curs_add_wch(3X)

📦 version 15.1, in freebsd 14.5, freebsd 15.1

💖 curs_add_wch 💖

okay bestie, welcome to the Library calls section of the manual (that's the 3X part if you were wondering, iykyk). this page is literally all about dropping complex characters into your curses windows. we're talking the fancy ones — wide chars, combining chars, all of it. no cap, this is the glow-up version of addch 🌈

✨ NAME ✨

add_wch, wadd_wch, mvadd_wch, mvwadd_wch, echo_wchar, wecho_wchar — add a curses complex character to a window, possibly advancing the cursor

so yeah. six functions, one mission: put a cchar_t on the screen and maybe scoot the cursor forward after. the "possibly" is doing a lot of heavy lifting there and we will get into it, bestie 💅

🦋 SYNOPSIS 🦋

first things first, you gotta pull in the header. she's iconic, she's necessary:

#include <curses.h>

🌸 the actual character-dropping functions

these four are the "just put it there" girlies:

int add_wch(const cchar_t * wch);
int wadd_wch(WINDOW * win, const cchar_t * wch);
int mvadd_wch(int y, int x, const cchar_t * wch);
int mvwadd_wch(WINDOW * win, int y, int x, const cchar_t * wch);

and these two are the "put it there and remember it so a later refresh redraws it" girlies:

int echo_wchar(const cchar_t * wch);
int wecho_wchar(WINDOW * win, const cchar_t *wch);

(yes, wecho_wchar really is written const cchar_t *wch with no space in the original, we do not fix her, she is perfect as she is 🫶)

🎀 the `WACS_*` constants, aka the line-drawing squad

these are (integer) constants and there are a lot of them. they're the classic box-drawing / symbol crew. buckle up bestie:

/* (integer) constants */
/* ... */ WACS_BLOCK;
/* ... */ WACS_BOARD;
/* ... */ WACS_BTEE;
/* ... */ WACS_BULLET;
/* ... */ WACS_CKBOARD;
/* ... */ WACS_DARROW;
/* ... */ WACS_DEGREE;
/* ... */ WACS_DIAMOND;
/* ... */ WACS_HLINE;
/* ... */ WACS_LANTERN;
/* ... */ WACS_LARROW;
/* ... */ WACS_LLCORNER;
/* ... */ WACS_LRCORNER;
/* ... */ WACS_LTEE;
/* ... */ WACS_PLMINUS;
/* ... */ WACS_PLUS;
/* ... */ WACS_RARROW;
/* ... */ WACS_RTEE;
/* ... */ WACS_S1;
/* ... */ WACS_S9;
/* ... */ WACS_TTEE;
/* ... */ WACS_UARROW;
/* ... */ WACS_ULCORNER;
/* ... */ WACS_URCORNER;
/* ... */ WACS_VLINE;

🧚 extensions

the bonus round. the DLC. the "we added more because we could" era:

/* extensions */
/* ... */ WACS_GEQUAL;
/* ... */ WACS_LEQUAL;
/* ... */ WACS_NEQUAL;
/* ... */ WACS_PI;
/* ... */ WACS_S3;
/* ... */ WACS_S7;
/* ... */ WACS_STERLING;

🔥 extensions for thick lines

thicc. bold. unbothered. these ones:

/* extensions for thick lines */
/* ... */ WACS_T_BTEE;
/* ... */ WACS_T_HLINE;
/* ... */ WACS_T_LLCORNER;
/* ... */ WACS_T_LRCORNER;
/* ... */ WACS_T_LTEE;
/* ... */ WACS_T_PLUS;
/* ... */ WACS_T_RTEE;
/* ... */ WACS_T_TTEE;
/* ... */ WACS_T_ULCORNER;
/* ... */ WACS_T_URCORNER;
/* ... */ WACS_T_VLINE;

💜 extensions for double lines

and the doubled-up divas, because sometimes one line is just not the moment:

/* extensions for double lines */
/* ... */ WACS_D_BTEE;
/* ... */ WACS_D_HLINE;
/* ... */ WACS_D_LLCORNER;
/* ... */ WACS_D_LRCORNER;
/* ... */ WACS_D_LTEE;
/* ... */ WACS_D_PLUS;
/* ... */ WACS_D_RTEE;
/* ... */ WACS_D_TTEE;
/* ... */ WACS_D_ULCORNER;
/* ... */ WACS_D_URCORNER;
/* ... */ WACS_D_VLINE;

okay so that's the cast of characters, literally ✨ we are not done though — this page keeps going, so don't you dare close the tab 🫶

💖 DESCRIPTION 💖

✨ wadd_wch ✨

Okay bestie, listen. wadd_wch writes the curses complex character wch to the window win, and then it may advance the cursor position — exactly analogously to how the standard C library's putwchar(3) does it. ncurses(3X) is the place to go for the whole family of variants, iykyk.

You build a curses complex character from a wchar_t using setcchar(3X). And a cchar_t can be copied from place to place using win_wch(3X) and wadd_wch — cute little copy-paste situation. curses defines constants to help you manipulate character attributes; peep curs_attr(3X). Also super important: a complex character whose only character component is a wide space, and whose only attribute is WA_NORMAL, counts as a blank character — which means it combines with the window's background character. See curs_bkgrnd(3X) for that whole vibe. 🌸

A lot of the behavior depends on whether the wide characters in wch are spacing or non-spacing. Head down to the “Complex Characters” subsection below for the full tea. ☕

If wch contains a spacing character, then any character sitting at the cursor gets removed first. The complex character wch, along with its attributes and color pair identifier, becomes the base of the active complex character.
If wch contains only non-spacing characters, they get combined with the active complex character. curses ignores its attributes and color pair identifier, and does not advance the cursor.

Further non-spacing characters you add with wadd_wch are not written at the new cursor position — nope — they combine with the active complex character instead, and they keep doing that until another spacing character is written to the window or the cursor is moved. 👑

If wch is a backspace, carriage return, line feed, or tab, the cursor moves appropriately within the window:

Backspace moves the cursor one character left; at the left margin of a window, it does literally nothing. 🙈
Carriage return moves the cursor to the left margin on the same line of the window.
Line feed does a clrtoeol(3X), then advances as if from the right margin.
Tab advances the cursor to the next tab stop (possibly on the next line); these are placed at every eighth column by default.

You can alter the tab interval with the TABSIZE extension; see curs_variables(3X).

If wch is any other nonprintable character, curses draws it in printable form using the same convention as wunctrl(3X). And heads up: calling win_wch(3X) on the location of a nonprintable character does not retrieve the character itself — it gives you its wunctrl(3X) representation instead. Plot twist. 😭

Adding spacing characters with wadd_wch causes it to wrap at the right margin of the window:

If the cursor is not at the bottom of the scrolling region and advancement occurs at the right margin, the cursor automatically wraps to the beginning of the next line. ✨
If the cursor is at the bottom of the scrolling region when advancement occurs at the right margin, and scrollok(3X) is enabled for win, the scrolling region scrolls up one line and the cursor wraps as above. Otherwise, advancement and scrolling do not occur, and wadd_wch returns ERR. 💀

A window's margins may coincide with the screen boundaries. This can be a whole problem when ncurses updates the screen to match the curses window. When their right and bottom margins coincide, ncurses uses different strategies to handle the variations of scrolling and wrapping at the lower-right corner, and which one it picks depends on the terminal capabilities:

If the terminal does not automatically wrap as characters are added at the right margin (i.e., auto right margins), ncurses writes the character directly.
If the terminal has auto right margins, but also has capabilities for turning auto margins off and on, ncurses turns the auto margin feature off temporarily when writing to the lower-right corner.
If the terminal has an insertion mode which can be turned off and on, ncurses writes the character just before the lower-right corner, and then inserts a character to push the update into the corner.

🎀 wecho_wchar 🎀

echo_wchar and wecho_wchar are equivalent to calling (w)add_wch followed by (w)refresh on stdscr or the specified window. curses interprets these functions as a hint that only a single (complex) character is being output — and for non-control characters, a considerable performance gain may be enjoyed by employing them. So like… free speed, bestie, take it. 🔥

🌈 Forms-Drawing Characters 🌈

curses defines macros starting with WACS_ that can be used with wadd_wch to write line-drawing and other symbols to the screen. ncurses calls these forms-drawing characters. ✨

curses uses the ACS default listed below if any of these things happen:

the terminal type lacks the acs_chars (acsc) capability;
that capability does not define a replacement for the character; or
the terminal type and locale configuration require Unicode to access these characters, but the library is unable to use Unicode.

The “acsc char” column corresponds to how the characters are specified in the acs_chars (acsc) string capability — and those characters in it may appear on the screen if the terminal type's database entry incorrectly advertises ACS support. 🙈 The name “ACS” originates in the Alternate Character Set feature of the DEC VT100 terminal. History class but make it terminal.

For each symbol below I'm giving you the Unicode Default, the ACS Default, the acsc char, and the Glyph Name, in that order:

WACS_BLOCK — U+25ae, #, 0 — solid square block
WACS_BOARD — U+2592, #, h — board of squares
WACS_BTEE — U+2534, +, v — bottom tee
WACS_BULLET — U+00b7, o, ~ — bullet
WACS_CKBOARD — U+2592, :, a — checker board (stipple)
WACS_DARROW — U+2193, v, . — arrow pointing down
WACS_DEGREE — U+00b0, ', f — degree symbol
WACS_DIAMOND — U+25c6, +, ` — diamond
WACS_GEQUAL — U+2265, >, > — greater-than-or-equal-to
WACS_HLINE — U+2500, -, q — horizontal line
WACS_LANTERN — U+2603, #, i — lantern symbol
WACS_LARROW — U+2190, <, , — arrow pointing left
WACS_LEQUAL — U+2264, <, y — less-than-or-equal-to
WACS_LLCORNER — U+2514, +, m — lower left-hand corner
WACS_LRCORNER — U+2518, +, j — lower right-hand corner
WACS_LTEE — U+2524, +, t — left tee
WACS_NEQUAL — U+2260, !, | — not-equal
WACS_PI — U+03c0, *, { — greek pi
WACS_PLMINUS — U+00b1, #, g — plus/minus
WACS_PLUS — U+253c, +, n — plus
WACS_RARROW — U+2192, >, + — arrow pointing right
WACS_RTEE — U+251c, +, u — right tee
WACS_S1 — U+23ba, -, o — scan line 1
WACS_S3 — U+23bb, -, p — scan line 3
WACS_S7 — U+23bc, -, r — scan line 7
WACS_S9 — U+23bd, _, s — scan line 9
WACS_STERLING — U+00a3, f, } — pound-sterling symbol
WACS_TTEE — U+252c, +, w — top tee
WACS_UARROW — U+2191, ^, - — arrow pointing up
WACS_ULCORNER — U+250c, +, l — upper left-hand corner
WACS_URCORNER — U+2510, +, k — upper right-hand corner
WACS_VLINE — U+2502, |, x — vertical line

The ncurses wide API also defines symbols for thick lines (acsc “J” through “N”, “T” through “X”, and “Q”):

Here the columns are Unicode Default, ASCII Default, acsc Char, Glyph Name:

WACS_T_BTEE — U+253b, +, V — thick tee pointing up
WACS_T_HLINE — U+2501, -, Q — thick horizontal line
WACS_T_LLCORNER — U+2517, +, M — thick lower left corner
WACS_T_LRCORNER — U+251b, +, J — thick lower right corner
WACS_T_LTEE — U+252b, +, T — thick tee pointing right
WACS_T_PLUS — U+254b, +, N — thick large plus
WACS_T_RTEE — U+2523, +, U — thick tee pointing left
WACS_T_TTEE — U+2533, +, W — thick tee pointing down
WACS_T_ULCORNER — U+250f, +, L — thick upper left corner
WACS_T_URCORNER — U+2513, +, K — thick upper right corner
WACS_T_VLINE — U+2503, |, X — thick vertical line

…and for double lines (acsc “A” through “I”, plus “R” and “Y”):

Same columns again — Unicode Default, ASCII Default, acsc Char, Glyph Name:

WACS_D_BTEE — U+2569, +, H — double tee pointing up
WACS_D_HLINE — U+2550, -, R — double horizontal line
WACS_D_LLCORNER — U+255a, +, D — double lower left corner
WACS_D_LRCORNER — U+255d, +, A — double lower right corner
WACS_D_LTEE — U+2560, +, F — double tee pointing right
WACS_D_PLUS — U+256c, +, E — double large plus
WACS_D_RTEE — U+2563, +, G — double tee pointing left
WACS_D_TTEE — U+2566, +, I — double tee pointing down
WACS_D_ULCORNER — U+2554, +, C — double upper left corner
WACS_D_URCORNER — U+2557, +, B — double upper right corner
WACS_D_VLINE — U+2551, |, Y — double vertical line

Unicode's descriptions for these characters differ slightly from ncurses — they introduce the term “light” (along with some less important details). Here are its descriptions for the normal, thick, and double horizontal lines:

U+2500 BOX DRAWINGS LIGHT HORIZONTAL
U+2501 BOX DRAWINGS HEAVY HORIZONTAL
U+2550 BOX DRAWINGS DOUBLE HORIZONTAL

⭐ RETURN VALUE ⭐

These functions return OK on success and ERR on failure. Simple as that, no cap. 💅

In ncurses, these functions fail if:

the curses screen has not been initialized,
(for functions taking a WINDOW pointer argument) win is a null pointer,
wrapping to a new line is impossible because scrollok(3X) has not been called on win (or stdscr, as applicable) when writing to its bottom right location is attempted, or
it is not possible to add a complete character at the cursor position.

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

💜 NOTES 💜

add_wch, mvadd_wch, mvwadd_wch, and echo_wchar may be implemented as macros. 👀

✨ EXTENSIONS ✨

Okay so these symbols — WACS_S3, WACS_S7, WACS_LEQUAL, WACS_GEQUAL, WACS_PI, WACS_NEQUAL, and WACS_STERLING — are not standard, bestie. Like, not even a little.

But here's the tea 🍵: tons of publicly available terminfo entries ship acs_chars (acsc) capabilities, and their key characters (pryz{|}) are embedded right up in there. A second-hand list of their character descriptions has come to light, and the ncurses devs were like "we're inventing WACS-prefixed names for these, periodt." 💅

🌍 PORTABILITY 🌍

If your app is out here using ncurses extensions, you should condition that use on whether the NCURSES_VERSION preprocessor macro is visible. No cap.

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

The defaults specified for forms-drawing characters apply in the POSIX locale. X/Open Curses makes it clear that the WACS_ symbols should be defined as a pointer to cchar_t data, e.g., in the discussion of border_set. But a few implementations are being messy 🙈:

NetBSD curses defines the symbols as a wchar_t within a cchar_t.
HP-UX curses equates some of the ACS_ symbols to the analogous WACS_ symbols as if the ACS_ symbols were wide characters. The misdefined symbols are the arrows and other symbols which are not used for line-drawing.

X/Open Curses does not specify symbols for thick- or double-lines. SVr4 curses implementations defined their line-drawing symbols in terms of intermediate symbols. ncurses extends those symbols, providing new definitions not found in SVr4 implementations.

Not all Unicode-capable terminals provide support for VT100-style alternate character sets (i.e., the acsc_chars (acsc) capability), with their corresponding line-drawing characters. X/Open Curses did not address the aspect of integrating Unicode with line-drawing characters. Existing implementations of System V curses (AIX, HP-UX, Solaris) use only the acsc_chars (acsc) character-mapping to provide this feature. As a result, those implementations can use only single-byte line-drawing characters. ncurses 5.3 (2002) provided a table of Unicode values to solve these problems. NetBSD curses incorporated that table in 2010. 🫶

ncurses uses the Unicode values instead of the terminal type description's acsc_chars (acsc) mapping as discussed in ncurses(3X) for the environment variable NCURSES_NO_UTF8_ACS. In contrast, for the same cases, the line-drawing characters described in addch(3X) will use only the ASCII default values. Yeah. It's giving inconsistent, but that's the lore. 💀

Having Unicode available does not solve all of the problems with line-drawing for curses:

The closest Unicode equivalents to the VT100 graphics S1, S3, S7, and S9 frequently are not displayed at the regular intervals which the terminal used.
The lantern is a special case. It originated with the AT&T 4410 terminal in the early 1980s. There is no accessible documentation depicting the lantern symbol on the AT&T terminal.

Lacking documentation, most readers assume that a storm lantern was intended. But there are several possibilities, all with problems. 😭

Unicode 6.0 (2010) does provide two lantern symbols: U+1F383 and U+1F3EE. Those were not available in 2002, and are irrelevant since they lie outside the Basic Multilingual Plane and as a result are unavailable on many terminals. They are not storm lanterns, in any case.

Most storm lanterns have a tapering glass chimney (to guard against tipping); some have a wire grid protecting the chimney.

For the tapering appearance, ☃ U+2603 was adequate. In use on a terminal, no one can tell what the image represents. Unicode calls it a snowman. ⛄ iconic behavior honestly

Others have suggested these alternatives: § U+00A7 (section mark), Θ U+0398 (theta), Φ U+03A6 (phi), δ U+03B4 (delta), ⌧ U+2327 (x in a rectangle), ╬ U+256C (forms double vertical and horizontal), and ☒ U+2612 (ballot box with x).

🦋 Complex Characters 🦋

The complex character type cchar_t can store more than one wide character (wchar_t). X/Open Curses does not mention this possibility, specifying behavior only where wch is a single character, either spacing or non-spacing.

ncurses assumes that wch is constructed using setcchar(3X), and in turn that the result

contains at most one spacing character at the beginning of its list of wide characters, and zero or more non-spacing characters, or
holds one non-spacing character.

In the latter case, ncurses adds the non-spacing character to the active complex character. Slay. ✨

📜 HISTORY 📜

X/Open Curses Issue 4 (1995) initially specified these functions. The System V Interface Definition (SVID) Version 4 of the same year specified functions named waddwch (and the usual variants), echowchar, and wechowchar. These were later additions to SVr4.x, not appearing in the first SVr4 (1989). They differed from X/Open's later wadd_wch and wecho_wchar in that they each took an argument of type wchar_t instead of cchar_t. SVID defined no WACS_ symbols. 💀

X/Open Curses Issue 4 also defined many of the WACS_ constants, excepting WACS_GEQUAL, WACS_LEQUAL, WACS_NEQUAL, WACS_PI, WACS_S3, WACS_S7, and WACS_STERLING; and those for drawing thick and double lines.

ncurses 5.3 (2002) furnished the remaining WACS_ constants. And that's the origin story bestie, we ate. 👑

👀 SEE ALSO 👀

curs_addch(3X) describes comparable functions of the ncurses library in its non-wide-character configuration.

Also go read these, they're all linked in the group chat:

curses(3X)
curs_addwstr(3X)
curs_add_wchstr(3X)
curs_attr(3X)
curs_bkgrnd(3X)
curs_clear(3X)
curs_getcchar(3X)
curs_outopts(3X)
curs_refresh(3X)
curs_variables(3X)
putwc(3)

That's the whole page, bestie! This one's from ncurses 6.6, dated 2025-11-11, and it lives at curs_add_wch(3X) — go forth and draw some lines, you've got this. 🎀💖✨

📦 where this page comes from

freebsd 14.5: base 14.5
freebsd 15.1: base 15.1
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on 2026-10-14: a language model's rewrite of the original, under its terms