CSS Print Profile

W3C Candidate Recommendation 25 February 2004

This version:
http://www.w3.org/TR/2004/CR-css-print-20040225
Latest version:
http://www.w3.org/TR/css-print
Previous Version:
http://www.w3.org/TR/2003/WD-css-print-20031218
Editors:
Jim Bigelow, Hewlett-Packard Company

Abstract

This specification defines a subset of Cascading Style Sheets Level 2, revision 1 [CSS21] and CSS3 module: Paged Media [PAGEMEDIA] specifically for printing to low-cost devices. It is designed for printing from mobile devices, where it is not feasible or desirable to install a printer-specific driver, and for situations were some variability between the device's view of the document and the formatting of the output is acceptable.

This profile is designed to work in conjunction with XHTML-Print [XHTMLPRINT] and defines a minimum level of conformance as well as an extension set that provides stronger layout control for the printing of mixed text and images, tables and image collections.

Status of this document

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

All sections of this document are normative unless noted as informative.

This document contains the CSS Print Profile W3C Candidate Recommendation of 25 February 2004, which has incorporated the disposition of Last Call comments

This specification is based, in large part, on a work by the same name, CSS Print Profile [CSSPP] from the Printer Working Group (PWG), a program of the IEEE Industry Standard and Technology Organization.

In order to exit the Candidate Recommendation phase, the following criteria must be satisfied:

  1. At least two implementations of all the required features of this specification.
  2. A minimum of six months of the CR period must be elapsed to ensure that enough time is given for providing implementation feedback.

A test suite for this specification will be created during the CR period. Detailed implementation requirements and the invitation for participation in the implementation report will be provided in the preliminary implementation report. Implementers are encouraged to provide feedback by 25 August 2004.

Comments and public discussion are to be sent to the mailing list www-style@w3.org (see instructions), which is preferred for discussion of this and other drafts in the Style area.

This document has been produced by the W3C CSS Working Group (Members only) as part of the W3C CSS Style Activity (see summary). The goals of the CSS Working Group are discussed in the CSS Working Group charter. Patent disclosures relevant to CSS may be found on the Working Group's public patent disclosure page.

Publication as a Candidate Recommendation does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or made obsolete by other documents at any time. It is inappropriate to cite this document as other than work in progress.

Contents

1. Overview

All sections of this document are normative unless noted as informative.

This document specifies a profile of the Cascading Style Sheets, level 2, revision 1 (CSS21) specification [CSS21] along with selected portions of the CSS3 module: Paged Media [PAGEMEDIA].

CSS21 specifies how developers can author style sheets for presenting documents across multiple devices and media types. While this is very important, it is also important that authors have an understanding of what features are supported on these different devices. Likewise, it is important that similar devices operate in a similar manner. Otherwise, authors will need to develop style sheets for each version of each device -- raising the cost of content development and decreasing interoperability.

The CSS Print Profile specifies a conformance profile for printing from mobile devices to low-cost printers, identifying a minimum set of properties, values, selectors, and cascading rules. This profile was designed in conjunction with XHTML-Print ([XHTMLPRINT]) for low cost printers that may not have a full-page buffer and that generally print from top-to-bottom and left-to-right with the paper in a portrait orientation.

This profile also contains an enhanced layout extension set that is the companion of the XHTML-Print extension set ([XHTMLPRINT] , Section 2.4) and supports more exacting page layouts and orientations. The enhanced layout extension may require full page buffering within the printer.

Conformance to this profile means that a user agent supports, at a minimum, the features defined in this specification. This subject is addressed in Section 2, Conformance, below.

2. Conformance

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 (see [RFC2119]). However, for readability, these words do not appear in all uppercase letters in this specification.

The primary role of a profile is to define a subset of features that provides a minimal guarantee of interoperability. In the case of the CSS Print Profile, this guarantee is that a conforming user agent will support the features defined in this specification following the CSS21 conformance clause ([CSS21] Section 3.2), recast and summarized below:

  1. A CSS Print Profile conforming user agent (PP-UA or more simply "printer") SHALL support the all and print CSS21 media types. A printer MAY support other CSS21 media types, as well.
  2. For each source document, a printer SHALL attempt to retrieve all associated style sheets that are appropriate for the supported media types. A failure to retrieve a style sheet due to problems such as a loss of network connection SHOULD NOT stop the printer from processing the document.
  3. A printer SHALL parse the style sheets according to this specification. In particular, the printer SHALL recognize all CSS Print Profile at-rules, blocks, declarations, and selectors. If a printer encounters a property that applies for a supported media type, the printer SHALL parse the value according to the property definition. This means that the printer SHALL accept all valid values and MAY ignore declarations with invalid values. A printer SHALL ignore rules that apply to unsupported media types.
  4. For each element in a document tree, the printer SHALL assign a value for every applicable property according to the property's definition and the rules of cascading and inheritance.
  5. If the source document comes with alternate style sheets (such as with the "alternate" keyword in HTML 4.01 [HTML4]), the printer MAY ignore the style sheet or treat it in some implementation dependent manner.

As with CSS21, there are qualifications to this conformance clause:

  1. Values MAY be approximated when REQUIRED by the printer.
  2. The inability of a printer to implement part of this specification due to the limitations of a particular device (e.g., a printer cannot render colors on a monochrome page) SHALL NOT imply non-conformance.

It is RECOMMENDED that authors use this conformance profile to take advantage of forward compatibility. Authors MAY use style properties with an understanding that the cascading rules are processed correctly and that unknown properties and values are ignored. For example:

  body {
    background-position: center center;
    background-position: 45% 55%;
  }
 

A printer that can accept percentage values for the background-position property will process the first background-position declaration and then replace that value with the second background-position declaration. A printer that cannot accept percentage values will process the first background-position declaration and ignore the second background-position declaration.

Each CSS construct in the following sections is annotated to indicate how it SHOULD be treated by a conforming printer:

Key Description
MUST Support is mandatory; a conforming printer MUST honor this property, although the values mandated for support MAY be a subset of the full range.
SHOULD The property is concerned with functionality that SHOULD be implemented but MAY be beyond the capability of a conforming printer. For example, a monochrome printer can only render a gray scale equivalent of color images.
MAY The property's functionality is considered too complex, either in processing or memory requirements, for a printer. For example, vertical alignment within table cells in table rows that span multiple pages could exceed a low cost printer's available memory.
N/A The construct does Not Apply to the printed page; a conforming printer MAY ignore this construct for one of the following reasons, but cannot treat it as an error:
  • The construct references some functionality that is not possible on the printed page, such as volume or :hover.
  • The attribute is not needed because the document encoding is restricted to Unicode.

2.1. Enhanced Layout Extension Conformance

Some print applications require a more exacting page layout than is available from a conforming printer (e.g., photo album pages or pages from a digital TV). The Enhanced Layout Extension increases the number of properties that a conforming printer MUST support and thereby the requirements of its memory and performance capabilities. These added CSS constructs are indicated with a " MUST", or an increased range of values, in the CSS Print-Enhanced columns below.

Printers supporting the Enhanced Layout Extension MUST also support the XHTML-Print Enhanced Layout Extension ([XHTMLPRINT], Section 2.4) and MAY also support an OPTIONAL, discoverable (via some means outside the scope of this document) Enhanced Layout Extension indicator. If support for this extension is indicated, all of the following properties marked with " MUST" for CSS Print-Enhanced, MUST be supported.

3. Selectors

In CSS21, pattern matching rules determine which style rules apply to elements in the document tree [CSS21].

The selectors, pseudo-elements, pseudo-classes, and at-rules that a printer MUST support are, with a few exceptions, the same as those that a mobile device MUST support ([CSSMOBILE], Selectors ) within the limits of the printed page. The rationale for these decisions is that the capabilities and limitations of a mobile devices are analogous to those of a low-cost printer. However, support for the following constructs exceeds that of mobile devices, since this profile is concerned with printing: portions of the @page at-rule, the page pseudo-selector :first, and top and bottom margin boxes.

Consideration is also given to low-cost printers that might not be able to store all the attributes of each element, but only keep the few that are necessary. Therefore, only Enhanced Layout Extension conforming printers MUST support attribute selectors.

The following table summarizes CSS Print Profile selector syntax. In addition to the selectors marked "MUST" in the CSS Print or CSS Print-Enhanced columns, the CSS Print Profile includes the CSS21 grouping mechanism (See [CSS21] Section 5.2.1).

Pattern Meaning Selector type CSS Print CSS Print-Enhanced
* Matches any element Universal selector MUST MUST
E Matches any E element (i.e., any element of type E) Type selectors MUST MUST
E F Matches any F element that is a descendant of an E element Descendant selectors MUST MUST
E > F Matches any F element that is a child of an element E Child selectors MUST MUST
E:first-child Matches element E when it is the first child of its parent The :first-child pseudo-class MAY MAY
E:link
E:visited
Matches element E if E is the source anchor of a hyperlink of which the target is not yet visited (:link) or already visited (:visited). The link pseudo-classes N/A N/A
E:active Matches E during certain user actions. The dynamic pseudo-classes N/A N/A
E:hover Matches E during certain user actions. The dynamic pseudo-classes N/A N/A
E:focus Matches E during certain user actions. The dynamic pseudo-classes N/A N/A
E:lang(c) Matches element of type E if it is in (human) language c (the document language specifies how language is determined). The :lang() pseudo-classes MAY MAY
E + F Matches any F element immediately preceded by an element E. Adjacent selectors MAY MAY
E[foo] Matches any E element with the "foo" attribute set (whatever the value). Attribute selectors MAY MUST
E[foo="warning"] Matches any E element whose "foo" attribute value is exactly equal to "warning". Attribute selectors MAY MUST
E[foo~="warning"] Matches any E element whose "foo" attribute value is a list of space-separated values, one of which is exactly equal to "warning". Attribute selectors MAY MUST
E[xml:lang|="en"] Matches any E element whose "xml:lang" attribute value has a hyphen-separated list of values beginning (from the left) with "en". Attribute selectors MAY MAY
E:first-line Matches the first formatted line of an E element. The :first-line pseudo-element MAY MAY
E:first-letter Matches the first formatted letter of an E element. The :first-letter pseudo-element MAY MAY
E:before Matches/creates generated content before an E element. The :before pseudo-element MAY MAY
E:after Matches/creates generated content after an E element. The :after pseudo-element MAY MAY
E.classid The same as E[class~=classid] Class selectors MUST MUST
E#myid Matches any E element id equal to "myid". ID selectors MUST MUST
@page :first Specifies style for the first page of a document Page pseudo-classes MUST MUST
@page :left Specifies style for the left pages of a document Page pseudo-classes MAY MAY
@page :right Specifies style for the right pages of a document Page pseudo-classes MAY MAY

Table Notes:

† if the printer supports the xml:lang attribute for the selection and control of language specific processing, then this selector MUST be supported.

3.1 at-rules

The CSS3 module: Paged Media [PAGEMEDIA] deprecates the top and bottom margin boxes defined by the @top and @bottom at-rules. These boxes are replaced by a series of boxes ranging across the top and bottom of the page that allow finer control and placement of content in running headers and footers. These margin boxes MUST be supported by a printer and, for compatibility with existing documents, the printer SHOULD also support the deprecated margin boxes. However, the printer MUST implement the behavior described in CSS3 module: Paged Media ([PAGEMEDIA], Page Selector and page context) where the use of an non-deprecated margin box eclipses the deprecated margin box.

The following table summarizes CSS Print Profile at-rule syntax.

at-rule Function CSS Print CSS Print-Enhanced
@import Imports an external style sheet. MAY MUST
@charset Defines character set for the style sheet. MUST MUST
@media Groups a set of style rules to apply only to one or more particular media. MUST MUST
@font-face Defines a named font-family, including for downloading. MAY MAY
@page Defines a (optionally named) page formatting context. MUST MUST
@color-profile Defines a named color-profile. MAY MAY
@bottom Defines an area on the page for a running footer [PAGEMEDIA] (deprecated) SHOULD SHOULD
@bottom-left-corner, @bottom-left,
@bottom-center, @bottom-right, @bottom-right-corner
Defines areas on the page within the running footer in the page's bottom margin [PAGEMEDIA] MUST MUST
@left Defines margin box in the page's left margin [PAGEMEDIA]. MAY MAY
@right Defines margin box in the page's right margin [PAGEMEDIA]. MAY MAY
@top Defines an area on the page for a running header [PAGEMEDIA] (deprecated) SHOULD SHOULD
@top-left-corner, @top-left,
@top-center,
@top-right,
@top-right-corner
Defines areas on the page within the running header in the page's top margin [PAGEMEDIA] MUST MUST

4. Properties

As with selectors, the properties a printer MUST support are the same as those that a mobile device MUST support ([CSSMOBILE], Properties) with the exception of those that don't apply to the page or are specifically targeted at media other than the page.

In some cases the allowable values for a printer are a subset of the full range of values to match the reduced memory and performance capabilities of a low-cost printer.

The following table summarizes CSS Print Profile properties and property values. Refer to CSS3 module: Paged Media [PAGEMEDIA]  for the definition of the image-orientation and size properties and CSS21 [CSS21] for the definition of all other properties and values.

Name CSS Print CSS Print-Enhanced CSS Values Initial value
'azimuth' N/A N/A <angle> | [[ left-side | far-left | left | center-left | center | center-right | right | far-right | right-side ] || behind ] | leftwards | rightwards | inherit center
'background' background-color | inherit ['background-color' || 'background-image' || 'background-repeat' || 'background-position'] | inherit ['background-color' || 'background-image' || 'background-repeat' || 'background-attachment' || 'background-position'] | inherit see individual properties
'background-attachment' MAY MAY scroll | fixed | inherit scroll
'background-color' MUST MUST <color> | transparent | inherit transparent
'background-image' MAY MUST <uri> | none | inherit none
'background-position' MAY MUST [ [ <percentage> | <length> ]{1,2} | [ [top | center | bottom] || [left | center | right] ] ] | inherit 0% 0%
'background-repeat' MAY MUST repeat | repeat-x | repeat-y | no-repeat | inherit repeat
'border' MAY MUST [ <border-width> || <border-style> || [<color> | transparent] ] | inherit see individual properties
'border-collapse' MAY MUST collapse | separate | inherit collapse
'border-color' MAY MUST [<color> | transparent]{1,4} | inherit see individual properties
'border-spacing' MAY MUST <length> <length>? | inherit 0
'border-style' MAY none, solid <border-style>{1,4} | inherit see individual properties
'border-top' 'border-right' 'border-bottom' 'border-left' MAY MUST [ <border-width> || <border-style> || [<color> | transparent] ] | inherit see individual properties
'border-top-color' 'border-right-color' 'border-bottom-color' 'border-left-color' MAY MUST <border-color> | transparent | inherit the value of the 'color' property
'border-top-style' 'border-right-style' 'border-bottom-style' 'border-left-style' MAY none, solid <border-style> | inherit none
'border-top-width' 'border-right-width' 'border-bottom-width' 'border-left-width' MAY MUST <border-width> | inherit medium
'border-width' MAY MUST <border-width>{1,4} | inherit see individual properties
'bottom' MAY MUST <length> | <percentage> | auto | inherit auto
'caption-side' MAY MUST top | bottom | left | right | inherit top
'clear' MAY MUST none | left | right | both | inherit none
'clip' MAY MUST <shape> | auto | inherit auto
'color' MUST MUST <color> | inherit depends on user agent
'content' inherit | [<string> | counter(pages)]+ inherit | [<string> | counter(pages)]+ [ <string> | <uri> | <counter> | attr(X) | open-quote | close-quote | no-open-quote | no-close-quote ]+ | inherit empty string
'counter-increment' "pages" "pages" [ <identifier> <integer> ]+ | none | inherit none
'counter-reset' MUST MUST [ <identifier> <integer>? ]+ | none | inherit none
'cue' N/A N/A [ 'cue-before' || 'cue-after' ] | inherit see individual properties
'cue-after' N/A N/A <uri> | none | inherit none
'cue-before' N/A N/A <uri> | none | inherit none
'cursor' N/A N/A [ [<uri> ,]* [ auto | crosshair | default | pointer | move | e-resize | ne-resize | nw-resize | n-resize | se-resize | sw-resize | s-resize | w-resize| text | wait | help ] ] | inherit auto
'direction' MAY MAY ltr | rtl | inherit ltr
'display' MAY inline | block | list-item | none |inherit inline | block | list-item | run-in | compact | marker | table | inline-table | table-row-group | table-header-group | table-footer-group | table-row | table-column-group | table-column | table-cell | table-caption | none | inherit inline
'elevation' N/A N/A <angle> | below | level | above | higher | lower | inherit level
'empty-cells' MAY MAY show | hide | inherit show
'float' MAY MUST left | right | none | inherit none
'font' [ [ 'font-style' || 'font-weight' ]? 'font-size' [ / 'line-height' ]? 'font-family' ] | inherit [ [ 'font-style' || 'font-variant' || 'font-weight' ]? 'font-size' [ / 'line-height' ]? 'font-family' ] | inherit [ [ 'font-style' || 'font-variant' || 'font-weight' ]? 'font-size' [ / 'line-height' ]? 'font-family' ] | caption | icon | menu | message-box | small-caption | status-bar | inherit see individual properties
'font-family' MUST* MUST* [[ <family-name> | <generic-family> ],]* [ <family-name> | <generic-family> ] | inherit depends on user agent
'font-size' MUST ** MUST ** <absolute-size> | <relative-size> | <length> | <percentage> | inherit medium
'font-size-adjust' MAY MAY <number> | none | inherit none
'font-stretch' MAY MAY normal | wider | narrower | ultra-condensed | extra-condensed | condensed | semi-condensed | semi-expanded | expanded | extra-expanded | ultra-expanded | inherit normal
'font-style' MUST ** MUST ** normal | italic | oblique | inherit normal
'font-variant' MAY MUST normal | small-caps | inherit normal
'font-weight' MUST ** MUST ** normal | bold | bolder | lighter | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900 | inherit normal
'height' MUST MUST <length> | <percentage> | auto | inherit auto
'image-orientation' MAY ±0deg | ±90deg | ±180deg | ±270deg | ±0rad | ±1.5708rad | ±3.1416rad | ±4.7124rad | ±0grad | ±100grad | ±200grad | ±300grad <angle> | auto auto
'left' MAY MUST <length> | <percentage> | auto | inherit auto
'letter-spacing' MAY MUST normal | <length> | inherit normal
'line-height' MUST MUST normal | <number> | <length> | <percentage> | inherit normal
'list-style' MAY MUST [ 'list-style-type' || 'list-style-position' || 'list-style-image' ] | inherit see individual properties
'list-style-image' MAY MUST <uri> | none | inherit none
'list-style-position' MUST MUST inside | outside | inherit outside
'list-style-type' disc, decimal, lower-alpha, upper-alpha, none and inherit disc, decimal, lower-alpha, upper-alpha, none and inherit disc | circle | square | decimal | decimal-leading-zero | lower-roman | upper-roman | lower-greek | lower-alpha | lower-latin | upper-alpha | upper-latin | hebrew | armenian | georgian | cjk-ideographic | hiragana | katakana | hiragana-iroha | katakana-iroha | none | inherit disc
'margin' MUST MUST <margin-width>{1,4} | inherit see individual properties
'margin-top' 'margin-right' 'margin-bottom' 'margin-left' MUST MUST <margin-width> | inherit 0
'marker-offset' MAY MAY <length> | auto | inherit auto
'marks' MAY MAY [ crop || cross ] | none | inherit none
'max-height' MAY MAY <length> | <percentage> | none | inherit none
'max-width' MAY MAY <length> | <percentage> | none | inherit none
'min-height' MAY MAY <length> | <percentage> | inherit 0
'min-width' MAY MAY <length> | <percentage> | inherit depends on user agent
'orphans' MAY MUST <integer> | inherit 2
'outline' N/A N/A [ 'outline-color' || 'outline-style' || 'outline-width' ] | inherit see individual properties
'outline-color' N/A N/A <color> | invert | inherit invert
'outline-style' N/A N/A <border-style> | inherit none
'outline-width' N/A N/A <border-width> | inherit medium
'overflow' MAY MUST visible | hidden | scroll | auto | inherit visible
'padding' MAY MUST <padding-width>{1,4} | inherit see individual properties
'padding-top' 'padding-right' 'padding-bottom' 'padding-left' MAY MUST <padding-width> | inherit 0
'page' MUST MUST <identifier> | auto auto
'page-break-after' auto | always | inherit auto | always | inherit auto | always | avoid | left | right | inherit auto
'page-break-before' auto | always | inherit auto | always | inherit auto | always | avoid | left | right | inherit auto
'page-break-inside' MUST MUST avoid | auto | inherit auto
'pause' N/A N/A [ [<time> | <percentage>]{1,2} ] | inherit depends on user agent
'pause-after' N/A N/A <time> | <percentage> | inherit depends on user agent
'pause-before' N/A N/A <time> | <percentage> | inherit depends on user agent
'pitch' N/A N/A <frequency> | x-low | low | medium | high | x-high | inherit medium
'pitch-range' N/A N/A <number> | inherit 50
'play-during' N/A N/A <uri> mix? repeat? | auto | none | inherit auto
'position' N/A MUST static | relative | absolute | fixed | inherit static
'quotes' MAY MAY [ <string><string>]+ | none | inherit depends on user agent
'richness' N/A N/A <number> | inherit 50
'right' MAY MUST <length> | <percentage> | auto | inherit auto
'size' [<length>{1,2}| letter | legal | ledger | A4 | A5 | A3 | B4 | B5 ] | auto | portrait | inherit [<length>{1,2} | letter | legal | ledger | A4 | A5 | A3 | B4 | B5 ] | auto | portrait | landscape | inherit 2 [<length>{1,2} | letter | legal | ledger | A4 | A5 | A3 | B4 | B5 ] | auto | portrait | landscape | inherit auto
'speak' N/A N/A normal | none | spell-out | inherit normal
'speak-header' N/A N/A once | always | inherit once
'speak-numeral' N/A N/A digits | continuous | inherit continuous
'speak-punctuation' N/A N/A code | none | inherit none
'speech-rate' N/A N/A <number> | x-slow | slow | medium | fast | x-fast | faster | slower | inherit medium
'stress' N/A N/A <number> | inherit 50
'table-layout' MAY MUST auto | fixed | inherit auto
'text-align' left | center | inherit left | right | center | inherit left | right | center | justify | <string> | inherit depends on user agent and writing direction
'text-decoration' none, underline, and inherit none, underline, and inherit none | [ underline || overline || line-through || blink ] | inherit none
'text-indent' MUST MUST <length> | <percentage> | inherit 0
'text-shadow' N/A N/A none | [<color> || <length> <length> <length>? ,]* [ <color> || <length> <length> <length>?] | inherit none
'text-transform' MAY MUST capitalize | uppercase | lowercase | none | inherit none
'top' MAY MUST <length> | <percentage> | auto | inherit auto
'unicode-bidi' MAY MAY normal | embed | bidi-override | inherit normal
'vertical-align' MAY MUST1 baseline | sub | super | top | text-top | middle | bottom | text-bottom | <percentage> | <length> | inherit baseline
'visibility' MAY MUST visible | hidden | collapse | inherit inherit
'voice-family' N/A N/A [[ <specific-voice> | <generic-voice> ],]* [ <specific-voice> | <generic-voice> ] | inherit depends on user agent
'volume' N/A N/A <number> | <percentage> | silent | x-soft | soft | medium | loud | x-loud | inherit medium
'white-space' MUST MUST normal | pre | nowrap | inherit normal
'widows' MAY MUST <integer> | inherit 2
'width' MUST MUST <length> | <percentage> | auto | inherit auto
'word-spacing' N/A N/A normal | <length> | inherit normal
'z-index' MAY MAY auto | <integer> | inherit auto

Table Note:

† Only the single identifier "pages" that represents the current page number is REQUIRED.

* It is RECOMMENDED that a printer minimally support "serif," "sans-serif," and "monospace" font families.

** The supported values SHOULD be appropriate to the fonts available to the printer.

‡ The printer MAY ignore positioned elements that are placed on the page before the position of the current element in the normal flow.

1 Vertical alignment is undefined across page boundaries.

2 The printer MAY ignore the value landscape if it lacks the memory to support landscape printing.

5. CSS Syntax

The CSS Print Profile uses the same syntax as specified in Cascading Style Sheets, Level 2, revision 1 (CSS21) [CSS21]. The CSS Print Profile uses a subset of the values used in CSS21. Specifically:

  1. The printer SHALL support integer and real numbers ([CSS21], Section 4.3.1).
  2. The printer SHALL support the following lengths ([CSS21], Section 4.3.2): The printer MAY support other lengths.
  3. The printer SHALL support percentage values ([CSS21], Section 4.3.3).
  4. The printer SHALL support URI values ([CSS21], Section 4.3.4).
  5. The printer SHALL support the "pages" counter value that tracks page numbers ([CSS21], Section 4.3.5).
  6. The printer SHALL support the following color values ([CSS21], Section 4.3.6): The printer MAY support other color values. The printer MAY support user preferences for colors ([CSS21], Section 18.2).
  7. The printer MAY support user preferences for fonts ([CSS21], Section 18.3).

Similarly, the CSS Print Profile requires that conforming user agents support the character encoding mechanisms specified in CSS21 [CSS21]. Specifically:

  1. The printer SHALL support priorities specified in CSS21 [CSS21] to determine a document's character encoding.
  2. The printer SHALL support the CSS21 @charset rules. However, if the character set specified by the @charset rule of a external style sheet is not supported by the printer, the style sheet will be ignored.

6. Assigning Property Values, Cascading, and Inheritance

In general, the CSS Print Profile uses the same cascading rules as in CSS21. Specifically:

  1. The printer SHALL assign values as described in CSS21 ([CSS21], Section 6.1).
  2. The printer SHALL support inheritance as described in CSS21 ([CSS21], Section 6.2).
  3. A printer supporting Enhanced Layout Extension conformance SHALL support the CSS21 @import rules as specified in CSS21 ([CSS21], Section 6.3).
  4. The printer SHALL support author originating style sheets. The printer MAY support user or user-agent originating style sheets ([CSS21], Section 6.4).
  5. The printer SHALL support all CSS21 cascading mechanisms ([CSS21] Sections 6.4.1-6.4.4).

7. Media Types

A CSS Print Profile conforming user agent SHALL be able to process media-dependent style sheets as specified in CSS21 ([CSS21], Section 7). Specifically:

  1. The printer SHALL support the CSS21 @media rules as specified in CSS21 ([CSS21], Section 7).
  2. The printer SHALL accept and process style sheets that target the print media type.
  3. The printer SHALL accept and process style sheets that target the all media type.
  4. The printer SHALL accept style sheets that contain other (non-print) media-dependent style sheets.
  5. The printer MAY process other media types (such as projection or handheld).

The printer is not REQUIRED to satisfy unreferenced CSS21 conformance statements pertaining to the print media type (see [CSS21], Section 7.3.1); the printer SHALL satisfy the conformance statements and references in this specification.

8. CSS Print Profile Properties and User Agent interactions

The following sections relax or otherwise modify the conformance requirements.

8.1 Nested Floats, Divs, and Absolutely Positioned Boxes

The nesting of floats, divs, and absolutely positioned boxes within themselves, each other, and table cells is discouraged since the nesting depth of these constructs is printer and implementation dependent. Therefore, a printer MAY support nesting of these constructs beyond an implementation dependent limit.

8.2 Page Breaks

If page-break-inside: avoid is specified for a long element and the printer is unable to buffer the entire element before committing it to paper, it SHOULD force a page break to occur before the long element and begin the element starting at the top of the next page. If the long element starts at the top of a page and exceeds the page length, the printer SHALL print as much as possible on the first page and then resume that element on the next and subsequent pages as REQUIRED to preserve the content. A printer is neither MAY perform scaling to fit the long element on a single page.

8.3 Page Size and Orientation

The page size and orientation values specified by CSS Print Profile Properties MUST override similar attributes contained within any commands and/or attributes provided by job-submission protocols.

Due to a printer's mechanical limitations, the actual printable area of the page is usually less than the page size. Results are printer-dependent when the page size specified by the CSS size property does not match the media size the printer chooses to print on. However, a printer SHOULD be guided by the page size value supplied by the CSS size property when choosing the media to print on.

8.3.1 Rendering Page Boxes that do not fit a Target Sheet

If a page box does not fit the target sheet dimensions, that is, the actual dimensions of the media the printer will be using, the printer MAY choose (in order of preference) to:

The printer MAY consult the user before performing these operations. Lacking "access" to the user, it MAY simply make a decision on its own.

8.3.2 Positioning the Page Box on the Sheet

When the page box is smaller than the dimensions of the media the printer is using, the printer MAY place the page box anywhere on the sheet. However, it is RECOMMENDED that the page box be centered on the sheet since this will align double-sided pages and avoid accidental loss of information that is printed near the edge of the sheet

8.4 Running Headers and Footers

Page headers and footers are useful in printed documents. CSS3 Paged Media Module [PAGEMEDIA] provides a mechanism for placing content into the top and bottom page margins thereby creating running headers and footers. The top and bottom margin areas are subdivided into a series of margin boxes that provide control over content placement within the headers and footers:

A printer MAY vertically align the content of the top margin boxes with the top of the box and the content of the bottom margin boxes with the bottom of the bottom margin boxes.

The top-center margin box MUST be centered on the page, however, the relative widths of the top-left, top-center, and top-right are implementation dependent. The same holds true for the bottom-left, bottom-center, and bottom-right margin boxes.

The following are sample XHTML/CSS fragments used to create running-headers and running-footers.

<style> 
 @page { 
   @top-left{
       font-family: Helvetica, Arial, sans-serif; 
       font-size: 18pt; 
       font-weight: bolder; 
       content: "XHTML-Print: A Proposal --- August 25, 2000"; 
   } 
 } 
</style>

The above example creates a running header that is left aligned, and bold in Helvetica, Arial or the default sans-serif eighteen point font whichever is available.

A printer MUST support a page counter, 'pages', that SHOULD be used to reference a page's page number. The counter MUST be incremented by the counter-increment property and reset to zero by the counter-reset property. Therefore, if the counter reset property is placed in any of the top margin boxes, the counter's value MUST be incremented at the top of the page, while if the property is placed in any of the bottom boxes it is incremented at the end of the page. If the counter-increment property is placed in the page context the counter MUST be incremented at the top of the page.

<style>
 @page {
  counter-increment: pages;
  @bottom-center {
      font-family: Times, Palatino, serif; 
      font-size: 12pt;
      font-weight: normal;
      content: "Page " counter(pages);
  }
 }
</style>

The above example creates a running footer such as "Page 14" centered on the page in Times, Palatino or the default serif twelve point font whichever is available. Note that since the counter named "pages" is both incremented and used by the @page rule, it will first be incremented and then used; so the footer on the first page will be "Page 1".

8.5 Default Style Sheets

This entire section is informative.

Appendix D of Cascading Style Sheets, Level 2, revision 1 ([CSS21], Appendix D) provides a sample style sheet. This sheet uses several properties that are not required of a conforming printer, even ones supporting the enhanced layout extensions (section 2.1).

8.5.1 Default Style Sheet Guidelines for printers

Developers of printers that do not implement the enhanced layout facilities are encouraged but not required to adhere to the following implementation guidelines that address unsupported properties. These guidelines are presented to promote consistency between printer implementations.

The guidelines below are annotated to show derivation of the guideline from the Cascading Style Sheets, Level 2, revision 1 [CSS21] style sheet.

  1. The address, blockquote, body, dd, div, dl, dt, h1, h2, h3, h4, h5, h6, hr, object, ol, p, pre, and ul elements should be treated as if their display property were set to block.
  2. The li element should be treated as if its display property were set to list-items.
  3. The table elements, table, tr, td, th, and caption, should have their standard meaning and display treatments: table, table-row, table-cell, and table-caption.
  4. The elements base, br, html, head, link, meta, param, style and title should be treated as if their display property were set to none.
  5. The remaining elements, a, abbr, acronym, b, big, cite, code, dfn, em, form, i, img, input, kbd, option, samp, small, select, strong, sub, sup, textarea, tt, and var, should be treated as if their display property were set to inline. A display property of inline for the elements img, input, select, and textarea allows document authors a flexibility not available if their display property were block.
    The above guidelines come from the following portion of the CSS21 default style sheet:
    
    ADDRESS, BLOCKQUOTE, BODY, DD, DIV, DL, DT, FIELDSET, FORM, 
    FRAME, FRAMESET, H1, H2, H3, H4, H5, H6, IFRAME, NOFRAMES, 
    OBJECT, OL, P, UL, APPLET, CENTER, DIR, HR, MENU, 
                  { display: block }
    LI            { display: list-item }
    HEAD          { display: none }
    TABLE         { display: table }
    TR            { display: table-row }
    THEAD         { display: table-header-group }
    TBODY         { display: table-row-group }
    TFOOT         { display: table-footer-group }
    COL           { display: table-column }
    COLGROUP      { display: table-column-group }
    TD, TH        { display: table-cell }
    CAPTION       { display: table-caption } 
    
  6. The edges of the content of body element should have 0.1 inch wide inset from the left, top, right, and bottom of the printable area of the page. Margin calculations will start from these offsets.
    The .1 inch figure comes from the calculation that 8 px divided by 75px/inch ( a normal display resolution) is about .1 inches.
    
    BODY          { padding: 8px; 
                    line-height: 1.33 } 
    
  7. The content of the sub element should be treated as if its vertical-align property were set to sub. Similarly, the content of the sup element should be treated as if its vertical-align property were set to sup.
    
    SUB             { vertical-align: sub }
    SUP             { vertical-align: super } 
    
  8. The hr element should be treated as if its area, as defined by its height and width, were outlined by a one pixel thick, solid line. The default line should be one pixel high and the width of the containing box.
    
    HR              { border: 1px inset } 
    
  9. The lower case letters of the content of the abbr and acronym elements should be rendered as scaled capital letters, at approximately 75% of their size at the current font size. Upper case letters will be unchanged. Printers may also choose to simply render lower case letters as upper case letters without scaling.
    The 75% figure above is only one way to approximate small-caps. The printer is free to use its own rendering of small-caps.
    
    ABBR, ACRONYM   { font-variant: small-caps; 
                      letter-spacing: 0.1em } 
    
  10. Page break avoidance both inside and after is removed for the elements h1, h2, h3, h4, h5, and h6. Therefore, the printer is not required to move the content of these elements from the bottom of one page to the top of the next.
    
    H1, H2, H3,
    H4, H5, H6    { page-break-after: avoid; 
                    page-break-inside: avoid }
    
  11. The printer need not avoid page breaks before the ul, ol, and dl elements.
    
    UL, OL, DL    { page-break-before: avoid } 
    
  12. The printer may choose its own, fixed value for the padding properties of elements where the Cascading Style Sheets, Level 2, revision 1 box model ([CSS21], Section 8) applies.
  13. The content of all elements, except hr, should be treated as if the element's border-style property were set to none.
  14. The content of all elements may be treated as if the element's overflow property were set to visible and the clip property set to auto.
    This guideline suggests consistent behavior among implementations.
  15. The content of all elements may be treated as if the element's positioning property were set to static.
    Elements should be treated as if they are in the normal flow.
  16. Tables should be treated as if the table-layout property were set to fixed.
    This guideline promotes consistency since
    • the table-layout property is not mandated
    • There isn't a CSS default style sheet rule for this property

The following style sheet is a modification of the sample sheet in Appendix D of Cascading Style Sheets, Level 2, revision 1 ([CSS21], Appendix D) and depends on the above guidelines.

th              { font-weight: bolder; text-align: center }
caption         { text-align: center }
body            { line-height: 1.33 }
h1              { font-size: 2em; margin: .67em 0 }
h2              { font-size: 1.5em; margin: .83em 0 }
h3              { font-size: 1.17em; margin: 1em 0 }
h4, p,
blockquote, ul,
form,
ol, dl          { margin: 1.33em 0 }
h5              { font-size: .83em; line-height: 1.17em; margin: 1.67em 0 }
h6              { font-size: .67em; margin: 2.33em 0 }
h1, h2, h3, h4,
h5, h6, b,
strong          { font-weight: bolder }
blockquote      { margin-left: 40px; margin-right: 40px }
i, cite, em,
var, address    { font-style: italic }
pre, tt, code,
kbd, samp       { font-family: monospace }
pre             { white-space: pre }
big             { font-size: 1.17em }
small, sub, sup { font-size: .83em }
ol, ul, dd      { margin-left: 40px }
ol              { list-style-type: decimal }
ol ul, ul ol,
ul ul, ol ol    { margin-top: 0; margin-bottom: 0 }
br       { content: "\A" }

@media print {
  @page         { margin: 10% }
  blockquote, 
  pre           { page-break-inside: avoid }
}

8.5.2 Default Style Sheet Guidelines for Enhanced Layout printers

Developers of printers conforming to the enhanced layout extensions (section 2.1) MUST implement more of Cascading Style Sheets, Level 2, revision 1 [CSS21] than conforming printers, although the set of properties and their values is still less than complete.

Developers of printers are encouraged but not required to adhere to the following implementation guidelines that address unsupported properties.

  1. The table elements, table, tr, td, th, and caption, should have their standard meaning and display treatments: table, table-row, table-cell, and table-caption.
  2. The rendering of the hr element is implementation dependent since support of the inset value of the border-style property is not required.
  3. Page break avoidance both inside and after is removed for the elements h1, h2, h3, h4, h5, and h6. Therefore, the printer need not be concerned with moving the content of these elements from the bottom of one page to the top of the next.
  4. The printer need not avoid page breaks before the ul, ol, and dl elements.

The following style sheet is a modification of the sample sheet in Appendix D of [CSS21] and depends on the above guidelines.

address,
blockquote, 
body, dd, div, 
dl, dt, 
form,
h1, h2, h3, h4, 
h5, h6, 
object, ol, p, 
ul,
hr, pr e        { display: block }
li              { display: list-item }
head            { display: none }
th              { font-weight: bolder; text-align: center }
caption         { text-align: center }
body            { padding: 8px; line-height: 1.33 }
h1              { font-size: 2em; margin: .67em 0 }
h2              { font-size: 1.5em; margin: .83em 0 }
h3              { font-size: 1.17em; margin: 1em 0 }
h4, p,
blockquote, ul,
form,
ol, dl,         { margin: 1.33em 0 }
h5              { font-size: .83em; line-height: 1.17em; margin: 1.67em 0 }
h6              { font-size: .67em; margin: 2.33em 0 }
h1, h2, h3, h4,
h5, h6, b,
strong          { font-weight: bolder }
blockquote      { margin-left: 40px; margin-right: 40px }
i, cite, em,
var, address    { font-style: italic }
pre, tt, code,
kbd, samp       { font-family: monospace }
pre             { white-space: pre }
big             { font-size: 1.17em }
small, sub, sup { font-size: .83em }
hr              { border: 1px  }
ol, ul, dd      { margin-left: 40px }
ol              { list-style-type: decimal }
ol ul, ul ol,
ul ul, ol ol    { margin-top: 0; margin-bottom: 0 }
br       { content: "\A" }

@media print {
  @page         { margin: 10% }
  blockquote, 
  pre           { page-break-inside: avoid }
}

9. Acknowledgements

This section is informative.

This specification was prepared by the W3C CSS Working Group. The participants at the time of publication were:

List will be inserted when this document becomes a Recommendation.

This specification is based, almost exclusively, on the specification of the same name, CSS Print Profile [CSSPP] from the Printer Working Group, a program of and through the IEEE Industry Standards and Technology Organization, Inc., and the editor wishes to express his gratitude to all those who contributed to it.

Appendix A. References

A.1 Normative References

[CSS21]
Cascading Style Sheets, Level 2, revision 1, B. Bos, et al., World Wide Web Consortium, 25 February 2004. This version of the Cascading Style Sheets, Level 2, revision 1 recommendation is http://www.w3.org/TR/2004/CR-CSS21-20040225. The latest version is available at http://www.w3.org/TR/CSS21.
[HTML4]
HTML 4.01 Specification, D. Raggett, A. Le Hors, and I. Jacobs, Editors. World Wide Web Consortium, 17 December 1997, revised 24 December 1999. This version of the HTML 4.01 Recommendation is http://www.w3.org/TR/1998/REC-html40-19980424. The latest version of HTML 4 is available at http://www.w3.org/TR/html4.
[PAGEMEDIA]
CSS3 Paged Media Module, W3C Candidate Recommendation, H. Lie and J. Bigelow, World Wide Web Consortium, 25 February 2004, Available from http://www.w3.org/TR/2004/CR-css3-page-20040225. The latest version is available at http://www.w3.org/TR/css3-page/
[RFC2119]
RFC2119 - Key words for use in RFCs to Indicate Requirement Levels, S. Bradner, The Internet Engineering Task Force, March 1997. It is available from http://www.ietf.org/rfc/rfc2119.txt?number=2119
[XHTMLPRINT]
XHTML-Print, W3C Candidate Recommendation, J. Bigelow, World Wide Web Consortium, 20 January 2004. Available from http://www.w3.org/TR/2004/CR-xhtml-print-20040120/. The latest version is available at http://www.w3.org/TR/xhtml-print/.

A.2 Informative References

[CSSPP]
CSS Print Profile, PWG Propose Standard 5102.2, D. Wright, J. Bigelow, eds. 28 March 2003. Available at: http://www.pwg.org/xhtml-print/HTML-Version/CSS-Print.html
[CSSMOBILE]
CSS Mobile Profile 1.0, W3C Candidate Recommendation 25 July 2002, T. Wugofski, D. Dominiak, R. Stark, T. Roy, at http://www.w3.org/TR/css-mobile.