Reading key presses(3)

NAME
Reading key presses - How to read key presses from the braille terminal. More...

  Defines
#define BRL_KEYBUF_SIZE 256
#define BRL_KEYCODE_MAX ((brl_keycode_t) (UINT32_MAX))

  Typedefs
typedef uint32_t brl_keycode_t

  Functions
int brlapi_readKey (int block, brl_keycode_t *code)
int brlapi_readCommand (int block, brl_keycode_t *code)
int brlapi_ignoreKeyRange (brl_keycode_t x, brl_keycode_t y)
int brlapi_ignoreKeySet (const brl_keycode_t *s, uint32_t n)
int brlapi_unignoreKeyRange (brl_keycode_t x, brl_keycode_t y)
int brlapi_unignoreKeySet (const brl_keycode_t *s, uint32_t n)

DETAILED DESCRIPTION

Once brlapi_getTty() is called, the application can call brlapi_readKey() or brlapi_readCommand() to read key presses. Not everyone can be called, it depends on parameters given to brlapi_getTty().

key presses are buffered, so that calling brlapi_readKey() in non-blocking mode from times to times should suffice.

DEFINE DOCUMENTATION

  #define BRL_KEYBUF_SIZE 256

buffer size

key presses won't be lost provided no more than BRL_KEYBUF_SIZE key presses are done between two calls to brlapi_read* if a call to another function is done in the meanwhile (which needs somewhere to put them before being able to get responses from the server)

  #define BRL_KEYCODE_MAX ((brl_keycode_t) (UINT32_MAX))

brl_keycode_t's biggest value

As defined in <inttypes.h>

TYPEDEF DOCUMENTATION

  typedef uint32_t brl_keycode_t

type for key codes

Its size is 32 bits, so driver implementors have to restrict themselves to a 32 bit space.

FUNCTION DOCUMENTATION

  int brlapi_ignoreKeyRange (brl_keycode_t x, brl_keycode_t y)

Ignore some key presses from the braille keyboard

This function asks the server to give keys between x and y to brltty, rather than returning them to the application via brlapi_read(Key|Command)()

Note:
The given codes are either raw keycodes if BRLKEYCODES was given to brlapi_getTty(), or brltty commands if BRLCOMMANDS was given.

  int brlapi_ignoreKeySet (const brl_keycode_t * s, uint32_t n)

Ignore some key presses from the braille keyboard

This function asks the server to give the n keys in set s to brltty, rather than returning them to the application via brlapi_read(Key|Command)()

Note:
The given codes are either raw keycodes if BRLKEYCODES was given to brlapi_getTty(), or brltty commands if BRLCOMMANDS was given.

  int brlapi_readCommand (int block, brl_keycode_t * code)

Read a command from the braille keyboard

This function returns brltty commands, as described in <brltty/brldefs.h> . These are hence pretty driver-independent, and should be used by default when no other option is possible.

It can be called only if BRLCOMMANDS was given to brlapi_getTty()

By default, all commands but those which restart drivers and switch virtual terminals are returned to the application and not to brltty. If the application doesn't want to see some command events, it should call either brlapi_ignoreKeySet() or brlapi_ignoreKeyRange()

Parameters:

block
    tells whether the call should block until a key is pressed (1) or should only probe key presses (0).

code
    holds the command code if a key press is indeed read.

Returns:
-1 on error and *code is then undefined, 0 if block was 0 and no key was pressed so far, or 1 and *code holds the command code.

  int brlapi_readKey (int block, brl_keycode_t * code)

Read a key from the braille keyboard

This function returns raw keycodes, as specified by the terminal driver. It generally corresponds to the code the terminal tells to the driver.

This should only be used to application which are dedicated to a particular braille terminal. Hence, checking the terminal type thanks to a call to brlapi_getDriverId() or even brlapi_getDriverName() before getting tty control is a pretty good idea.

It can be called only if BRLKEYCODES was given to brlapi_getTty()

By default, all the keypresses will be passed to the client, none will go through brltty, so the application will have to handle console switching itself.

Parameters:

block
    tells whether the call should block until a key is pressed (1) or should only probe key presses (0),

code
    holds the key code if a key press is indeed read.

Returns:
-1 on error and *code is then undefined, 0 if block was 0 and no key was pressed so far, or 1 and *code holds the key code.

  int brlapi_unignoreKeyRange (brl_keycode_t x, brl_keycode_t y)

Unignore some key presses from the braille keyboard

This function asks the server to return keys between x and y to the application, and not give them to brltty.

Note:
You shouldn't ask the server to give you key presses which are usually used to switch between TTYs, unless you really know what you are doing !

Note:
The given codes are either raw keycodes if BRLKEYCODES was given to brlapi_getTty(), or brltty commands if BRLCOMMANDS was given.

  int brlapi_unignoreKeySet (const brl_keycode_t * s, uint32_t n)

Unignore some key presses from the braille keyboard

This function asks the server to return all n keys in set s to the application, and not give them to brltty.

Note:
You shouldn't ask the server to give you key presses which are usually used to switch between TTYs, unless you really know what you are doing !

Note:
The given codes are either raw keycodes if BRLKEYCODES was given to brlapi_getTty(), or brltty commands if BRLCOMMANDS was given.