+
+</PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
+
+</PRE><H3><a name="h3-Overview">Overview</a></H3><PRE>
+ <B>curses</B> supports color attributes on terminals with that capability. To
+ use these routines <B>start_color</B> must be called, usually right after
+ <B>initscr</B>. 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
+ <B>init_pair</B>. After it has been initialized, <B>COLOR_PAIR</B>(<I>n</I>) 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 <B>init_color</B> to change the definition of a color. The rou-
+ tines <B>has_colors</B> and <B>can_change_color</B> return <B>TRUE</B> or <B>FALSE</B>, depending
+ on whether the terminal has color capabilities and whether the program-
+ mer can change the colors. The routine <B>color_content</B> allows a program-
+ mer to extract the amounts of red, green, and blue components in an
+ initialized color. The routine <B>pair_content</B> allows a programmer to
+ find out how a given color-pair is currently defined.
+
+
+</PRE><H3><a name="h3-Color-Rendering">Color Rendering</a></H3><PRE>
+ The <B>curses</B> library combines these inputs to produce the actual fore-
+ ground and background colors shown on the screen:
+
+ <B>o</B> per-character video attributes (e.g., via <B>waddch</B>),
+
+ <B>o</B> the window attribute (e.g., by <B>wattrset</B>), and
+
+ <B>o</B> the background character (e.g., <B>wbkgdset</B>).
+
+ Per-character and window attributes are usually set by a parameter con-
+ taining video attributes including a color pair value. Some functions
+ such as <B>wattr_set</B> 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 <B>waddch</B>.
+
+ The <B>curses</B> library does the actual work of combining these color pairs
+ in an internal function called from <B>waddch</B>:
+
+ <B>o</B> If the parameter passed to <B>waddch</B> is <I>blank</I>, and it uses the special
+ color pair 0,
+
+ <B>o</B> <B>curses</B> next checks the window attribute.
+
+ <B>o</B> If the window attribute does not use color pair 0, <B>curses</B> uses
+ the color pair from the window attribute.
+
+ <B>o</B> Otherwise, <B>curses</B> uses the background character.
+
+ <B>o</B> If the parameter passed to <B>waddch</B> is <I>not</I> <I>blank</I>, or it does not use
+ the special color pair 0, <B>curses</B> prefers the color pair from the
+ parameter, if it is nonzero. Otherwise, it tries the window attri-
+ bute next, and finally the background character.
+
+ Some <B>curses</B> functions such as <B>wprintw</B> call <B>waddch</B>. Those do not com-
+ bine its parameter with a color pair. Consequently those calls use on-
+ ly the window attribute or the background character.
+
+
+</PRE><H2><a name="h2-CONSTANTS">CONSTANTS</a></H2><PRE>
+ In <B><curses.h></B> the following macros are defined. These are the standard
+ colors (ISO-6429). <B>curses</B> also assumes that <B>COLOR_BLACK</B> is the default
+ background color for all terminals.
+
+ <B>COLOR_BLACK</B>
+ <B>COLOR_RED</B>
+ <B>COLOR_GREEN</B>
+ <B>COLOR_YELLOW</B>
+ <B>COLOR_BLUE</B>
+ <B>COLOR_MAGENTA</B>
+ <B>COLOR_CYAN</B>
+ <B>COLOR_WHITE</B>
+
+ Some terminals support more than the eight (8) "ANSI" colors. There
+ are no standard names for those additional colors.
+
+
+</PRE><H2><a name="h2-VARIABLES">VARIABLES</a></H2><PRE>
+
+</PRE><H3><a name="h3-COLORS">COLORS</a></H3><PRE>
+ is initialized by <B>start_color</B> to the maximum number of colors the ter-
+ minal can support.
+
+
+</PRE><H3><a name="h3-COLOR_PAIRS">COLOR_PAIRS</a></H3><PRE>
+ is initialized by <B>start_color</B> to the maximum number of color pairs the
+ terminal can support.
+
+
+</PRE><H2><a name="h2-FUNCTIONS">FUNCTIONS</a></H2><PRE>
+
+</PRE><H3><a name="h3-start_color">start_color</a></H3><PRE>
+ The <B>start_color</B> 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 <B>initscr</B>. <B>start_color</B> does this:
+
+ <B>o</B> It initializes two global variables, <B>COLORS</B> and <B>COLOR_PAIRS</B> (re-
+ spectively defining the maximum number of colors and color-pairs
+ the terminal can support).
+
+ <B>o</B> It initializes the special color pair <B>0</B> to the default foreground
+ and background colors. No other color pairs are initialized.
+
+ <B>o</B> It restores the colors on the terminal to the values they had when
+ the terminal was just turned on.
+
+ <B>o</B> If the terminal supports the <B>initc</B> (<B>initialize_color</B>) capability,
+ <B>start_color</B> 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 <B>hls</B> (<B>hue_lightness_saturation</B>) 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 <B>680</B> or <B>0</B> depending on whether the corresponding red,
+ green, or blue component is used or not. That permits using <B>1000</B>
+ 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 <B>1000</B>.
+ SVr4 uses a similar scheme, but uses <B>1000</B> for the components of the
+ initial eight colors.
+
+ <B>start_color</B> does not attempt to set the terminal's color palette to
+ match its built-in table. An application may use <B>init_color</B> 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:
+
+ <B>o</B> <B>COLORS</B> corresponds to the terminal database's <B>max_colors</B> capabili-
+ ty, (see <B><A HREF="terminfo.5.html">terminfo(5)</A></B>).
+
+ <B>o</B> color values are expected to be in the range <B>0</B> to <B>COLORS-1</B>, inclu-
+ sive (including <B>0</B> and <B>COLORS-1</B>).
+
+ <B>o</B> a special color value <B>-1</B> is used in certain extended functions to
+ denote the <I>default</I> <I>color</I> (see <B><A HREF="default_colors.3X.html">use_default_colors(3X)</A></B>).
+
+ <B>o</B> <B>COLOR_PAIRS</B> corresponds to the terminal database's <B>max_pairs</B> capa-
+ bility, (see <B><A HREF="terminfo.5.html">terminfo(5)</A></B>).
+
+ <B>o</B> legal color pair values are in the range <B>1</B> to <B>COLOR_PAIRS-1</B>, inclu-
+ sive.
+
+ <B>o</B> color pair <B>0</B> is special; it denotes "no color".
+
+ Color pair <B>0</B> 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.
+
+
+</PRE><H3><a name="h3-has_colors">has_colors</a></H3><PRE>
+ The <B>has_colors</B> routine requires no arguments. It returns <B>TRUE</B> if the
+ terminal can manipulate colors; otherwise, it returns <B>FALSE</B>. 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.
+
+
+</PRE><H3><a name="h3-can_change_color">can_change_color</a></H3><PRE>
+ The <B>can_change_color</B> routine requires no arguments. It returns <B>TRUE</B> if
+ the terminal supports colors and can change their definitions; other,
+ it returns <B>FALSE</B>. This routine facilitates writing terminal-indepen-
+ dent programs.
+
+
+</PRE><H3><a name="h3-init_pair">init_pair</a></H3><PRE>
+ The <B>init_pair</B> 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:
+
+ <B>o</B> The first argument must be a legal color pair value. If default
+ colors are used (see <B><A HREF="default_colors.3X.html">use_default_colors(3X)</A></B>) the upper limit is ad-
+ justed to allow for extra pairs which use a default color in fore-
+ ground and/or background.
+
+ <B>o</B> 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 <B>0</B> via the <B>as-</B>
+ <B><A HREF="assume_default_colors.3X.html">sume_default_colors(3X)</A></B> routine, or to specify the use of default col-
+ ors (color number <B>-1</B>) if you first invoke the <B><A HREF="default_colors.3X.html">use_default_colors(3X)</A></B>
+ routine.
+
+
+</PRE><H3><a name="h3-init_extended_pair">init_extended_pair</a></H3><PRE>
+ Because <B>init_pair</B> uses signed <B>short</B>s for its parameters, that limits
+ color-pairs and color-values to 32767 on modern hardware. The exten-
+ sion <B>init_extended_pair</B> uses <B>int</B>s for the color-pair and color-value,
+ allowing a larger number of colors to be supported.
+
+
+</PRE><H3><a name="h3-init_color">init_color</a></H3><PRE>
+ The <B>init_color</B> 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).
+
+ <B>o</B> The first argument must be a legal color value; default colors are
+ not allowed here. (See the section <B>Colors</B> for the default color
+ index.)
+
+ <B>o</B> Each of the last three arguments must be a value in the range <B>0</B>
+ through <B>1000</B>.
+
+ When <B>init_color</B> is used, all occurrences of that color on the screen
+ immediately change to the new definition.
+
+
+</PRE><H3><a name="h3-init_extended_color">init_extended_color</a></H3><PRE>
+ Because <B>init_color</B> uses signed <B>short</B>s for its parameters, that limits
+ color-values and their red, green, and blue components to 32767 on mod-
+ ern hardware. The extension <B>init_extended_color</B> uses <B>int</B>s for the col-
+ or value and for setting the red, green, and blue components, allowing
+ a larger number of colors to be supported.
+
+
+</PRE><H3><a name="h3-color_content">color_content</a></H3><PRE>
+ The <B>color_content</B> 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 <B>short</B>s for
+ storing the information about the amounts of red, green, and blue com-
+ ponents in the given color.
+
+ <B>o</B> The first argument must be a legal color value, i.e., <B>0</B> through
+ <B>COLORS-1</B>, inclusive.
+
+ <B>o</B> The values that are stored at the addresses pointed to by the last
+ three arguments are in the range <B>0</B> (no component) through <B>1000</B>
+ (maximum amount of component), inclusive.
+
+
+</PRE><H3><a name="h3-extended_color_content">extended_color_content</a></H3><PRE>
+ Because <B>color_content</B> uses signed <B>short</B>s for its parameters, that lim-
+ its color-values and their red, green, and blue components to 32767 on
+ modern hardware. The extension <B>extended_color_content</B> uses <B>int</B>s for
+ the color value and for returning the red, green, and blue components,
+ allowing a larger number of colors to be supported.
+
+
+</PRE><H3><a name="h3-pair_content">pair_content</a></H3><PRE>
+ The <B>pair_content</B> 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 <B>short</B>s for storing the foreground and
+ the background color numbers.
+
+ <B>o</B> The first argument must be a legal color value, i.e., in the range
+ <B>1</B> through <B>COLOR_PAIRS-1</B>, inclusive.
+
+ <B>o</B> The values that are stored at the addresses pointed to by the sec-
+ ond and third arguments are in the range <B>0</B> through <B>COLORS</B>, inclu-
+ sive.
+
+
+</PRE><H3><a name="h3-extended_pair_content">extended_pair_content</a></H3><PRE>
+ Because <B>pair_content</B> uses signed <B>short</B>s for its parameters, that limits
+ color-pair and color-values to 32767 on modern hardware. The extension
+ <B>extended_pair_content</B> uses <B>int</B>s for the color pair and for returning
+ the foreground and background colors, allowing a larger number of col-
+ ors to be supported.
+
+
+</PRE><H3><a name="h3-reset_color_pairs">reset_color_pairs</a></H3><PRE>
+ The extension <B>reset_color_pairs</B> tells ncurses to discard all of the
+ color-pair information which was set with <B>init_pair</B>. It also touches
+ the current- and standard-screens, allowing an application to switch
+ color palettes rapidly.
+
+
+</PRE><H3><a name="h3-PAIR_NUMBER">PAIR_NUMBER</a></H3><PRE>
+ <B>PAIR_NUMBER(</B><I>attrs</I>) extracts the color value from its <I>attrs</I> parameter
+ and returns it as a color pair number.
+
+
+</PRE><H3><a name="h3-COLOR_PAIR">COLOR_PAIR</a></H3><PRE>
+ Its inverse <B>COLOR_PAIR(</B><I>n</I><B>)</B> 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 <B>attr_set</B>
+ (which pass the color pair as a separate parameter) rather than the
+ legacy functions such as <B>attrset</B>.
+
+
+</PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
+ The routines <B>can_change_color</B> and <B>has_colors</B> return <B>TRUE</B> or <B>FALSE</B>.
+
+ All other routines return the integer <B>ERR</B> upon failure and an <B>OK</B> (SVr4
+ specifies only "an integer value other than <B>ERR</B>") upon successful com-
+ pletion.
+
+ X/Open defines no error conditions. SVr4 does document some error con-
+ ditions which apply in general:
+
+ <B>o</B> This implementation will return <B>ERR</B> on attempts to use color values
+ outside the range <B>0</B> to <B>COLORS</B>-1 (except for the default colors ex-
+ tension), or use color pairs outside the range <B>0</B> to <B>COLOR_PAIRS-1</B>.
+
+ Color values used in <B>init_color</B> must be in the range <B>0</B> to <B>1000</B>.
+
+ An error is returned from all functions if the terminal has not
+ been initialized.
+
+ An error is returned from secondary functions such as <B>init_pair</B> if
+ <B>start_color</B> was not called.
+
+ <B>o</B> SVr4 does much the same, except that it returns <B>ERR</B> from <B>pair_con-</B>
+ <B>tent</B> if the pair was not initialized using <B>init_pairs</B> and it re-
+ turns <B>ERR</B> from <B>color_content</B> if the terminal does not support
+ changing colors.
+
+ This implementation does not return <B>ERR</B> for either case.
+
+ Specific functions make additional checks:
+
+ <B>init_color</B>
+ returns an error if the terminal does not support this feature,
+ e.g., if the <B>initialize_color</B> capability is absent from the
+ terminal description.
+
+ <B>start_color</B>
+ returns an error if the color table cannot be allocated.
+
+
+</PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
+ In the <B>ncurses</B> implementation, there is a separate color activation
+ flag, color palette, color pairs table, and associated <B>COLORS</B> and <B>COL-</B>
+ <B>OR_PAIRS</B> counts for each screen; the <B>start_color</B> 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 <B><A HREF="curs_bkgd.3X.html">curs_bkgd(3X)</A></B>.
+
+ Several caveats apply on older x86 machines (e.g., i386, i486) with
+ VGA-compatible graphics:
+
+ <B>o</B> COLOR_YELLOW is actually brown. To get yellow, use COLOR_YELLOW
+ combined with the <B>A_BOLD</B> attribute.
+
+ <B>o</B> 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