1curs_attr(3X)                                                    curs_attr(3X)
2
3
4

NAME

6       attr_get, wattr_get, attr_set, wattr_set, attr_off, wattr_off, attr_on,
7       wattr_on, attroff, wattroff, attron, wattron, attrset, wattrset, chgat,
8       wchgat, mvchgat, mvwchgat, color_set, wcolor_set, standend, wstandend,
9       standout, wstandout - curses character and window attribute control
10       routines
11

SYNOPSIS

13       #include <curses.h>
14
15       int attr_get(attr_t *attrs, short *pair, void *opts);
16       int wattr_get(WINDOW *win, attr_t *attrs, short *pair, void *opts);
17       int attr_set(attr_t attrs, short pair, void *opts);
18       int wattr_set(WINDOW *win, attr_t attrs, short pair, void *opts);
19
20       int attr_off(attr_t attrs, void *opts);
21       int wattr_off(WINDOW *win, attr_t attrs, void *opts);
22       int attr_on(attr_t attrs, void *opts);
23       int wattr_on(WINDOW *win, attr_t attrs, void *opts);
24
25       int attroff(int attrs);
26       int wattroff(WINDOW *win, int attrs);
27       int attron(int attrs);
28       int wattron(WINDOW *win, int attrs);
29       int attrset(int attrs);
30       int wattrset(WINDOW *win, int attrs);
31
32       int chgat(int n, attr_t attr, short pair, const void *opts);
33       int wchgat(WINDOW *win,
34             int n, attr_t attr, short pair, const void *opts);
35       int mvchgat(int y, int x,
36             int n, attr_t attr, short pair, const void *opts);
37       int mvwchgat(WINDOW *win, int y, int x,
38             int n, attr_t attr, short pair, const void *opts);
39
40       int color_set(short pair, void* opts);
41       int wcolor_set(WINDOW *win, short pair, void* opts);
42
43       int standend(void);
44       int wstandend(WINDOW *win);
45       int standout(void);
46       int wstandout(WINDOW *win);
47

DESCRIPTION

49       These  routines  manipulate the current attributes of the named window,
50       which then apply to all characters that are  written  into  the  window
51       with  waddch,  waddstr  and  wprintw.  Attributes are a property of the
52       character, and move with the character through any  scrolling  and  in‐
53       sert/delete  line/character  operations.   To the extent possible, they
54       are displayed as appropriate modifications to the graphic rendition  of
55       characters put on the screen.
56
57       These  routines do not affect the attributes used when erasing portions
58       of the window.  See curs_bkgd(3X) for functions which  modify  the  at‐
59       tributes used for erasing and clearing.
60
61       Routines  which  do  not have a WINDOW* parameter apply to stdscr.  For
62       example, attr_set is the stdscr variant of wattr_set.
63
64   Window attributes
65       There are two sets of functions:
66
67       •   functions for manipulating the window attributes  and  color:  wat‐
68           tr_set and wattr_get.
69
70       •   functions  for manipulating only the window attributes (not color):
71           wattr_on and wattr_off.
72
73       The wattr_set function sets the current attributes of the given  window
74       to attrs, with color specified by pair.
75
76       Use wattr_get to retrieve attributes for the given window.
77
78       Use  attr_on  and  wattr_on  to turn on window attributes, i.e., values
79       OR'd together in attr, without affecting  other  attributes.   Use  at‐
80       tr_off  and  wattr_off to turn off window attributes, again values OR'd
81       together in attr, without affecting other attributes.
82
83   Legacy window attributes
84       The X/Open window attribute routines which set or get, turn on  or  off
85       are extensions of older routines which assume that color pairs are OR'd
86       into the attribute parameter.  These newer routines use similar  names,
87       because X/Open simply added an underscore (_) for the newer names.
88
89       The int datatype used in the legacy routines is treated as if it is the
90       same size as chtype (used by addch(3X)).  It holds the common video at‐
91       tributes  (such  as  bold,  reverse),  as well as a few bits for color.
92       Those bits correspond to the A_COLOR symbol.  The COLOR_PAIR macro pro‐
93       vides  a value which can be OR'd into the attribute parameter.  For ex‐
94       ample, as long as that value fits into the  A_COLOR  mask,  then  these
95       calls produce similar results:
96
97           attrset(A_BOLD | COLOR_PAIR(pair));
98           attr_set(A_BOLD, pair, NULL);
99
100       However, if the value does not fit, then the COLOR_PAIR macro uses only
101       the bits that fit.  For example, because in ncurses A_COLOR  has  eight
102       (8) bits, then COLOR_PAIR(259) is 4 (i.e., 259 is 4 more than the limit
103       255).
104
105       The PAIR_NUMBER macro extracts a pair number from an int  (or  chtype).
106       For  example,  the input and output values in these statements would be
107       the same:
108
109           int value = A_BOLD | COLOR_PAIR(input);
110           int output = PAIR_NUMBER(value);
111
112       The attrset routine is a legacy feature predating SVr4 curses but  kept
113       in X/Open Curses for the same reason that SVr4 curses kept it: compati‐
114       bility.
115
116       The remaining attr* functions operate exactly  like  the  corresponding
117       attr_*  functions,  except  that they take arguments of type int rather
118       than attr_t.
119
120       There is no corresponding attrget function as such  in  X/Open  Curses,
121       although ncurses provides getattrs (see curs_legacy(3X)).
122
123   Change character rendition
124       The  routine  chgat changes the attributes of a given number of charac‐
125       ters starting at the current cursor location of stdscr.   It  does  not
126       update  the cursor and does not perform wrapping.  A character count of
127       -1 or greater than the remaining  window  width  means  to  change  at‐
128       tributes  all the way to the end of the current line.  The wchgat func‐
129       tion generalizes this to any window; the mvwchgat function does a  cur‐
130       sor move before acting.
131
132       In  these  functions, the color pair argument is a color-pair index (as
133       in the first argument of init_pair, see curs_color(3X)).
134
135   Change window color
136       The routine color_set sets the current color of the given window to the
137       foreground/background  combination  described by the color pair parame‐
138       ter.
139
140   Standout
141       The routine standout is the same as  attron(A_STANDOUT).   The  routine
142       standend  is  the  same as attrset(A_NORMAL) or attrset(0), that is, it
143       turns off all attributes.
144
145       X/Open does not mark these “restricted”, because
146
147       •   they have well established legacy use, and
148
149       •   there is no ambiguity about the way the attributes  might  be  com‐
150           bined with a color pair.
151

VIDEO ATTRIBUTES

153       The following video attributes, defined in <curses.h>, can be passed to
154       the routines attron, attroff, and attrset, or OR'd with the  characters
155       passed to addch (see curs_addch(3X)).
156
157              Name           Description
158              ─────────────────────────────────────────────────────────────────
159              A_NORMAL       Normal display (no highlight)
160              A_STANDOUT     Best highlighting mode of the terminal.
161              A_UNDERLINE    Underlining
162              A_REVERSE      Reverse video
163              A_BLINK        Blinking
164              A_DIM          Half bright
165              A_BOLD         Extra bright or bold
166              A_PROTECT      Protected mode
167              A_INVIS        Invisible or blank mode
168              A_ALTCHARSET   Alternate character set
169              A_ITALIC       Italics (non-X/Open extension)
170              A_CHARTEXT     Bit-mask to extract a character
171              A_COLOR        Bit-mask to extract a color (legacy routines)
172
173       These  video  attributes are supported by attr_on and related functions
174       (which also support the attributes recognized by attron, etc.):
175
176              Name            Description
177              ─────────────────────────────────────────
178              WA_HORIZONTAL   Horizontal highlight
179              WA_LEFT         Left highlight
180              WA_LOW          Low highlight
181              WA_RIGHT        Right highlight
182              WA_TOP          Top highlight
183              WA_VERTICAL     Vertical highlight
184
185       The return values of many of these routines are  not  meaningful  (they
186       are  implemented  as macro-expanded assignments and simply return their
187       argument).  The SVr4 manual page claims (falsely) that  these  routines
188       always return 1.
189

NOTES

191       These functions may be macros:
192
193              attroff,  wattroff, attron, wattron, attrset, wattrset, standend
194              and standout.
195
196       Color pair values can only be OR'd with attributes if the  pair  number
197       is less than 256.  The alternate functions such as color_set can pass a
198       color pair value directly.  However, ncurses ABI 4 and 5 simply OR this
199       value  within  the  alternate functions.  You must use ncurses ABI 6 to
200       support more than 256 color pairs.
201

HISTORY

203       X/Open Curses is largely based  on  SVr4  curses,  adding  support  for
204       “wide-characters”  (not  specific to Unicode).  Some of the X/Open dif‐
205       ferences from SVr4 curses address the way video attributes can  be  ap‐
206       plied  to  wide-characters.   But aside from that, attrset and attr_set
207       are similar.  SVr4 curses provided the basic features for  manipulating
208       video  attributes.  However, earlier versions of curses provided a part
209       of these features.
210
211       As seen in 2.8BSD, curses assumed 7-bit characters,  using  the  eighth
212       bit  of  a byte to represent the standout feature (often implemented as
213       bold and/or reverse video).  The BSD curses library provided  functions
214       standout  and  standend which were carried along into X/Open Curses due
215       to their pervasive use in legacy applications.
216
217       Some terminals in the 1980s  could  support  a  variety  of  video  at‐
218       tributes,  although the BSD curses library could do nothing with those.
219       System V (1983) provided an improved curses library.  It defined the A_
220       symbols  for  use  by  applications to manipulate the other attributes.
221       There are few useful references for the chronology.
222
223       Goodheart's book UNIX Curses Explained (1991)  describes  SVr3  (1987),
224       commenting on several functions:
225
226       •   the  attron,  attroff, attrset functions (and most of the functions
227           found in SVr4 but not in BSD curses) were introduced by System V,
228
229       •   the alternate character set feature with A_ALTCHARSET was added  in
230           SVr2 and improved in SVr3 (by adding acs_map[]),
231
232start_color  and  related color-functions were introduced by System
233           V.3.2,
234
235       •   pads, soft-keys were added in SVr3, and
236
237       Goodheart did not mention the background character or the cchar_t type.
238       Those are respectively SVr4 and X/Open features.  He did mention the A_
239       constants, but did not indicate their values.  Those were not the  same
240       in different systems, even for those marked as System V.
241
242       Different  Unix  systems  used  different  sizes  for the bit-fields in
243       chtype for characters and colors, and took into account  the  different
244       integer sizes (32-bit versus 64-bit).
245
246       This  table  showing  the number of bits for A_COLOR and A_CHARTEXT was
247       gleaned from the curses header files for various operating systems  and
248       architectures.   The inferred architecture and notes reflect the format
249       and size of the defined constants as well as clues such as  the  alter‐
250       nate  character  set implementation.  A 32-bit library can be used on a
251       64-bit system, but not necessarily the reverse.
252
253              Year   System        Arch    Color   Char   Notes
254              ────────────────────────────────────────────────────────────────
255              1992   Solaris 5.2   32      6       17     SVr4 curses
256              1992   HPUX 9        32      no      8      SVr2 curses
257              1992   AIX 3.2       32      no      23     SVr2 curses
258              1994   OSF/1 r3      32      no      23     SVr2 curses
259              1995   HP-UX 10.00   32      6       16     SVr3 “curses_colr”
260              1995   HP-UX 10.00   32      6       8      SVr4, X/Open curses
261              1995   Solaris 5.4   32/64   7       16     X/Open curses
262              1996   AIX 4.2       32      7       16     X/Open curses
263              1996   OSF/1 r4      32      6       16     X/Open curses
264
265              1997   HP-UX 11.00   32      6       8      X/Open curses
266              2000   U/Win         32/64   7/31    16     uses chtype
267
268       Notes:
269
270          Regarding HP-UX,
271
272          •   HP-UX 10.20 (1996) added support for 64-bit  PA-RISC  processors
273              in 1996.
274
275          •   HP-UX  10.30 (1997) marked “curses_colr” obsolete.  That version
276              of curses was dropped with HP-UX 11.30 in 2006.
277
278          Regarding OSF/1 (and Tru64),
279
280          •   These used 64-bit hardware.  Like ncurses, the OSF/1 curses  in‐
281              terface is not customized for 32-bit and 64-bit versions.
282
283          •   Unlike other systems which evolved from AT&T code, OSF/1 provid‐
284              ed a new implementation for X/Open curses.
285
286          Regarding Solaris,
287
288          •   The initial release of Solaris was in 1992.
289
290          •   The xpg4 (X/Open) curses was developed by MKS from 1990 to 1995.
291              Sun's copyright began in 1996.
292
293          •   Sun updated the X/Open curses interface after 64-bit support was
294              introduced in 1997, but did not modify the  SVr4  curses  inter‐
295              face.
296
297          Regarding U/Win,
298
299          •   Development  of  the  curses  library  began in 1991, stopped in
300              2000.
301
302          •   Color support was added in 1998.
303
304          •   The library uses only chtype (no cchar_t).
305
306       Once X/Open curses was adopted in the mid-1990s, the  constraint  of  a
307       32-bit interface with many colors and wide-characters for chtype became
308       a moot point.  The cchar_t structure (whose size and  members  are  not
309       specified in X/Open Curses) could be extended as needed.
310
311       Other interfaces are rarely used now:
312
313       •   BSD  curses was improved slightly in 1993/1994 using Keith Bostic's
314           modification to make the library 8-bit clean for nvi(1).  He  moved
315           standout attribute to a structure member.
316
317           The  resulting  4.4BSD curses was replaced by ncurses over the next
318           ten years.
319
320       •   U/Win is rarely used now.
321

EXTENSIONS

323       This implementation provides the A_ITALIC attribute for terminals which
324       have  the  enter_italics_mode (sitm) and exit_italics_mode (ritm) capa‐
325       bilities.  Italics are not mentioned in X/Open Curses.  Unlike the oth‐
326       er  video attributes, A_ITALIC is unrelated to the set_attributes capa‐
327       bilities.  This implementation makes the  assumption  that  exit_attri‐
328       bute_mode may also reset italics.
329
330       Each  of  the functions added by XSI Curses has a parameter opts, which
331       X/Open Curses still (after more than twenty  years)  documents  as  re‐
332       served for future use, saying that it should be NULL.  This implementa‐
333       tion uses that parameter in ABI 6 for the functions which have a color-
334       pair parameter to support extended color pairs:
335
336       •   For functions which modify the color, e.g., wattr_set and wattr_on,
337           if opts is set it is treated as a pointer to int, and used  to  set
338           the color pair instead of the short pair parameter.
339
340       •   For functions which retrieve the color, e.g., wattr_get, if opts is
341           set it is treated as a pointer to int, and  used  to  retrieve  the
342           color  pair  as  an int value, in addition to retrieving it via the
343           standard pointer to short parameter.
344
345       •   For functions which turn attributes off, e.g., wattr_off, the  opts
346           parameter is ignored except except to check that it is NULL.
347

PORTABILITY

349       These functions are supported in the XSI Curses standard, Issue 4.  The
350       standard defined the dedicated type for highlights, attr_t,  which  was
351       not defined in SVr4 curses.  The functions taking attr_t arguments were
352       not supported under SVr4.
353
354       Very old versions of this library did not force an update of the screen
355       when  changing  the  attributes.   Use  touchwin to force the screen to
356       match the updated attributes.
357
358       The XSI Curses standard states that whether the  traditional  functions
359       attron/attroff/attrset  can  manipulate  attributes other than A_BLINK,
360       A_BOLD, A_DIM, A_REVERSE, A_STANDOUT, or A_UNDERLINE is  “unspecified”.
361       Under  this implementation as well as SVr4 curses, these functions cor‐
362       rectly manipulate all  other  highlights  (specifically,  A_ALTCHARSET,
363       A_PROTECT, and A_INVIS).
364
365       XSI Curses added these entry points:
366
367              attr_get, attr_on, attr_off, attr_set, wattr_on, wattr_off, wat‐
368              tr_get, wattr_set
369
370       The new functions are intended to work with a new series  of  highlight
371       macros prefixed with WA_.  The older macros have direct counterparts in
372       the newer set of names:
373
374              Name            Description
375              ────────────────────────────────────────────────────────────
376              WA_NORMAL       Normal display (no highlight)
377              WA_STANDOUT     Best highlighting mode of the terminal.
378              WA_UNDERLINE    Underlining
379              WA_REVERSE      Reverse video
380              WA_BLINK        Blinking
381              WA_DIM          Half bright
382              WA_BOLD         Extra bright or bold
383              WA_ALTCHARSET   Alternate character set
384
385       XSI curses does not assign values to these symbols, nor does  it  state
386       whether or not they are related to the similarly-named A_NORMAL, etc.:
387
388       •   The  XSI  curses standard specifies that each pair of corresponding
389           A_ and WA_-using functions operates on the  same  current-highlight
390           information.
391
392       •   However, in some implementations, those symbols have unrelated val‐
393           ues.
394
395           For example, the Solaris xpg4 (X/Open) curses declares attr_t to be
396           an unsigned short integer (16-bits), while chtype is a unsigned in‐
397           teger (32-bits).  The WA_ symbols in this case are  different  from
398           the  A_  symbols because they are used for a smaller datatype which
399           does not represent A_CHARTEXT or A_COLOR.
400
401           In this implementation (as in many others), the values happen to be
402           the  same  because it simplifies copying information between chtype
403           and cchar_t variables.
404
405       •   Because ncurses's attr_t can hold a  color  pair  (in  the  A_COLOR
406           field),  a  call to wattr_on, wattr_off, or wattr_set may alter the
407           window's color.  If the color pair information in the attribute pa‐
408           rameter is zero, no change is made to the window's color.
409
410           This is consistent with SVr4 curses; X/Open Curses does not specify
411           this.
412
413       The XSI standard extended conformance level adds new highlights A_HORI‐
414       ZONTAL,  A_LEFT,  A_LOW,  A_RIGHT, A_TOP, A_VERTICAL (and corresponding
415       WA_ macros for each).  As of August 2013, no  known  terminal  provides
416       these highlights (i.e., via the sgr1 capability).
417

RETURN VALUE

419       All routines return the integer OK on success, or ERR on failure.
420
421       X/Open does not define any error conditions.
422
423       This implementation
424
425       •   returns an error if the window pointer is null.
426
427       •   returns an error if the color pair parameter for wcolor_set is out‐
428           side the range 0..COLOR_PAIRS-1.
429
430       •   does not return an error if either of the parameters  of  wattr_get
431           used for retrieving attribute or color-pair values is NULL.
432
433       Functions  with  a  “mv”  prefix  first perform a cursor movement using
434       wmove, and return an error if the position is outside the window, or if
435       the window pointer is null.
436

SEE ALSO

438       curses(3X), curs_addch(3X), curs_addstr(3X), curs_bkgd(3X),
439       curs_printw(3X), curs_variables(3X)
440
441
442
443                                                                 curs_attr(3X)
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