ncurses 6.4 - patch 20231007

[ncurses.git] / man / curs_terminfo.3x

'\" t
.\"***************************************************************************
.\" Copyright 2018-2022,2023 Thomas E. Dickey                                *
.\" Copyright 1998-2016,2017 Free Software Foundation, Inc.                  *
.\"                                                                          *
.\" Permission is hereby granted, free of charge, to any person obtaining a  *
.\" copy of this software and associated documentation files (the            *
.\" "Software"), to deal in the Software without restriction, including      *
.\" without limitation the rights to use, copy, modify, merge, publish,      *
.\" distribute, distribute with modifications, sublicense, and/or sell       *
.\" copies of the Software, and to permit persons to whom the Software is    *
.\" furnished to do so, subject to the following conditions:                 *
.\"                                                                          *
.\" The above copyright notice and this permission notice shall be included  *
.\" in all copies or substantial portions of the Software.                   *
.\"                                                                          *
.\" THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS  *
.\" OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF               *
.\" MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.   *
.\" IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,   *
.\" DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR    *
.\" OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR    *
.\" THE USE OR OTHER DEALINGS IN THE SOFTWARE.                               *
.\"                                                                          *
.\" Except as contained in this notice, the name(s) of the above copyright   *
.\" holders shall not be used in advertising or otherwise to promote the     *
.\" sale, use or other dealings in this Software without prior written       *
.\" authorization.                                                           *
.\"***************************************************************************
.\"
.\" $Id: curs_terminfo.3x,v 1.112 2023/10/07 21:19:07 tom Exp $
.TH curs_terminfo 3X 2023-10-07 "ncurses 6.4" "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
..
.
.ds n 5
.SH NAME
\fB\%del_curterm\fP,
\fB\%mvcur\fP,
\fB\%putp\fP,
\fB\%restartterm\fP,
\fB\%set_curterm\fP,
\fB\%setupterm\fP,
\fB\%tigetflag\fP,
\fB\%tigetnum\fP,
\fB\%tigetstr\fP,
\fB\%tiparm\fP,
\fB\%tiparm_s\fP,
\fB\%tiscan_s\fP,
\fB\%tparm\fP,
\fB\%tputs\fP,
\fB\%vid_attr\fP,
\fB\%vid_puts\fP,
\fB\%vidattr\fP,
\fB\%vidputs\fP \-
\fIcurses\fR interfaces to \fIterminfo\fR database
.SH SYNOPSIS
.nf
\fB#include <curses.h>
\fB#include <term.h>
.PP
\fBTERMINAL *cur_term;
.PP
\fBconst char * const boolnames[];
\fBconst char * const boolcodes[];
\fBconst char * const boolfnames[];
\fBconst char * const numnames[];
\fBconst char * const numcodes[];
\fBconst char * const numfnames[];
\fBconst char * const strnames[];
\fBconst char * const strcodes[];
\fBconst char * const strfnames[];
.PP
\fBint setupterm(const char *\fIterm\fP, int \fIfiledes\fP, int *\fIerrret\fP);
\fBTERMINAL *set_curterm(TERMINAL *\fInterm\fP);
\fBint del_curterm(TERMINAL *\fIoterm\fP);
\fBint restartterm(const char *\fIterm\fP, int \fIfiledes\fP, int *\fIerrret\fP);
.PP
\fBchar *tparm(const char *\fIstr\fP, ...);
        \fIor
\fBchar *tparm(const char *\fIstr\fP, long \fIp1 ... \fPlong \fIp9\fP);
.PP
\fBint tputs(const char *\fIstr\fP, int \fIaffcnt\fP, int (*\fIputc\fP)(int));
\fBint putp(const char *\fIstr\fP);
.PP
\fBint vidputs(chtype \fIattrs\fP, int (*\fIputc\fP)(int));
\fBint vidattr(chtype \fIattrs\fP);
\fBint vid_puts(attr_t \fIattrs\fP, short \fIpair\fP, void *\fIopts\fP, int (*\fIputc\fP)(int));
\fBint vid_attr(attr_t \fIattrs\fP, short \fIpair\fP, void *\fIopts\fP);
.PP
\fBint mvcur(int \fIoldrow\fP, int \fIoldcol\fP, int \fInewrow\fP, int \fInewcol\fP);
.PP
\fBint tigetflag(const char *\fIcapname\fP);
\fBint tigetnum(const char *\fIcapname\fP);
\fBchar *tigetstr(const char *\fIcapname\fP);
.PP
\fBchar *tiparm(const char *\fIstr\fP, ...);
.PP
\fI/* extensions */
\fBchar *tiparm_s(int \fIexpected\fP, int \fImask\fP, const char *\fIstr\fP, ...);
\fBint tiscan_s(int *\fIexpected\fP, int *\fImask\fP, const char *\fIstr\fP);
.fi
.SH DESCRIPTION
These low-level routines must be called by programs that have to deal
directly with the \fIterminfo\fP database to handle certain terminal
capabilities, such as programming function keys.
For all other
functionality, \fIcurses\fP routines are more suitable and their use is
recommended.
.PP
None of these functions use (or are aware of) multibyte character strings
such as UTF-8:
.bP
capability names use the POSIX portable character set
.bP
capability string values have no associated encoding;
they are strings of 8-bit characters.
.SS Initialization
Initially, \fBsetupterm\fP should be called.
The high-level curses functions \fBinitscr\fP and
\fBnewterm\fP call \fBsetupterm\fP to initialize the
low-level set of terminal-dependent variables
[listed in \fBterminfo\fP(\*n)].
.PP
Applications can use the
terminal capabilities either directly (via header definitions),
or by special functions.
The header files \fBcurses.h\fP and \fBterm.h\fP should be included (in this
order) to get the definitions for these strings, numbers, and flags.
.PP
The \fBterminfo\fP variables
\fBlines\fP and \fBcolumns\fP are initialized by \fBsetupterm\fP as
follows:
.bP
If \fBuse_env(FALSE)\fP has been called, values for
\fBlines\fP and \fBcolumns\fP specified in \fBterminfo\fP are used.
.bP
Otherwise, if the environment variables \fBLINES\fP and \fBCOLUMNS\fP
exist, their values are used.
If these environment variables do not
exist and the program is running in a window, the current window size
is used.
Otherwise, if the environment variables do not exist, the
values for \fBlines\fP and \fBcolumns\fP specified in the
\fBterminfo\fP database are used.
.PP
Parameterized strings should be passed through \fBtparm\fP to instantiate them.
All \fBterminfo\fP strings
(including the output of \fBtparm\fP)
should be printed
with \fBtputs\fP or \fBputp\fP.
Call \fBreset_shell_mode\fP to restore the
tty modes before exiting [see \fBcurs_kernel\fP(3X)].
.PP
Programs which use
cursor addressing should
.bP
output \fBenter_ca_mode\fP upon startup and
.bP
output \fBexit_ca_mode\fP before exiting.
.PP
Programs which execute shell subprocesses should
.bP
call \fBreset_shell_mode\fP and
output \fBexit_ca_mode\fP before the shell
is called and
.bP
output \fBenter_ca_mode\fP and
call \fBreset_prog_mode\fP after returning from the shell.
.PP
The \fBsetupterm\fP routine reads in the \fBterminfo\fP database,
initializing the \fBterminfo\fP structures, but does not set up the
output virtualization structures used by \fBcurses\fP.
These are its parameters:
.RS 3
.TP 5
\fIterm\fP
is the terminal type, a character string.
If \fIterm\fP is null, the environment variable \fBTERM\fP is used.
.TP 5
\fIfiledes\fP
is the file descriptor used for getting and setting terminal I/O modes.
.IP
Higher-level applications use \fBnewterm\fP(3X) for initializing the terminal,
passing an output \fIstream\fP rather than a \fIdescriptor\fP.
In curses, the two are the same because \fBnewterm\fP calls \fBsetupterm\fP,
passing the file descriptor derived from its output stream parameter.
.TP 5
\fIerrret\fP
points to an optional location where an error status can be returned to
the caller.
If \fIerrret\fP is not null,
then \fBsetupterm\fP returns \fBOK\fP or
\fBERR\fP and stores a status value in the integer pointed to by
\fIerrret\fP.
A return value of \fBOK\fP combined with status of \fB1\fP in \fIerrret\fP
is normal.
.IP
If \fBERR\fP is returned, examine \fIerrret\fP:
.RS
.TP 5
.B 1
means that the terminal is hardcopy, cannot be used for \fIcurses\fP applications.
.IP
\fB\%setupterm\fP determines if the entry is a hardcopy type by
checking the \fBhc\fP (\fBhardcopy\fP) capability.
.TP 5
.B 0
means that the terminal could not be found,
or that it is a generic type,
having too little information for \fIcurses\fP applications to run.
.IP
\fB\%setupterm\fP determines if the entry is a generic type by
checking the \fBgn\fP \%(\fBgeneric_type\fP) capability.
.TP 5
.B \-1
means that the \fIterminfo\fP database could not be found.
.RE
.IP
If \fIerrret\fP is
null, \fB\%setupterm\fP prints an error message upon finding an error
and exits.
Thus, the simplest call is:
.IP
\fBsetupterm((char *)0, 1, (int *)0);\fP,
.PP
which uses all the defaults and sends the output to \fBstdout\fP.
.RE
.\" ***************************************************************************
.SS The Terminal State
The \fBsetupterm\fP routine stores its information about the terminal
in a \fBTERMINAL\fP structure pointed to by the global variable \fBcur_term\fP.
If it detects an error,
or decides that the terminal is unsuitable (hardcopy or generic),
it discards this information,
making it not available to applications.
.PP
If \fBsetupterm\fP is called repeatedly for the same terminal type,
it will reuse the information.
It maintains only one copy of a given terminal's capabilities in memory.
If it is called for different terminal types,
\fBsetupterm\fP allocates new storage for each set of terminal capabilities.
.PP
The \fBset_curterm\fP routine sets \fBcur_term\fP to
\fInterm\fP, and makes all of the \fBterminfo\fP boolean, numeric, and
string variables use the values from \fInterm\fP.
It returns the old value of \fBcur_term\fP.
.PP
The \fBdel_curterm\fP routine frees the space pointed to by
\fIoterm\fP and makes it available for further use.
If \fIoterm\fP is
the same as \fBcur_term\fP, references to any of the \fBterminfo\fP
boolean, numeric, and string variables thereafter may refer to invalid
memory locations until another \fBsetupterm\fP has been called.
.PP
The \fBrestartterm\fP routine is similar to \fBsetupterm\fP and \fBinitscr\fP,
except that it is called after restoring memory to a previous state (for
example, when reloading a game saved as a core image dump).
\fBrestartterm\fP assumes that the windows and the input and output options
are the same as when memory was saved,
but the terminal type and baud rate may be different.
Accordingly, \fBrestartterm\fP saves various tty state bits,
calls \fBsetupterm\fP, and then restores the bits.
.\" ***************************************************************************
.SS Formatting Output
The \fBtparm\fP routine instantiates the string \fIstr\fP with
parameters \fIpi\fP.  A pointer is returned to the result of \fIstr\fP
with the parameters applied.
Application developers should keep in mind these quirks of the interface:
.bP
Although \fBtparm\fP's actual parameters may be integers or strings,
the prototype expects \fBlong\fP (integer) values.
.bP
Aside from the \fBset_attributes\fP (\fBsgr\fP) capability,
most terminal capabilities require no more than one or two parameters.
.bP
Padding information is ignored by \fBtparm\fP;
it is interpreted by \fBtputs\fP.
.bP
The capability string is null-terminated.
Use \*(``\e200\*('' where an ASCII NUL is needed in the output.
.PP
\fBtiparm\fP is a newer form of \fBtparm\fP which uses \fI<stdarg.h>\fP
rather than a fixed-parameter list.
Its numeric parameters are integers (int) rather than longs.
.PP
Both \fBtparm\fP and \fBtiparm\fP assume that the application passes
parameters consistent with the terminal description.
Two extensions are provided as alternatives to deal with untrusted data:
.bP
\fBtiparm_s\fP is an extension which is a safer formatting function
than \fBtparm\fR or \fBtiparm\fR,
because it allows the developer to tell the curses
library how many parameters to expect in the parameter list,
and which may be string parameters.
.IP
The \fImask\fP parameter has one bit set for each of the parameters
(up to 9) which will be passed as char* rather than numbers.
.bP
The extension \fBtiscan_s\fP allows the application
to inspect a formatting capability to see what the curses library would assume.
.\" ***************************************************************************
.SS Output Functions
The \fBtputs\fP routine applies padding information
(i.e., by interpreting marker embedded in the terminfo capability
such as \*(``$<5>\*('' as 5 milliseconds)
to the string
\fIstr\fP and outputs it:
.bP
The \fIstr\fP parameter must be a terminfo string
variable or the return value from
\fBtparm\fP, \fBtiparm\fP, \fBtgetstr\fP, or \fBtgoto\fP.
.IP
The \fBtgetstr\fP and \fBtgoto\fP functions are part of the \fItermcap\fP
interface,
which happens to share this function name with the \fIterminfo\fP interface.
.bP
\fIaffcnt\fP is the number of lines affected, or 1 if
not applicable.
.bP
\fIputc\fP is a \fBputchar\fP-like routine to which
the characters are passed, one at a time.
.PP
The \fBputp\fR routine calls \fBtputs(\fIstr\fB, 1, putchar)\fR.
The output of \fBputp\fP always goes to \fBstdout\fP, rather than
the \fIfiledes\fP specified in \fBsetupterm\fP.
.PP
The \fBvidputs\fP routine displays the string on the terminal in the
video attribute mode \fIattrs\fP, which is any combination of the
attributes listed in \fBcurses\fP(3X).
The characters are passed to
the \fBputchar\fP-like routine \fIputc\fP.
.PP
The \fBvidattr\fP routine is like the \fBvidputs\fP routine, except
that it outputs through \fBputchar\fP.
.PP
The \fBvid_attr\fP and \fBvid_puts\fP routines correspond
to vidattr and vidputs, respectively.
They use a set of arguments for representing the video attributes plus color,
i.e.,
.bP
\fIattrs\fP of type \fBattr_t\fP for the attributes and
.bP
\fIpair\fP of type \fBshort\fP for the color-pair number.
.PP
The \fBvid_attr\fP and \fBvid_puts\fP routines
are designed to use the attribute constants with the \fBWA_\fP prefix.
.PP
X/Open Curses reserves the \fIopts\fP argument for future use,
saying that applications must provide a null pointer for that argument.
As an extension,
this implementation allows \fIopts\fP to be used as a pointer to \fBint\fP,
which overrides the \fIpair\fP (\fBshort\fP) argument.
.PP
The \fBmvcur\fP routine provides low-level cursor motion.
It takes effect immediately (rather than at the next refresh).
Unlike the other low-level output functions,
which either write to the standard output or pass an output function parameter,
\fBmvcur\fP uses an output file descriptor derived from
the output stream parameter of \fBnewterm\fP(3X).
.PP
While \fBputp\fP and \fBmvcur\fP are low-level functions which
do not use the high-level curses state,
they are declared in \fB\%<curses.h>\fP because System\ V did this
(see \fIHISTORY\fP).
.\" ***************************************************************************
.SS Terminal Capability Functions
The \fBtigetflag\fP, \fBtigetnum\fP and \fBtigetstr\fP routines return
the value of the capability corresponding to the \fBterminfo\fP
\fIcapname\fP passed to them, such as \fBxenl\fP.
The \fIcapname\fP for each capability is given in the table column entitled
\fIcapname\fP code in the capabilities section of \fBterminfo\fP(\*n).
.PP
These routines return special values to denote errors.
.PP
The \fBtigetflag\fP routine returns
.TP
\fB\-1\fP
if \fIcapname\fP is not a boolean capability,
or
.TP
\fB0\fP
if it is canceled or absent from the terminal description.
.PP
The \fBtigetnum\fP routine returns
.TP
\fB\-2\fP
if \fIcapname\fP is not a numeric capability, or
.TP
\fB\-1\fP
if it is canceled or absent from the terminal description.
.PP
The \fBtigetstr\fP routine returns
.TP
\fB(char *)\-1\fP
if \fIcapname\fP is not a string capability,
or
.TP
\fB0\fP
if it is canceled or absent from the terminal description.
.\" ***************************************************************************
.SS Terminal Capability Names
These null-terminated arrays contain
.bP
the short \fIterminfo\fP names (\*(``codes\*(''),
.bP
the \fItermcap\fP names (\*(``names\*(''), and
.bP
the long \fIterminfo\fP names (\*(``fnames\*('')
.PP
for each of the predefined \fIterminfo\fP variables:
.PP
.RS
.nf
\fBconst char *boolnames[]\fP, \fB*boolcodes[]\fP, \fB*boolfnames[]\fP
\fBconst char *numnames[]\fP, \fB*numcodes[]\fP, \fB*numfnames[]\fP
\fBconst char *strnames[]\fP, \fB*strcodes[]\fP, \fB*strfnames[]\fP
.fi
.RE
.\" ***************************************************************************
.SS Releasing Memory
Each successful call to \fBsetupterm\fP allocates memory to hold the terminal
description.
As a side-effect, it sets \fBcur_term\fP to point to this memory.
If an application calls
.IP
\fBdel_curterm(cur_term);\fP
.PP
the memory will be freed.
.PP
The formatting functions \fBtparm\fP and \fBtiparm\fP extend the storage
allocated by \fBsetupterm\fP:
.bP
the \*(``static\*('' terminfo variables [a-z].
Before ncurses 6.3, those were shared by all screens.
With ncurses 6.3, those are allocated per screen.
See \fBterminfo\fP(\*n) for details.
.bP
to improve performance, ncurses 6.3 caches the result of analyzing terminfo
strings for their parameter types.
That is stored as a binary tree referenced from the \fBTERMINAL\fP structure.
.PP
The higher-level \fBinitscr\fP and \fBnewterm\fP functions use \fBsetupterm\fP.
Normally they do not free this memory, but it is possible to do that using
the \fBdelscreen\fP(3X) function.
.\" ***************************************************************************
.SH RETURN VALUE
Routines that return an integer return \fBERR\fP upon failure and \fBOK\fP
(SVr4 only specifies \*(``an integer value other than \fBERR\fP\*('')
upon successful completion,
unless otherwise noted in the preceding routine descriptions.
.PP
Routines that return pointers always return \fBNULL\fP on error.
.PP
X/Open defines no error conditions.
In this implementation
.RS 3
.TP 5
\fBdel_curterm\fP
returns an error
if its terminal parameter is null.
.TP 5
\fBputp\fP
calls \fBtputs\fP, returning the same error-codes.
.TP 5
\fBrestartterm\fP
returns an error
if the associated call to \fBsetupterm\fP returns an error.
.TP 5
\fBsetupterm\fP
returns an error
if it cannot allocate enough memory, or
create the initial windows (stdscr, curscr, newscr).
Other error conditions are documented above.
.TP 5
\fBtparm\fP
returns a null if the capability would require unexpected parameters,
e.g., too many, too few, or incorrect types
(strings where integers are expected, or vice versa).
.TP 5
\fBtputs\fP
returns an error if the string parameter is null.
It does not detect I/O errors:
X/Open states that \fBtputs\fP ignores the return value
of the output function \fIputc\fP.
.RE
.\" ***************************************************************************
.SS Compatibility macros
This implementation provides a few macros for compatibility with systems
before SVr4 (see \fIHISTORY\fP).
Those include
\fBcrmode\fP,
\fBfixterm\fP,
\fBgettmode\fP,
\fBnocrmode\fP,
\fBresetterm\fP,
\fBsaveterm\fP, and
\fBsetterm\fP.
.PP
In SVr4, those are found in \fB<curses.h>\fP,
but except for \fBsetterm\fP, are likewise macros.
The one function, \fBsetterm\fP, is mentioned in the manual page.
The manual page notes that the \fBsetterm\fP routine
was replaced by \fB\%setupterm\fP, stating that the call
.IP
\fBsetupterm(\fIterm\fB, 1, (int *)0)\fR
.PP
provides the same functionality as \fBsetterm(\fIterm\fB)\fR,
and is not recommended for new programs.
This implementation provides each of those symbols
as macros for BSD compatibility,
.\" ***************************************************************************
.SH HISTORY
SVr2 introduced the terminfo feature.
Its programming manual mentioned the following low-level functions.
.PP
.TS
lB lB
lB lx.
Function        Description
_
fixterm restore tty to \*(``in curses\*('' state
gettmode        establish current tty modes
mvcur   low level cursor motion
putp    T{
utility function that uses \fBtputs\fP to send characters via \fBputchar\fP.
T}
resetterm       set tty modes to \*(``out of curses\*('' state
resetty reset tty flags to stored value
saveterm        save current modes as \*(``in curses\*('' state
savetty store current tty flags
setterm establish terminal with given type
setupterm       establish terminal with given type
tparm   instantiate a string expression with parameters
tputs   apply padding information to a string
vidattr like \fBvidputs\fP, but outputs through \fBputchar\fP
vidputs T{
output a string to put terminal in a specified video attribute mode
T}
.TE
.PP
The programming manual also mentioned
functions provided for \fItermcap\fP compatibility
(commenting that they \*(``may go away at a later date\*('').
.PP
.TS
lB lB
lB lx.
Function        Description
_
tgetent look up \fItermcap\fP entry for given \fIname\fP
tgetflag        get boolean entry for given \fIid\fP
tgetnum get numeric entry for given \fIid\fP
tgetstr get string entry for given \fIid\fP
tgoto   apply parameters to given capability
tputs   T{
apply padding to capability, calling a function to put characters
T}
.TE
.PP
Early terminfo programs obtained capability values from the
\fBTERMINAL\fP structure initialized by \fBsetupterm\fP.
.PP
SVr3 extended terminfo by adding functions to retrieve capability values
(like the termcap interface),
and reusing \fBtgoto\fP and \fBtputs\fP:
.PP
.TS
lB lB
lB lx.
Function        Description
_
tigetflag       get boolean entry for given \fIid\fP
tigetnum        get numeric entry for given \fIid\fP
tigetstr        get string entry for given \fIid\fP
.TE
.PP
SVr3 also replaced several of the SVr2 \fIterminfo\fP functions
which had no counterpart in the \fItermcap\fP interface,
documenting them as obsolete.
.PP
.TS
lB lB
l  lx.
Function        Replaced by
_
crmode  cbreak
fixterm reset_prog_mode
gettmode        \fIn/a\fP
nocrmode        nocbreak
resetterm       reset_shell_mode
saveterm        def_prog_mode
setterm setupterm
.TE
.PP
SVr3 kept the \fBmvcur\fP, \fBvidattr\fP and \fBvidputs\fP functions,
along with \fBputp\fP, \fBtparm\fP and \fBtputs\fP.
The latter were needed to support padding,
and handling functions such as \fBvidattr\fP
(which used more than the two parameters supported by \fBtgoto\fP).
.PP
SVr3 introduced the functions for switching between terminal
descriptions, e.g., \fBset_curterm\fP.
Some of that was incremental improvements to the SVr2 library:
.bP
The \fBTERMINAL\fP type definition was introduced in SVr3.01,
for the \fBterm\fP structure provided in SVr2.
.bP
The various global variables such as \fBboolnames\fP were mentioned
in the programming manual at this point,
though the variables were provided in SVr2.
.PP
SVr4 added the \fBvid_attr\fP and \fBvid_puts\fP functions.
.PP
There are other low-level functions declared in the \fIcurses\fP header files
on Unix systems,
but none were documented.
The functions marked \*(``obsolete\*('' remained in use
by the Unix \fBvi\fP(1) editor.
.SH PORTABILITY
.SS Extensions
The functions marked as extensions were designed for \fBncurses\fP(3X),
and are not found in SVr4 curses, 4.4BSD curses,
or any other previous version of curses.
.SS Legacy functions
X/Open notes that \fBvidattr\fP and \fBvidputs\fP may be macros.
.PP
The function \fBsetterm\fP is not described by X/Open and must
be considered non-portable.
All other functions are as described by X/Open.
.SS Legacy data
\fBsetupterm\fP copies the terminal name to the array \fBttytype\fP.
This is not part of X/Open Curses, but is assumed by some applications.
.PP
Other implementions may not declare the capability name arrays.
Some provide them without declaring them.
X/Open does not specify them.
.PP
Extended terminal capability names, e.g., as defined by \fB@TIC@\ \-x\fP,
are not stored in the arrays described here.
.SS Output buffering
Older versions of \fBncurses\fP assumed that the file descriptor passed to
\fBsetupterm\fP from \fBinitscr\fP or \fBnewterm\fP uses buffered I/O,
and would write to the corresponding stream.
In addition to the limitation that the terminal was left in block-buffered
mode on exit (like System V curses),
it was problematic because \fBncurses\fP
did not allow a reliable way to cleanup on receiving SIGTSTP.
.PP
The current version (ncurses6)
uses output buffers managed directly by \fBncurses\fP.
Some of the low-level functions described in this manual page write
to the standard output.
They are not signal-safe.
The high-level functions in \fBncurses\fP use
alternate versions of these functions
using the more reliable buffering scheme.
.SS Function prototypes
The X/Open Curses prototypes are based on the SVr4 curses header declarations,
which were defined at the same time the C language was first standardized in
the late 1980s.
.bP
X/Open Curses uses \fBconst\fP less effectively than a later design might,
in some cases applying it needlessly to values are already constant,
and in most cases overlooking parameters which normally would use \fBconst\fP.
Using constant parameters for functions which do not use \fBconst\fP
may prevent the program from compiling.
On the other hand, \fIwritable strings\fP are an obsolescent feature.
.IP
As an extension, this implementation can be configured to change the
function prototypes to use the \fBconst\fP keyword.
The \fIncurses\fP ABI 6 enables this feature by default.
.bP
X/Open Curses prototypes \fBtparm\fP with a fixed number of parameters,
rather than a variable argument list.
.IP
This implementation uses a variable argument list, but can be
configured to use the fixed-parameter list.
Portable applications should provide 9 parameters after the format;
zeroes are fine for this purpose.
.IP
In response to review comments by Thomas E. Dickey,
X/Open Curses Issue 7 proposed the \fBtiparm\fP function in mid-2009.
.IP
While \fBtiparm\fP is always provided in ncurses,
the older form is only available as a build-time configuration option.
If not specially configured, \fBtparm\fP is the same as \fBtiparm\fP.
.PP
Both forms of \fBtparm\fP have drawbacks:
.bP
Most of the calls to \fBtparm\fP use only one or two parameters.
Passing nine on each call is awkward.
.IP
Using \fBlong\fP for the numeric parameter type is a workaround
to make the parameter use the same amount of stack as a pointer.
That approach dates back to the mid-1980s, before C was standardized.
Since then, there is a standard
(and pointers are not required to fit in a long).
.bP
Providing the right number of parameters for a variadic function
such as \fBtiparm\fP can be a problem, in particular for string parameters.
However, only a few terminfo capabilities use string parameters
(e.g., the ones used for programmable function keys).
.IP
The ncurses library checks usage of these capabilities,
and returns an error if the capability mishandles string parameters.
But it cannot check if a calling program provides strings in the right
places for the \fBtparm\fP calls.
.IP
The \fB@TPUT@\fR(1) program checks its use of these capabilities with a table,
so that it calls \fBtparm\fP correctly.
.SS Special TERM treatment
If configured to use the terminal-driver,
e.g., for the MinGW port,
.bP
\fBsetupterm\fP interprets a missing/empty TERM variable as the
special value \*(``unknown\*(''.
.IP
SVr4 curses uses the
special value \*(``dumb\*(''.
.IP
The difference between the two is that
the former uses the \fBgn\fP (\fBgeneric_type\fR) terminfo capability,
while the latter does not.
A generic terminal is unsuitable for full-screen applications.
.bP
\fBsetupterm\fP allows explicit use of the
the windows console driver by checking if $TERM is set to
\*(``#win32con\*('' or an abbreviation of that string.
.SS Other portability issues
In System V Release 4, \fBset_curterm\fP has an \fBint\fP return type and
returns \fBOK\fP or \fBERR\fP.  We have chosen to implement the X/Open Curses
semantics.
.PP
In System V Release 4, the third argument of \fBtputs\fP has the type
\fBint (*putc)(char)\fP.
.PP
At least one implementation of X/Open Curses (Solaris) returns a value
other than \fBOK\fP/\fBERR\fP from \fBtputs\fP.
That returns the length of the string, and does no error-checking.
.PP
X/Open notes that after calling \fBmvcur\fP, the curses state may not match the
actual terminal state, and that an application should touch and refresh
the window before resuming normal curses calls.
Both \fBncurses\fP and System V Release 4 curses implement \fBmvcur\fP using
the SCREEN data allocated in either \fBinitscr\fP or \fBnewterm\fP.
So though it is documented as a terminfo function,
\fBmvcur\fP is really a curses function which is not well specified.
.PP
X/Open states that the old location must be given for \fBmvcur\fP.
This implementation allows the caller to use \-1's for the old ordinates.
In that case, the old location is unknown.
.SH SEE ALSO
\fB\%curses\fP(3X),
\fB\%curs_initscr\fP(3X),
\fB\%curs_kernel\fP(3X),
\fB\%curs_memleaks\fP(3X),
\fB\%curs_termcap\fP(3X),
\fB\%curs_variables\fP(3X),
\fB\%term_variables\fP(3X),
\fB\%putc\fP(3),
\fB\%terminfo\fP(\*n)