* sale, use or other dealings in this Software without prior written *
* authorization. *
****************************************************************************
- * @Id: curs_color.3x,v 1.37 2015/04/04 19:42:47 tom Exp @
+ * @Id: curs_color.3x,v 1.38 2015/05/23 21:36:35 tom Exp @
-->
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
</PRE>
<H3><a name="h3-Overview">Overview</a></H3><PRE>
- <STRONG>curses</STRONG> support color attributes on terminals with that ca-
- pability. To use these routines <STRONG>start_color</STRONG> must be
+ <STRONG>curses</STRONG> supports color attributes on terminals with that
+ capability. To use these routines <STRONG>start_color</STRONG> must be
called, usually right after <STRONG>initscr</STRONG>. Colors are always
used in pairs (referred to as color-pairs). A color-pair
consists of a foreground color (for characters) and a
how a given color-pair is currently defined.
+</PRE>
+<H3><a name="h3-Color-Rendering">Color Rendering</a></H3><PRE>
+ The <STRONG>curses</STRONG> library combines these inputs to produce the
+ actual foreground and background colors shown on the
+ screen:
+
+ <STRONG>o</STRONG> per-character video attributes (e.g., via <STRONG>waddch</STRONG>),
+
+ <STRONG>o</STRONG> the window attribute (e.g., by <STRONG>wattrset</STRONG>), and
+
+ <STRONG>o</STRONG> the background character (e.g., <STRONG>wbkgdset</STRONG>).
+
+ Per-character and window attributes are usually set by a
+ parameter containing video attributes including a <STRONG>COL-</STRONG>
+ <STRONG>OR_PAIR</STRONG> value. Some functions such as <STRONG>wattr_set</STRONG> use a
+ separate 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 <STRONG>waddch</STRONG>.
+
+ The <STRONG>curses</STRONG> library does the actual work of combining these
+ color pairs in an internal function called from <STRONG>waddch</STRONG>:
+
+ <STRONG>o</STRONG> If the parameter passed to <STRONG>waddch</STRONG> is <EM>blank</EM>, and it us-
+ es the special color pair 0,
+
+ <STRONG>o</STRONG> <STRONG>curses</STRONG> next checks the window attribute.
+
+ <STRONG>o</STRONG> If the window attribute does not use color pair 0,
+ <STRONG>curses</STRONG> uses the color pair from the window at-
+ tribute.
+
+ <STRONG>o</STRONG> Otherwise, <STRONG>curses</STRONG> uses the background character.
+
+ <STRONG>o</STRONG> If the parameter passed to <STRONG>waddch</STRONG> is <EM>not</EM> <EM>blank</EM>, or it
+ does not use the special color pair 0, <STRONG>curses</STRONG> 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 <STRONG>curses</STRONG> functions such as <STRONG>wprintw</STRONG> call <STRONG>waddch</STRONG>. Those
+ do not combine its parameter with a color pair. Conse-
+ quently those calls use only the window attribute or the
+ background character.
+
+
</PRE>
<H3><a name="h3-Routine-Descriptions">Routine Descriptions</a></H3><PRE>
The <STRONG>start_color</STRONG> 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 <STRONG>initscr</STRONG>.
+ 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 <STRONG>initscr</STRONG>.
<STRONG>start_color</STRONG> does this:
- <STRONG>o</STRONG> It initializes two global variables, <STRONG>COLORS</STRONG> and <STRONG>COL-</STRONG>
- <STRONG>OR_PAIRS</STRONG> (respectively defining the maximum number of
+ <STRONG>o</STRONG> It initializes two global variables, <STRONG>COLORS</STRONG> and <STRONG>COL-</STRONG>
+ <STRONG>OR_PAIRS</STRONG> (respectively defining the maximum number of
colors and color-pairs the terminal can support).
<STRONG>o</STRONG> It initializes the special color pair <STRONG>0</STRONG> to the default
- foreground and background colors. No other color
+ foreground and background colors. No other color
pairs are initialized.
- <STRONG>o</STRONG> It restores the colors on the terminal to the values
+ <STRONG>o</STRONG> It restores the colors on the terminal to the values
they had when the terminal was just turned on.
- <STRONG>o</STRONG> If the terminal supports the <STRONG>initc</STRONG> (<STRONG>initialize_color</STRONG>)
+ <STRONG>o</STRONG> If the terminal supports the <STRONG>initc</STRONG> (<STRONG>initialize_color</STRONG>)
capability, <STRONG>start_color</STRONG> 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 <STRONG>hls</STRONG> (<STRONG>hue_lightness_sat-</STRONG>
<STRONG>uration</STRONG>) 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
+ 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 <STRONG>1000</STRONG>.
- <STRONG>start_color</STRONG> does not attempt to set the terminal's
- color palette to match its built-in table. An appli-
- cation may use <STRONG>init_color</STRONG> to alter the internal table
+ <STRONG>start_color</STRONG> does not attempt to set the terminal's
+ color palette to match its built-in table. An appli-
+ cation may use <STRONG>init_color</STRONG> 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
+ These limits apply to color values and color pairs. Val-
+ ues outside these limits are not legal, and may result in
a runtime error:
<STRONG>o</STRONG> <STRONG>COLORS</STRONG> corresponds to the terminal database's <STRONG>max_col-</STRONG>
<STRONG>o</STRONG> color values are expected to be in the range <STRONG>0</STRONG> to <STRONG>COL-</STRONG>
<STRONG>ORS-1</STRONG>, inclusive (including <STRONG>0</STRONG> and <STRONG>COLORS-1</STRONG>).
- <STRONG>o</STRONG> a special color value <STRONG>-1</STRONG> is used in certain extended
- functions to denote the <EM>default</EM> <EM>color</EM> (see <STRONG>use_de-</STRONG>
+ <STRONG>o</STRONG> a special color value <STRONG>-1</STRONG> is used in certain extended
+ functions to denote the <EM>default</EM> <EM>color</EM> (see <STRONG>use_de-</STRONG>
<STRONG>fault_colors</STRONG>).
- <STRONG>o</STRONG> <STRONG>COLOR_PAIRS</STRONG> corresponds to the terminal database's
- <STRONG>max_pairs</STRONG> capability, which is typically a signed
+ <STRONG>o</STRONG> <STRONG>COLOR_PAIRS</STRONG> corresponds to the terminal database's
+ <STRONG>max_pairs</STRONG> capability, which is typically a signed
16-bit integer (see <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>).
- <STRONG>o</STRONG> legal color pair values are in the range <STRONG>1</STRONG> to <STRONG>COL-</STRONG>
+ <STRONG>o</STRONG> legal color pair values are in the range <STRONG>1</STRONG> to <STRONG>COL-</STRONG>
<STRONG>OR_PAIRS-1</STRONG>, inclusive.
<STRONG>o</STRONG> color pair <STRONG>0</STRONG> is special; it denotes "no color".
- Color pair <STRONG>0</STRONG> is assumed to be white on black, but is
+ Color pair <STRONG>0</STRONG> 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 <STRONG>init_pair</STRONG> 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
+ The <STRONG>init_pair</STRONG> 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:
- <STRONG>o</STRONG> The first argument must be a legal color pair value.
- If default colors are used (see <STRONG>use_default_colors</STRONG>)
- the upper limit is adjusted to allow for extra pairs
- which use a default color in foreground and/or back-
+ <STRONG>o</STRONG> The first argument must be a legal color pair value.
+ If default colors are used (see <STRONG>use_default_colors</STRONG>)
+ the upper limit is adjusted to allow for extra pairs
+ which use a default color in foreground and/or back-
ground.
- <STRONG>o</STRONG> The second and third arguments must be legal color
+ <STRONG>o</STRONG> 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 <STRONG>0</STRONG>
- via the <STRONG>assume_default_colors</STRONG> routine, or to specify the
- use of default colors (color number <STRONG>-1</STRONG>) if you first in-
+ As an extension, ncurses allows you to set color pair <STRONG>0</STRONG>
+ via the <STRONG>assume_default_colors</STRONG> routine, or to specify the
+ use of default colors (color number <STRONG>-1</STRONG>) if you first in-
voke the <STRONG>use_default_colors</STRONG> routine.
- The <STRONG>init_color</STRONG> 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
+ The <STRONG>init_color</STRONG> 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 <STRONG>Colors</STRONG> for the default color in-
+ be a legal color value; default colors are not allowed
+ here. (See the section <STRONG>Colors</STRONG> for the default color in-
dex.) Each of the last three arguments must be a value in
- the range <STRONG>0</STRONG> through <STRONG>1000</STRONG>. When <STRONG>init_color</STRONG> is used, all
+ the range <STRONG>0</STRONG> through <STRONG>1000</STRONG>. When <STRONG>init_color</STRONG> is used, all
occurrences of that color on the screen immediately change
to the new definition.
- The <STRONG>has_colors</STRONG> routine requires no arguments. It returns
- <STRONG>TRUE</STRONG> if the terminal can manipulate colors; otherwise, it
+ The <STRONG>has_colors</STRONG> routine requires no arguments. It returns
+ <STRONG>TRUE</STRONG> if the terminal can manipulate colors; otherwise, it
returns <STRONG>FALSE</STRONG>. 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-
+ independent programs. For example, a programmer can use
+ it to decide whether to use color or some other video at-
tribute.
- The <STRONG>can_change_color</STRONG> routine requires no arguments. It
- returns <STRONG>TRUE</STRONG> if the terminal supports colors and can
- change their definitions; other, it returns <STRONG>FALSE</STRONG>. This
+ The <STRONG>can_change_color</STRONG> routine requires no arguments. It
+ returns <STRONG>TRUE</STRONG> if the terminal supports colors and can
+ change their definitions; other, it returns <STRONG>FALSE</STRONG>. This
routine facilitates writing terminal-independent programs.
- The <STRONG>color_content</STRONG> routine gives programmers a way to find
+ The <STRONG>color_content</STRONG> 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 <STRONG>short</STRONG>s for storing the information
- about the amounts of red, green, and blue components in
+ and three addresses of <STRONG>short</STRONG>s 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., <STRONG>0</STRONG> through <STRONG>COLORS-1</STRONG>, inclusive. The values
- that are stored at the addresses pointed to by the last
- three arguments are in the range <STRONG>0</STRONG> (no component) through
+ value, i.e., <STRONG>0</STRONG> through <STRONG>COLORS-1</STRONG>, inclusive. The values
+ that are stored at the addresses pointed to by the last
+ three arguments are in the range <STRONG>0</STRONG> (no component) through
<STRONG>1000</STRONG> (maximum amount of component), inclusive.
- The <STRONG>pair_content</STRONG> 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 <STRONG>short</STRONG>s for storing the foreground and the background
- color numbers. The first argument must be a legal color
- value, i.e., in the range <STRONG>1</STRONG> through <STRONG>COLOR_PAIRS-1</STRONG>, inclu-
+ The <STRONG>pair_content</STRONG> 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 <STRONG>short</STRONG>s for storing the foreground and the background
+ color numbers. The first argument must be a legal color
+ value, i.e., in the range <STRONG>1</STRONG> through <STRONG>COLOR_PAIRS-1</STRONG>, inclu-
sive. The values that are stored at the addresses pointed
- to by the second and third arguments are in the range <STRONG>0</STRONG>
+ to by the second and third arguments are in the range <STRONG>0</STRONG>
through <STRONG>COLORS</STRONG>, inclusive.
</PRE>
<H3><a name="h3-Colors">Colors</a></H3><PRE>
In <STRONG><curses.h></STRONG> the following macros are defined. These are
- the default colors. <STRONG>curses</STRONG> also assumes that <STRONG>COLOR_BLACK</STRONG>
+ the default colors. <STRONG>curses</STRONG> also assumes that <STRONG>COLOR_BLACK</STRONG>
is the default background color for all terminals.
<STRONG>COLOR_BLACK</STRONG>
</PRE>
<H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
- The routines <STRONG>can_change_color()</STRONG> and <STRONG>has_colors()</STRONG> return
+ The routines <STRONG>can_change_color()</STRONG> and <STRONG>has_colors()</STRONG> return
<STRONG>TRUE</STRONG> or <STRONG>FALSE</STRONG>.
All other routines return the integer <STRONG>ERR</STRONG> upon failure and
- an <STRONG>OK</STRONG> (SVr4 specifies only "an integer value other than
+ an <STRONG>OK</STRONG> (SVr4 specifies only "an integer value other than
<STRONG>ERR</STRONG>") upon successful completion.
- X/Open defines no error conditions. This implementation
- will return <STRONG>ERR</STRONG> on attempts to use color values outside
+ X/Open defines no error conditions. This implementation
+ will return <STRONG>ERR</STRONG> on attempts to use color values outside
the range <STRONG>0</STRONG> to COLORS-1 (except for the default colors ex-
- tension), or use color pairs outside the range <STRONG>0</STRONG> to <STRONG>COL-</STRONG>
- <STRONG>OR_PAIRS-1</STRONG>. Color values used in <STRONG>init_color</STRONG> must be in
- the range <STRONG>0</STRONG> to <STRONG>1000</STRONG>. An error is returned from all func-
- tions if the terminal has not been initialized. An error
- is returned from secondary functions such as <STRONG>init_pair</STRONG> if
+ tension), or use color pairs outside the range <STRONG>0</STRONG> to <STRONG>COL-</STRONG>
+ <STRONG>OR_PAIRS-1</STRONG>. Color values used in <STRONG>init_color</STRONG> must be in
+ the range <STRONG>0</STRONG> to <STRONG>1000</STRONG>. An error is returned from all func-
+ tions if the terminal has not been initialized. An error
+ is returned from secondary functions such as <STRONG>init_pair</STRONG> if
<STRONG>start_color</STRONG> was not called.
<STRONG>init_color</STRONG>
- returns an error if the terminal does not support
- this feature, e.g., if the <EM>initialize</EM><STRONG>_</STRONG><EM>color</EM> capa-
+ returns an error if the terminal does not support
+ this feature, e.g., if the <EM>initialize</EM><STRONG>_</STRONG><EM>color</EM> capa-
bility is absent from the terminal description.
<STRONG>start_color</STRONG>
- returns an error if the color table cannot be al-
+ returns an error if the color table cannot be al-
located.
</PRE>
<H2><a name="h2-NOTES">NOTES</a></H2><PRE>
- In the <EM>ncurses</EM> implementation, there is a separate color
+ In the <EM>ncurses</EM> 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 <STRONG>start_color</STRONG> function only affects the current screen.
+ sociated COLORS and COLOR_PAIRS counts for each screen;
+ the <STRONG>start_color</STRONG> 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 <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG>.
- Several caveats apply on 386 and 486 machines with VGA-
+ Several caveats apply on 386 and 486 machines with VGA-
compatible graphics:
- <STRONG>o</STRONG> COLOR_YELLOW is actually brown. To get yellow, use
+ <STRONG>o</STRONG> COLOR_YELLOW is actually brown. To get yellow, use
COLOR_YELLOW combined with the <STRONG>A_BOLD</STRONG> attribute.
<STRONG>o</STRONG> 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).
<STRONG>o</STRONG> Color RGB values are not settable.
</PRE>
<H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
- This implementation satisfies XSI Curses's minimum maxi-
+ This implementation satisfies XSI Curses's minimum maxi-
mums for <STRONG>COLORS</STRONG> and <STRONG>COLOR_PAIRS</STRONG>.
- The <STRONG>init_pair</STRONG> routine accepts negative values of fore-
- ground and background color to support the <STRONG>use_de-</STRONG>
- <STRONG>fault_colors</STRONG> extension, but only if that routine has been
+ The <STRONG>init_pair</STRONG> routine accepts negative values of fore-
+ ground and background color to support the <STRONG>use_de-</STRONG>
+ <STRONG>fault_colors</STRONG> extension, but only if that routine has been
first invoked.
- The assumption that <STRONG>COLOR_BLACK</STRONG> is the default background
- color for all terminals can be modified using the <STRONG>as-</STRONG>
+ The assumption that <STRONG>COLOR_BLACK</STRONG> is the default background
+ color for all terminals can be modified using the <STRONG>as-</STRONG>
<STRONG>sume_default_colors</STRONG> extension.
- This implementation checks the pointers, e.g., for the
- values returned by <STRONG>color_content</STRONG> and <STRONG>pair_content</STRONG>, and
+ This implementation checks the pointers, e.g., for the
+ values returned by <STRONG>color_content</STRONG> and <STRONG>pair_content</STRONG>, and
will treat those as optional parameters when null.
<li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
<ul>
<li><a href="#h3-Overview">Overview</a></li>
+<li><a href="#h3-Color-Rendering">Color Rendering</a></li>
<li><a href="#h3-Routine-Descriptions">Routine Descriptions</a></li>
<li><a href="#h3-Colors">Colors</a></li>
</ul>
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