curs_threads(3X)curs_threads(3X)NAME
use_screen, use_window - curses thread support
SYNOPSIS
#include <curses.h>
typedef int (*NCURSES_WINDOW_CB)(WINDOW *, void *); typedef int
(*NCURSES_SCREEN_CB)(SCREEN *, void *);
int set_escdelay(int size);
int set_tabsize(int size);
int use_screen(SCREEN *scr, NCURSES_WINDOW_CB func, void *data);
int use_window(WINDOW *win, NCURSES_SCREEN_CB func, void *data);
DESCRIPTION
This implementation can be configured to provide rudimentary support
for multi-threaded applications. This makes a different set of li‐
braries, e.g., libncursest since the binary interfaces are different.
Rather than modify the interfaces to pass a thread specifier to each
function, it adds a few functions which can be used in any configura‐
tion which hide the mutex's needed to prevent concurrent use of the
global variables when configured for threading.
In addition to forcing access to members of the WINDOW structure to be
via functions (see curs_opaque(3x)), it makes functions of the common
global variables, e.g., COLORS, COLOR_PAIRS, COLS, ESCDELAY, LINES,
TABSIZE curscr, newscr and ttytype. Those variables are maintained as
read-only values, stored in the SCREEN structure.
Even this is not enough to make a thread-safe application using curses.
A multi-threaded application would be expected to have threads updating
separate windows (within the same device), or updating on separate
screens (on different devices). Also, a few of the global variables
are considered writable by some applications. The functions described
here address these special situations.
The ESCDELAY and TABSIZE global variables are modified by some applica‐
tions. To modify them in any configuration, use the set_escdelay or
set_tabsize functions. Other global variables are not modifiable.
The use_window and use_screen functions provide coarse granularity mu‐
texes for their respective WINDOW and SCREEN parameters, and call a us‐
er-supplied function, passing it a data parameter, and returning the
value from the user-supplied function to the application.
USAGE
All of the ncurses library functions assume that the locale is not al‐
tered during operation. In addition, they use data which is maintained
within a hierarchy of scopes.
- global data, e.g., used in the low-level terminfo or termcap
interfaces.
- terminal data, e.g., associated with a call to set_curterm.
The terminal data are initialized when screens are created.
- screen data, e.g., associated with a call to newterm or
initscr.
- window data, e.g., associated with a call to newwin or sub‐
win. Windows are associated with screens. Pads are not nec‐
essarily associated with a particular screen.
Most curses applications operate on one or more windows with‐
in a single screen.
- reentrant, i.e., it uses only the data passed as parameters.
This table lists the scope of data used for each symbol in the ncurses
library when it is configured to support threading:
RETURN VALUE
These functions all return TRUE or FALSE, except as noted.
NOTES
Both a macro and a function are provided for each name.
PORTABILITY
These routines are specific to ncurses. They were not supported on
Version 7, BSD or System V implementations. It is recommended that any
code depending on ncurses extensions be conditioned using NCURSES_VER‐
SION.
SEE ALSOcurses(3X), curs_opaque(3X)curs_threads(3X)
