curs_add_wch(3x) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | PORTABILITY | SEE ALSO | COLOPHON

curs_add_wch(3X)                                        curs_add_wch(3X)

NAME         top

       add_wch, wadd_wch, mvadd_wch, mvwadd_wch, echo_wchar, wecho_wchar
       - add a complex character and rendition to a curses window, then
       advance the cursor

SYNOPSIS         top

       #include <curses.h>

       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 );

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

DESCRIPTION         top

   add_wch
       The add_wch, wadd_wch, mvadd_wch, and mvwadd_wch functions put
       the complex character wch into the given window at its current
       position, which is then advanced.  These functions perform
       wrapping and special-character processing as follows:

       •   If wch refers to a spacing character, then any previous
           character at that location is removed.  A new character
           specified by wch is placed at that location with rendition
           specified by wch.  The cursor then advances to the next
           spacing character on the screen.

       •   If wch refers to a non-spacing character, all previous
           characters at that location are preserved.  The non-spacing
           characters of wch are added to the spacing complex character,
           and the rendition specified by wch is ignored.

       •   If the character part of wch is a tab, newline, backspace or
           other control character, the window is updated and the cursor
           moves as if addch were called.

   echo_wchar
       The echo_wchar function is functionally equivalent to a call to
       add_wch followed by a call to refresh(3X).  Similarly, the
       wecho_wchar is functionally equivalent to a call to wadd_wch
       followed by a call to wrefresh.  The knowledge that only a single
       character is being output is taken into consideration and, for
       non-control characters, a considerable performance gain might be
       seen by using the *echo* functions instead of their equivalents.

   Line Graphics
       Like addch(3X), addch_wch accepts symbols which make it simple to
       draw lines and other frequently used special characters.  These
       symbols correspond to the same VT100 line-drawing set as
       addch(3X).

       ACS               Unicode    ASCII     acsc    Glyph
       Name              Default    Default   char    Name
       ────────────────────────────────────────────────────────────────────────
       WACS_BLOCK        0x25ae     #         0       solid square block
       WACS_BOARD        0x2592     #         h       board of squares
       WACS_BTEE         0x2534     +         v       bottom tee
       WACS_BULLET       0x00b7     o         ~       bullet
       WACS_CKBOARD      0x2592     :         a       checker board (stipple)

       WACS_DARROW       0x2193     v         .       arrow pointing down
       WACS_DEGREE       0x00b0     '         f       degree symbol
       WACS_DIAMOND      0x25c6     +         `       diamond
       WACS_GEQUAL       0x2265     >         >       greater-than-or-equal-to
       WACS_HLINE        0x2500     -         q       horizontal line
       WACS_LANTERN      0x2603     #         i       lantern symbol
       WACS_LARROW       0x2190     <         ,       arrow pointing left
       WACS_LEQUAL       0x2264     <         y       less-than-or-equal-to
       WACS_LLCORNER     0x2514     +         m       lower left-hand corner
       WACS_LRCORNER     0x2518     +         j       lower right-hand corner
       WACS_LTEE         0x2524     +         t       left tee
       WACS_NEQUAL       0x2260     !         |       not-equal
       WACS_PI           0x03c0     *         {       greek pi
       WACS_PLMINUS      0x00b1     #         g       plus/minus
       WACS_PLUS         0x253c     +         n       plus
       WACS_RARROW       0x2192     >         +       arrow pointing right
       WACS_RTEE         0x251c     +         u       right tee
       WACS_S1           0x23ba     -         o       scan line 1
       WACS_S3           0x23bb     -         p       scan line 3
       WACS_S7           0x23bc     -         r       scan line 7
       WACS_S9           0x23bd     _         s       scan line 9
       WACS_STERLING     0x00a3     f         }       pound-sterling symbol
       WACS_TTEE         0x252c     +         w       top tee
       WACS_UARROW       0x2191     ^         -       arrow pointing up
       WACS_ULCORNER     0x250c     +         l       upper left-hand corner
       WACS_URCORNER     0x2510     +         k       upper right-hand corner
       WACS_VLINE        0x2502     |         x       vertical line

       The wide-character configuration of ncurses also defines symbols
       for thick lines (acsc “J” to “V”):

       ACS               Unicode   ASCII     acsc    Glyph
       Name              Default   Default   char    Name
       ───────────────────────────────────────────────────────────────────────
       WACS_T_BTEE       0x253b    +         V       thick tee pointing up
       WACS_T_HLINE      0x2501    -         Q       thick horizontal line
       WACS_T_LLCORNER   0x2517    +         M       thick lower left corner
       WACS_T_LRCORNER   0x251b    +         J       thick lower right corner
       WACS_T_LTEE       0x252b    +         T       thick tee pointing right
       WACS_T_PLUS       0x254b    +         N       thick large plus
       WACS_T_RTEE       0x2523    +         U       thick tee pointing left
       WACS_T_TTEE       0x2533    +         W       thick tee pointing down
       WACS_T_ULCORNER   0x250f    +         L       thick upper left corner
       WACS_T_URCORNER   0x2513    +         K       thick upper right corner
       WACS_T_VLINE      0x2503    |         X       thick vertical line

       and for double-lines (acsc “A” to “I”):

       ACS               Unicode   ASCII     acsc    Glyph
       Name              Default   Default   char    Name
       ────────────────────────────────────────────────────────────────────────
       WACS_D_BTEE       0x2569    +         H       double tee pointing up
       WACS_D_HLINE      0x2550    -         R       double horizontal line
       WACS_D_LLCORNER   0x255a    +         D       double lower left corner
       WACS_D_LRCORNER   0x255d    +         A       double lower right corner
       WACS_D_LTEE       0x2560    +         F       double tee pointing right
       WACS_D_PLUS       0x256c    +         E       double large plus
       WACS_D_RTEE       0x2563    +         G       double tee pointing left
       WACS_D_TTEE       0x2566    +         I       double tee pointing down
       WACS_D_ULCORNER   0x2554    +         C       double upper left corner
       WACS_D_URCORNER   0x2557    +         B       double upper right corner
       WACS_D_VLINE      0x2551    |         Y       double vertical line

       Unicode's descriptions for these characters differs slightly from
       ncurses, by introducing the term “light” (along with 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         top

       All routines return the integer ERR upon failure and OK on
       success.

       X/Open does not define any error conditions.  This implementation
       returns an error

       •   if the window pointer is null or

       •   if it is not possible to add a complete character in the
           window.

       The latter may be due to different causes:

       •   If scrollok is not enabled, writing a character at the lower
           right margin succeeds.  However, an error is returned because
           it is not possible to wrap to a new line

       •   If an error is detected when converting a multibyte character
           to a sequence of bytes, or if it is not possible to add all
           of the resulting bytes in the window, an error is returned.

       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.

NOTES         top

       Note that add_wch, mvadd_wch, mvwadd_wch, and echo_wchar may be
       macros.

PORTABILITY         top

       All of these functions are described in the XSI Curses standard,
       Issue 4.  The defaults specified for line-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.  A few implementations are problematic:

       •   NetBSD curses defines the symbols as a wchar_t within a
           cchar_t.

       •   HPUX 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 define symbols for thick- or double-lines.
       SVr4 curses implementations defined their line-drawing symbols in
       terms of intermediate symbols.  This implementation extends those
       symbols, providing new definitions which are not in the SVr4
       implementations.

       Not all Unicode-capable terminals provide support for VT100-style
       alternate character sets (i.e., the 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 Unix curses (AIX, HPUX,
       Solaris) use only the acsc character-mapping to provide this
       feature.  As a result, those implementations can only use 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.

       In this implementation, the Unicode values are used instead of
       the terminal description's 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 curs_addch(3X) will use only the ASCII default
       values.

       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 BMP and as a result are
           not generally available in 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.

           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).

SEE ALSO         top

       curses(3X), curs_addch(3X), curs_attr(3X), curs_clear(3X),
       curs_outopts(3X), curs_refresh(3X), putwc(3)

COLOPHON         top

       This page is part of the ncurses (new curses) project.
       Information about the project can be found at 
       ⟨https://www.gnu.org/software/ncurses/ncurses.html⟩.  If you have
       a bug report for this manual page, send it to
       bug-ncurses-request@gnu.org.  This page was obtained from the
       project's upstream Git mirror of the CVS repository
       ⟨git://ncurses.scripts.mit.edu/ncurses.git⟩ on 2021-08-27.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2021-05-23.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

                                                        curs_add_wch(3X)