+/***@page m17nDatabaseFormat Data format of the m17n database
+
+@section dbformat General format
+
+The mdatabase_load () function returns the data specified by tags in
+the form of plist if the first tag is not @c Mchartable nor @c
+Mcharset. The keys of the returned plist are limited to
+<tt>Minteger</tt>, <tt>Msymbol</tt>, <tt>Mtext</tt>, and
+<tt>Mplist</tt>. The type of the value is unambiguously determined by
+the corresponding key. If the key is <tt>Minteger</tt>, the value is
+an integer. If the key is <tt>Msymbol</tt>, the value is a symbol.
+And so on.
+
+A number of expressions are possible to represent a plist. For
+instance, we can use the form <tt>(K1:V1, K2:V2, ..., Kn:Vn)</tt> to
+represent a plist whose first property key and value are K1 and V1,
+second key and value are K2 and V2, and so on. However, we can use a
+simpler expression here because the types of plists used in the m17n
+database are fairly restricted.
+
+Hereafter, we use an expression, which is similar to S-expression, to
+represent a plist. (Actually, the default database loader of the m17n
+library is designed to read data files written in this expression.)
+
+The expression consists of one or more <i>elements</i>. Each element
+represents a property, i.e. a single element of a plist.
+
+Elements are separated by one or more <i>whitespaces</i>, i.e. a space
+(code 32), a tab (code 9), or a newline (code 10). Comments begin
+with a semicolon (<tt>;</tt>) and extend to the end of the line.
+
+The key and the value of each property are determined based on the
+type of the element as explained below.
+
+<ul>
+
+<li> INTEGER
+
+An element that matches the regular expression <tt>-?[0-9]+</tt> or
+<tt>0[xX][0-9A-Fa-f]+</tt> represents a property whose key is
+<tt>Minteger</tt>. An element matching the former expression is
+interpreted as an integer in decimal notation, and one matching the
+latter is interpreted as an integer in hexadecimal notation. The
+value of the property is the result of interpretation.
+
+For instance, the element <tt>0xA0</tt> represents a property whose value is
+160 in decimal.
+
+<li> SYMBOL
+
+An element that matches the regular expression
+<tt>[^-0-9(]([^\\()]|\\.)+</tt> represents a property whose key is
+<tt> Msymbol</tt>. In the element, <tt>\\t</tt>, <tt>\\n</tt>,
+<tt>\\r</tt>, and <tt>\\e</tt> 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 value of the property is the symbol having the
+resulting string as its name.
+
+For instance, the element <tt>abc\ def</tt> represents a property
+whose value is the symbol having the name "abc def".
+
+<li> M-TEXT
+
+An element that matches the regular expression <tt>"([^"]|\\")*"</tt>
+represents a property whose key is <tt>Mtext</tt>. The backslash escape
+explained above also applies here. Moreover, each part in the
+element matching the regular expression <tt>
+\\[xX][0-9A-Fa-f][0-9A-Fa-f]</tt> 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.
+
+<li> PLIST
+
+Zero or more elements surrounded by a pair of parentheses represent a
+property whose key is <tt>Mplist</tt>. 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.
+
+</ul>
+
+EXAMPLE
+
+Here is an example of plist that is written in the expression
+explained above.
+
+@verbatim
+abc 123 (pqr 0xff) "m\"text" (_\\_ ("string" xyz) -456)
+@endverbatim
+
+It represents the following plist:
+
+@verbatim
+(Msymbol:abc,
+ Minteger:123,
+ Mplist:(Msymbol:pqr,
+ Minteger:255),
+ Mtext:m"text,
+ Mplist:(Msymbol:_\_,
+ Mplist:(Mtext:string,
+ Msymbol:xyz),
+ Minteger:-456))
+@endverbatim
+
+@section fontenc Font Encoding
+
+The m17n library loads information about the encoding of each font
+form the m17n database by the tags \<font, encoding\>. 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 symbol representing a charset. 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), which 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 \<font,
+resize\>. 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 \<fontset, FONTSET-NAME\>. The plist format of the data is
+as follows:
+
+@verbatim
+FONTSET ::=
+ PER-SCRIPT * PER-CHARSET * FALLBACK *
+
+PER-SCRIPT ::=
+ '(' SCRIPT PER-LANGUAGE + ')'
+
+PER-LANGUAGE ::=
+ '(' LANGUAGE FONT-SPEC-ELEMENT + ')'
+
+PER-CHARSET ::=
+ '(' CHARSET FONT-SPEC-ELEMENT + ')'
+
+FALLBACK ::=
+ 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 does not have @c Mlangauge text property, try all
+three fonts.
+
+@section flt Font Layout Table
+
+Usually, the rendering engine converts character codes of 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 the information equivarent to 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
+\<font, layouter, FLT-NAME\>. The plist format of the data is as
+follows:
+
+@verbinclude flt.txt
+
+@section im Input Method
+
+@verbinclude im.txt
+
+*/
+
+////
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