# Proposals for the future of CSS Paged Media

Unofficial Proposal Draft, 12 May 2023

More details about this document

This version:
  https://drafts.csswg.org/css-page-4/
Issue Tracking:
  CSSWG Issues Repository
Editor:
  Daniel Glazman (Disruptive Innovations)
Suggest an Edit for this Spec:
  GitHub Editor

Copyright © 2023 World Wide Web Consortium. W3C® liability, trademark and permissive document license rules apply.

## Abstract

A list of issues with the current CSS page model, and possibly directions to explore for fixing it.

CSS is a language for describing the rendering of structured documents (such as HTML and XML) on screen, on paper, etc.

## Status of this document

This section describes the status of this document at the time of its publication. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.

Please send feedback by filing issues in GitHub (preferred), including the spec code “css-page” in the title, like this: “[css-page] …summary of comment…”. All issues and comments are archived. Alternately, feedback can be sent to the (archived) public mailing list www-style@w3.org.

This document is governed by the 2 November 2021 W3C Process Document.

This document was produced by a group operating under the W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

## 1. The CSS 3 Page Model

This section is informative.

The current Page Model, as described in CSS3 Module: Paged Media [CSS3PAGE], is the following one: the printable area of a page, the page box, is made of one page box itself divided in four areas:

The CSS3 Page Model

1. the page margin; that area is itself divided into 16 page-margin boxes (@top-left-corner, @top-left, @top-center, etc. )

   The 16 page-margin boxes
   (with highlight of 3 of them)

2. the page border

3. the page padding

4. and finally the page area containing the boxes generated by the flow of the main contents of the document.

It’s is possible to flow content, for instance page headers and footers or footnotes, into a page-margin box using features introduced by the CSS Generated Content for Paged Media Module [CSS3GCPM].

It is also possible to define multiple page templates for a single document using the @page at-rule that allows to select the first page, left pages, right pages or named pages of a paginated flow.

If this page model allowed the publishing industry to adopt HTML and CSS as pivot formats, it starts showing its limits for the following reasons:

- the 16 page-margin boxes are an extension of the print features offered by desktop browsers. Desktop browsers usually offer control over 6 page-margin boxes only. Only one desktop browser claims implementation of the page model described above in the fourteen last years. The other desktop browsers' control over the 6 page-margin boxes is then not achieved through the cascade of CSS UA stylesheets.

- no editing environment available on the market and in particular Wysiwyg text editor (for instance like Microsoft Word) implements such a box model.

- it’s not possible with the current model to position headers and footers (for instance the HTML5 header and footer elements) arbitrarily in the page area.

- the @page at-rule currently allows nested at-rules only for the definition of page-margin boxes. Similarly, the set of CSS properties applicable to a page box is limited and it is impossible in this model to use CSS Regions Module Level 3 [CSS3-REGIONS] to flow content into a given predefined area of a page, exclude an area from the page using CSS 3 Exclusions and Shapes Module [CSS3-EXCLUSIONS], lay out the page area into a grid using CSS Grid Layout [CSS3-GRID-LAYOUT] or using ''@slot rules that were discussed multiple times by the CSS Working Group in the recent past. The successful electronic book editing environment of Apple Inc., iBooks Author, already allows @page rules to specify arbitrary slots, arbitrary exclusions and shapes, and extends the list of applicable properties; most of its advanced layout capabilities are based on these features.

- the @page rule of CSS 2.1 [CSS21] is intended for use on print media, not dynamic media. The spread of complex HTML-based slideshows and electronic book viewers has shown that the Page Model should also apply to screen media and alike.

- ++TBD

## Conformance

### 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 classes

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.

#### Implementations of Unstable and Proprietary Features

To avoid clashes with future stable CSS features, the CSSWG recommends following best practices for the implementation of unstable features and proprietary extensions to CSS.

### 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.

## Index

### Terms defined by this specification

- page area, in § 1
- page border, in § 1
- page box, in § 1
- page margin, in § 1
- page-margin boxes, in § 1
- page padding, in § 1

### Terms defined by reference

- [CSS3PAGE] defines the following terms:
  - @page

## References

### Normative References

[CSS21]
  Bert Bos; et al. Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification. URL: https://drafts.csswg.org/css2/
[CSS3-EXCLUSIONS]
  Rossen Atanassov; Vincent Hardy; Alan Stearns. CSS Exclusions Module Level 1. URL: https://drafts.csswg.org/css-exclusions/
[CSS3-GRID-LAYOUT]
  Tab Atkins Jr.; et al. CSS Grid Layout Module Level 1. URL: https://drafts.csswg.org/css-grid/
[CSS3-REGIONS]
  Rossen Atanassov; Alan Stearns. CSS Regions Module Level 1. URL: https://drafts.csswg.org/css-regions/
[CSS3GCPM]
  Dave Cramer. CSS Generated Content for Paged Media Module. URL: https://drafts.csswg.org/css-gcpm/
[CSS3PAGE]
  Elika Etemad; Simon Sapin. CSS Paged Media Module Level 3. URL: https://drafts.csswg.org/css-page-3/
[RFC2119]
  S. Bradner. Key words for use in RFCs to Indicate Requirement Levels. March 1997. Best Current Practice. URL: https://datatracker.ietf.org/doc/html/rfc2119