Contents
Files with names of the form *.ttb are text tables, and with names of the form *.tti are text subtables. They are used by BRLTTY to translate the characters on the screen into their corresponding 8-dot computer braille representations (see Braille Dots for details).
Text tables can usually be found in the /etc/brltty/Text/ directory (see Local Customization for more details). See Text Table List for a list of BRLTTY's text tables.
A text table consists of a sequence of directives, one per line, which define how each character is to be represented in braille. UTF-8 character encoding must be used. Whitespace (blanks, tabs) at the beginning of a line, as well as before and/or after any operand of any directive, is ignored. Lines containing only whitespace are ignored. If the first non-whitespace character of a line is # then that line is a comment and is ignored.
The precedence for determining the braille representation for a character is as follows:
If the character is within the Unicode braille Row (U+2800 through U+28FF) then its low-order eight bits are used as follows:
Hex | Binary | Dot |
01 | 00000001 | 1 |
02 | 00000010 | 2 |
04 | 00000100 | 3 |
08 | 00001000 | 4 |
10 | 00010000 | 5 |
20 | 00100000 | 6 |
40 | 01000000 | 7 |
80 | 10000000 | 8 |
If the character is within the Unicode private use row U+F000 through U+F0FF then its low-order byte is:
An explicit representation (defined via The Char Directive, The Glyph Directive, or The Byte Directive.
An equivalent representation (defined via The Alias Directive).
The explicit representation of the Unicode base character.
The explicit representation of the transliterated ASCII character.
The explicit representation of the Unicode Replacement Character (U+FFFD).
The explicit representation of a question mark (?).
All eight braille dots.
char character dots # comment
Use this directive to specify how a Unicode character is to be represented in braille. A character defined via this directive can also be entered from a braille keyboard. If several characters have the same braille representation then only one of them should be defined via this directive - the others should be defined via The Glyph Directive (which has the same syntax). If more than one character with the same braille representation is defined via this directive (which is allowed for backward compatibility) then the first one is used when entered from a braille keyboard.
Examples:
char a 1 char b (12) char c ( 4 1 ) char \\ 12567 char \s 0 char \x20 () char \<LATIN_SMALL_LETTER_D> 145
glyph character dots # comment
Use this directive to specify how a Unicode character is to be represented in braille. A character defined via this directive is output-only - it can't be entered from a braille keyboard.
See The Char Directive for examples.
input character dots # comment
Use this directive to specify how a Unicode character is to be entered from a braille keyboard. A character defined via this directive is input-only - its actual braille representation isn't defined.
See The Char Directive for examples.
alias from to # comment
Use this directive to define the from Unicode character such that it has the same braille representation as the to Unicode character. See The String Operand for details on how to specify both operands.
byte byte dots # comment
Use this directive to specify how a character in the local character set is to be represented in braille. It has been retained for backward compatibility but should not be used. Unicode characters should be defined (via either The Char Directive or The Glyph Directive) so that the text table remains valid regardless of what the local character set is.
ifGlyph character directive
Use this directive to only process one or more directives if a character has a braille representation.
Examples:
ifGlyph C alias \u2103 C # degree Celsius
ifNotGlyph character directive
Use this directive to only process one or more directives if a character doesn't have a braille representation.
Examples:
ifNotGlyph \s glyph \s 0
ifInput cell directive
Use this directive to only process one or more directives if a character can be entered from a braille keyboard.
ifNotInput cell directive
Use this directive to only process one or more directives if a character can't be entered from a braille keyboard.
include file # comment
Use this directive to include the content of another file. It is recursive, which means that an included file can itself include yet another file. Care must be taken to ensure that an "include loop" is not created.
assign variable value
Use this directive to create or update a variable associated with the current nesting level (see The BeginVariables Directive) of the current include level (see The Include Directive). The variable is visible to the current and to lower include levels, but not to higher include levels.
Examples:
assign nullValue assign shortValue word assign longValue a\svalue\swith\sspaces assign IndirectValue \{variableName}
assignDefault variable value
Use this directive to assign a default value to a variable associated with the current nesting level (see The BeginVariables Directive) of the current include level (see The Include Directive). It's functionally equivalent to:
ifNotVar variable assign variable value
See The Assign Directive and The IfNotVar Directive for more details.
Examples:
assignDefault format plain\stext
ifVar variable directive
Use this directive to only process one or more directives if a variable exists.
Examples:
ifVar var1 ifVar var2 assign concatenation \{var1}\{var2}
ifNotVar variable directive
Use this directive to only process one or more directives if a variable doesn't exist.
Examples:
ifNotVar var1 assign var1 default\svalue
beginVariables
Use this directive to open a new variable nesting level. The Assign Directive) will define variables at this new nesting level, and will hide variables with the same names in any previous nesting level. These variables will remain defined until The EndVariables Directive that is at the same variable nesting level.
Examples:
assign x 1 # \{x} evaluates to 1 beginVariables # \{x} still evaluates to 1 assign x 2 # \{x} now evaluates to 2 endVariables # \{x} evaluates to 1 again
endVariables
Use this directive to close the current variable nesting level. See The BeginVariables Directive for details.
listVariables
Use this directive to list all of the currently defined variables. It can be helpful when debugging.
endIf
Use this directive to terminate the current conditional nesting level.
Examples:
ifVar x These lines will be processed if a variable named x exists. endIf
else
Use this directive to negate the test associated with the current conditional nesting level.
Examples:
assign x some\svalue ifVar x These lines will be processed. else These lines won't be processed. endIf
A string operand may be specified as a non-whitespace sequence of:
Any single character other than a backslash (\\) or a white-space character.
A backslash-prefixed special character. These are:
Sequence | Meaning |
\b | The backspace character. |
\f | The formfeed character. |
\n | The newline character. |
\o### | The three-digit octal representation of a character. |
\r | The carriage return character. |
\R | The Unicode replacement character. |
\s | The space character. |
\t | The horizontal tab character. |
\u#### | The four-digit hexadecimal representation of a character. |
\U######## | The eight-digit hexadecimal representation of a character. |
\v | The vertical tab character. |
\x## | The two-digit hexadecimal representation of a character. |
\X## | (the case of the X and of the digits isn't significant) |
\<name> | The Unicode name of a character (use _ for space). |
\{variable} | The value of a variable. |
\\ | A literal backslash. |
\# | A literal number sign. |
A dots operand is a sequence of one to eight dot numbers. If the dot numbers are enclosed within (parentheses) then they may be separated from one another by whitespace. A dot number is a digit within the range 1-8 as defined by the standard braille dot numbering convention (see Braille Dots for details). The special dot number 0 is recognized when not enclosed within (parentheses), and means no dots - it may not be used in conjunction with any other dot number.
A cell operand is a sequence of one to eight dot numbers. A dot number is a digit within the range 1-8 as defined by the standard braille dot numbering convention (see Braille Dots for details). The special dot number 0 is recognized, and means no dots - it may not be used in conjunction with any other dot number.
name | description |
---|---|
auto | locale-based autoselection |
ar | Arabic (generic) |
as | Assamese |
awa | Awadhi |
bg | Bulgarian |
bh | Bihari |
bn | Bengali |
bo | Tibetan |
bra | Braj |
brf | Braille Ready Format (for viewing .brf files within an editor or pager) |
cs | Czech |
cy | Welsh |
da | Danish |
da-1252 | Danish (Svend Thougaard, 2002–11–18) |
da-lt | Danish (LogText) |
de | German |
dra | Dravidian |
el | Greek |
en | English |
en_CA | English (Canada) |
en_GB | English (United Kingdom) |
en_US | English (United States) |
en-nabcc | English (North American Braille Computer Code) |
eo | Esperanto |
es | Spanish |
et | Estonian |
fi | Finnish |
fr | French |
fr_CA | French (Canada) |
fr_FR | French (France) |
fr-2007 | French (unified 2007) |
fr-cbifs | French (Code Braille Informatique Français Standard) |
fr-vs | French (VisioBraille) |
ga | Irish |
gd | Gaelic |
gon | Gondi |
gu | Gujarati |
he | Hebrew |
hi | Hindi |
hr | Croatian |
hu | Hungarian |
hy | Armenian |
is | Icelandic |
it | Italian |
kha | Khasi |
kn | Kannada |
kok | Konkani |
kru | Kurukh |
lt | Lituanian |
lv | Latvian |
mg | Malagasy |
mi | Maori |
ml | Malayalam |
mni | Manipuri |
mr | Marathi |
mt | Maltese |
mun | Munda |
mwr | Marwari |
ne | Nepali |
new | Newari |
nl | Dutch |
nl_BE | Dutch (Belgium) |
nl_NL | Dutch (Netherlands) |
no | Norwegian |
no-generic | Norwegian (with support for other languages) |
no-oup | Norwegian (Offentlig utvalg for punktskrift) |
nwc | Newari (old) |
or | Oriya |
pa | Panjabi |
pi | Pali |
pl | Polish |
pt | Portuguese |
ro | Romanian |
ru | Russian |
se | Sami (Northern) |
sa | Sanskrit |
sat | Santali |
sd | Sindhi |
sk | Slovak |
sl | Slovenian |
sv | Swedish |
sv-1989 | Swedish (1989 standard) |
sv-1996 | Swedish (1996 standard) |
sw | Swahili |
ta | Tamil |
te | Telugu |
tr | Turkish |
uk | Ukrainian |
vi | Vietnamese |