Man Linux: Main Page and Category List

NAME

       Reading key presses -

       How to read key presses from the braille terminal.

   Data Structures
       struct brlapi_expandedKeyCode_t
       struct brlapi_describedKeyCode_t
       struct brlapi_range_t

   Defines
       #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_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 (brlapi_range_t ranges[],
           unsigned int count)
       int BRLAPI_STDCALL brlapi__ignoreKeyRanges (brlapi_handle_t *handle,
           brlapi_range_t ranges[], unsigned int count)
       int BRLAPI_STDCALL brlapi_acceptKeyRanges (brlapi_range_t ranges[],
           unsigned int count)
       int BRLAPI_STDCALL brlapi__acceptKeyRanges (brlapi_handle_t *handle,
           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 fore BrlAPI 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.

Define 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.

   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().

   #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,
       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,
       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_acceptKeyRanges (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.

       Parameters:
           ranges key ranges, which are inclusive
           count number of ranges

       Note:
           The given codes should be raw keycodes (i.e. some driver name was
           given to brlapi_enterTtyMode())

   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.

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

       Note:
           The given codes should be brltty commands (NULL or '' was given to
           brlapi_enterTtyMode())

   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 (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().

       Parameters:
           ranges key ranges, which are inclusive
           count number of ranges

       Note:
           The given codes should be raw keycodes (i.e. some driver name was
           given to brlapi_enterTtyMode())

   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().

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

       Note:
           The given codes should be brltty commands (NULL or '' was given to
           brlapi_enterTtyMode())

   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 <brltty/brldefs.h> . 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 some driver name was given to brlapi_enterTtyMode(), a raw keycode
       is returned, as specified by the terminal 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() 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 trafic 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, brlapi_readKey() will
           return -1, brlapi_errno will be BRLAPI_ERROR_LIBCERR and errno will
           be EINTR.

Author

       Generated automatically by Doxygen for BrlAPI from the source code.