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42 <H1 class="no-header">curs_color 3x 2023-09-23 ncurses 6.4 Library calls</H1>
44 <STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG> Library calls <STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>
49 </PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
50 <STRONG>start_color</STRONG>, <STRONG>has_colors</STRONG>, <STRONG>can_change_color</STRONG>, <STRONG>init_pair</STRONG>, <STRONG>init_color</STRONG>,
51 <STRONG>init_extended_pair</STRONG>, <STRONG>init_extended_color</STRONG>, <STRONG>color_content</STRONG>, <STRONG>pair_content</STRONG>,
52 <STRONG>extended_color_content</STRONG>, <STRONG>extended_pair_content</STRONG>, <STRONG>reset_color_pairs</STRONG>,
53 <STRONG>COLOR_PAIR</STRONG>, <STRONG>PAIR_NUMBER</STRONG> - manipulate terminal colors with <EM>curses</EM>
56 </PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
57 <STRONG>#include</STRONG> <STRONG><curses.h></STRONG>
59 <STRONG>int</STRONG> <STRONG>start_color(void);</STRONG>
61 <STRONG>bool</STRONG> <STRONG>has_colors(void);</STRONG>
62 <STRONG>bool</STRONG> <STRONG>can_change_color(void);</STRONG>
64 <STRONG>int</STRONG> <STRONG>init_pair(short</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>f</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>b</EM><STRONG>);</STRONG>
65 <STRONG>int</STRONG> <STRONG>init_color(short</STRONG> <EM>color</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>r</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>g</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>b</EM><STRONG>);</STRONG>
66 <EM>/*</EM> <EM>extensions</EM> <EM>*/</EM>
67 <STRONG>int</STRONG> <STRONG>init_extended_pair(int</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>f</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>b</EM><STRONG>);</STRONG>
68 <STRONG>int</STRONG> <STRONG>init_extended_color(int</STRONG> <EM>color</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>r</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>g</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>b</EM><STRONG>);</STRONG>
70 <STRONG>int</STRONG> <STRONG>color_content(short</STRONG> <EM>color</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>r</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>g</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>b</EM><STRONG>);</STRONG>
71 <STRONG>int</STRONG> <STRONG>pair_content(short</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>f</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>b</EM><STRONG>);</STRONG>
72 <EM>/*</EM> <EM>extensions</EM> <EM>*/</EM>
73 <STRONG>int</STRONG> <STRONG>extended_color_content(int</STRONG> <EM>color</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>r</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>g</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>b</EM><STRONG>);</STRONG>
74 <STRONG>int</STRONG> <STRONG>extended_pair_content(int</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>f</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>b</EM><STRONG>);</STRONG>
76 <EM>/*</EM> <EM>extensions</EM> <EM>*/</EM>
77 <STRONG>void</STRONG> <STRONG>reset_color_pairs(void);</STRONG>
79 <STRONG>int</STRONG> <STRONG>COLOR_PAIR(int</STRONG> <EM>n</EM><STRONG>);</STRONG>
80 <STRONG>PAIR_NUMBER(</STRONG><EM>attrs</EM><STRONG>);</STRONG>
83 </PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
85 </PRE><H3><a name="h3-Overview">Overview</a></H3><PRE>
86 <EM>curses</EM> supports color attributes on terminals with that capability. To
87 use these routines <STRONG>start_color</STRONG> must be called, usually right after
88 <STRONG>initscr</STRONG>. Colors are always used in pairs (referred to as color-pairs).
89 A color-pair consists of a foreground color (for characters) and a
90 background color (for the blank field on which the characters are
91 displayed). A programmer initializes a color-pair with the routine
92 <STRONG>init_pair</STRONG>. After it has been initialized, <STRONG>COLOR_PAIR</STRONG>(<EM>n</EM>) can be used to
93 convert the pair to a video attribute.
95 If a terminal is capable of redefining colors, the programmer can use
96 the routine <STRONG>init_color</STRONG> to change the definition of a color. The
97 routines <STRONG>has_colors</STRONG> and <STRONG>can_change_color</STRONG> return <STRONG>TRUE</STRONG> or <STRONG>FALSE</STRONG>,
98 depending on whether the terminal has color capabilities and whether
99 the programmer can change the colors. The routine <STRONG>color_content</STRONG> allows
100 a programmer to extract the amounts of red, green, and blue components
101 in an initialized color. The routine <STRONG>pair_content</STRONG> allows a programmer
102 to find out how a given color-pair is currently defined.
105 </PRE><H3><a name="h3-Color-Rendering">Color Rendering</a></H3><PRE>
106 The <EM>curses</EM> library combines these inputs to produce the actual
107 foreground and background colors shown on the screen:
109 <STRONG>o</STRONG> per-character video attributes (e.g., via <STRONG>waddch</STRONG>),
111 <STRONG>o</STRONG> the window attribute (e.g., by <STRONG>wattrset</STRONG>), and
113 <STRONG>o</STRONG> the background character (e.g., <STRONG>wbkgdset</STRONG>).
115 Per-character and window attributes are usually set by a parameter
116 containing video attributes including a color pair value. Some
117 functions such as <STRONG>wattr_set</STRONG> use a separate parameter which is the color
120 The background character is a special case: it includes a character
121 value, just as if it were passed to <STRONG>waddch</STRONG>.
123 The <EM>curses</EM> library does the actual work of combining these color pairs
124 in an internal function called from <STRONG>waddch</STRONG>:
126 <STRONG>o</STRONG> If the parameter passed to <STRONG>waddch</STRONG> is <EM>blank</EM>, and it uses the special
129 <STRONG>o</STRONG> <EM>curses</EM> next checks the window attribute.
131 <STRONG>o</STRONG> If the window attribute does not use color pair 0, <EM>curses</EM> uses
132 the color pair from the window attribute.
134 <STRONG>o</STRONG> Otherwise, <EM>curses</EM> uses the background character.
136 <STRONG>o</STRONG> If the parameter passed to <STRONG>waddch</STRONG> is <EM>not</EM> <EM>blank</EM>, or it does not use
137 the special color pair 0, <EM>curses</EM> prefers the color pair from the
138 parameter, if it is nonzero. Otherwise, it tries the window
139 attribute next, and finally the background character.
141 Some <EM>curses</EM> functions such as <STRONG>wprintw</STRONG> call <STRONG>waddch</STRONG>. Those do not
142 combine its parameter with a color pair. Consequently those calls use
143 only the window attribute or the background character.
146 </PRE><H2><a name="h2-CONSTANTS">CONSTANTS</a></H2><PRE>
147 In <STRONG><curses.h></STRONG> the following macros are defined. These are the standard
148 colors (ISO-6429). <EM>curses</EM> also assumes that <STRONG>COLOR_BLACK</STRONG> is the default
149 background color for all terminals.
151 <STRONG>COLOR_BLACK</STRONG>
152 <STRONG>COLOR_RED</STRONG>
153 <STRONG>COLOR_GREEN</STRONG>
154 <STRONG>COLOR_YELLOW</STRONG>
155 <STRONG>COLOR_BLUE</STRONG>
156 <STRONG>COLOR_MAGENTA</STRONG>
157 <STRONG>COLOR_CYAN</STRONG>
158 <STRONG>COLOR_WHITE</STRONG>
160 Some terminals support more than the eight (8) "ANSI" colors. There
161 are no standard names for those additional colors.
164 </PRE><H2><a name="h2-VARIABLES">VARIABLES</a></H2><PRE>
166 </PRE><H3><a name="h3-COLORS">COLORS</a></H3><PRE>
167 is initialized by <STRONG>start_color</STRONG> to the maximum number of colors the
168 terminal can support.
171 </PRE><H3><a name="h3-COLOR_PAIRS">COLOR_PAIRS</a></H3><PRE>
172 is initialized by <STRONG>start_color</STRONG> to the maximum number of color pairs the
173 terminal can support.
176 </PRE><H2><a name="h2-FUNCTIONS">FUNCTIONS</a></H2><PRE>
178 </PRE><H3><a name="h3-start_color">start_color</a></H3><PRE>
179 The <STRONG>start_color</STRONG> routine requires no arguments. It must be called if
180 the programmer wants to use colors, and before any other color
181 manipulation routine is called. It is good practice to call this
182 routine right after <STRONG>initscr</STRONG>. <STRONG>start_color</STRONG> does this:
184 <STRONG>o</STRONG> It initializes two global variables, <STRONG>COLORS</STRONG> and <STRONG>COLOR_PAIRS</STRONG>
185 (respectively defining the maximum number of colors and color-pairs
186 the terminal can support).
188 <STRONG>o</STRONG> It initializes the special color pair <STRONG>0</STRONG> to the default foreground
189 and background colors. No other color pairs are initialized.
191 <STRONG>o</STRONG> It restores the colors on the terminal to the values they had when
192 the terminal was just turned on.
194 <STRONG>o</STRONG> If the terminal supports the <STRONG>initc</STRONG> (<STRONG>initialize_color</STRONG>) capability,
195 <STRONG>start_color</STRONG> initializes its internal table representing the red,
196 green, and blue components of the color palette.
198 The components depend on whether the terminal uses CGA (aka "ANSI")
199 or HLS (i.e., the <STRONG>hls</STRONG> (<STRONG>hue_lightness_saturation</STRONG>) capability is
200 set). The table is initialized first for eight basic colors
201 (black, red, green, yellow, blue, magenta, cyan, and white), using
202 weights that depend upon the CGA/HLS choice. For "ANSI" colors the
203 weights are <STRONG>680</STRONG> or <STRONG>0</STRONG> depending on whether the corresponding red,
204 green, or blue component is used or not. That permits using <STRONG>1000</STRONG>
205 to represent bold/bright colors. After the initial eight colors
206 (if the terminal supports more than eight colors) the components
207 are initialized using the same pattern, but with weights of <STRONG>1000</STRONG>.
208 SVr4 uses a similar scheme, but uses <STRONG>1000</STRONG> for the components of the
209 initial eight colors.
211 <STRONG>start_color</STRONG> does not attempt to set the terminal's color palette to
212 match its built-in table. An application may use <STRONG>init_color</STRONG> to
213 alter the internal table along with the terminal's color.
215 These limits apply to color values and color pairs. Values outside
216 these limits are not legal, and may result in a runtime error:
218 <STRONG>o</STRONG> <STRONG>COLORS</STRONG> corresponds to the terminal database's <STRONG>max_colors</STRONG>
219 capability, (see <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>).
221 <STRONG>o</STRONG> color values are expected to be in the range <STRONG>0</STRONG> to <STRONG>COLORS-1</STRONG>,
222 inclusive (including <STRONG>0</STRONG> and <STRONG>COLORS-1</STRONG>).
224 <STRONG>o</STRONG> a special color value <STRONG>-1</STRONG> is used in certain extended functions to
225 denote the <EM>default</EM> <EM>color</EM> (see <STRONG><A HREF="default_colors.3x.html">use_default_colors(3x)</A></STRONG>).
227 <STRONG>o</STRONG> <STRONG>COLOR_PAIRS</STRONG> corresponds to the terminal database's <STRONG>max_pairs</STRONG>
228 capability, (see <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>).
230 <STRONG>o</STRONG> legal color pair values are in the range <STRONG>1</STRONG> to <STRONG>COLOR_PAIRS-1</STRONG>,
233 <STRONG>o</STRONG> color pair <STRONG>0</STRONG> is special; it denotes "no color".
235 Color pair <STRONG>0</STRONG> is assumed to be white on black, but is actually
236 whatever the terminal implements before color is initialized. It
237 cannot be modified by the application.
240 </PRE><H3><a name="h3-has_colors">has_colors</a></H3><PRE>
241 The <STRONG>has_colors</STRONG> routine requires no arguments. It returns <STRONG>TRUE</STRONG> if the
242 terminal can manipulate colors; otherwise, it returns <STRONG>FALSE</STRONG>. This
243 routine facilitates writing terminal-independent programs. For
244 example, a programmer can use it to decide whether to use color or some
245 other video attribute.
248 </PRE><H3><a name="h3-can_change_color">can_change_color</a></H3><PRE>
249 The <STRONG>can_change_color</STRONG> routine requires no arguments. It returns <STRONG>TRUE</STRONG> if
250 the terminal supports colors and can change their definitions; other,
251 it returns <STRONG>FALSE</STRONG>. This routine facilitates writing terminal-
252 independent programs.
255 </PRE><H3><a name="h3-init_pair">init_pair</a></H3><PRE>
256 The <STRONG>init_pair</STRONG> routine changes the definition of a color-pair. It takes
257 three arguments: the number of the color-pair to be changed, the
258 foreground color number, and the background color number. For portable
261 <STRONG>o</STRONG> The first argument must be a legal color pair value. If default
262 colors are used (see <STRONG><A HREF="default_colors.3x.html">use_default_colors(3x)</A></STRONG>) the upper limit is
263 adjusted to allow for extra pairs which use a default color in
264 foreground and/or background.
266 <STRONG>o</STRONG> The second and third arguments must be legal color values.
268 If the color-pair was previously initialized, the screen is refreshed
269 and all occurrences of that color-pair are changed to the new
272 As an extension, ncurses allows you to set color pair <STRONG>0</STRONG> via the
273 <STRONG><A HREF="default_colors.3x.html">assume_default_colors(3x)</A></STRONG> routine, or to specify the use of default
274 colors (color number <STRONG>-1</STRONG>) if you first invoke the <STRONG><A HREF="default_colors.3x.html">use_default_colors(3x)</A></STRONG>
278 </PRE><H3><a name="h3-init_extended_pair">init_extended_pair</a></H3><PRE>
279 Because <STRONG>init_pair</STRONG> uses signed <STRONG>short</STRONG>s for its parameters, that limits
280 color-pairs and color-values to 32767 on modern hardware. The
281 extension <STRONG>init_extended_pair</STRONG> uses <STRONG>int</STRONG>s for the color-pair and color-
282 value, allowing a larger number of colors to be supported.
285 </PRE><H3><a name="h3-init_color">init_color</a></H3><PRE>
286 The <STRONG>init_color</STRONG> routine changes the definition of a color. It takes
287 four arguments: the number of the color to be changed followed by three
288 RGB values (for the amounts of red, green, and blue components).
290 <STRONG>o</STRONG> The first argument must be a legal color value; default colors are
291 not allowed here. (See the section <STRONG>Colors</STRONG> for the default color
294 <STRONG>o</STRONG> Each of the last three arguments must be a value in the range <STRONG>0</STRONG>
295 through <STRONG>1000</STRONG>.
297 When <STRONG>init_color</STRONG> is used, all occurrences of that color on the screen
298 immediately change to the new definition.
301 </PRE><H3><a name="h3-init_extended_color">init_extended_color</a></H3><PRE>
302 Because <STRONG>init_color</STRONG> uses signed <STRONG>short</STRONG>s for its parameters, that limits
303 color-values and their red, green, and blue components to 32767 on
304 modern hardware. The extension <STRONG>init_extended_color</STRONG> uses <STRONG>int</STRONG>s for the
305 color value and for setting the red, green, and blue components,
306 allowing a larger number of colors to be supported.
309 </PRE><H3><a name="h3-color_content">color_content</a></H3><PRE>
310 The <STRONG>color_content</STRONG> routine gives programmers a way to find the intensity
311 of the red, green, and blue (RGB) components in a color. It requires
312 four arguments: the color number, and three addresses of <STRONG>short</STRONG>s for
313 storing the information about the amounts of red, green, and blue
314 components in the given color.
316 <STRONG>o</STRONG> The first argument must be a legal color value, i.e., <STRONG>0</STRONG> through
317 <STRONG>COLORS-1</STRONG>, inclusive.
319 <STRONG>o</STRONG> The values that are stored at the addresses pointed to by the last
320 three arguments are in the range <STRONG>0</STRONG> (no component) through <STRONG>1000</STRONG>
321 (maximum amount of component), inclusive.
324 </PRE><H3><a name="h3-extended_color_content">extended_color_content</a></H3><PRE>
325 Because <STRONG>color_content</STRONG> uses signed <STRONG>short</STRONG>s for its parameters, that
326 limits color-values and their red, green, and blue components to 32767
327 on modern hardware. The extension <STRONG>extended_color_content</STRONG> uses <STRONG>int</STRONG>s for
328 the color value and for returning the red, green, and blue components,
329 allowing a larger number of colors to be supported.
332 </PRE><H3><a name="h3-pair_content">pair_content</a></H3><PRE>
333 The <STRONG>pair_content</STRONG> routine allows programmers to find out what colors a
334 given color-pair consists of. It requires three arguments: the color-
335 pair number, and two addresses of <STRONG>short</STRONG>s for storing the foreground and
336 the background color numbers.
338 <STRONG>o</STRONG> The first argument must be a legal color value, i.e., in the range
339 <STRONG>1</STRONG> through <STRONG>COLOR_PAIRS-1</STRONG>, inclusive.
341 <STRONG>o</STRONG> The values that are stored at the addresses pointed to by the
342 second and third arguments are in the range <STRONG>0</STRONG> through <STRONG>COLORS</STRONG>,
346 </PRE><H3><a name="h3-extended_pair_content">extended_pair_content</a></H3><PRE>
347 Because <STRONG>pair_content</STRONG> uses signed <STRONG>short</STRONG>s for its parameters, that limits
348 color-pair and color-values to 32767 on modern hardware. The extension
349 <STRONG>extended_pair_content</STRONG> uses <STRONG>int</STRONG>s for the color pair and for returning
350 the foreground and background colors, allowing a larger number of
351 colors to be supported.
354 </PRE><H3><a name="h3-reset_color_pairs">reset_color_pairs</a></H3><PRE>
355 The extension <STRONG>reset_color_pairs</STRONG> tells ncurses to discard all of the
356 color-pair information which was set with <STRONG>init_pair</STRONG>. It also touches
357 the current- and standard-screens, allowing an application to switch
358 color palettes rapidly.
361 </PRE><H3><a name="h3-PAIR_NUMBER">PAIR_NUMBER</a></H3><PRE>
362 <STRONG>PAIR_NUMBER(</STRONG><EM>attrs</EM>) extracts the color value from its <EM>attrs</EM> parameter
363 and returns it as a color pair number.
366 </PRE><H3><a name="h3-COLOR_PAIR">COLOR_PAIR</a></H3><PRE>
367 Its inverse <STRONG>COLOR_PAIR(</STRONG><EM>n</EM><STRONG>)</STRONG> converts a color pair number to an attribute.
368 Attributes can hold color pairs in the range 0 to 255. If you need a
369 color pair larger than that, you must use functions such as <STRONG>attr_set</STRONG>
370 (which pass the color pair as a separate parameter) rather than the
371 legacy functions such as <STRONG>attrset</STRONG>.
374 </PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
375 The routines <STRONG>can_change_color</STRONG> and <STRONG>has_colors</STRONG> return <STRONG>TRUE</STRONG> or <STRONG>FALSE</STRONG>.
377 All other routines return the integer <STRONG>ERR</STRONG> upon failure and an <STRONG>OK</STRONG> (SVr4
378 specifies only "an integer value other than <STRONG>ERR</STRONG>") upon successful
381 X/Open defines no error conditions. SVr4 does document some error
382 conditions which apply in general:
384 <STRONG>o</STRONG> This implementation will return <STRONG>ERR</STRONG> on attempts to use color values
385 outside the range <STRONG>0</STRONG> to <STRONG>COLORS</STRONG>-1 (except for the default colors
386 extension), or use color pairs outside the range <STRONG>0</STRONG> to
387 <STRONG>COLOR_PAIRS-1</STRONG>.
389 Color values used in <STRONG>init_color</STRONG> must be in the range <STRONG>0</STRONG> to <STRONG>1000</STRONG>.
391 An error is returned from all functions if the terminal has not
394 An error is returned from secondary functions such as <STRONG>init_pair</STRONG> if
395 <STRONG>start_color</STRONG> was not called.
397 <STRONG>o</STRONG> SVr4 does much the same, except that it returns <STRONG>ERR</STRONG> from
398 <STRONG>pair_content</STRONG> if the pair was not initialized using <STRONG>init_pairs</STRONG> and
399 it returns <STRONG>ERR</STRONG> from <STRONG>color_content</STRONG> if the terminal does not support
402 This implementation does not return <STRONG>ERR</STRONG> for either case.
404 Specific functions make additional checks:
406 <STRONG>init_color</STRONG>
407 returns an error if the terminal does not support this feature,
408 e.g., if the <STRONG>initialize_color</STRONG> capability is absent from the
409 terminal description.
411 <STRONG>start_color</STRONG>
412 returns an error if the color table cannot be allocated.
415 </PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
416 In the <EM>ncurses</EM> implementation, there is a separate color activation
417 flag, color palette, color pairs table, and associated <STRONG>COLORS</STRONG> and
418 <STRONG>COLOR_PAIRS</STRONG> counts for each screen; the <STRONG>start_color</STRONG> function only
419 affects the current screen. The SVr4/XSI interface is not really
420 designed with this in mind, and historical implementations may use a
421 single shared color palette.
423 Setting an implicit background color via a color pair affects only
424 character cells that a character write operation explicitly touches.
425 To change the background color used when parts of a window are blanked
426 by erasing or scrolling operations, see <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG>.
428 Several caveats apply on older x86 machines (e.g., i386, i486) with
429 VGA-compatible graphics:
431 <STRONG>o</STRONG> COLOR_YELLOW is actually brown. To get yellow, use COLOR_YELLOW
432 combined with the <STRONG>A_BOLD</STRONG> attribute.
434 <STRONG>o</STRONG> The A_BLINK attribute should in theory cause the background to go
435 bright. This often fails to work, and even some cards for which it
436 mostly works (such as the Paradise and compatibles) do the wrong
437 thing when you try to set a bright "yellow" background (you get a
438 blinking yellow foreground instead).
440 <STRONG>o</STRONG> Color RGB values are not settable.
443 </PRE><H2><a name="h2-HISTORY">HISTORY</a></H2><PRE>
444 SVr3.2 introduced color support to curses in 1987.
446 SVr4 made internal changes, e.g., moving the storage for the color
447 state from <STRONG>SP</STRONG> (the <STRONG>SCREEN</STRONG> structure) to <STRONG>cur_term</STRONG> (the <STRONG>TERMINAL</STRONG>
448 structure), but provided the same set of library functions.
450 SVr4 curses limits the number of color pairs to 64, reserving color
451 pair zero (0) as the terminal's initial uncolored state. This limit
452 arises because the color pair information is a bitfield in the <STRONG>chtype</STRONG>
453 data type (denoted by <STRONG>A_COLOR</STRONG>).
455 Other implementations of curses had different limits:
457 <STRONG>o</STRONG> PCCurses (1987-1990) provided for only eight (8) colors.
459 <STRONG>o</STRONG> PDCurses (1992-present) inherited the 8-color limitation from
460 PCCurses, but changed this to 256 in version 2.5 (2001), along with
461 changing <STRONG>chtype</STRONG> from 16-bits to 32-bits.
463 <STRONG>o</STRONG> X/Open Curses (1992-present) added a new structure <STRONG>cchar_t</STRONG> to store
464 the character, attributes and color-pair values, allowing increased
465 range of color-pairs. Both color-pairs and color-values used a
466 signed <STRONG>short</STRONG>, limiting values to 15 bits.
468 <STRONG>o</STRONG> ncurses (1992-present) uses eight bits for <STRONG>A_COLOR</STRONG> in <STRONG>chtype</STRONG>
471 Version 5.3 provided a wide-character interface (2002), but left
472 color-pairs as part of the attributes-field.
474 Since version 6 (2015), ncurses uses a separate <STRONG>int</STRONG> for color-pairs
475 in the <STRONG>cchar_t</STRONG> values. When those color-pair values fit in 8 bits,
476 ncurses allows color-pairs to be manipulated via the functions
477 using <STRONG>chtype</STRONG> values.
479 <STRONG>o</STRONG> NetBSD curses used 6 bits from 2000 (when colors were first
480 supported) until 2004. At that point, NetBSD changed to use 10
481 bits. As of 2021, that size is unchanged. Like ncurses before
482 version 6, the NetBSD color-pair information is stored in the
483 attributes field of <STRONG>cchar_t</STRONG>, limiting the number of color-pairs by
484 the size of the bitfield.
487 </PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
489 </PRE><H3><a name="h3-Extensions">Extensions</a></H3><PRE>
490 The functions marked as extensions were designed for <STRONG><A HREF="ncurses.3x.html">ncurses(3x)</A></STRONG>, and
491 are not found in SVr4 curses, 4.4BSD curses, or any other previous
495 </PRE><H3><a name="h3-Standards">Standards</a></H3><PRE>
496 This implementation satisfies XSI Curses's minimum maximums for <STRONG>COLORS</STRONG>
497 and <STRONG>COLOR_PAIRS</STRONG>.
499 The <STRONG>init_pair</STRONG> routine accepts negative values of foreground and
500 background color to support the <STRONG><A HREF="default_colors.3x.html">use_default_colors(3x)</A></STRONG> extension, but
501 only if that routine has been first invoked.
503 The assumption that <STRONG>COLOR_BLACK</STRONG> is the default background color for all
504 terminals can be modified using the <STRONG><A HREF="default_colors.3x.html">assume_default_colors(3x)</A></STRONG>
507 This implementation checks the pointers, e.g., for the values returned
508 by <STRONG>color_content</STRONG> and <STRONG>pair_content</STRONG>, and will treat those as optional
509 parameters when null.
511 X/Open Curses does not specify a limit for the number of colors and
512 color pairs which a terminal can support. However, in its use of <STRONG>short</STRONG>
513 for the parameters, it carries over SVr4's implementation detail for
514 the compiled terminfo database, which uses signed 16-bit numbers. This
515 implementation provides extended versions of those functions which use
516 <STRONG>short</STRONG> parameters, allowing applications to use larger color- and pair-
519 The <STRONG>reset_color_pairs</STRONG> function is an extension of ncurses.
522 </PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
523 <STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>, <STRONG><A HREF="curs_initscr.3x.html">curs_initscr(3x)</A></STRONG>, <STRONG><A HREF="curs_attr.3x.html">curs_attr(3x)</A></STRONG>, <STRONG><A HREF="curs_variables.3x.html">curs_variables(3x)</A></STRONG>,
524 <STRONG><A HREF="default_colors.3x.html">default_colors(3x)</A></STRONG>
528 ncurses 6.4 2023-09-23 <STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>
532 <li><a href="#h2-NAME">NAME</a></li>
533 <li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
534 <li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
536 <li><a href="#h3-Overview">Overview</a></li>
537 <li><a href="#h3-Color-Rendering">Color Rendering</a></li>
540 <li><a href="#h2-CONSTANTS">CONSTANTS</a></li>
541 <li><a href="#h2-VARIABLES">VARIABLES</a>
543 <li><a href="#h3-COLORS">COLORS</a></li>
544 <li><a href="#h3-COLOR_PAIRS">COLOR_PAIRS</a></li>
547 <li><a href="#h2-FUNCTIONS">FUNCTIONS</a>
549 <li><a href="#h3-start_color">start_color</a></li>
550 <li><a href="#h3-has_colors">has_colors</a></li>
551 <li><a href="#h3-can_change_color">can_change_color</a></li>
552 <li><a href="#h3-init_pair">init_pair</a></li>
553 <li><a href="#h3-init_extended_pair">init_extended_pair</a></li>
554 <li><a href="#h3-init_color">init_color</a></li>
555 <li><a href="#h3-init_extended_color">init_extended_color</a></li>
556 <li><a href="#h3-color_content">color_content</a></li>
557 <li><a href="#h3-extended_color_content">extended_color_content</a></li>
558 <li><a href="#h3-pair_content">pair_content</a></li>
559 <li><a href="#h3-extended_pair_content">extended_pair_content</a></li>
560 <li><a href="#h3-reset_color_pairs">reset_color_pairs</a></li>
561 <li><a href="#h3-PAIR_NUMBER">PAIR_NUMBER</a></li>
562 <li><a href="#h3-COLOR_PAIR">COLOR_PAIR</a></li>
565 <li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
566 <li><a href="#h2-NOTES">NOTES</a></li>
567 <li><a href="#h2-HISTORY">HISTORY</a></li>
568 <li><a href="#h2-PORTABILITY">PORTABILITY</a>
570 <li><a href="#h3-Extensions">Extensions</a></li>
571 <li><a href="#h3-Standards">Standards</a></li>
574 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>