Parameter management

How to manage BrlAPI parameters. More...

Macros
#define	BRLAPI_PARAMF_LOCAL   0X00
#define	BRLAPI_PARAMF_GLOBAL   0X01
#define	BRLAPI_PARAMF_SELF   0X02

Typedefs
typedef uint32_t	brlapi_param_flags_t
typedef void(*	brlapi_paramCallback_t) (brlapi_param_t parameter, brlapi_param_subparam_t subparam, brlapi_param_flags_t flags, void *priv, const void *data, size_t len)
typedef void *	brlapi_paramCallbackDescriptor_t

Functions
ssize_t BRLAPI_STDCALL	brlapi_getParameter (brlapi_param_t parameter, brlapi_param_subparam_t subparam, brlapi_param_flags_t flags, void *data, size_t len)
ssize_t BRLAPI_STDCALL	brlapi__getParameter (brlapi_handle_t *handle, brlapi_param_t parameter, brlapi_param_subparam_t subparam, brlapi_param_flags_t flags, void *data, size_t len)
void *BRLAPI_STDCALL	brlapi_getParameterAlloc (brlapi_param_t parameter, brlapi_param_subparam_t subparam, brlapi_param_flags_t flags, size_t *len)
void *BRLAPI_STDCALL	brlapi__getParameterAlloc (brlapi_handle_t *handle, brlapi_param_t parameter, brlapi_param_subparam_t subparam, brlapi_param_flags_t flags, size_t *len)
int BRLAPI_STDCALL	brlapi_setParameter (brlapi_param_t parameter, brlapi_param_subparam_t subparam, brlapi_param_flags_t flags, const void *data, size_t len)
int BRLAPI_STDCALL	brlapi__setParameter (brlapi_handle_t *handle, brlapi_param_t parameter, brlapi_param_subparam_t subparam, brlapi_param_flags_t flags, const void *data, size_t len)
brlapi_paramCallbackDescriptor_t BRLAPI_STDCALL	brlapi_watchParameter (brlapi_param_t parameter, brlapi_param_subparam_t subparam, brlapi_param_flags_t flags, brlapi_paramCallback_t func, void *priv, void *data, size_t len)
brlapi_paramCallbackDescriptor_t BRLAPI_STDCALL	brlapi__watchParameter (brlapi_handle_t *handle, brlapi_param_t parameter, brlapi_param_subparam_t subparam, brlapi_param_flags_t flags, brlapi_paramCallback_t func, void *priv, void *data, size_t len)
int BRLAPI_STDCALL	brlapi_unwatchParameter (brlapi_paramCallbackDescriptor_t descriptor)
int BRLAPI_STDCALL	brlapi__unwatchParameter (brlapi_handle_t *handle, brlapi_paramCallbackDescriptor_t descriptor)
enum	brlapi_param_t {   BRLAPI_PARAM_SERVER_VERSION = 0 , BRLAPI_PARAM_CLIENT_PRIORITY = 1 , BRLAPI_PARAM_DRIVER_NAME = 2 , BRLAPI_PARAM_DRIVER_CODE = 3 ,   BRLAPI_PARAM_DRIVER_VERSION = 4 , BRLAPI_PARAM_DEVICE_MODEL = 5 , BRLAPI_PARAM_DEVICE_CELL_SIZE = 31 , BRLAPI_PARAM_DISPLAY_SIZE = 6 ,   BRLAPI_PARAM_DEVICE_IDENTIFIER = 7 , BRLAPI_PARAM_DEVICE_SPEED = 8 , BRLAPI_PARAM_DEVICE_ONLINE = 9 , BRLAPI_PARAM_RETAIN_DOTS = 10 ,   BRLAPI_PARAM_COMPUTER_BRAILLE_CELL_SIZE = 11 , BRLAPI_PARAM_LITERARY_BRAILLE = 12 , BRLAPI_PARAM_CURSOR_DOTS = 13 , BRLAPI_PARAM_CURSOR_BLINK_PERIOD = 14 ,   BRLAPI_PARAM_CURSOR_BLINK_PERCENTAGE = 15 , BRLAPI_PARAM_RENDERED_CELLS = 16 , BRLAPI_PARAM_SKIP_IDENTICAL_LINES = 17 , BRLAPI_PARAM_AUDIBLE_ALERTS = 18 ,   BRLAPI_PARAM_CLIPBOARD_CONTENT = 19 , BRLAPI_PARAM_BOUND_COMMAND_KEYCODES = 20 , BRLAPI_PARAM_COMMAND_KEYCODE_NAME = 21 , BRLAPI_PARAM_COMMAND_KEYCODE_SUMMARY = 22 ,   BRLAPI_PARAM_DEFINED_DRIVER_KEYCODES = 23 , BRLAPI_PARAM_DRIVER_KEYCODE_NAME = 24 , BRLAPI_PARAM_DRIVER_KEYCODE_SUMMARY = 25 , BRLAPI_PARAM_COMPUTER_BRAILLE_ROWS_MASK = 26 ,   BRLAPI_PARAM_COMPUTER_BRAILLE_ROW_CELLS = 27 , BRLAPI_PARAM_COMPUTER_BRAILLE_TABLE = 28 , BRLAPI_PARAM_LITERARY_BRAILLE_TABLE = 29 , BRLAPI_PARAM_MESSAGE_LOCALE = 30 ,   BRLAPI_PARAM_DRIVER_PROPERTY_VALUE = 32 , BRLAPI_PARAM_COUNT = 33 }

Detailed Description

There are several kinds of parameters:

• states associated with the braille device itself, such as its size or parameters of the device port
• states of the BrlAPI connection itself, such as the displaying level or key passing preferences.
• general states such as the cut buffer,
• braille parameters: braille table, contraction, cursor shape, etc,
• browse parameters: line skip, beep, etc.

Some of them are subdivided in subparameters. Others have only subparameter 0.

Some of them are read-only, others are read/write.

A client can either request the immediate content of a parameter by using brlapi_getParameter(); set the content of a parameter by using brlapi_setParameter(); or register a callback that may be called immediately and on each change of a given parameter, by using brlapi_watchParameter().

Macro Definition Documentation

BRLAPI_PARAMF_GLOBAL

#define BRLAPI_PARAMF_GLOBAL   0X01

Refer to the global value instead of the value local to the connection

BRLAPI_PARAMF_LOCAL

#define BRLAPI_PARAMF_LOCAL   0X00

Refer to the value local to the connection instead of the global value

BRLAPI_PARAMF_SELF

#define BRLAPI_PARAMF_SELF   0X02

Specify whether to receive notifications of value self-changes

Typedef Documentation

brlapi_param_flags_t

typedef uint32_t brlapi_param_flags_t

Flags for parameter requests

brlapi_paramCallback_t

typedef void(* brlapi_paramCallback_t) (brlapi_param_t parameter, brlapi_param_subparam_t subparam, brlapi_param_flags_t flags, void *priv, const void *data, size_t len)

Callback for parameter changes

When a parameter gets changed, application-defined callbacks set by the brlapi_watchParameter() function are called.

Parameters

parameter	is the parameter that changed;
subparam	is a specific instance of the parameter;
flags	specify which value and how it was changed;
priv	is the void pointer that was passed to the brlapi_watchParameter call which registered the callback;
data	is a buffer containing the new value of the parameter;
len	is the size of the data.

This callback only gets called when the application calls some brlapi_ function (i.e. BrlAPI gets direct control of the execution), BrlAPI itself does not start a separate thread or such.

If an application wants to see such event trigger a callback getting called e.g. in another thread, it can use brlapi_pause() to give BrlAPI an opportunity to receive messages and call the callbacks.

brlapi_paramCallbackDescriptor_t

typedef void* brlapi_paramCallbackDescriptor_t

Type for callback descriptors This is returned by brlapi_watchParameter, to be passed to brlapi_unwatchParameter.

Enumeration Type Documentation

brlapi_param_t

enum brlapi_param_t

Enumerator
BRLAPI_PARAM_SERVER_VERSION	Version of the server: uint32_t
BRLAPI_PARAM_CLIENT_PRIORITY	Priority of the client: uint32_t (from 0 through 100, default is 50)
BRLAPI_PARAM_DRIVER_NAME	Full name of the driver: string
BRLAPI_PARAM_DRIVER_CODE	Code (short name) of the driver: string
BRLAPI_PARAM_DRIVER_VERSION	Version of the driver: string
BRLAPI_PARAM_DEVICE_MODEL	Model of the device: string
BRLAPI_PARAM_DEVICE_CELL_SIZE	Number of dots in a cell: uint8_t
BRLAPI_PARAM_DISPLAY_SIZE	Dimensions of the braille display: { uint32_t columns; uint32_t rows; }
BRLAPI_PARAM_DEVICE_IDENTIFIER	Identifier of the device: string
BRLAPI_PARAM_DEVICE_SPEED	Speed of the device: uint32_t
BRLAPI_PARAM_DEVICE_ONLINE	Device is online: boolean
BRLAPI_PARAM_RETAIN_DOTS	Pass dot combinations (rather than characters): boolean
BRLAPI_PARAM_COMPUTER_BRAILLE_CELL_SIZE	Number of dots used to render a computer braille character: uint8_t (8 or 6)
BRLAPI_PARAM_LITERARY_BRAILLE	Whether braille is literary (rather than computer): boolean
BRLAPI_PARAM_CURSOR_DOTS	Representation of the cursor: uint8_t (ISO 11548-1)
BRLAPI_PARAM_CURSOR_BLINK_PERIOD	Blinking period of the cursor: uint32_t (milliseconds)
BRLAPI_PARAM_CURSOR_BLINK_PERCENTAGE	Portion of the blinking period that the cursor is visible: uint8_t (from 0 through 100)
BRLAPI_PARAM_RENDERED_CELLS	Cells rendered by the client: uint8_t[] (ISO 11548-1), one cell per element
BRLAPI_PARAM_SKIP_IDENTICAL_LINES	Whether to skip identical screen lines: boolean
BRLAPI_PARAM_AUDIBLE_ALERTS	Whether to use audible alerts: boolean
BRLAPI_PARAM_CLIPBOARD_CONTENT	Content of the clipboard: UTF-8 string
BRLAPI_PARAM_BOUND_COMMAND_KEYCODES	Commands bound by the driver: uint64_t[], one command keycode per element
BRLAPI_PARAM_COMMAND_KEYCODE_NAME	Name for a command keycode (specified via the subparam argument): string (usually a few characters)
BRLAPI_PARAM_COMMAND_KEYCODE_SUMMARY	Description for a command keycode (specified via the subparam argument): string (usually a few words)
BRLAPI_PARAM_DEFINED_DRIVER_KEYCODES	Keycodes defined by the driver: uint64_t[], one keycode per element
BRLAPI_PARAM_DRIVER_KEYCODE_NAME	Name for a driver keycode (specified via the subparam argument): string (usually a few characters)
BRLAPI_PARAM_DRIVER_KEYCODE_SUMMARY	Description for a driver keycode (specified via the subparam argument): string (usually a few words)
BRLAPI_PARAM_COMPUTER_BRAILLE_ROWS_MASK	Set of Unicode rows that are defined for computer braille (from U+0000 through U+10FFFF): uint8_t[544], one bit per row, eight rows per element
BRLAPI_PARAM_COMPUTER_BRAILLE_ROW_CELLS	Computer braille cells for a Unicode row (specified via the subparam argument): uint8_t[256] (ISO 11548-1), one cell per element
BRLAPI_PARAM_COMPUTER_BRAILLE_TABLE	Name of the computer braille table: string
BRLAPI_PARAM_LITERARY_BRAILLE_TABLE	Name of the literary braille table: string
BRLAPI_PARAM_MESSAGE_LOCALE	Locale to use for messages: string
BRLAPI_PARAM_DRIVER_PROPERTY_VALUE	Value of a driver-specific property: uint32_t
BRLAPI_PARAM_COUNT

Function Documentation

brlapi__getParameter()

ssize_t BRLAPI_STDCALL brlapi__getParameter	(	brlapi_handle_t *	handle,
		brlapi_param_t	parameter,
		brlapi_param_subparam_t	subparam,
		brlapi_param_flags_t	flags,
		void *	data,
		size_t	len )

brlapi__getParameterAlloc()

void *BRLAPI_STDCALL brlapi__getParameterAlloc	(	brlapi_handle_t *	handle,
		brlapi_param_t	parameter,
		brlapi_param_subparam_t	subparam,
		brlapi_param_flags_t	flags,
		size_t *	len )

brlapi__setParameter()

int BRLAPI_STDCALL brlapi__setParameter	(	brlapi_handle_t *	handle,
		brlapi_param_t	parameter,
		brlapi_param_subparam_t	subparam,
		brlapi_param_flags_t	flags,
		const void *	data,
		size_t	len )

brlapi__unwatchParameter()

int BRLAPI_STDCALL brlapi__unwatchParameter	(	brlapi_handle_t *	handle,
		brlapi_paramCallbackDescriptor_t	descriptor )

brlapi__watchParameter()

brlapi_paramCallbackDescriptor_t BRLAPI_STDCALL brlapi__watchParameter	(	brlapi_handle_t *	handle,
		brlapi_param_t	parameter,
		brlapi_param_subparam_t	subparam,
		brlapi_param_flags_t	flags,
		brlapi_paramCallback_t	func,
		void *	priv,
		void *	data,
		size_t	len )

brlapi_getParameter()

ssize_t BRLAPI_STDCALL brlapi_getParameter	(	brlapi_param_t	parameter,
		brlapi_param_subparam_t	subparam,
		brlapi_param_flags_t	flags,
		void *	data,
		size_t	len )

Get the content of a parameter

brlapi_getParameter gets the current content of a parameter

Parameters

parameter	is the parameter whose content shall be gotten;
subparam	is a specific instance of the parameter;
flags	specify which value and how it should be returned;
data	is a buffer where content of the parameter shall be stored;
len	is the size of the buffer.

Returns

the real size of the parameter's content. If the parameter does not fit in the provided buffer, it is truncated to len bytes (but the real size of the parameter is still returned). In that case, the client must call brlapi_getParameter again with a big enough buffer.

brlapi_getParameterAlloc()

void *BRLAPI_STDCALL brlapi_getParameterAlloc	(	brlapi_param_t	parameter,
		brlapi_param_subparam_t	subparam,
		brlapi_param_flags_t	flags,
		size_t *	len )

Return the content of a parameter

brlapi_getParameterAlloc gets the current content of a parameter, by returning it as a newly-allocated buffer. The buffer is allocated to one byte more than the parameter value. This byte is set to zero. This allows, for string parameters, to be able to immediately use it as a C string.

Parameters

parameter	is the parameter whose content shall be gotten;
subparam	is a specific instance of the parameter;
flags	specify which value and how it should be returned;
len	is the address where to store the size of the parameter value.

Returns

a newly-allocated buffer that contains the value of the parameter. The caller must call free() on it after use. NULL is returned on errors

brlapi_setParameter()

int BRLAPI_STDCALL brlapi_setParameter	(	brlapi_param_t	parameter,
		brlapi_param_subparam_t	subparam,
		brlapi_param_flags_t	flags,
		const void *	data,
		size_t	len )

Set the content of a parameter

brlapi_setParameter sets the content of a parameter

Parameters

parameter	is the parameter to set;
subparam	is a specific instance of the parameter;
flags	specify which value and how it should be set;
data	is a buffer containing the data to store in the parameter;
len	is the size of the data.

Returns

0 on success, -1 on error (read-only parameter for instance).

brlapi_unwatchParameter()

int BRLAPI_STDCALL brlapi_unwatchParameter

(

brlapi_paramCallbackDescriptor_t

descriptor

)

Clear a parameter change callback

brlapi_unwatchParameter unregisters a parameter change callback: the callback function previously registered with brlapi_watchParameter will not be called any longer.

Parameters

descriptor

refers to the callback to be removed.

Returns

0 on success, -1 on error.

brlapi_watchParameter()

brlapi_paramCallbackDescriptor_t BRLAPI_STDCALL brlapi_watchParameter	(	brlapi_param_t	parameter,
		brlapi_param_subparam_t	subparam,
		brlapi_param_flags_t	flags,
		brlapi_paramCallback_t	func,
		void *	priv,
		void *	data,
		size_t	len )

Set a parameter change callback

brlapi_watchParameter registers a parameter change callback: whenever the given parameter changes, the given function is called.

Parameters

parameter	is the parameter to watch;
subparam	is a specific instance of the parameter;
flags	specify which value and how it should be monitored;
func	is the function to call on parameter change;
priv	is a void pointer which will be passed as such to the function;
data	is a buffer where the current content of the parameter shall be stored;
len	is the size of the buffer.

Returns

the callback descriptor (to be passed to brlapi_unwatchParameter to unregister the callback), or NULL on error.

Note

Default parameter callbacks don't do anything, except the ones for display size which just raise SIGWINCH.

If data is NULL, the callback will be called immediately by brlapi_watchParameter, for providing the initial value