diff options
Diffstat (limited to 'man/2/w3c-css')
| -rw-r--r-- | man/2/w3c-css | 349 |
1 files changed, 349 insertions, 0 deletions
diff --git a/man/2/w3c-css b/man/2/w3c-css new file mode 100644 index 00000000..44a1ebfc --- /dev/null +++ b/man/2/w3c-css @@ -0,0 +1,349 @@ +.TH W3C-CSS 2 +.SH NAME +w3c-css \- cascading style sheet parser +.SH SYNOPSIS +.EX +include "css.m"; + +css := load CSS CSS->PATH; + +Stylesheet: adt { + charset: string; + imports: list of ref Import; + statements: list of ref Statement; +}; + +Import: adt { + name: string; + media: list of string; +}; + +Statement: adt { + pick{ + Media => + media: list of string; + rules: list of ref Statement.Ruleset; + Page => + pseudo: string; + decls: list of ref Decl; + Ruleset => + selectors: list of Selector; + decls: list of ref Decl; + } +}; + +Decl: adt { + property: string; + values: list of ref Value; + important: int; +}; + +Selector: type list of (int, Simplesel); # (combinator, simplesel) +Simplesel: type list of ref Select; + +Select: adt { + name: string; + pick{ + Element or ID or Any or Class or Pseudo => + # empty + Attrib => + op: string; # "=" "~=" "|=" + value: ref Value; # optional Ident or String + Pseudofn => + arg: string; + } +}; + +Value: adt { + sep: int; # operator preceding this term + pick{ + String or + Number or + Percentage or + Url or + Unicoderange => + value: string; + Hexcolour => + value: string; # as given + rgb: (int, int, int); # converted + RGB => + args: cyclic list of ref Value; # as given + rgb: (int, int, int); # converted + Ident => + name: string; + Unit => + value: string; # int or float + units: string; # suffix giving units + Function => + name: string; + args: cyclic list of ref Value; + } +}; + +init: fn(diag: int); +parse: fn(s: string): (ref Stylesheet, string); +parsedecl: fn(s: string): (list of ref Decl, string); +.EE +.SH DESCRIPTION +.B Css +implements a parser for the World-Wide Web Consortium's Cascading +Style Sheet, specification 2.1. +.PP +.B Init +must be called before any other operation in the module. +If +.I diag +is non-zero, the module will print diagnostics on standard output for +malformed or unrecognised items that are ignored during parsing (as +required by the specification). +.PP +.B Parse +takes a complete stylesheet in string +.IR s , +parses it, and returns a tuple +.BI ( sheet,\ err ) +where +.I sheet +refers to a +.B Stylesheet +value containing the logical content of +.IR s , +as described below. +On a fatal error, +.I sheet +is nil and +.I err +is a diagnostic. +Most syntactic errors are ignored, as the specification requires. +.PP +In some applications there can be auxiliary declarations outside a stylesheet. +.B Parsedecl +takes a string +.I s +containing a sequence of declarations, and returns a tuple +.BI ( decls,\ err ) +where +.I decls +is a list of references to +.B Decl +values, each representing a single +.I declaration +in +.IR s . +On a fatal error, +.I decls +is nil, and +.I err +is a diagnostic. +.PP +The adts represent an abstract syntax of the CSS grammar. +The concrete syntax is presented below in an extended BNF, +derived from the reference grammar, +with each section labelled by the name of the corresponding adts. +(Compared to the reference grammar in the +specification, it abstracts away from the complex rules about where whitespace can appear.) +.TP +.B Stylesheet +.EX +.ft R +\f2stylesheet\fP ::= [ '\f5@charset\fP' STRING '\f5;\fP' ] \f2import\fP* \f2statement\fP* +.EE +.IP +Limbo lists represent lists of items in the grammar. +Nil values denote optional components that are missing. +Upper-case names such as +IDENT, +STRING +and +NUMBER +are terminals; see the CSS specification for their +often subtle definitions. +They are usually represented +by Limbo string values in the adts. +.TP +.B Import +.EX +.ft R +\f2import\fP ::= '\f5@import\fP' (\f2STRING\fP|\f2uri\fP) [\f2medium\fP ('\f5,\fP' \f2medium\fP)*] '\f5;\fP' +\f2uri\fP ::= '\f5url(\fP' STRING '\f5)\fP' +.EE +.IP +.B Import.name +holds the text of the +STRING +or +.IR uri . +.TP +.B Statement +.EX +.ft R +\f2statement\fP ::= \f2ruleset\fP | \f2media\fP | \f2page\fP +\f2media\fP ::= '\f5@media\fP' \f2medium\fP ('\f5,\fP' \f2medium\fP)* '\f5{\fP' \f2ruleset\fP* '\f5}\fP' +\f2medium\fP ::= IDENT +\f2page\fP ::= '\f5@page\fP' [\f2pseudo_page\fP] '\f5{\fP' \f2declaration\fP ('\f5;\fP' \f2declaration\fP)* '\f5}\fP' +\f2pseudo_page\fP ::= '\f5:\fP' IDENT +\f2ruleset\fP ::= \f2selector\fP ('\f5,\fP' \f2selector\fP)* '\f5{\fP' \f2declaration\fP ('\f5;\fP' \f2declaration\fP)* '\f5}\fP' +.EE +.IP +.B Statement +is not in the reference grammar, but is introduced here to give a name corresponding +to the pick adt. +.TP +.B Decl +.EX +.ft R +\f2declaration\fP ::= \f2property\fP '\f5:\fP' \f2expr\fP ['\f5!\fP' '\f5important\fP'] | /* \f2empty\fP */ +\f2property\fP ::= IDENT +.EE +.B Decl.values +is a list representing the terms of the +.I expr +(see below for details). +.BR Decl 's +field +.B important +is non-zero if the optional `important' priority is given. +.TP +.B "list of ref Value" +.EX +.ft R +\f2expr\fP ::= \f2term\fP (\f2operator\fP \f2term\fP)* +\f2operator\fP ::= '\f5/\fP' | '\f5,\fP' | /* \f2empty\fP */ +.EE +.IP +An +.I expr +is always represented as a list of references to +.B Value +in some containing structure +(where +.B Value +represents a +.IR term , +see below). +The +.I operator +preceding each +.I term +appears as the field +.B sep +of the corresponding +.BR Value , +where a space character represents `empty' (concatenation). +.TP +.BR Selector +.EX +.ft R +\f2selector\fP ::= \f2simple_selector\fP (\f2combinator\fP \f2simple_selector\fP)* +\f2combinator\fP ::= '\f5+\fP' | '\f5>\fP' | /* \f2empty\fP */ +.EE +.IP +.B Selector +is just a type synonym for a list of tuples, say +.BI ( com,\ simplesel ) +where the +.I simplesel +value represents +.I simple_selector +(see below), and the integer +.I com +is one of the characters space (representing `empty'), +.RB ` > ' +or +.RB ` + ', +giving the combinator that preceded the simple selector. +(The first in the list is always space.) +.TP +.BR Simplesel ", " Select +.EX +.ft R +\f2simple_selector\fP ::= \f2element_name\fP (\f2hash\fP | \f2class\fP | \f2attrib\fP | \f2pseudo\fP)* + | (\f2hash\fP | \f2class\fP | \f2attrib\fP | \f2pseudo\fP)+ +\f2hash\fP ::= '\f5#\fP' NAME +\f2class\fP ::= '\f5.\fP' IDENT +\f2element_name\fP ::= IDENT | '\f5*\fP' +\f2attrib\fP ::= '\f5[\fP' IDENT [('\f5=\fP' | '\f5|=\fP' | '\f5~=\fP') (IDENT | STRING)] '\f5]\fP' +\f2pseudo\fP ::= '\f5:\fP' ( IDENT | IDENT '\f5(\fP' [IDENT] '\f5)\fP' ) +.EE +.IP +A +.I simple_selector +is represented by +.BR Simplesel , +a list of references to +.B Select +values, each representing one +.I element_name +or qualifier. +An +.I element_name +is represented by +.B Select.Element +for an +IDENT, +or +.B Select.Any +for +.RB ` * '. +The qualifiers are +.I hash +.RB ( Select.ID ), +.I class +.RB ( Select.Class ), +.I attrib +.RB ( Select.Attrib , +where the comparison operator is the string +.BR op ), +.I pseudo +(either +.B Select.Pseudo +if a plain identifier, or +.B Select.Pseudofn +for a function with optional parameter). +.TP +.B Value +.EX +.ft R +\f2term\fP ::= ['\f5+\fP' | '\f5-\fP'] (NUMBER | \f2percent\fP | \f2unit\fP) | STRING | IDENT | \f2uri\fP | \f2function\fP | \f2hexcolour\fP | \f2rgb\fP +\f2function\fP ::= IDENT '\f5(\fP' \f2expr\fP '\f5)\fP' +\f2hash\fP ::= '\f5#\fP' NAME +\f2hexcolour\fP ::= '\f5#\fP' HEXDIGIT+ +\f2percent\fP ::= NUMBER '\f5%\fP' +\f2unit\fP ::= NUMBER STRING +\f2rgb\fP ::= '\f5rgb(\fP' \f2term\fP '\f5,\fP' \f2term\fP '\f5,\fP' \f2term\fP '\f5)\fP' +\f2uri\fP ::= '\f5url(\fP' STRING '\f5)\fP' +.EE +.IP +Any sign before a +.BR Number , +.B Percentage +or +.B Unit +appears as the first character of +.BR value . +All the dimensional units (LENGTH, EMS, EXS, ANGLE, TIME, FREQ and others) +in the reference grammar are mapped to +.BR Value.Unit , +with the field +.B units +containing the name of the relevant unit (eg, +.LR cm , +.LR in , +etc.) in lower case. +Values and names appear shorn of the surrounding punctuation. +.B Value.Hexcolour +includes the original sequence of hex digits as a string, +and a decoding of it as an +.B rgb +triple. +The arguments to the CSS +.B rgb +function are similarly presented in original and decoded forms, in +.BR Value.RGB . +Other function references are returned uninterpreted in +.BR Value.Function . +.SH SOURCE +.B /appl/lib/w3c/css.b +.SH SEE ALSO +``Cascading Style Sheets, level 2 revision 1'', +.B http://www.w3.org/TR/CSS21 |