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.\" $Id: curs_kernel.3x,v 1.61 2024/04/20 21:24:19 tom Exp $
.TH curs_kernel 3X 2024-04-20 "ncurses 6.5" "Library calls"
.ie \n(.g \{\
.ds `` \(lq
.ds '' \(rq
.\}
.el \{\
.ie t .ds `` ``
.el   .ds `` ""
.ie t .ds '' ''
.el   .ds '' ""
.\}
.
.de bP
.ie n  .IP \(bu 4
.el    .IP \(bu 2
..
.SH NAME
\fB\%def_prog_mode\fP,
\fB\%def_shell_mode\fP,
\fB\%reset_prog_mode\fP,
\fB\%reset_shell_mode\fP,
\fB\%resetty\fP,
\fB\%savetty\fP,
\fB\%getsyx\fP,
\fB\%setsyx\fP,
\fB\%ripoffline\fP,
\fB\%curs_set\fP,
\fB\%napms\fP \-
low-level \fIcurses\fR routines
.SH SYNOPSIS
.nf
\fB#include <curses.h>
.PP
\fBint def_prog_mode(void);
\fBint def_shell_mode(void);
.PP
\fBint reset_prog_mode(void);
\fBint reset_shell_mode(void);
.PP
\fBint resetty(void);
\fBint savetty(void);
.PP
\fBvoid getsyx(int \fIy\fP, int \fIx\fP);
\fBvoid setsyx(int \fIy\fP, int \fIx\fP);
.PP
\fBint ripoffline(int \fIline\fP, int (*\fIinit\fP)(WINDOW *, int));
\fBint curs_set(int \fIvisibility\fP);
\fBint napms(int \fIms\fP);
.fi
.SH DESCRIPTION
The following routines give low-level access
to various \fBcurses\fP capabilities.
These routines typically are used inside library routines.
.SS "def_prog_mode, def_shell_mode"
The \fBdef_prog_mode\fP and \fBdef_shell_mode\fP routines save the
current terminal modes as the \*(``program\*(''
(in \fBcurses\fP) or \*(``shell\*(''
(not in \fBcurses\fP) state for use by the \fBreset_prog_mode\fP and
\fBreset_shell_mode\fP routines.
This is done automatically by \fBinitscr\fP.
There is one such save area for each screen context
allocated by \fBnewterm\fP.
.SS "reset_prog_mode, reset_shell_mode"
The \fBreset_prog_mode\fP and \fBreset_shell_mode\fP routines restore
the terminal to \*(``program\*('' (in \fBcurses\fP) or \*(``shell\*('' (out of
\fBcurses\fP) state.
These are done automatically by \fBendwin\fP(3X) and,
after an \fBendwin\fP, by \fBdoupdate\fP,
so they normally are not called.
.SS "resetty, savetty"
The \fBresetty\fP and \fBsavetty\fP routines save and restore the
state of the terminal modes.
\fBsavetty\fP saves the current state in
a buffer and \fBresetty\fP restores the state to what it was at the
last call to \fBsavetty\fP.
.SS getsyx
The \fBgetsyx\fP routine returns the current coordinates
of the \fIvirtual screen\fP cursor in \fIy\fP and \fIx\fP.
If \fBleaveok\fP is currently \fBTRUE\fP, then
\fB\-1\fP,\fB\-1\fP is returned.
If lines have been removed from the top of the
screen, using \fBripoffline\fP, \fIy\fP and \fIx\fP include these lines;
therefore, \fIy\fP and \fIx\fP should be used only as arguments for
\fBsetsyx\fP.
.PP
Few applications will use this feature,
most use \fBgetyx\fP instead.
.SS setsyx
The \fBsetsyx\fP routine sets
the \fIvirtual screen\fP cursor to \fIy\fP, \fIx\fP.
If \fIy\fP and \fIx\fP are both \fB\-1\fP, then
\fBleaveok\fP is set.
The two routines \fBgetsyx\fP and \fBsetsyx\fP
are designed to be used by a library routine, which manipulates
\fBcurses\fP windows but does not want to change the current position
of the program's cursor.
The library routine would call \fBgetsyx\fP
at the beginning, do its manipulation of its own windows, do a
\fBwnoutrefresh\fP on its windows, call \fBsetsyx\fP, and then call
\fBdoupdate\fP.
.PP
Few applications will use this feature,
most use \fBwmove\fP instead.
.SS ripoffline
.B \%ripoffline
provides access to the same facility that \fB\%slk_init\fP(3X) uses to
reduce the size of the screen.
\fB\%ripoffline\fP must be called before \fBinitscr\fP or
\fBnewterm\fP is called, to prepare these initial actions:
.bP
If \fIline\fP is positive, a line is removed from the top of \fBstdscr\fP.
.bP
if \fIline\fP is negative, a line is removed from the bottom.
.PP
When the resulting initialization is done inside \fBinitscr\fP, the
routine \fBinit\fP (supplied by the user) is called with two
arguments:
.bP
a window pointer to the one-line window that has been
allocated and
.bP
an integer with the number of columns in the window.
.PP
Inside this initialization routine, the integer variables \fBLINES\fP
and \fBCOLS\fP (defined in \fB<curses.h>\fP) are not guaranteed to be
accurate and \fBwrefresh\fP or \fBdoupdate\fP must not be called.
It is allowable to call \fBwnoutrefresh\fP during the initialization routine.
.PP
\fBripoffline\fP can be called up to five times before calling \fBinitscr\fP or
\fBnewterm\fP.
.SS curs_set
The \fBcurs_set\fP routine sets the cursor state to invisible,
normal, or very visible for \fBvisibility\fP equal to \fB0\fP,
\fB1\fP, or \fB2\fP respectively.
If the terminal supports the \fIvisibility\fP requested,
the previous \fIcursor\fP state is returned;
otherwise, \fBERR\fP is returned.
.SS napms
.B \%napms
sleeps for
.I ms
milliseconds.
If
.I ms
exceeds 30,000
(thirty seconds),
it is capped at that value.
.SH RETURN VALUE
Except for \fBcurs_set\fP, these routines always return \fBOK\fP.
.PP
\fBcurs_set\fP
returns the previous cursor state, or \fBERR\fP if the
requested \fIvisibility\fP is not supported.
.PP
X/Open defines no error conditions.
In this implementation
.TP 5
\fBdef_prog_mode\fP, \fBdef_shell_mode\fP, \fBreset_prog_mode\fP, \fBreset_shell_mode\fP
return an error
if the terminal was not initialized, or
if the I/O call to obtain the terminal settings fails.
.TP 5
\fBripoffline\fP
returns an error if the maximum number of ripped-off lines
exceeds the maximum (5).
.SH NOTES
Note that \fBgetsyx\fP is a macro, so \fB&\fP is not necessary before
the variables \fIy\fP and \fIx\fP.
.PP
Older SVr4 man pages warn that the return value
of \fBcurs_set\fP \*(``is currently incorrect\*(''.
This implementation gets it right, but it may be unwise to count
on the correctness of the return value anywhere else.
.PP
Both \fI\%ncurses\fP and SVr4 will call \fBcurs_set\fP in \fBendwin\fP
if \fBcurs_set\fP
has been called to make the cursor other than normal, i.e., either
invisible or very visible.
There is no way for \fI\%ncurses\fP to determine the initial cursor
state to restore that.
.SH PORTABILITY
The \fIvirtual screen\fP functions \fBsetsyx\fP and \fBgetsyx\fP
are not described in X/Open Curses, Issue 4.
All other functions are as described in X/Open Curses.
.PP
The SVr4 documentation describes \fBsetsyx\fP and \fBgetsyx\fP
as having return type int.
This is misleading, as they are macros with no documented semantics
for the return value.
.PP
If interrupted, \fI\%ncurses\fP restarts \fBnapms\fP.
That, and the limitation to 30 seconds,
are different from other implementations.
.SH SEE ALSO
\fB\%curses\fP(3X),
\fB\%curs_initscr\fP(3X),
\fB\%curs_outopts\fP(3X),
\fB\%curs_refresh\fP(3X),
\fB\%curs_scr_dump\fP(3X),
\fB\%curs_slk\fP(3X),
\fB\%curs_variables\fP(3X)