curs_attr.3x man page

attr_get, wattr_get, attr_set, wattr_set, attr_off, wattr_off, attr_on, wattr_on, attroff, wattroff, attron, wattron, attrset, wattrset, chgat, wchgat, mvchgat, mvwchgat, color_set, wcolor_set, standend, wstandend, standout, wstandoutcurses character and window attribute control routines

Synopsis

#include <curses.h>

int attr_get(attr_t *attrs, short *pair, void *opts);
int wattr_get(WINDOW *win, attr_t *attrs, short *pair, void *opts);
int attr_set(attr_t attrs, short pair, void *opts);
int wattr_set(WINDOW *win, attr_t attrs, short pair, void *opts);

int attr_off(attr_t attrs, void *opts);
int wattr_off(WINDOW *win, attr_t attrs, void *opts);
int attr_on(attr_t attrs, void *opts);
int wattr_on(WINDOW *win, attr_t attrs, void *opts);

int attroff(int attrs);
int wattroff(WINDOW *win, int attrs);
int attron(int attrs);
int wattron(WINDOW *win, int attrs);
int attrset(int attrs);
int wattrset(WINDOW *win, int attrs);

int chgat(int n, attr_t attr, short pair, const void *opts);
int wchgat(WINDOW *win,
     int n, attr_t attr, short pair, const void *opts);
int mvchgat(int y, int x,
     int n, attr_t attr, short pair, const void *opts);
int mvwchgat(WINDOW *win, int y, int x,
     int n, attr_t attr, short pair, const void *opts);

int color_set(short pair, void* opts);
int wcolor_set(WINDOW *win, short pair, void* opts);

int standend(void);
int wstandend(WINDOW *win);
int standout(void);
int wstandout(WINDOW *win);

Description

These routines manipulate the current attributes of the named window, which then apply to all characters that are written into the window with waddch, waddstr and wprintw. Attributes are a property of the character, and move with the character through any scrolling and insert/delete line/character operations. To the extent possible, they are displayed as appropriate modifications to the graphic rendition of characters put on the screen.

These routines do not affect the attributes used when erasing portions of the window. See curs_bkgd(3X) for functions which modify the attributes used for erasing and clearing.

Routines which do not have a WINDOW* parameter apply to stdscr. For example, attr_set is the stdscr variant of wattr_set.

Window attributes

There are two sets of functions:

  • functions for manipulating the window attributes and color: wattr_set and wattr_get.
  • functions for manipulating only the window attributes (not color): wattr_on and wattr_off.

The wattr_set function sets the current attributes of the given window to attrs, with color specified by pair.

Use wattr_get to retrieve attributes for the given window.

Use attr_on and wattr_on to turn on window attributes, i.e., values OR'd together in attr, without affecting other attributes. Use attr_off and wattr_off to turn off window attributes, again values OR'd together in attr, without affecting other attributes.

Legacy window attributes

Most of the window attribute routines are extensions of older routines which assume that color pairs are OR'd into the attribute parameter. These older routines use the same name, omitting an underscore (_).

The attrset routine is a legacy feature predating SVr4 curses but kept in X/Open Curses for the same reason that SVr4 curses kept it: compatibility.

The remaining attr* functions operate exactly like the corresponding attr_* functions, except that they take arguments of type int rather than attr_t.

There is no corresponding attrget function as such in X/Open Curses, although ncurses provides getattrs (see curs_legacy(3X)).

Change character rendition

The routine chgat changes the attributes of a given number of characters starting at the current cursor location of stdscr. It does not update the cursor and does not perform wrapping. A character count of -1 or greater than the remaining window width means to change attributes all the way to the end of the current line. The wchgat function generalizes this to any window; the mvwchgat function does a cursor move before acting.

In these functions, the color pair argument is a color-pair index (as in the first argument of init_pair, see curs_color(3X)).

Change window color

The routine color_set sets the current color of the given window to the foreground/background combination described by the color pair parameter.

Standout

The routine standout is the same as attron(A_STANDOUT). The routine standend is the same as attrset(A_NORMAL) or attrset(0), that is, it turns off all attributes.

X/Open does not mark these "restricted", because

  • they have well established legacy use, and
  • there is no ambiguity about the way the attributes might be combined with a color pair.

Video Attributes

The following video attributes, defined in <curses.h>, can be passed to the routines attron, attroff, and attrset, or OR'd with the characters passed to addch (see curs_addch(3X)).

Name Description
A_NORMAL Normal display (no highlight)
A_STANDOUT Best highlighting mode of the terminal.
A_UNDERLINE Underlining
A_REVERSE Reverse video
A_BLINK Blinking
A_DIM Half bright
A_BOLD Extra bright or bold
A_PROTECT Protected mode
A_INVIS Invisible or blank mode
A_ALTCHARSET Alternate character set
A_ITALIC Italics (non-X/Open extension)
A_CHARTEXT Bit-mask to extract a character

These video attributes are supported by attr_on and related functions (which also support the attributes recognized by attron, etc.):

Name Description
WA_HORIZONTAL Horizontal highlight
WA_LEFT Left highlight
WA_LOW Low highlight
WA_RIGHT Right highlight
WA_TOP Top highlight
WA_VERTICAL Vertical highlight

The return values of many of these routines are not meaningful (they are implemented as macro-expanded assignments and simply return their argument). The SVr4 manual page claims (falsely) that these routines always return 1.

Notes

These functions may be macros:

attroff, wattroff, attron, wattron, attrset, wattrset, standend and standout.

Color pair values can only be OR'd with attributes if the pair number is less than 256. The alternate functions such as color_set can pass a color pair value directly. However, ncurses ABI 4 and 5 simply OR this value within the alternate functions. You must use ncurses ABI 6 to support more than 256 color pairs.

Extensions

This implementation provides the A_ITALIC attribute for terminals which have the enter_italics_mode (sitm) and exit_italics_mode (ritm) capabilities. Italics are not mentioned in X/Open Curses. Unlike the other video attributes, A_ITALIC is unrelated to the set_attributes capabilities. This implementation makes the assumption that exit_attribute_mode may also reset italics.

Each of the functions added by XSI Curses has a parameter opts, which X/Open Curses still (after more than twenty years) documents as reserved for future use, saying that it should be NULL. This implementation uses that parameter in ABI 6 for the functions which have a color-pair parameter to support extended color pairs:

The remaining functions which have opts, but do not manipulate color, e.g., wattr_on and wattr_off are not used by this implementation except to check that they are NULL.

Portability

These functions are supported in the XSI Curses standard, Issue 4. The standard defined the dedicated type for highlights, attr_t, which was not defined in SVr4 curses. The functions taking attr_t arguments were not supported under SVr4.

Very old versions of this library did not force an update of the screen when changing the attributes. Use touchwin to force the screen to match the updated attributes.

The XSI Curses standard states that whether the traditional functions attron/attroff/attrset can manipulate attributes other than A_BLINK, A_BOLD, A_DIM, A_REVERSE, A_STANDOUT, or A_UNDERLINE is "unspecified". Under this implementation as well as SVr4 curses, these functions correctly manipulate all other highlights (specifically, A_ALTCHARSET, A_PROTECT, and A_INVIS).

XSI Curses added these entry points:

attr_get, attr_on, attr_off, attr_set, wattr_on, wattr_off, wattr_get, wattr_set

The new functions are intended to work with a new series of highlight macros prefixed with WA_. The older macros have direct counterparts in the newer set of names:

Name Description
WA_NORMAL Normal display (no highlight)
WA_STANDOUT Best highlighting mode of the terminal.
WA_UNDERLINE Underlining
WA_REVERSE Reverse video
WA_BLINK Blinking
WA_DIM Half bright
WA_BOLD Extra bright or bold
WA_ALTCHARSET Alternate character set

The XSI curses standard specifies that each pair of corresponding A_ and WA_-using functions operates on the same current-highlight information.

The XSI standard extended conformance level adds new highlights A_HORIZONTAL, A_LEFT, A_LOW, A_RIGHT, A_TOP, A_VERTICAL (and corresponding WA_ macros for each). As of August 2013, no known terminal provides these highlights (i.e., via the sgr1 capability).

Return Value

All routines return the integer OK on success, or ERR on failure.

X/Open does not define any error conditions.

This implementation

Functions with a "mv" prefix first perform a cursor movement using wmove, and return an error if the position is outside the window, or if the window pointer is null.

See Also

curses(3X), curs_addch(3X), curs_addstr(3X), curs_bkgd(3X), curs_printw(3X), curs_variables(3X)