Abstract
This module contains the features of CSS relating to text decoration, such as underlines, text shadows, and emphasis marks.
CSS is a language for describing the rendering of structured documents
(such as HTML and XML)
on screen, on paper, in speech, etc.
Status of this document
Table of Contents
This is just a place to keep ideas at the moment.
It has no status at W3C and has not yet been discussed by the CSSWG.
1. Things To Include Here
In addition to all of the features in Level 3, a completed initial draft of this module will include:
- text-shadow with spread
- fill/stroke on text
- a text-decoration-offset property
- a text-line-width property
2. Rescued L3 Brainstorming: Ignore For Now
2.1.
Emphasis Mark Skip: the text-emphasis-skip property
This section is under brainstorming.
It’s also not yet clear if this property is needed quite yet, despite differences in desired behavior among publications.
| Name: |
text-emphasis-skip |
| Value: |
spaces ||
punctuation ||
symbols ||
narrow
|
| Initial: |
spaces
|
| Applies to: |
all elements |
| Inherited: |
yes |
| Percentages: |
N/A |
| Media: |
visual |
| Computed value: |
as specified |
This property describes for which characters marks are drawn.
The values have following meanings:
- spaces
-
Skip Word separators or characters
belonging to the Unicode separator category (Z*).
(But note that emphasis marks are drawn for a space
that combines with any combining characters.)
- punctuation
-
Skip punctuation.
Punctuation in this definition includes characters belonging to
the Unicode Pc, Pd, Ps, Pe, Pi, or Pf categories.
It also includes characters where the Unicode category is Po and
the Sentence_Break property [UAX29] of the Unicode database
[UAX44] is ATerm, Close, SContinue, or STerm.
- symbols
- Skip symbols.
Symbols in this definition includes characters belonging to
the Unicode S* category.
It also includes the Unicode Po category
that are not defined as punctuation above.
- narrow
- Skip characters where the East_Asian_Width property [UAX11]
of the Unicode database [UAX44] is not F (Fullwidth) or W (Wide).
Characters belonging to the Unicode classes for control codes
and unassigned characters (Cc, Cf, Cn) are skipped
regardless of the value of this property.
This syntax requires UA to implement drawing marks for spaces.
Is there any use case for doing so?
If not, should we modify the syntax not to allow drawing marks for spaces?
Document conventions
Conformance requirements are expressed with a combination of
descriptive assertions and RFC 2119 terminology. The key words "MUST",
"MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT",
"RECOMMENDED", "MAY", and "OPTIONAL" in the normative parts of this
document are to be interpreted as described in RFC 2119.
However, for readability, these words do not appear in all uppercase
letters in this specification.
All of the text of this specification is normative except sections
explicitly marked as non-normative, examples, and notes. [RFC2119]
Examples in this specification are introduced with the words "for example"
or are set apart from the normative text with class="example",
like this:
This is an example of an informative example.
Informative notes begin with the word "Note" and are set apart from the
normative text with class="note", like this:
Note, this is an informative note.
Advisements are normative sections styled to evoke special attention and are
set apart from other normative text with <strong class="advisement">, like
this:
UAs MUST provide an accessible alternative.
Conformance to this specification
is defined for three conformance classes:
- style sheet
- A CSS
style sheet.
- renderer
- A UA
that interprets the semantics of a style sheet and renders
documents that use them.
- authoring tool
- A UA
that writes a style sheet.
A style sheet is conformant to this specification
if all of its statements that use syntax defined in this module are valid
according to the generic CSS grammar and the individual grammars of each
feature defined in this module.
A renderer is conformant to this specification
if, in addition to interpreting the style sheet as defined by the
appropriate specifications, it supports all the features defined
by this specification by parsing them correctly
and rendering the document accordingly. However, the inability of a
UA to correctly render a document due to limitations of the device
does not make the UA non-conformant. (For example, a UA is not
required to render color on a monochrome monitor.)
An authoring tool is conformant to this specification
if it writes style sheets that are syntactically correct according to the
generic CSS grammar and the individual grammars of each feature in
this module, and meet all other conformance requirements of style sheets
as described in this module.
Partial implementations
So that authors can exploit the forward-compatible parsing rules to
assign fallback values, CSS renderers must
treat as invalid (and ignore
as appropriate) any at-rules, properties, property values, keywords,
and other syntactic constructs for which they have no usable level of
support. In particular, user agents must not selectively
ignore unsupported component values and honor supported values in a single
multi-value property declaration: if any value is considered invalid
(as unsupported values must be), CSS requires that the entire declaration
be ignored.
Experimental implementations
To avoid clashes with future CSS features, the CSS2.1 specification
reserves a prefixed
syntax for proprietary and experimental extensions to CSS.
Prior to a specification reaching the Candidate Recommendation stage
in the W3C process, all implementations of a CSS feature are considered
experimental. The CSS Working Group recommends that implementations
use a vendor-prefixed syntax for such features, including those in
W3C Working Drafts. This avoids incompatibilities with future changes
in the draft.
Non-experimental implementations
Once a specification reaches the Candidate Recommendation stage,
non-experimental implementations are possible, and implementors should
release an unprefixed implementation of any CR-level feature they
can demonstrate to be correctly implemented according to spec.
To establish and maintain the interoperability of CSS across
implementations, the CSS Working Group requests that non-experimental
CSS renderers submit an implementation report (and, if necessary, the
testcases used for that implementation report) to the W3C before
releasing an unprefixed implementation of any CSS features. Testcases
submitted to W3C are subject to review and correction by the CSS
Working Group.
Further information on submitting testcases and implementation reports
can be found from on the CSS Working Group’s website at
http://www.w3.org/Style/CSS/Test/.
Questions should be directed to the
public-css-testsuite@w3.org
mailing list.
References
Normative References
- [UAX11]
- Asmus Freytag. East Asian Width. 23 March 2001. Unicode Standard Annex #11. URL: http://www.unicode.org/unicode/reports/tr11/tr11-8.html
- [UAX29]
- Mark Davis. Text Boundaries. 25 March 2005. Unicode Standard Annex #29. URL: http://www.unicode.org/unicode/reports/tr29/tr29-9.html
- [UAX44]
- Mark Davis; Ken Whistler. Unicode Character Database. 25 September 2013. URL: http://www.unicode.org/reports/tr44/
- [rfc2119]
- S. Bradner. Key words for use in RFCs to Indicate Requirement Levels. March 1997. Best Current Practice. URL: https://tools.ietf.org/html/rfc2119
Index
- narrow, 2.1
- punctuation, 2.1
- spaces, 2.1
- symbols, 2.1
- text-emphasis-skip, 2.1
Property Index
| Name |
Value |
Initial |
Applies to |
Inh. |
%ages |
Media |
Computed value |
| text-emphasis-skip |
spaces ||
punctuation ||
symbols ||
narrow |
spaces |
all elements |
yes |
N/A |
visual |
as specified |
Issues Index
This is just a place to keep ideas at the moment.
It has no status at W3C and has not yet been discussed by the CSSWG.
↵ This section is under brainstorming.
It’s also not yet clear if this property is needed quite yet, despite differences in desired behavior among publications.
↵ This syntax requires UA to implement drawing marks for spaces.
Is there any use case for doing so?
If not, should we modify the syntax not to allow drawing marks for spaces?
↵