brlapi_keys(3)                      BrlAPI                      brlapi_keys(3)



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


SYNOPSIS
   Data Structures
       struct brlapi_expandedKeyCode_t
       struct brlapi_describedKeyCode_t
       struct brlapi_range_t

   Macros
       #define brlapi_ignoreAllKeys()
           brlapi_ignoreKeys(brlapi_rangeType_all, NULL, 0)
       #define brlapi_acceptAllKeys()
           brlapi_acceptKeys(brlapi_rangeType_all, NULL, 0)
       #define BRLAPI_UC_ROW   0x2800UL
       #define brlapi__ignoreAllKeys(handle)   brlapi__ignoreKeys(handle,
           brlapi_rangeType_all, NULL, 0)
       #define brlapi__acceptAllKeys(handle)   brlapi__acceptKeys(handle,
           brlapi_rangeType_all, NULL, 0)

   Enumerations
       enum brlapi_rangeType_t { brlapi_rangeType_all, brlapi_rangeType_type,
           brlapi_rangeType_command, brlapi_rangeType_key,
           brlapi_rangeType_code }

   Functions
       int BRLAPI_STDCALL brlapi_expandKeyCode (brlapi_keyCode_t code,
           brlapi_expandedKeyCode_t *expansion)
       int BRLAPI_STDCALL brlapi_describeKeyCode (brlapi_keyCode_t code,
           brlapi_describedKeyCode_t *description)
       int BRLAPI_STDCALL brlapi_readKey (int wait, brlapi_keyCode_t *code)
       int BRLAPI_STDCALL brlapi__readKey (brlapi_handle_t *handle, int wait,
           brlapi_keyCode_t *code)
       int BRLAPI_STDCALL brlapi_readKeyWithTimeout (int timeout_ms,
           brlapi_keyCode_t *code)
       int BRLAPI_STDCALL brlapi__readKeyWithTimeout (brlapi_handle_t *handle,
           int timeout_ms, brlapi_keyCode_t *code)
       int BRLAPI_STDCALL brlapi_ignoreKeys (brlapi_rangeType_t type, const
           brlapi_keyCode_t keys[], unsigned int count)
       int BRLAPI_STDCALL brlapi__ignoreKeys (brlapi_handle_t *handle,
           brlapi_rangeType_t type, const brlapi_keyCode_t keys[], unsigned
           int count)
       int BRLAPI_STDCALL brlapi_acceptKeys (brlapi_rangeType_t type, const
           brlapi_keyCode_t keys[], unsigned int count)
       int BRLAPI_STDCALL brlapi__acceptKeys (brlapi_handle_t *handle,
           brlapi_rangeType_t type, const brlapi_keyCode_t keys[], unsigned
           int count)
       int BRLAPI_STDCALL brlapi__ignoreAllKeys (brlapi_handle_t *handle)
       int BRLAPI_STDCALL brlapi__acceptAllKeys (brlapi_handle_t *handle)
       int BRLAPI_STDCALL brlapi_ignoreKeyRanges (const brlapi_range_t
           ranges[], unsigned int count)
       int BRLAPI_STDCALL brlapi__ignoreKeyRanges (brlapi_handle_t *handle,
           const brlapi_range_t ranges[], unsigned int count)
       int BRLAPI_STDCALL brlapi_acceptKeyRanges (const brlapi_range_t
           ranges[], unsigned int count)
       int BRLAPI_STDCALL brlapi__acceptKeyRanges (brlapi_handle_t *handle,
           const brlapi_range_t ranges[], unsigned int count)

Detailed Description
       Once brlapi_enterTtyMode() has been called, the application can call
       brlapi_readKey() to read key presses. Either key codes (see Types and
       Defines forBrlAPI Key Codes) or commands will be returned, depending on
       parameters given to brlapi_enterTtyMode().

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

Macro Definition Documentation
   #define brlapi__acceptAllKeys(handle)   brlapi__acceptKeys(handle,
       brlapi_rangeType_all, NULL, 0)
   #define brlapi__ignoreAllKeys(handle)   brlapi__ignoreKeys(handle,
       brlapi_rangeType_all, NULL, 0)
   int BRLAPI_STDCALL brlapi_acceptAllKeys(void)
       brlapi_acceptKeys(brlapi_rangeType_all, NULL, 0)
       Accept all key presses from the braille keyboard

       This function asks the server to give all keys to the application, and
       not give them to brltty.

       Warning: after calling this function, make sure to call
       brlapi_ignoreKeys() for ignoring important keys like
       BRL_CMD_SWITCHVT_PREV/NEXT and such.

       The sets of such keys are reset on brlapi_enterTtyMode call.

   int BRLAPI_STDCALL brlapi_ignoreAllKeys(void)
       brlapi_ignoreKeys(brlapi_rangeType_all, NULL, 0)
       Ignore all key presses from the braille keyboard

       This function asks the server to give all keys to brltty, rather than
       returning them to the application via brlapi_readKey().

       The sets of such keys are reset on brlapi_enterTtyMode call.

   #define BRLAPI_UC_ROW   0x2800UL
       Unicode braille row

Enumeration Type Documentation
   enum brlapi_rangeType_t
       types of key ranges

       Enumerator

       brlapi_rangeType_all
              all keys, code must be 0

       brlapi_rangeType_type
              all keys of a given type

       brlapi_rangeType_command
              all keys of a given command block, i.e. matching the key type
              and command parts

       brlapi_rangeType_key
              a given key with any flags

       brlapi_rangeType_code
              a given key code

Function Documentation
   int BRLAPI_STDCALL brlapi__acceptAllKeys (brlapi_handle_t * handle)
   int BRLAPI_STDCALL brlapi__acceptKeyRanges (brlapi_handle_t * handle, const
       brlapi_range_t ranges[], unsigned int count)
   int BRLAPI_STDCALL brlapi__acceptKeys (brlapi_handle_t * handle,
       brlapi_rangeType_t type, const brlapi_keyCode_t keys[], unsigned int
       count)
   int BRLAPI_STDCALL brlapi__ignoreAllKeys (brlapi_handle_t * handle)
   int BRLAPI_STDCALL brlapi__ignoreKeyRanges (brlapi_handle_t * handle, const
       brlapi_range_t ranges[], unsigned int count)
   int BRLAPI_STDCALL brlapi__ignoreKeys (brlapi_handle_t * handle,
       brlapi_rangeType_t type, const brlapi_keyCode_t keys[], unsigned int
       count)
   int BRLAPI_STDCALL brlapi__readKey (brlapi_handle_t * handle, int wait,
       brlapi_keyCode_t * code)
   int BRLAPI_STDCALL brlapi__readKeyWithTimeout (brlapi_handle_t * handle,
       int timeout_ms, brlapi_keyCode_t * code)
   int BRLAPI_STDCALL brlapi_acceptKeyRanges (const brlapi_range_t ranges[],
       unsigned int count)
       Accept some key presses from the braille keyboard

       This function asks the server to return the provided key ranges
       (inclusive) to the application, and not give them to brltty.

       The sets of such keys are reset on brlapi_enterTtyMode call.

       Parameters
           ranges key ranges, which are inclusive, see Types and Defines
           forBrlAPI Key Codes about key ranges
           count number of ranges

   int BRLAPI_STDCALL brlapi_acceptKeys (brlapi_rangeType_t type, const
       brlapi_keyCode_t keys[], unsigned int count)
       Accept some key presses from the braille keyboard

       This function asks the server to give the provided keys to the
       application, and not give them to brltty.

       The sets of such keys are reset on brlapi_enterTtyMode call.

       Parameters
           type type of keys to be ignored
           keys array of keys to be ignored
           count number of keys

   int BRLAPI_STDCALL brlapi_describeKeyCode (brlapi_keyCode_t code,
       brlapi_describedKeyCode_t * description)
       Describe the components of a key code.

       Parameters
           code the keycode to be described
           description pointer to the structure that receives the description

       Returns
           0 on success, -1 on error

   int BRLAPI_STDCALL brlapi_expandKeyCode (brlapi_keyCode_t code,
       brlapi_expandedKeyCode_t * expansion)
       Expand the components of a key code

       Parameters
           code the key code to be expanded
           expansion pointer to the structure that receives the components

       Returns
           0 on success, -1 on error

   int BRLAPI_STDCALL brlapi_ignoreKeyRanges (const brlapi_range_t ranges[],
       unsigned int count)
       Ignore some key presses from the braille keyboard

       This function asks the server to give the provided key ranges to
       brltty, rather than returning them to the application via
       brlapi_readKey().

       The sets of such keys are reset on brlapi_enterTtyMode call.

       Parameters
           ranges key ranges, which are inclusive, see Types and Defines
           forBrlAPI Key Codes about key ranges
           count number of ranges

   int BRLAPI_STDCALL brlapi_ignoreKeys (brlapi_rangeType_t type, const
       brlapi_keyCode_t keys[], unsigned int count)
       Ignore some key presses from the braille keyboard

       This function asks the server to give the provided keys to brltty,
       rather than returning them to the application via brlapi_readKey().

       The sets of such keys are reset on brlapi_enterTtyMode call.

       Parameters
           type type of keys to be ignored
           keys array of keys to be ignored
           count number of keys

   int BRLAPI_STDCALL brlapi_readKey (int wait, brlapi_keyCode_t * code)
       Read a key from the braille keyboard

       This function returns one key press's code.

       If NULL or '' was given to brlapi_enterTtyMode(), a brltty command is
       returned, as described in the documentation for brlapi_keyCode_t . It
       is hence pretty driver-independent, and should be used by default when
       no other option is possible.

       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
       brlapi_ignoreKeys()

       If a driver name was given to brlapi_enterTtyMode(), a driver-specific
       keycode is returned, as specified by the braille driver, usually in
       <brltty/brldefs-xy> where xy is the driver's code. It generally
       corresponds to the very code that the terminal tells to the driver.
       This should only be used by applications which are dedicated to a
       particular braille terminal. Hence, checking the terminal type thanks
       to a call to brlapi_getDriverName() before getting tty control is a
       pretty good idea.

       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 for instance.

       Parameters
           wait 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 or signal interrupt 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.

       Programming hints:

       If your application is only driven by braille command keypresses, you
       can just call brlapi_readKey(1, &code) so that it keeps blocking,
       waiting for keypresses.

       Else, you'll probably want to use the file descriptor returned by
       brlapi_openConnection() or brlapi_getFileDescriptor() in your 'big
       polling loop'. For instance:

       +o in a select() loop, just add it to the readfds and exceptfds file
         descriptor sets;

       +o in a gtk or atspi application, use g_io_add_watch(fileDescriptor,
         G_IO_IN|G_IO_ERR|G_IO_HUP, f, data) for adding a callback called f;

       +o in an Xt/Xaw/motif-based application, use XtAppAddInput(app_context,
         fileDescriptor, XtInputReadMask|XtInputExceptMask, f, data)

       +o etc.

       and then, when you detect inbound traffic on the file descriptor, do
       something like this:

       while (brlapi_readKey(0, &code) { // process keycode code // ... }

       The while loop is needed for processing all pending key presses, else
       some of them may be left in libbrlapi's internal key buffer and you
       wouldn't get them immediately.

       Note
           If the read is interrupted by a signal or by a parameter change
           notification, brlapi_readKey() will return -1, brlapi_errno will be
           BRLAPI_ERROR_LIBCERR and errno will be EINTR.

   int BRLAPI_STDCALL brlapi_readKeyWithTimeout (int timeout_ms,
       brlapi_keyCode_t * code)
       Read a key from the braille keyboard, unless a timeout expires

       This function works like brlapi_readKey, except that parameter wait is
       replaced by a timeout_ms parameter

       Parameters
           timeout_ms specifies how long the function should wait for a
           keypress.
           code holds the key code if a key press is indeed read.

       Returns
           -1 on error, signal interrupt or parameter change notification and
           *code is then undefined, 0 if the timeout expired and no key was
           pressed, or 1 and *code holds the key code.

       If the timeout expires without any key being pressed, 0 is returned.

       If timeout_ms is set to 0, this function looks for key events that have
       been already received, but does not wait at all if no event was
       received.

       If timeout_ms is set to a negative value, this function behaves like
       brlapi_readKey, i.e. it uses an infinite timeout.

Author
       Generated automatically by Doxygen for BrlAPI from the source code.



Version 0.8                     Mon Apr 6 2026                  brlapi_keys(3)
