Cascading Style Sheets, level 1 Cascading Style Sheets, level 1This is a W3C Working Draft for review by W3C members and other interested parties. It is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to use W3C Working Drafts as reference material or to cite them as other than "work in progress". A list of current W3C tech reports can be found at: http://www.w3.org/pub/WWW/TR/
Note: since working drafts are subject to frequent change, you are advised to reference the above URL, rather than the URLs for working drafts themselves.
This document specifies level 1 of the Cascading Style Sheet machanism (CSS1). CSS1 is a simple style sheet language that allows authors and readers to influence the presentation of HTML documents. E.g., a publisher can suggest font families, colors and layout for a document, while the reader can ask for the document to be magnified. By attaching style to HTML elements, document structure and device-independence is preserved.
We encourage programmers and authors to start experimenting with style sheets. Comments can be sent to the www-style@w3.org mailing list, or directly to the authors. For background material, see the resource page on HTML style sheets.
Designing simple style sheets is easy. One only need to know a little HTML and some basic desktop publishing terminology. E.g., to set the text color of H1 elements to blue, one can say:
H1 { color: blue }
The example consists of two main parts: selector (H1) and declaration
(color: blue). The declaration has two parts, property (color) and
value (blue). While the example above only tries to influence one of
the properties needed for rendering an HTML document, it qualifies as
a style sheet on its own. One of the fundamental features of CSS is
that style sheets are combined.
The selector is the link between the HTML document and the style, and all HTML elements are possible selectors. HTML elements are defined in the HTML specifications, and the CSS specification only defines a syntax for how to address them. Also, the list of properties and values are defined in this specification.
In order for the style sheet to influence the presentation, the user agent (UA, often a "web browser" or "web client") must be aware of its existence. Another W3C working draft will describe how to link HTML with style sheets. The example below is sure to be obsoleted by the forth-coming document, but describes how style sheet containment is implemented in the Arena browser:
<HEAD>
<TITLE>Title</TITLE>
<LINK REL=STYLESHEET HREF="bill.style" TITLE="Bill's own style">
<STYLE NOTATION=CSS>
H1 { color: blue }
</STYLE>
</HEAD>
The LINK
element references an external style sheet, while the proposed STYLE
element has a style sheet as content.
By declaring the NOTATION, the STYLE element can be used for other style sheet notations as well. For LINKed style sheets, the HTTP Content-Type field will declare the notation. The TITLE attribute assigns a name to a style sheet for user interaction purposes.
CSS rules can possibly also be included in HTML attributes:
<H1 STYLE="font-family: helvetica">Headline</A> <P STYLE="font: 12pt helvetica bold">Paragraph</A>This use of the style language mixes content with style, and one loses the corresponding advantages of traditional style sheets.
H1, H2, H3 { font-family: helvetica }
Similarly, declarations can be grouped:
H1 {
font-size: 12pt;
font-leading: 2pt;
font-family: helvetica;
font-weight: bold;
font-style: normal
}
In addition, some properties have their own grouping syntax:
H1 { font: 12pt/14pt helvetica bold normal }
which is equivalent to the previous example.
<H1>The headline <EM>is</EM> important!</H1>Since no color has been assigned to EM, the emphasized "is" will inherit the color of the surrounding element, i.e. it will also appear in blue. Other style properties are likewise inherited, e.g. font family and size.
Inheritance starts at the oldest ancestor, i.e. the top-level element. In HTML, this is is the 'HTML' element (although many HTML authors omit this tag). In order to set a "default" style property, one should use 'HTML' as selector:
HTML { color: dark-blue }
Some style properties are not inherited from the parent to the child. In most cases, it is intuitive why this is not the case. E.g., the 'background' property does not inherit since the parent element's background shine through by default.
<HTML>
<HEAD>
<TITLE>Title</TITLE>
<STYLE NOTATION=CSS>
H1.punk { color: #00FF00 }
</STYLE>
</HEAD>
<BODY>
<H1 CLASS=punk>Way too green</H1>
</BODY>
</HTML>
[ID="z098y"] { font-size: xx-large }
The notation is borrowed from CSS2 which will allow addressing based
on any attribute.
A.link { color: red } -- unvisited link --
A.visited { color: blue } -- visited links --
A.active { color: orange } -- active links --
$CANVAS { background: blue/red }
On a screen, the above example describes a background which is blue at
the top of the screen and fades into red at the bottom of the screen.
This part is optional in CSS1
Inheritance saves CSS designers a lot of typing. Instead of setting all style properties, one can create defaults and then list the exceptions. If one want to give EM elements within H1 a different color, one may specify:
H1 { color: blue }
EM { color: light-blue }
When this style sheet is in effect, all emphasized sections,
within or outside H1 will turn light-blue. Probably, one only wanted
EMs within H1 to turn light-blue. One can specify this with:
(H1) EM { color: light-blue }
The selector is now a search pattern. Only the last element of the
search pattern is addressed (in this case the EM element), and only so if the
search pattern matches. In the example above, the search pattern
matches if EM is a descendant of H1, i.e. if EM is inside an H1
element.
(LI) (LI) P { font-size: small }
(LI) (LI) (LI) P { font-size: x-small }
Here, the first selector matches P elements with at least two LI
ancestors. The second selector matches a subset of the first matches,
i.e. P elements with at least three LI ancestors. The
conflict is resolved by the second selector being more specific (due to
the longer search pattern).
Search patterns can contain elements and/or classes:
(P.reddish) punk { color: red }
This selector matches all elements with subclass 'punk' and an
ancestor of element P and subclass 'reddish'.
Textual comments in a CSS style sheet start and end with two dashes:
EM { color: red } -- red, really red!! --
The CSS1 specification defines a list of style properties that a style sheet can influence. The goal is to be able to describe typography at the level of common desktop publishing. The following example, which includes a drop-cap initial and small-caps text, suggests the bounds of current properties:
<HTML>
<HEAD>
<TITLE>Title</TITLE>
<STYLE NOTATION=CSS>
P {
text-effect: drop-cap,
font-size: 12pt,
alt-font-size: 24pt -- assuming leading is zero --
}
EM { font-style: small-caps }
</STYLE
</HEAD>
<BODY>
<P><EM>The first</EM> few words of an article in The Economist..
</BODY>
</HTML>
If an ASCII-based UA supports these properties (we do not expect them
to), the above could be formatted as:
___ | HE FIRST few words |of an article in the Economist..The example shows the need for a new generic character-level element in HTML which doesn't bring with it any rendering conventions. We suggest adding a short HTML tag (e.g. 'C') for this, but the definition is outside the scope of this specification.
@import "http://www.style.org/punk.css"
H1 { color: red } -- override imported sheet --
In case of a direct conflict, the imported style sheet has lower weight than the one from where it is being imported.
Sometimes conflicts will arise between the style sheets that influence the presentation. Conflict resolution is based on each style declaration having a weight. By default, the weights of the reader's declarations is less that the weights of declarations in incoming documents. I.e., if there are conflicts between the style sheets of an incoming document and the reader's personal sheets, the incoming declarations will be used.
Style sheet designers can increase the weights of their declarations:
H1 { color: red ! important }
P { font-size: 12pt ! legal "IATA regulations" }
The '! legal ..' construct is used if there are legal reasons
behind the declaration, and the trailing string is a short reference to
the statutes. 'Important' and 'legal' declarations have the same
weight.
An important (or legal) reader declaration will override an incoming declaration with normal weight. An important (or legal) incoming declaration will override an important (or legal) reader declaration. Users should be notified when a style sheet is in effect, and be allowed to turn style sheets on and off.
The reference to the statutes should be displayed to the reader as a warning when the UA is not able to honor a legal declaration. The reader should acknowledge the warning with an action, e.g. a mouse click. Situations where the warning should be displayed include:
Conflicting rules are intrinsic to the CSS mechanism, and should be resolved in the following manner:
'HTML' < 'LI' < '(UL) (OL) LI' < '(UL) (OL) LI.red'.
The search for the property value can be terminated whenever one rule has a higher weight than the other rules who apply to the same element/property.
This strategy gives incoming style sheets considerably higher weight than those of the reader. It is therefore important that the reader has the ability to turn off the influence of style sheets, e.g. through a pull-down menu.
Note that special rules apply to tables.
The following example with pseudo-constants shows how margins and padding format:
<STYLE NOTATION=CSS>
UL {
background: red;
margin: A B C D; -- let's pretend we have constants in CSS1 --
padding: E F G H -- " --
}
LI {
background: blue;
color: white; -- so text is white on blue --
margin: a b c d; -- let's pretend we have constants in CSS1 --
padding: e f g h -- " --
}
</STYLE>
<UL>
<LI>1st element of list
<LI>2nd element of list
</UL>
________________________________________________________
| |
| A UL margin (transparent) |
| _______________________________________________ |
| D | | B |
| | E UL padding (red) | |
| | _______________________________________ | |
| | H | | F | |
| | | a LI margin (transparent, | | |
| | | so red shines through) | | |
| | | _______________________________ | | |
| | | d | | b | | |
| | | | e LI padding (blue) | | | |
| | | | | | | |
| | | | h 1st element of list f | | | |
| | | | | | | |
| | | | g | | | |
| | | |_______________________________| | | |
| | | | | |
| | | max(a, c) | | |
| | | | | |
| | | _______________________________ | | |
| | | | | | | |
| | | d | e LI padding (blue) | | | |
| | | | | | | |
| | | | h 2nd element of list f | | | |
| | | | | | | |
| | | | g | | | |
| | | |_______________________________| | | |
| | | | | |
| | | c LI margin (transparent, | | |
| | | so red shines through) | | |
| | |_______________________________________| | |
| | | |
| | G | |
| |_______________________________________________| |
| |
| C |
|________________________________________________________|
Technically, padding and margin properties are not inherited. But, as the example shows, the placement of a rendered element is relative to ancestors and siblings.
Horizontally, boxes inherit the width of the parent element (i.e. after the margin and padding have been deducted).
Vertically, all boxes are attached to the above box. Note that the above box doesn't necessarily contain the preceding HTML element. Since boxes are stacked vertically, some interesting effects can be achieved if sequential boxes don't end up on top of each other. In this way, "sideheads" and simple multiple-column layouts can be supported:
_______________________________________________
| |
| (BODY margins & box) |
| ______________ _____________________ |
| | |;;;;;;| | |
| | (H1 box) |;;;;;;| (P box) | |
| | |;;;;;;| | |
| | Headline... |;;;;;;| While.the.paragraph | |
| | comes.here. |;;;;;;| starts.here.and.... | |
| |______________|;;;;;;| continues.below.the | |
| ;;;;;;;;;;;;;;;;;;;;;;| box.to.the.left.... | |
| ;;;;;;;;;;;;;;;;;;;;;;|_____________________| |
| ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; |
|_______________________________________________|
^ ^ ^ ^
0% 35% 50% 100%
The above could be realized through:
H1 {
margin-left: 0%;
margin-right: 65% -- (100% minus 35%) --
}
P {
margin-left: 50%;
margin-right: 0%
}
The percentages are relative to the width of the parent element.
[A property to describe if an element "float upwards" should be added]
Style sheets influence the presentation of documents by assigning values to style properties. This section lists the suggested style properties, and their corresponding units, of CSS1.
The list of CSS1 properties has been kept to a minimum, while making sure commonly used styles can be expressed. Depending on the formatting model and the resources available, some properties can prove hard to incorporate into existing UA implementations (e.g. 'text-effect' and 'flow'), and can be considered optional. [strengthen definition]
Also, an ASCII-based UA in a monochrome environment is not able to honor color values, but may try to do layout based on the style properties.
This specification suggests a liberal terminology for describing fonts, and a level of detail similar to common desktop publishing applications.
Font sizes can either be set to an absolute height using 'font-size', or to a relative index using 'font-size-index'. If defined, 'font-size' will take precedence.
If the value is an integer number, it is to be interpreted as an index. Index 0 corresponds to 'medium' (the actual size is application dependent and/or set-able by the user). A scaling factor of 1.44 is suggested between adjacent indexes, e.g. if the 'medium' font is 10pt, the 'large' font could be 14.4pt (or 14pt, which may be more easily available). If the number is a floating point, the UA should interpolate a font size if possible. Otherwise, it should round off to the closest integer index.
Percentage is relative to the font-size of the parent element.
Note that an application may reinterpret an explicit size, depending on the context. E.g., inside a VR scene a font may get a different size because of perspective distortion.
The value is a prioritized list of font family names and/or generic family names. List items are separated by white space and spaces in font family names are replaced with dashes.
In level 1, the following generic families are defined:
Style sheet writers are encouraged to offer a generic font family at the end of the list:
font-family: univers helvetica sans-serifIdeally, the style sheet writer should specify only one font, and the font manager should return the best alternative (perhaps by taking visual similarity, visual quality and performance into account). Unfortunately, current rendering environments do not offer this level of service, and it is beyond the style sheet mechanism to do so. Therefore, a prioritized list of alternative families can be supplied. This practice poses one problem: the UA must be able to determine if a font selection has been successful or not to know how far it should proceed in the list. One example: if the style sheet asks for 'univers' and the window system is smart enough to suggest 'helvetica' (which looks almost identical) as a replacement, is this a success or failure? This specification leaves the answer undefined for now.
Where extra-light = -3, light = -2, demi-light = -1, etc.
If the desired font weight is not available, the UA selects a substitution order. Non-integer font weights are allowed.
Percentage values refer to the font weight of the parent element.
If the preferred font style cannot be accomplished, the following substitutions should be attempted by the UA:
italic -> oblique oblique -> italic * -> normal
If 'small-caps' are not available, capitals letter of a smaller font size can be used to render small characters if the resolution of the output medium is appropriate for this.
Leading refers to the extra space between lines. A percentage unit is relative to the font size. E.g.:
P { font-leading: 20%; font-size: 10pt }
Here, the leading would be 2pt.
This is a conventional shorthand notation from the typography community to set font-size, font-leading, font-family, font-style, and font-weight. Setting the properties individually override the shorthand notation if the weight is otherwise the same.
Note that it is the line height, not the leading, that is specified. The relationship is: line-height = font-size + font-leading.
See the section on units for a description.
[should image URIs be allowed?]
This property does not inherit, but unless set explicitly the parent's background will shine through due to the initial transparent value.
If an image is found through the URI, it takes precedence over color. The color is used:
Using the delimiting '/', two different backgrounds can be described ('bg1' and 'bg2'). The resulting background is a fade between 'bg1' and 'bg2'. The 'bg-light-source' property specifies from where 'bg2' is to be "emitted".
This property describes how the background image should be laid out. By default, the background image is repeated in both x and y direction, and the image is scrolled along with the other content. A 'fixed' background is fixed with regard to the canvas.
The property describes the initial position of a background image specified with the 'background' property. If only one value is given, it sets both the horizontal and vertical offset of the background image. If two values are given, the horizontal position comes first.
With a value pair of '0% 0%', the upper left corner of the image is placed in the upper left corner of the element. A value pair of '100% 100%' places the lower right corner of the image in the lower right corner of the element.
[should one have to address $CANVAS to make something go into the lower right corner of the wendow?]
[A new property with great potential]
The values are shorthands for north, north-west, west etc.
This property specifies the point or vector from where 'bg2' (if defined in the 'background' element) is to be "emitted". If only a point is defined (e.g. SW as indicated on the chart below), it will aquire the 'bg2' background. As one moves away from the point, the background will gradually change to 'bg1'.
NW N NE W E SW S SE
If a vector is specified with two points, the light-source changes accordingly.
Default text spacing is 0%. The UA is free to select the text spacing algorithm, but both the word spacing and the letter spacing should be affected. The specified percentage is the target vertical length of the formatted text as compared to the standard text spacing. E.g., a text spacing of 20% will make the formatted text 20% longer.
Formatters should treat unknown values as 'box' (a simple rectangle).
The color of the decoration is based on the color of the text.
The property affects the vertical positioning of text: 'sub' will make the text subscripted, while 'super' will superscript the text.
'capitalize' uppercases the first character of each word.
'none' is used to neutralize an inherited value.
All text effects are rendered using the alternate properties.
This property describes how text is aligned. It applies only to elements that have a break before them (i.e. only block-level elements in CSS1).
This property is not inherited.
Extra indent that only applies to the first formatted line. May be negative ('outdent'). The property only applies to block-level elements. An indent is not inserted in the middle of an element that was broken by another (such as 'BR' in HTML).
Percentage values are relative to the width of the parent element.
Some typographic styles require an alternate set of properties to be rendered. In CSS1, this is the case for 'text-effect' as well as the 'alt-firstline'.
The following properties influence the "alternate" rendering:
alt-font alt-font-family alt-font-size alt-font-leading alt-font-weight alt-font-style alt-color alt-background alt-text-spacing alt-text-decoration alt-text-position alt-text-transform
How much space to insert between the border of the frame and the content (e.g. text or image). The color of the padding area is controlled with the 'background' property. See the formatting model for more on these properties.
Percentage values are relative to the width of the parent element.
Padding values are >= 0.
The order is top, right, bottom, left. If there is only one value, it applies to all sides, if there are two or three, the missing values are taken from the opposite side.
The property is shorthand for setting 'padding-top', 'padding-right' 'padding-bottom' and 'padding-left' separately. The individual declarations take precedence if the weights are otherwise equal.
The minimal horizontal distance between the element's box and surrounding elements.
Horizontal margins may be negative.
See the formatting model for a description of the relationship between these properties and 'width'.
Percentage values are relative to the width of the parent element.
The vertical space between two blocks of text is the maximum of all bottom margin and top margin specifications between the two. See the formatting model for an example.
Percentage values are relative to the width of the parent element. [rationale]
Vertical margins are >= 0.
The four lengths apply to top, right, bottom and left respectively. If there is only one value, it applies to all sides, if there are two or three, the missing values are taken from the opposite side.
The property is shorthand for setting 'margin-top', 'margin-right' 'margin-bottom' and 'margin-left' separately. The individual declarations take precedence if the weights are otherwise equal.
This property decides if an element is block-level (e.g. H1 in HTML) or inline (e.g. EM in HTML). For HTML documents, the initial value will be taken from the HTML specification.
This property is not inherited.
This property can be applied to text, but it is most useful with inline images and similar insertions. The width is to be enforced by scaling the image if necessary. When scaling, the aspect ration of the image should be preserved.
Percentage values are relative to the width of the parent element.
See the formatting model for a description of the relationship between this property and 'margin-left' and 'margin-right'.
With the value 'normal', the element will be displayed in the main text. 'float-left' and 'float-right' will make the element float to the margin. This property is most often used with inline images.
Keyword values are: none | dotted | single | double | thin-thick | thick-thin | beveled
The four keywords apply to top, right, bottom and left respectively. If there is only one values, it applies to all sides, if there are two or three, the missing values are taken from the opposite side.
The 'thin-thick' ('thik-thin') keyword requests a frame with the outer (inner) frame 'thin' and the inner (outer) frame 'thick'. The space between the two has the background color of the cell.
This property is not inherited. (If UL has a frame around it, you don't want each LI inside to inherit this frame.
A frame-style of 'none' requests no visible frame around the element. However, the corresponding frame-width must be non-zero for this to be achieved, otherwise the frame will be inherited from surrounding elements.
Additional suggested keyword values include: dotted, wavy, baroque, filet, art-deco, raised, lowered, etched. shadow.
A width is either a length or one of the keywords `thin', `medium' or `thick'. The four widths apply to top, right, bottom and left respectively. If there is only one value, it applies to all sides, if there are two or three, the missing values are taken from the opposite side.
A frame-width of 0 requests the frame to be inherited from surrounding elements.
This attribute describes the color of the frame surrounding an element.
Numbers can be from -2 to 2, corresponding, respectively, to the keywords. All 'pagebreak-before' and 'pagebreak-after' values that apply between two elements are combined according to the following table:
|-2 -1 0 1 2 --+-------------- -2|-2 -2 -2 -2 2 -1|-2 -1 -1 1 2 0|-2 -1 0 1 2 1|-2 1 1 1 2 2| 2 2 2 2 2In algorithmic terms: take the one with the largest absolute value; if they are the same, use the positive value.
Values can be -2, -1 or 0 meaning, respectively, never allow page-break inside element ('never'), discourage page-break inside element ('discourage'), or neutral about page-break inside element ('neutral').
This property applies only to the children of the element where it is specified. In HTML, it is typically used on the 'UL' and 'OL' elements.
[This is possibly the most powerful property of them all]
The property suggests a magnification factor for all spatial properties. E.g., by setting the magnification of the top-level element to 2, all length units (e.g. margins, font sizes, images) will be scaled accordingly.
Percentage values that refer to other spatial units are not scaled. [We also need a property to describe the PRE element]
inches (in) pixels (px) centimeters (cm) millimeters (mm) ems (em) -- the width of the character 'M' -- ens (en) -- half the width of an em -- points (pt) picas (pc)
In most cases, a percentage unit is relative to a length unit. 'text-spacing' is an example of a property that is not relative to a length unit.
A color is a either a color name, 3-tuple or a hex-color. A short list of supported color names should be added, e.g., black, white, red, green, blue, yellow, cyan, magenta, pink, brown, gray, orange, purple, turquoise, violet. Also, prefixing color names with 'light-' or 'dark-' is allowed, e.g. 'light-blue' and 'dark-gray'.
The RGB color model is being used in color specifications. Other color models should be kept in mind for later extensions.
Different ways to specify red:
EM { color: #F00 }
EM { color: #FF0000 }
EM { color: 255 0 0 } -- integer range: 0-255 --
EM { color: 1.0 0.0 0.0 } -- float range: 0.0 - 1.0 --
EM { color: red }
A Uniform Resource Identifier (URI) should be enclosed in quotes:
BODY { background: "http://www.bg.com/pinkish.gif" }
Partial URIs are interpreted relative to the source of the style
sheet, not relative to the document.
Tables do not easily lend themselves to the tree-structured approach of SGML, and some special rules apply to the presentation of tables. All examples in this section are written according to current version of the HTML3 table model.
In many cases, writing style sheets for HTML tables is like writing style sheets for any other HTML element. Most of the normal CSS addressing scheme and style properties can be reused:
TABLE { font: 12pt helvetica } -- set the default font for table content --
TFOOT { background: yellow } -- set the default background for the footer cells --
TH { font-weight: bold } -- set the default font-weight for the header cells --
Some style properties are especially useful in tables:
TR.europe { frame-style: double }
The example above requests for row elements with subclass 'europe' to get a double border around them. Note that the 'frame-style' attribute does not inherit, so only the outside frame of the row, not each cell within the row, will get this style. Similarly, columns can be addressed with the 'COL' and 'COLGROUP' element:
COLGROUP { frame-style: none single; -- set vertical, no horizontal --
frame-color: "http://www.style.com/cool/bg.gif" blue;
frame-width: 0.5cm }
Note! One fundamental principle of CSS is that properties attached to one element only applies to that element and descendants. Attaching style to 'COL' and 'COLGROUP' breaks with this principle as they have no content, and the properties assigned may influence the presentation of other elements. We are working on a general model to easier support various table models.
The example above gives all 'COLGROUP' elements a 0.5cm single vertical border between them. The border will be blue when the requested image is not available. There is no horizontal border.
Frame widths between adjacent cells do not add up. Rather, the distance between two adjacent cells is the maximum of the two corresponding frame widths:
[ID=foo] { padding: a b c d;
frame-width: x x e x;
}
[ID=bar] { padding: A B C D;
frame-width: E x x x;
}
_______________________
| a padding |
| ________________ |
| d | cell content | b |
| | ID=foo | |
| |________________| |
| c |
|________________________|
max (e, E) frame
_______________________
| A padding |
| ________________ |
| D | cell content | B |
| | ID=bar | |
| |________________| |
| C |
|________________________|
Note that the elements inside 'TABLE' do not include the margin
properties. The only exception is the 'CAPTION' element and its
children.
Some terms may have spellings in different traditions. The following aliases should be accepted:
color : colour italic : italics
[The grammar is slightly out or date, but will be updated ASAP]
This is the grammar for CSS. It consists of two parts: a context free grammar in Yacc/Bison format and a lexical analyzer in Lex/Flex format. The formal grammar supports both CSS1 and CSS2. Although CSS1 grammar is a little simpler, we encourage implementation to parse style sheets of both levels.
%expect 2
/*
There are two shift/reduce conflicts in more_terms,
because op can be empty
*/
%token IMPORT DEFINE ARCHFORM IMPORTANT LEGAL
%token INTERPOLATEHI INTERPOLATELO PLUS_EQ MINUS_EQ STAR_EQ SLASH_EQ
%token STRING HEXCOLOR
%token IDENT ENVVAR
%token NUMBER LENGTH EMS NCHARS PERCENTAGE
%%
stylesheet
: imports defs rules
;
imports
: imports IMPORT url
| /* empty */
;
url
: STRING
;
defs
: defs constant_def
| defs archform_def
| /* empty */
;
constant_def
: DEFINE unique_id '=' value ';'
;
unique_id
: IDENT
;
archform_def
: ARCHFORM attrname
;
attrname
: IDENT
;
rules
: rule_seq media_rules
;
media_rules
: media_rules medium rule_seq
| /* empty */
;
medium
: ':' IDENT other_media ':'
;
other_media
: other_media '&' IDENT
| /* empty */
;
rule_seq
: rule_seq rule
| /* empty */
;
rule
: selector_seq '{' declaration_seq '}'
;
selector_seq
: selector_seq ',' selector
| selector
;
selector
: toplevel
| ancestors predecessor_opt elemspec
;
toplevel
: '*'
;
ancestors
: ancestors predecessor_opt ancestor
| /* empty */
;
ancestor
: '(' elemspec ')'
;
predecessor_opt
: predecessor
| /* empty */
;
predecessor
: '/' elemname '/'
;
elemname
: IDENT
| IDENT '.' IDENT
;
elemspec
: elemname attrspec_seq
| attrspec_seq
;
attrspec_seq
: attrspec_seq attrspec
| /* empty */
;
attrspec
: '[' attrname constval_opt ']'
;
constval_opt
: '=' constval
| /* empty */
;
constval
: NUMBER
| STRING
| IDENT
;
declaration_seq
: declaration_seq ',' declaration
| declaration
;
declaration
: property ':' value priority_opt
| property op_eq value priority_opt
;
priority_opt
: IMPORTANT
| LEGAL STRING
| /* empty */
;
property
: IDENT
;
/*
* Operator precedence: high to low
* 5: + - (monadic plus, monadic minus)
* 4: * / % (multiply, divide, remainder)
* 3: + - (plus, minus)
* 2: << >> (interpolate low, interpolate high)
* 1: ([=space] concatenate)
*/
value
: value1 value
| value1
;
value1
: value2 INTERPOLATELO value1
| value2 INTERPOLATEHI value1
| value2
;
value2
: value3 '+' value2
| value3 '-' value2
| value3
;
value3
: value4 '*' value3
| value4 '/' value3
| value4 '%' value3
| value4
;
value4
: '+' term
| '-' term
| term
;
term
: LENGTH
| EMS
| NCHARS
| STRING
| HEXCOLOR
| NUMBER
| PERCENTAGE
| IDENT
| attref
| envref
| '(' value ')'
;
attref
: '[' attrname ']'
;
envref
: ENVVAR
;
op_eq
: PLUS_EQ
| MINUS_EQ
| STAR_EQ
| SLASH_EQ
;
%{
#include "y.tab.h"
#include "constants.h"
/*
The constants include definitions similar to the following:
#define WEEK (7 * DAY)
#define DAY (24 * HOUR)
#define HOUR (60 * MINUTE)
#define MINUTE (60 * SECOND)
#define SECOND 1
#define INCH (25.4 * MM)
#define CM (10 * MM)
#define MM 1
#define PICA (12 * INCH/72 * MM)
#define POINT (INCH/72 * MM)
*/
%}
%a 3000
%o 4000
urlchar [a-zA-Z0-9:/_%~!@#$?*+{};.,|=`'-]
d [0-9]
notnm [^a-zA-Z0-9-]
nmchar [a-zA-Z0-9-]|\\\.
nmstrt [a-zA-Z]
w [ \t\n]*
num {d}+|{d}*\.{d}+
h [0-9a-fA-F]
hexcolor #{h}{h}{h}|#{h}{h}{h}{h}{h}{h}|#{h}{h}{h}{h}{h}{h}{h}{h}{h}
ident {nmstrt}{nmchar}*
%x COMMENT
%%
"--" {BEGIN(COMMENT);}
<COMMENT>"--" {BEGIN(INITIAL);}
<COMMENT>\n {/* ignore */}
<COMMENT>. {/* ignore */}
@import return IMPORT;
@archform return ARCHFORM;
@define return DEFINE;
"!"{w}legal {return LEGAL;}
"!"{w}important {return IMPORTANT;}
"$"{ident} {return ENVVAR;}
{hexcolor} {return HEXCOLOR;}
{ident} {return IDENT;}
\"[^"\n]*\" |
\'[^'\n]*\' {yylval.str = noquotes(yytext); return STRING;}
{num} {yylval.num = atof(yytext); return NUMBER;}
{num}{w}"%" {yylval.num = atof(yytext); return PERCENTAGE;}
{num}{w}pt/{notnm} {yylval.num = atof(yytext) * POINT; return LENGTH;}
{num}{w}mm/{notnm} {yylval.num = atof(yytext); return LENGTH;}
{num}{w}cm/{notnm} {yylval.num = atof(yytext) * CM; return LENGTH;}
{num}{w}pc/{notnm} {yylval.num = atof(yytext) * PICA; return LENGTH;}
{num}{w}inch/{notnm} {yylval.num = atof(yytext) * INCH; return LENGTH;}
{num}{w}px/{notnm} {yylval.num = atof(yytext) * pixelwd; return LENGTH;}
{num}{w}em/{notnm} {yylval.num = atof(yytext); return EMS;}
{num}{w}ch/{notnm} {yylval.num = atof(yytext); return NCHARS;}
{num}{w}d/{notnm} |
{num}{w}day/{notnm} |
{num}{w}days/{notnm} {yylval.num = atof(yytext) * DAY; return NUMBER;}
{num}{w}w/{notnm} |
{num}{w}week/{notnm} |
{num}{w}weeks/{notnm} {yylval.num = atof(yytext) * WEEK; return NUMBER;}
{num}{w}h/{notnm} |
{num}{w}hour/{notnm} |
{num}{w}hours/{notnm} {yylval.num = atof(yytext) * HOUR; return NUMBER;}
{num}{w}m/{notnm} |
{num}{w}min/{notnm} |
{num}{w}minute/{notnm} |
{num}{w}minutes/{notnm} {yylval.num = atof(yytext) * MINUTE; return NUMBER;}
{num}{w}s/{notnm} |
{num}{w}sec/{notnm} |
{num}{w}second/{notnm} |
{num}{w}seconds/{notnm} {yylval.num = atof(yytext) * SECOND; return NUMBER;}
"<<" return INTERPOLATELO;
">>" return INTERPOLATEHI;
"+:" return PLUS_EQ;
"-:" return MINUS_EQ;
"*:" return STAR_EQ;
"/:" return SLASH_EQ;
":" return ':';
"." return '.';
"/" return '/';
"*" return '*';
"+" return '+';
"-" return '-';
"=" return '=';
"(" return '(';
")" return ')';
"{" return '{';
"}" return '}';
"[" return '[';
"]" return ']';
";" return ';';
"&" return '&';
"," return ',';
[ \t]+ {/* ignore whitespace */}
\n {/* ignore whitespace */}
. {yyerror("Illegal character");}
During the short life of HTML, there have been several style sheet proposals to which this proposal is indebted. The following people's proposals have been influential:
The following style sheet is written according to the suggested rendering in the HTML 2.0 specification. Some styles, e.g. top-level font family, have been added for completeness.
-- first, set some properties to the top-level element --
-- the will inherit nicely down the tree --
HTML {
font-family: serif;
font-size: medium;
font-weight: medium;
text-align: left;
margin: 0.5em 0
}
-- the rendering instructions for the H* elements are --
-- quite detailed --
H1, H2, H3, H4 { margin-top: 1em; margin-bottom: 1em }
H5, H6 { margin-top: 1em }
H1, H2, H4, H6 { font-weight: bold }
H3, H5 { font-style: italic }
H1 { font-size: xx-large; align: center }
H2 { font-size: x-large }
H3 { font-size: large }
B, STRONG { font-weight: bold }
I, CITE, EM, VAR, ADDRESS, BLOCKQUOTE { font-style: italic }
PRE, TT, CODE, KBD, SAMP { font-family: monospace }
ADDRESS { margin-left: 3em }
BLOCKQUOTE { margin-left: 3em; margin-right: 3em }
UL, DIR { list-style: disc }
OL { list-style: decimal }
MENU { margin: 0 0 }
LI { margin-left: 3em }
DT { margin-bottom: 0 }
DD { margin-top: 0; margin-left: 5em }
A.link { color: red } -- unvisited link --
A.visited { color: dark-red } -- visited links --
A.active { color: orange } -- active links --