freebsd-dev/sys/teken/libteken/teken.3

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.Dd May 9, 2011
.Dt TEKEN 3
.Os
.Sh NAME
.Nm teken
.Nd xterm-like terminal emulation interface
.Sh LIBRARY
.Lb libteken
.Sh SYNOPSIS
.In teken.h
.Ft void
.Fn teken_init "teken_t *t" "const teken_funcs_t *funcs" "void *thunk"
.Ft void
.Fn teken_input "teken_t *t" "const void *buf" "size_t nbytes"
.Ft const teken_pos_t *
.Fn teken_get_winsize "teken_t *t"
.Ft void
.Fn teken_set_winsize "teken_t *t" "const teken_pos_t *size"
.Ft const teken_pos_t *
.Fn teken_get_cursor "teken_t *t"
.Ft void
.Fn teken_set_cursor "teken_t *t" "const teken_pos_t *pos"
.Ft const teken_attr_t *
.Fn teken_get_curattr "teken_t *t"
.Ft void
.Fn teken_set_curattr "teken_t *t" "const teken_attr_t *attr"
.Ft const teken_attr_t *
.Fn teken_get_defattr "teken_t *t"
.Ft void
.Fn teken_set_defattr "teken_t *t" "const teken_attr_t *attr"
.Ft const char *
.Fn teken_get_sequence "teken_t *t" "unsigned int id"
.Ft teken_color_t
.Fn teken_256to8 "teken_color_t color"
.Ft void
.Fn teken_get_defattr_cons25 "teken_t *t" "int *fg" "int *bg"
.Ft void
.Fn teken_set_8bit "teken_t *t"
.Ft void
.Fn teken_set_cons25 "teken_t *t"
.Sh DESCRIPTION
The
.Nm
library implements the input parser of a 256-color xterm-like terminal.
It converts a stream of UTF-8 encoded characters into a series of
primitive drawing instructions that can be used by a console driver or
terminal emulator to render a terminal application.
.Pp
The
.Fn teken_init
function is used to initialize terminal state object
.Fa t ,
having type
.Vt teken_t .
The supplied
.Vt teken_funcs_t
structure
.Fa funcs
contains a set of callback functions, which are called when supplying
data to
.Fn teken_input .
The
.Fa thunk
argument stores an arbitrary pointer, which is passed to each invocation
of the callback functions.
.Pp
The
.Vt teken_funcs_t
structure stores the following callbacks:
.Bd -literal -offset indent
typedef struct {
	tf_bell_t     *tf_bell;     /* Audible/visible bell. */
	tf_cursor_t   *tf_cursor;   /* Move cursor to x/y. */
	tf_putchar_t  *tf_putchar;  /* Put Unicode character at x/y. */
	tf_fill_t     *tf_fill;     /* Fill rectangle with character. */
	tf_copy_t     *tf_copy;     /* Copy rectangle to new location. */
	tf_param_t    *tf_param;    /* Miscellaneous options. */
	tf_respond_t  *tf_respond;  /* Send response string to user. */
} teken_funcs_t;
.Ed
.Pp
All callbacks must be provided, though unimplemented callbacks may some
times be sufficient.
The actual types of these callbacks can be found in
.In teken.h .
.Pp
By default,
.Fn teken_init
initializes the
.Vt teken_t
structure to emulate a terminal having 24 rows and 80 columns.
The
.Fn teken_get_winsize
and
.Fn teken_set_winsize
functions can be used to obtain and modify the dimensions of the
terminal.
.Pp
Even though the cursor position is normally controlled by input of data
through
.Fn teken_input
and returned by the
.Fn tf_cursor
callback, it can be obtained and modified manually using the
.Fn teken_get_cursor
and
.Fn teken_set_cursor
functions.
The same holds for
.Fn teken_get_curattr
and
.Fn teken_set_curattr ,
which can be used to change the currently selected font attributes and
foreground and background color.
.Pp
By default,
.Nm
emulates a white-on-black terminal, which means the default foreground
color is white, while the background color is black.
These defaults can be modified using
.Fn teken_get_defattr
and
.Fn teken_set_defattr .
.Pp
The
.Fn teken_get_sequence
function is a utility function that can be used to obtain escape
sequences of special keyboard keys, generated by user input.
The
.Fa id
parameter must be one of the
.Dv TKEY_*
parameters listed in
.In teken.h .
.Sh LEGACY FEATURES
This library also provides a set of functions that shouldn't be used in
any modern applications.
.Pp
The
.Fn teken_256to8
function converts a color code to one of the 8 primary colors, allowing
the terminal to be rendered on graphics hardware that only supports 8 or
16 colors (e.g. VGA).
.Pp
The
.Fn teken_get_defattr_cons25
function obtains the default terminal attributes as a pair of foreground
and background colors, using ANSI color numbering.
.Pp
The
.Fn teken_set_8bit
function disables UTF-8 processing and switches to 8-bit character mode,
which can be used to support character sets like CP437 and ISO-8859-1.
.Pp
The
.Fn teken_set_cons25
function switches terminal emulation to
.Dv cons25 ,
which is used by versions of
.Fx
prior to 9.0.
.Sh SEE ALSO
.Xr ncurses 3 ,
.Xr termcap 3 ,
.Xr syscons 4 .
.Sh HISTORY
The
.Nm
library appeared in
.Fx 8.0 ,
though it was only available and used inside the kernel.
In
.Fx 9.0 ,
the
.Nm
library appeared in userspace.
.Sh AUTHORS
.An Ed Schouten Aq ed@FreeBSD.org
.Sh SECURITY CONSIDERATIONS
The
.Fn tf_respond
callback is used to respond to device status requests commands generated
by an application.
In the past, there have been various security issues, where a malicious
application sends a device status request before termination, causing
the generated response to be interpreted by applications such as
.Xr sh 1 .
.Pp
.Nm
only implements a small subset of responses which are unlikely to cause
any harm.
Still, it is advised to leave
.Fn tf_respond
unimplemented.