csswg-drafts/css-page-4/Overview.bs at trigger-scope · DavMila/csswg-drafts · GitHub

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<pre class=metadata>
Title: Proposals for the future of CSS Paged Media
Shortname: css-page
Level: 4
Group: csswg
Status: UD
Work Status: exploring
ED: https://drafts.csswg.org/css-page-4/
Editor: Daniel Glazman, Disruptive Innovations
Abstract: A list of issues with the current CSS page model, and possibly directions to explore for fixing it.
</pre>

<h2 id=css-page-model>The CSS 3 Page Model</h2>

This section is informative.

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

<figure>
	<img src="images/PageBox.png" width="267" height="266"
	     alt="CSS 3 Paged Media's page model">
	<figcaption>The CSS3 Page Model</figcaption>
</figure>

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

	<figure>
		<img src="images/RightMarginBoxes.png" width="181" height="226">
		     alt="CSS 3 page-margin boxes">
		<figcaption>The 16 page-margin boxes<br>
			(with highlight of 3 of them)<br>
		</figcaption>
	</figure>

2. the <dfn export>page border</dfn>
3. the <dfn export>page padding</dfn>
4. and finally the <dfn export>page area</dfn>
	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
<cite>CSS Generated Content for Paged Media Module </cite>[[!CSS3GCPM]].

It is also possible to define multiple page templates for a single document
using the <span class="css">@page</span> 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
	<cite>CSS Regions Module Level 3</cite> [[!CSS3-REGIONS]]
	to flow content into a given predefined area of a page,
	exclude an area from the page using
	<cite>CSS 3 Exclusions and Shapes Module</cite> [[!CSS3-EXCLUSIONS]],
	lay out the page area into a grid using
	<cite>CSS Grid Layout</cite> [[!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 <cite>CSS 2.1</cite> [[!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

<h2 class=no-num id=privacy>Privacy Considerations</h2>

No new privacy considerations have been reported on this specification.

<h2 class=no-num id=security>Security Considerations</h2>

No new security considerations have been reported on this specification.