touch(3NCURSES) Library calls touch(3NCURSES)
NAME
touchwin, touchline, untouchwin, wtouchln, is_linetouched, is_wintouched
- control terminal output refresh in a curses window
SYNOPSIS
#include <curses.h>
int touchline(WINDOW *win, int start, int count);
int touchwin(WINDOW *win);
int wtouchln(WINDOW *win, int y, int n, int changed);
int untouchwin(WINDOW *win);
bool is_linetouched(WINDOW *win, int line);
bool is_wintouched(WINDOW *win);
DESCRIPTION
The touchwin and touchline routines throw away all optimization informa-
tion about which parts of the window have been touched, by pretending
that the entire window has been drawn on. This is sometimes necessary
when using overlapping windows, since a change to one window affects the
other window, but the records of which lines have been changed in the
other window do not reflect the change. The routine touchline only pre-
tends that count lines have been changed, beginning with line start.
The untouchwin routine marks all lines in the window as unchanged since
the last call to wrefresh.
The wtouchln routine makes n lines in the window, starting at line y,
look as if they have (changed=1) or have not (changed=0) been changed
since the last call to wrefresh.
The is_linetouched and is_wintouched routines return TRUE if the speci-
fied line/window was modified since the last call to wrefresh; otherwise
they return FALSE. In addition, is_linetouched returns ERR if line is
not valid for the given window.
RETURN VALUE
Functions returning integers return ERR upon failure and OK upon suc-
cess.
In ncurses,
is_linetouched
returns ERR if the window pointer is null, or if the line number
is outside the window boundaries.
The constant ERR is distinct from TRUE and FALSE, which are the
normal return values of this function. Because the function re-
turns a bool, returning ERR (which is neither TRUE nor FALSE)
may not be supported by the compiler.
To provide error-checking and also match the X/Open function
prototype, the ERR is provided by a macro named is_linetouched.
The actual function returns FALSE when it detects an error.
wtouchln
returns ERR if the window pointer is null, or if the line number
is outside the window boundaries.
NOTES
All of these functions except wtouchln may be implemented as macros.
PORTABILITY
X/Open Curses Issue 4 describes these functions. It specifies no error
conditions for them.
SVr4 describes a successful return value except where “otherwise noted”
as “an integer value other than ERR”.
SVr4 does not check win to ensure that it is not a null pointer.
HISTORY
SVr2 (1984) introduced touchwin,
SVr3 (1987) added touchline. SVr3.1 later that year supplied
is_linetouched, is_wintouched, untouchwin, and wtouchln.
SEE ALSO
ncurses(3NCURSES), refresh(3NCURSES), curses_variables(3NCURSES)
ncurses 6.5 2025-01-18 touch(3NCURSES)
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