +156,74 @@
COLOR_CYANCOLOR_WHITE
- Some terminals support more than the eight (8) "ANSI" colors. There
+ Some terminals support more than the eight (8) "ANSI" colors. There
are no standard names for those additional colors.
- is initialized by start_color to the maximum number of colors the ter-
+ is initialized by start_color to the maximum number of colors the ter-
minal can support.
- is initialized by start_color to the maximum number of color pairs the
+ is initialized by start_color to the maximum number of color pairs the
terminal can support.
- 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
+ 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
+ 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).
- o It initializes the special color pair 0 to the default foreground
+ 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
+ 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.
+ 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.
+ 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), using
+ weights that depend upon the CGA/HLS choice. For "ANSI" colors the
+ weights are 680 or 0 depending on whether the corresponding red,
+ green, or blue component is used or not. That permits using 1000
+ to represent bold/bright colors. After the initial eight colors
+ (if the terminal supports more than eight colors) the components
+ are initialized using the same pattern, but with weights of 1000.
+ SVr4 uses a similar scheme, but uses 1000 for the components of the
+ initial eight colors.
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 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-
+ 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-
+ 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).
+ o a special color value -1 is used in certain extended functions to
+ denote the defaultcolor (see use_default_colors(3x)).
- oCOLOR_PAIRS corresponds to the terminal database's max_pairs capa-
+ 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-
@@ -225,98 +232,131 @@
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-
+ 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
+ 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
+ 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-
+ 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-
+ 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 first argument must be a legal color pair value. If default
+ colors are used (see use_default_colors(3x)) the upper limit is ad-
+ justed to allow for extra pairs which use a default color in fore-
+ ground 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-
+ 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)
+ 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.
+
+
+ Because init_pair uses signed shorts for its parameters, that limits
+ color-pairs and color-values to 32767 on modern hardware. The exten-
+ sion init_extended_pair uses ints for the color-pair and color-value,
+ allowing a larger number of colors to be supported.
- The init_color routine changes the definition of a color. It takes
+ 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
+ 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
+ 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
+ When init_color is used, all occurrences of that color on the screen
immediately change to the new definition.
+
+ Because init_color uses signed shorts for its parameters, that limits
+ color-values and their red, green, and blue components to 32767 on mod-
+ ern hardware. The extension init_extended_color uses ints for the col-
+ or value and for setting the red, green, and blue components, allowing
+ a larger number of colors to be supported.
+
+
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-
+ 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
+ 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
+ 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.
+
+ Because color_content uses signed shorts for its parameters, that lim-
+ its color-values and their red, green, and blue components to 32767 on
+ modern hardware. The extension extended_color_content uses ints for
+ the color value and for returning the red, green, and blue components,
+ allowing a larger number of colors to be supported.
+
+
- The pair_content routine allows programmers to find out what colors a
- given color-pair consists of. It requires three arguments: the color-
+ 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
+ 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-
+ 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.
+
+ Because pair_content uses signed shorts for its parameters, that limits
+ color-pair and color-values to 32767 on modern hardware. The extension
+ extended_pair_content uses ints for the color pair and for returning
+ the foreground and background colors, allowing a larger number of col-
+ ors to be supported.
+
+
+
+ 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.
+
+
PAIR_NUMBER(attrs) extracts the color value from its attrs parameter
and returns it as a color pair number.
@@ -337,13 +377,29 @@
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.
+ X/Open defines no error conditions. SVr4 does document some error con-
+ ditions which apply in general:
+
+ o 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 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.
+
+ o SVr4 does much the same, except that it returns ERR from pair_con-
+ tent if the pair was not initialized using init_pairs and it re-
+ turns ERR from color_content if the terminal does not support
+ changing colors.
+
+ This implementation does not return ERR for either case.
+
+ Specific functions make additional checks:
init_color
returns an error if the terminal does not support this feature,
@@ -440,9 +496,14 @@