attroff3ncurses

Usage

Overview

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 bkgd(3NCURSES) for functions which modify the attributes used for erasing and clearing.

attrset(A_BOLD | COLOR_PAIR(pair));
attr_set(A_BOLD, pair, NULL);

int value = A_BOLD | COLOR_PAIR(input);
int output = PAIR_NUMBER(value);

Return value

These functions return OK on success and ERR on failure.

In ncurses, they return ERR if win is NULL.

wcolor_set returns ERR if pair is outside the range 0..COLOR_PAIRS-1.

wattr_get does not fail if its attrs or pair parameter is NULL.

Functions prefixed with “mv” first perform cursor movement and fail if the position (y, x) is outside the window boundaries.

Notes

attr_on, attr_off, attr_set, wattr_set, chgat, mvchgat, mvwchgat, wchgat, and color_set are part of ncurses's wide-character API, and are not available in its non-wide configuration.

attron, wattron, attroff, wattroff, attrset, wattrset, standout, and standend may be implemented as macros.

Color pair values may be logically “or”-ed 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 logically “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:

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For functions which modify the color, e.g., wattr_set and wattr_on, if opts is set it is treated as a pointer to int, and used to set the color pair instead of the short pair parameter.

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For functions which retrieve the color, e.g., wattr_get, if opts is set it is treated as a pointer to int, and used to retrieve the color pair as an int value, in addition to retrieving it via the standard pointer to short parameter.

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For functions which turn attributes off, e.g., wattr_off, the opts parameter is ignored except to check that it is NULL.

Portability

These functions are described in X/Open Curses Issue 4. It specifies no error conditions for them.

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.

SVr4 describes the functions not taking attr_t or pair arguments as always returning 1.

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.

X/Open Curses 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).

X/Open Curses added these entry points:

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:

X/Open Curses does not assign values to these symbols, nor does it state whether or not they are related to the similarly-named A_NORMAL, etc.:

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X/Open Curses specifies that each pair of corresponding A_ and WA_-using functions operates on the same current-highlight information.

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However, in some implementations, those symbols have unrelated values.

For example, the Solaris xpg4 (X/Open) curses declares attr_t to be an unsigned short integer (16-bits), while chtype is a unsigned integer (32-bits). The WA_ symbols in this case are different from the A_ symbols because they are used for a smaller datatype which does not represent A_CHARTEXT or A_COLOR.

In this implementation (as in many others), the values happen to be the same because it simplifies copying information between chtype and cchar_t variables.

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Because ncurses's attr_t can hold a color pair (in the A_COLOR field), a call to wattr_on, wattr_off, or wattr_set may alter the window's color. If the color pair information in the attribute parameter is zero, no change is made to the window's color.

This is consistent with SVr4 curses; X/Open Curses does not specify this.

The X/Open Curses 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).