/***@page m17nDatabaseFormat DatabaseFormat
This section describes the formats of predefined @e plist @e type data
in the m17n database.
@section dbformat General format
The m17n library expects that the function mdatabase_load () returns a
plist of a specific format on loading data identified by a specific
set of tags. As the plist format used for the database data is
strongly limited, we can use the equivalent text of simple syntax
(S-expression) to represent the plist as below.
The text consists of one or more @e elements . Each element
represents a property, i.e. a single element of a plist, and the
sequence of the elements constitute a plist.
Elements are separated by one or more @e whitespaces, i.e. a space
(code 32), a tab (code 9), or a newline (code 10). Comments begin
with a semicolon (;) and extend to the end of the line.
The key and the value of each property are determined based on the
form of element as below:
- INTEGER
An element that matches the regular expression @c -?[0-9]+ or @c
0[xX][0-9A-Fa-f]+ represents a property whose key is @c Minteger . An
element matching the former expression is interpreted as an integer in
decimal notation, and one matching the latter expression is
interpreted as an integer in hexadecimal notation. The resulting
integer is the value of the property.
For instance, the element 0xA0 represents a property whose value is
the integer 160.
- SYMBOL
An element that matchs the regular expression @c
[^-0-9(]([^\\()]|\\.)+ represents a property whose key is @c Msymbol .
In the sequence, @c \\t , @c \\n , @c \\r , and @c \\e are replaced
with tab (code 9), newline (code 10), carriage return (code 13), and
escape (code 27) respectively. Other characters following a backslash
is interpreted as it is. The symbol having the name of the resulting
sequence is the value of the property.
For instance, the element abc\ def represents a property
whose value is the symbol of name "abc def".
- M-TEXT
An element that matches the regular expression @c "([^"]|\\")*"
represents a property whose key is @c Mtext . The backslash escape
explained above also applies here. Moreover, each part in the
sequence matching the regular expression @c
\\[xX][0-9A-Fa-f][0-9A-Fa-f] is replaced with its hexadecimal
interpretation.
After having resolved the backslash escapes, the byte sequence between
the double quotes is interpreted as a UTF-8 sequence and decoded into
an M-text. This M-text is the value of the property.
- PLIST
An element that is preceded by a left parenthesis, followed zero or
more elements, and terminated by a right parenthesis represents a
property whose key is @c Mplist . Parentheses also serve as a
separator, which means whitespaces before and after a parenthesis can
be omitted. The value of the property is a plist, which is the result
of recursive interpretation of the elements between the parentheses.
EXAMPLE
Suppose (K1:V1, K2:V2, ... ,Kn:Vn) represents a plist whose first
property key and value are K1 and V1, second key and value are K2 and
V2, and so on. Then the line:
@verbatim
abc 123 (pqr 0xff) "m\"text" (_\\_ ("string" xyz) -456)
@endverbatim
is interpreted as follows.
@verbatim
(Msymbol:abc,
Minteger:123,
Mplist:(Msymbol:pqr,
Minteger:255),
Mtext:m"text,
Mplist:(Msymbol:_\_,
Mplist:(Mtext:string,
Msymbol:xyz),
Minteger:-456))
@endverbatim
The default database loader of the m17n library actually read a text
of this syntax from the database file.
Here after we describes the plist format of each data by this syntax.
@section fontenc Font Encoding
The m17n library loads information about the encoding of each font
form the m17n database by the tags \. The plist
format of the data is as follows:
@verbatim
FONT-ENCODING ::=
'(' PER-FONT-INFO * ')'
PER-FONT-INFO ::=
'(' FONT-SPEC ENCODING ')'
FONT-SPEC ::=
'('
[ FOUNDRY FAMILY [ WEIGHT [ STYLE [ STRETCH [ ADSTYLE ] ] ] ] ] REGISTRY
')'
@endverbatim
@c FOUNDRY to @c REGISTRY are symbols specifying the corresponding
XLFD font name fields. Omitted symbols are regarded as @c nil, and
@c nil means a wild card. For instance, this @c FONT-SPEC:
@verbatim
(nil alice0\ lao iso8859-1)
@endverbatim
should be applied to all fonts whose family is "alice0 lao", and
registry is "iso8859-1".
@c ENCODING is a charset symbol. A font matching @c FONT-SPEC
supports all characters of the charset, and a character code is mapped
to the corresponding glyph code of the font by this charset.
@section fontsize Font Resizing
In some case, a font contains incorrect information about its size
(typically in the case of a hacked TrueType font), and results in a
bad text layout when such a font is used in combination with the other
fonts. To overcome this problem, the m17n library loads information
about font-size correction from the m17n database by the tags \. The plist format of the data is as follows:
@verbatim
FONT-RESIZE ::=
'(' PER-FONT-INFO * ')'
PER-FONT-INFO ::=
'(' FONT-SPEC RESIZE-RATIO ')'
FONT-SPEC ::=
'('
[ FOUNDRY FAMILY [ WEIGHT [ STYLE [ STRETCH [ ADSTYLE ] ] ] ] ] REGISTRY
')'
@endverbatim
The meanings of @c FOUNDRY to @c REGISTRY are the same as @e Font @e
Encoding. @c RESIZE-RATIO is an integer number specifying by
percentage how much the font-size must be adjusted. For instance,
this @c PER-FONT-INFO:
@verbatim
((devanagari-cdac) 150)
@endverbatim
means that, to use a font of registry "devanagari-cdac" with a
specific size, we have to open an 1.5 times bigger one.
@section fontset Fontset
The m17n library loads a fontset definition from the m17n database by
the tags \. The plist format of the data is
as follows:
@verbatim
FONTSET ::=
'(' PER-SCRIPT + ')'
PER-SCRIPT ::=
'(' SCRIPT PER-LANGUAGE + ')'
PER-LANGUAGE ::=
'(' LANGUAGE FONT-SPEC-ELEMENT + ')'
FONT-SPEC-ELEMENT ::=
'(' FONT-SPEC [ FLT-NAME ] ')'
FONT-SPEC ::=
'('
[ FOUNDRY FAMILY [ WEIGHT [ STYLE [ STRETCH [ ADSTYLE ] ] ] ] ] REGISTRY
')'
@endverbatim
@c SCRIPT is a symbol of script name (e.g. latin, han), or @c nil. @c
LANGUAGE is a two-letter symbol of language name code defined by ISO
639 (e.g. ja, zh) or @c nil. The meanings of @c FOUNDRY to @c
REGISTRY are the same as @e Font @e Encoding. @c FLT-NAME is a name
of @ref flt.
For instance, this @c PER_SCRIPT:
@verbatim
(han
(ja
((jisx0208.1983-0)))
(zh
((gb2312.1980-0)))
(nil
((big5-0))))
@endverbatim
instructs the rendering engine to use a font of registry
"jisx0208.1983-0" for a "han" character that has @c Mlanguage text
propert "ja" if the character is in the repertories of such fonts.
Otherwise, try a font of registry "gb2312.1980-0" or "big5-0". If a
"han" character doesn not have @c Mlangauge text property, try all
three fonts.
@section flt Font Layout Table
Usually, the rendering engine converts character codes of a text into
glyph codes one by one by consulting information about encoding of
each selected font. But, for rendering a text that requires
complicated layouting (e.g. Thai and Indic), such an one to one
conversion is not sufficient. In addition, some glyphs must be
shifted 2-dimensionally on the screen. For such a case, a font layout
table (FLT in short) must be used.
A FLT can contain all the information in OpenType Layout Table (CMAP,
GSUB, and GPOS) in addition to the information about how to extract a
grapheme cluster and how to re-order characters.
The m17n library loads a FLT from the m17n database by the tags
\. The plist format of the data is as
follows:
@verbinclude flt.txt
@section im Input Method
@verbinclude im.txt
*/
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