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$Id: curs_inch.3x,v 1.70 2025/02/15 19:36:03 tom Exp $
.\} .\} . .. \%inch, \%winch, \%mvinch, \%mvwinch - get a curses character from a window

#include <curses.h>

chtype inch(void);
chtype winch(WINDOW * win);
chtype mvinch(int y, int x);
chtype mvwinch(WINDOW * win, int y, int x);

\%winch returns the curses character, including its attributes and color pair identifier, at the cursor position in the window win "." Subsection \*(``Video Attributes\*('' of \%attron(3X) explains how to extract these data from a chtype "." \%ncurses(3X) describes the variants of this function. These functions return OK on success and ERR on failure.

In \%ncurses "," they return ERR if win is NULL "."

Functions prefixed with \*(``mv\*('' first perform cursor movement and fail if the position ( y , x ) is outside the window boundaries.

\%inch , \%mvinch , and \%mvwinch may be implemented as macros.

These functions do not fail if the window contains cells of curses complex characters; that is, if they contain characters with codes wider than eight bits (or greater than 255 as an unsigned decimal integer). They instead extract only the low-order eight bits of the character code from the cell.

X/Open Curses Issue 4 describes these functions. It specifies no error conditions for them. The original curses in 4BSD (1980) defined \%winch as a macro accessing the \%WINDOW structure member representing character cell data, at that time a char "," containing only a 7-bit ASCII character code and a \*(``standout\*(`` attribute bit, the only one the library supported.

SVr2 curses (1984) extended this approach, widening the character code to eight bits and permitting several attributes to be combined with it by storing them together in a \%chtype "," an alias of "unsigned short" "." ...indirectly through a preprocessor macro named CHTYPE, encouraging
builders to change the typedef to `char` or `long` as desired. More
innocent times with respect to ABI compatibility concerns... --GBR
Because a macro was used, its value was not type-checked as a function return value could have been. Goodheart documented SVr3 (1987) \%winch as returning an int "." ...but the implementation remained unchanged.
SVr3.1's (1987) \%chtype became an alias of "unsigned long" "," using 16 bits for the character code and widening the type in practical terms to 32 bits, as 64-bit Unix systems were not yet in wide use, and fixed-width integral types would not be standard until ISO C99. Cray's UNICOS was 1985 (how many shops had Crays?). DEC OSF/1 for
the Alpha arrived in 1993. --GBR
SVr3.2 (1988) added a 6-bit color pair identifier alongside the attributes.

\%curs_in_wch(3X) describes comparable functions of the \%ncurses library in its wide-character configuration \%( ncursesw ).

\%curses(3X), \%curs_instr(3X)