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brlapi_keys(3) Library Functions Manual brlapi_keys(3)

NAME

brlapi_keys - Reading key presses


- 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()
#define brlapi_acceptAllKeys()
#define BRLAPI_UC_ROW 0x2800UL
#define brlapi__ignoreAllKeys(handle)
#define brlapi__acceptAllKeys(handle)

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)

Value:

brlapi__acceptKeys(handle, brlapi_rangeType_all, NULL, 0)








#define brlapi__ignoreAllKeys( handle)


Value:


brlapi__ignoreKeys(handle, brlapi_rangeType_all, NULL, 0)










int BRLAPI_STDCALL brlapi_acceptAllKeys( void)


Value:


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)


Value:


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
  





  

  
all keys, code must be 0

  

  
all keys of a given type

  

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

  

  
a given key with any flags

  

  
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:




    
  
  • in a select() loop, just add it to the readfds and exceptfds file
      descriptor sets;
    • 
  
  • 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;
    • 
  
  • in an Xt/Xaw/motif-based application, use XtAppAddInput(app_context,
      fileDescriptor, XtInputReadMask|XtInputExceptMask, f, data)
    • 
  
  • 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 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


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