Tty getting & leaving(3)

NAME
Tty getting & leaving - How to take control of ttys for direct braille display / read. More...

  Defines
#define BRLKEYCODES 1
#define BRLCOMMANDS 2

  Functions
int brlapi_getTty (int tty, int how)
int brlapi_leaveTty (void)

DETAILED DESCRIPTION

Before being able to write on the braille display, the application must tell the server which tty it will handle. Some checking is done just to be sure that only one client gets control of each tty.

The application must also specify how braille keys will be delivered to it. Two ways are possible: KEYCODES and COMMANDS

KEYCODES are specific to each braille driver, since the raw keycode, as defined in the driver will be given for each key press. Using them leads to building highly driver-dependent applications, which can yet sometimes be useful to mimic existing proprietary applications for instance.

COMMANDS means that applications will get exactly the same values as brltty. This allows driver-independent clients, which will hopefully be nice to use with a lot of different terminals

See also:
brlapi_readKey() brlapi_readCommand()

DEFINE DOCUMENTATION

  #define BRLCOMMANDS 2

ask for brltty commands

  #define BRLKEYCODES 1

ask for raw driver keycodes

FUNCTION DOCUMENTATION

  int brlapi_getTty (int tty, int how)

ask for some tty, with some key mechanism

Parameters:

tty * - If tty>0, application takes control of the specified tty;

if tty<=0, the library first looks at a CONTROLVT environment variable to get the tty number. If none is found, the WINDOWID is tried (for an xterm case), and if none is found, it tries to get it from /proc/self/stat

Parameters:

how tells whether the application wants brlapi_readKey() to return keycodes or brltty commands: either BRLKEYCODES or BRLCOMMANDS;In an X window environment, CONTROLVT might be useful. XFree86 >=4.4 defines an XFree86_VT root window property which exactly holds the used VT, so that it should be given to brlapi_getTty. If it isn't available, one may, right into .xsession and .xinitrc, grep X's log, for instance:

CONTROLVT='$(grep 'using VT number' '/var/log/XFree86.$(echo '$DISPLAY' | sed -e 's/^.*::*\([0-9]*\).*$/\1/').log' | sed -e 's/^.*using VT number \([0-9]*\).*$/\1/')'

CONTROLVT should also be propagated when running remote applications via ssh, for instance, along with BRLAPI_HOSTNAME and the authentication key.

Returns:
the used tty number on success, -1 on error

See also:
brlapi_leaveTty()

  int brlapi_leaveTty (void)

stop controlling the tty

Returns:
0 on success, -1 on error.

See also:
brlapi_getTty()