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

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.\" $Id: curs_util.3x,v 1.35 2012/07/15 00:23:52 tom Exp $
.TH curs_util 3X ""
.de bP
.IP \(bu 4
..
.na
.hy 0
.SH NAME
\fBdelay_output\fR,
\fBfilter\fR,
\fBflushinp\fR,
\fBgetwin\fR,
\fBkey_name\fR,
\fBkeyname\fR,
\fBnofilter\fR,
\fBputwin\fR,
\fBunctrl\fR,
\fBuse_env\fR,
\fBuse_tioctl\fR,
\fBwunctrl\fR \- miscellaneous \fBcurses\fR utility routines
.ad
.hy
.SH SYNOPSIS
\fB#include <curses.h>\fR
.sp
\fBchar *unctrl(chtype c);\fR
.br
\fBwchar_t *wunctrl(cchar_t *c);\fR
.br
\fBchar *keyname(int c);\fR
.br
\fBchar *key_name(wchar_t w);\fR
.br
\fBvoid filter(void);\fR
.br
\fBvoid nofilter(void);\fR
.br
\fBvoid use_env(bool f);\fR
.br
\fBvoid use_tioctl(bool f);\fR
.br
\fBint putwin(WINDOW *win, FILE *filep);\fR
.br
\fBWINDOW *getwin(FILE *filep);\fR
.br
\fBint delay_output(int ms);\fR
.br
\fBint flushinp(void);\fR
.br
.SH DESCRIPTION
The \fBunctrl\fR routine returns a character string which is a printable
representation of the character \fIc\fR, ignoring attributes.
Control characters are displayed in the \fB^\fR\fIX\fR notation.
Printing characters are displayed as is.
The corresponding \fBwunctrl\fR returns a printable representation of
a wide character.
.PP
The \fBkeyname\fR routine returns a character string corresponding to the key \fIc\fR:
.RS 3
.bP
Printable characters are displayed as themselves, e.g., a one-character string containing the key.
.bP
Control characters are displayed in the \fB^\fR\fIX\fR notation.
.bP
DEL (character 127) is displayed as \fB^?\fP.
.bP
Values above 128 are either meta characters
(if the screen has not been initialized,
or if \fBmeta\fP has been called with a TRUE parameter),
shown in the \fBM\-\fR\fIX\fR notation,
or are displayed as themselves.
In the latter case, the values may not be printable;
this follows the X/Open specification.
.bP
Values above 256 may be the names of the names of function keys.
.bP
Otherwise (if there is no corresponding name) the function returns null,
to denote an error.
X/Open also lists an "UNKNOWN KEY" return value, which some implementations
return rather than null.
.RE
.LP
The corresponding \fBkey_name\fR returns a character string corresponding
to the wide-character value \fIw\fR.
The two functions do not return the same set of strings;
the latter returns null where the former would display a meta character.
.PP
The \fBfilter\fR routine, if used, must be called before \fBinitscr\fR or
\fBnewterm\fR are called.  The effect is that, during those calls, \fBLINES\fR
is set to 1; the capabilities \fBclear\fR, \fBcup\fR, \fBcud\fR, \fBcud1\fR,
\fBcuu1\fR, \fBcuu\fR, \fBvpa\fR are disabled; and the \fBhome\fR string is
set to the value of \fBcr\fR.
.PP
The \fBnofilter\fP routine cancels the effect of a preceding \fBfilter\fP
call.
That allows the caller to initialize a screen on a different device,
using a different value of \fB$TERM\fP.
The limitation arises because the \fBfilter\fP routine modifies the
in-memory copy of the terminal information.
.PP
The \fBuse_env\fR routine, if used,
should be called before \fBinitscr\fR or
\fBnewterm\fR are called
(because those compute the screen size).
It modifies the way \fBncurses\fP treats environment variables
when determining the screen size.
.bP
Normally ncurses looks first at the terminal database for the screen size.
.IP
If \fBuse_env\fP was called with \fBFALSE\fP for parameter,
it stops here.
.bP
Then it asks for the screen size via operating system calls.
If successful,
it overrides the values from the terminal database.
.bP
Finally, ncurses examines the
\fBLINES\fR or \fBCOLUMNS\fR environment variables,
using a value in those to override the results
from the operating system or terminal database.
.IP
Ncurses also updates the screen size in response to SIGWINCH,
unless overridden by the \fBLINES\fR or \fBCOLUMNS\fR environment variables,
.PP
The \fBuse_tioctl\fR routine, if used,
should be called before \fBinitscr\fR or \fBnewterm\fR are called
(because those compute the screen size).
After \fBuse_tioctl\fR is called with \fBTRUE\fR as an argument,
ncurses modifies the last step in its computation of screen size as follows:
.bP
checks if the \fBLINES\fR and \fBCOLUMNS\fR environment variables
are set to a number greater than zero.
.bP
for each, ncurses updates the corresponding environment variable
with the value that it has obtained via operating system call
or from the terminal database.
.bP
ncurses re-fetches the value of the environment variables so that
it is still the environment variables which set the screen size.
.PP
The \fBputwin\fR routine writes all data associated with window \fIwin\fR into
the file to which \fIfilep\fR points.  This information can be later retrieved
using the \fBgetwin\fR function.
.PP
The \fBgetwin\fR routine reads window related data stored in the file by
\fBputwin\fR.  The routine then creates and initializes a new window using that
data.  It returns a pointer to the new window.
.PP
The \fBdelay_output\fR routine inserts an \fIms\fR millisecond pause
in output.  This routine should not be used extensively because
padding characters are used rather than a CPU pause.
If no padding character is specified, this uses \fBnapms\fR to perform the delay.
.PP
The \fBflushinp\fR routine throws away any typeahead that has been typed by the
user and has not yet been read by the program.
.SH RETURN VALUE
Except for \fBflushinp\fR, routines that return an integer return \fBERR\fR
upon failure and \fBOK\fR (SVr4 specifies only "an integer value other than
\fBERR\fR") upon successful completion.
.PP
Routines that return pointers return \fBNULL\fR on error.
.PP
X/Open does not define any error conditions.
In this implementation
.RS 3
.TP 5
\fBflushinp\fR
returns an error if the terminal was not initialized.
.TP 5
\fBmeta\fR
returns an error if the terminal was not initialized.
.TP 5
\fBputwin\fP
returns an error if the associated \fBfwrite\fP calls return an error.
.RE
.SH PORTABILITY
The XSI Curses standard, Issue 4 describes these functions.
It states that \fBunctrl\fR and \fBwunctrl\fR will return a null pointer if
unsuccessful, but does not define any error conditions.
This implementation checks for three cases:
.RS 3
.bP
the parameter is a 7-bit US\-ASCII code.
This is the case that X/Open Curses documented.
.bP
the parameter is in the range 128\-159, i.e., a C1 control code.
If \fBuse_legacy_coding\fP has been called with a \fB2\fP parameter,
\fBunctrl\fP returns the parameter, i.e., a one-character string with
the parameter as the first character.
Otherwise, it returns ``~@'', ``~A'', etc., analogous to ``^@'', ``^A'', C0 controls.
.IP
X/Open Curses does not document whether \fBunctrl\fP can be called before
initializing curses.
This implementation permits that,
and returns the ``~@'', etc., values in that case.
.bP
parameter values outside the 0 to 255 range.
\fBunctrl\fP returns a null pointer.
.RE
.PP
The SVr4 documentation describes the action of \fBfilter\fR only in the vaguest
terms.  The description here is adapted from the XSI Curses standard (which
erroneously fails to describe the disabling of \fBcuu\fR).
.PP
The strings returned by \fBunctrl\fR in this implementation are determined
at compile time,
showing C1 controls from the upper-128 codes with a `~' prefix rather than `^'.
Other implementations have different conventions.
For example, they may show both sets of control characters with `^',
and strip the parameter to 7 bits.
Or they may ignore C1 controls and treat all of the upper-128 codes as
printable.
This implementation uses 8 bits but does not modify the string to reflect
locale.
The \fBuse_legacy_coding\fP function allows the caller to
change the output of \fBunctrl\fP.
.PP
Likewise, the \fBmeta\fP function allows the caller to change the
output of \fBkeyname\fP, i.e.,
it determines whether to use the `M\-' prefix
for ``meta'' keys (codes in the range 128 to 255).
Both \fBuse_legacy_coding\fP and \fBmeta\fP succeed only after
curses is initialized. 
X/Open Curses does not document the treatment of codes 128 to 159.
When treating them as ``meta'' keys
(or if \fBkeyname\fP is called before initializing curses),
this implementation returns strings ``M\-^@'', ``M\-^A'', etc.
.PP
The \fBkeyname\fP function may return the names of user-defined
string capabilities which are defined in the terminfo entry via the \fB\-x\fP
option of \fB@TIC@\fP.
This implementation automatically assigns at run-time keycodes to 
user-defined strings which begin with "k".
The keycodes start at KEY_MAX, but are not guaranteed to be 
the same value for different runs because user-defined codes are
merged from all terminal descriptions which have been loaded.
The \fBuse_extended_names\fP function controls whether this data is
loaded when the terminal description is read by the library.
.PP
The \fBnofilter\fP and \fBuse_tioctl\fP 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_VERSION.
.SH SEE ALSO
\fBlegacy_coding\fR(3X),
\fBcurses\fR(3X),
\fBcurs_initscr\fR(3X),
\fBcurs_kernel\fR(3X),
\fBcurs_scr_dump\fR(3X),
\fBcurs_variables\fR(3X),
\fBlegacy_coding\fR(3X).