X Locale Database Definition
Yoshio Horiuchi
IBM Japan

Copyright © IBM Corporation 1994

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1. General

An X Locale Database contains the subset of a user’s environment that depends on language, in X Window System. It is made up from one or more categories. Each category consists of some classes and sub-classes.

It is provided as a plain ASCII text file, so a user can change its contents easily. It allows a user to customize the behavior of internationalized portion of Xlib without changing Xlib itself.

This document describes;

Database Format Definition

Contents of Database in sample implementation

Since it is hard to define the set of required information for all platforms, only the flexible database format is defined. The available entries in database are implementation dependent.

2. Database Format Definition

The X Locale Database contains one or more category definitions. This section describes the format of each category definition.

The category definition consists of one or more class definitions. Each class definition has a pair of class name and class value, or has several subclasses which are enclosed by the left brace ({) and the right brace (}).

Comments can be placed by using the number sign character (#). Putting the number sign character on the top of the line indicates that the entire line is comment. Also, putting any whitespace character followed by the number sign character indicates that a part of the line (from the number sign to the end of the line) is comment. A line can be continued by placing backslash (\) character as the last character on the line; this continuation character will be discarded from the input. Comment lines cannot be continued on a subsequent line using an escaped new line character.

X Locale Database only accepts XPCS, the X Portable Character Set. The reserved symbols are; the quotation mark("), the number sign (#), the semicolon(;), the backslash(\), the left brace({) and the right brace(}).

The format of category definition is;

CategoryDefinition ::= CategoryHeader CategorySpec CategoryTrailer
CategoryHeader ::= CategoryName NL
CategorySpec ::= { ClassSpec }
CategoryTrailer ::= "END" Delimiter CategoryName NL
CategoryName ::= String
ClassSpec ::= ClassName Delimiter ClassValue NL
ClassName ::= String
ClassValue ::= ValueList | "{" NL { ClassSpec } "}"
ValueList ::= Value | Value ";" ValueList
Value ::= ValuePiece | ValuePiece Value
ValuePiece ::= String | QuotedString | NumericString
String ::= Char { Char }
QuotedString ::= """ QuotedChar { QuotedChar } """
NumericString ::= "\\o" OctDigit { OctDigit }
| "\\d" DecDigit { DecDigit }
| "\\x" HexDigit { HexDigit }
Char ::= <XPCS except NL, Space or unescaped reserved symbols>
QuotedChar ::= <XPCS except unescaped """>
OctDigit ::= <character in the range of "0" - "7">
DecDigit ::= <character in the range of "0" - "9">
HexDigit ::= <character in the range of "0" - "9", "a" - "f", "A" - "F">
Delimiter ::= Space { Space }
Space ::= <space> | <horizontal tab>
NL ::= <newline>

Elements separated by vertical bar (|) are alternatives. Curly braces ({...}) indicate zero or more repetitions of the enclosed elements. Square brackets ([...]) indicate that the enclosed element is optional. Quotes ("...") are used around literal characters.

The backslash, which is not the top character of the NumericString, is recognized as an escape character, so that the next one character is treated as a literal character. For example, the two-character sequence, ‘‘\"’’(the backslash followed by the quotation mark) is recognized and replaced with a quotation mark character. Any whitespace character, that is not the Delimiter, unquoted and unescaped, is ignored.

3. Contents of Database

The available categories and classes depend on implementation, because different platform will require different information set. For example, some platform have system locale but some platform don’t. Furthermore, there might be a difference in functionality even if the platform has system locale.

In current sample implementation, categories listed below are available.

XLC_FONTSET XFontSet relative information
XLC_XLOCALE Character classification and conversion information

4. XLC_FONTSET Category

The XLC_FONTSET category defines the XFontSet relative information. It contains the CHARSET_REGISTRY-CHARSET_ENCODING name and character mapping side (GL, GR, etc), and is used in Output Method (OM).

class super class description
fsN Nth fontset (N=0,1,2, ...)

charset fsN list of encoding name
font fsN list of font encoding name

Includes an encoding information for Nth charset, where N is the index number (0,1,2,...). If there are 4 charsets available in current locale, 4 fontsets, fs0, fs1, fs2 and fs3, should be defined. This class has two subclasses, ‘charset’ and ‘font’.

charset
Specifies an encoding information to be used internally in Xlib for this fontset. The format of value is;

EncodingInfo ::= EncodingName [ ":" EncodingSide ]
EncodingName ::= CHARSET_REGISTRY-CHARSET_ENCODING
EncodingSide ::= "GL" | "GR"

For detail definition of CHARSET_REGISTRY-CHARSET_ENCODING, refer "X Logical Font Descriptions" document.

example:

Specifies a list of encoding information which is used for searching appropriate font for this fontset. The left most entry has highest priority.

5. XLC_XLOCALE Category

The XLC_XLOCALE category defines character classification, conversion and other character attributes.

class super class description
encoding_name codeset name
mb_cur_max MB_CUR_MAX
state_depend_encoding state dependent or not
wc_encoding_mask for parsing wc string
wc_shift_bits for conversion between wc and mb
csN Nth charset (N=0,1,2,...)

side csN mapping side (GL, etc)
length csN length of a character
mb_encoding csN for parsing mb string
wc_encoding csN for parsing wc string
ct_encoding csN list of encoding name for ct

encoding_name
Specifies a codeset name of current locale.

mb_cur_max
Specifies a maximum allowable number of bytes in a multi-byte character. It is corresponding to MB_CUR_MAX of "ISO/IEC 9899:1990 C Language Standard".

state_depend_encoding
Indicates a current locale is state dependent. The value should be specified "True" or "False".

wc_encoding_mask
Specifies a bit-mask for parsing wide-char string. Each wide character is applied bit-and operation with this bit-mask, then is classified into the unique charset, by using ‘wc_encoding’.

wc_shift_bits
Specifies a number of bit to be shifted for converting from a multi-byte character to a wide character, and vice-versa.

Includes a character set information for Nth charset, where N is the index number (0,1,2,...). If there are 4 charsets available in current locale, cs0, cs1, cs2 and cs3 should be defined. This class has five subclasses, ‘side’, ‘length’, ‘mb_encoding’ ‘wc_encoding’ and ‘ct_encoding’.

Specifies a mapping side of this charset. The format of this value is;

Side ::= EncodingSide [‘‘:Default’’]

The suffix ":Default" can be specified. It indicates that a character belongs to the specified side is mapped to this charset in initial state.

length
Specifies a number of bytes of a multi-byte character of this charset. It should not contain the length of any single-shift sequence.

mb_encoding
Specifies a list of shift sequence for parsing multi-byte string. The format of this value is;

MBEncoding ::= ShiftType ShiftSequence
| ShiftType ShiftSequence ";" MBEncoding
ShiftType ::= "<SS>" | "<LSL>" | "<LSR>"
ShiftSequence ::= SequenceValue | SequenceValue ShiftSequence
SequenceValue ::= NumericString

shift types:
<SS> Indicates single shift sequence
<LSL> Indicates locking shift left sequence
<LSR> Indicates locking shift right sequence

example:

wc_encoding
Specifies an integer value for parsing wide-char string. It is used to determine the charset for each wide character, after applying bit-and operation using ‘wc_encoding_mask’. This value should be unique in all csN classes.

ct_encoding
Specifies a list of encoding information that can be used for Compound Text.

6. Sample of X Locale Database

The following is sample X Locale Database file.

# $Xorg: LocaleDB.ms,v 1.3 2000/08/17 19:42:49 cpqbld Exp $
# XLocale Database Sample for ja_JP.euc
#

#

#
XLC_FONTSET

}

}

}

# }
END XLC_FONTSET

#

#
XLC_XLOCALE

}

}

}

# #if HasWChar32

# #else

# #endif

# }

END XLC_XLOCALE

7. Reference

[1] ISO/IEC 9899:1990 C Language Standard

[2] X Logical Font Descriptions

1