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Paged media (e.g., paper, transparencies, pages that are displayed on computer screens, etc.) differ from continuous media in that the content of the document is split into one or more discrete pages. To handle page breaks, CSS2 extends the visual formatting model as follows:
The CSS2CSS 2.1 page model specifies how a
document is formatted within a rectangular area --the page box -- that has a finite width and height.. The page box does not necessarily correspond to the real sheet where the
document will ultimately be rendered (paper, transparency, screen,
etc.). The CSS page model specifies formatting in the page box, but it is theuser agent's responsibility to transferagent is responsible for transferring the page box to the
sheet. SomeTransfer possibilities include:
The page box is a rectangular region that contains two areas:
Note. In CSS2, the border properties and padding properties do not apply to pages; they may in the future.Authors can specify the dimensions, orientation, margins, etc.margins of a page box withininside an @page rule. An @page rule
consists of the keyword "@page", a page selector (followed with no intervening spacefollowed by an optional page
pseudo-class), andselector, followed by a block of declarations. The declarations (saidare
said to be in the page context )..
The page
selector specifies for which pages the declarations
apply. In CSS2,CSS 2.1, page selectors may designate the first page,
all left pages, all right pages,or a page with a specific name. The dimensions of the page box are set with the 'size' property. The dimensions of the page area are the dimensions of the page box minus the margin area. Example(s): For example, the following @page rule sets the page box size to 8.5 x 11 inches and creates '2cm' margin onall sides between the page box edge and the page area: @page { size 8.5in 11in; margin: 2cm } The 'marks' property in an @page rule specifies crop and cross marks for the page box.right pages
The margin properties ('margin-top', 'margin-right', 'margin-bottom', 'margin-left', and 'margin') apply within the page context. The following diagram shows the relationships between the sheet, page box, and page margins:
Here is '0'.a simple example which sets all page margins on all pages:
@page { margin: 3cm; }
The page context has no notion of
fonts, so 'em' and 'ex' units are not allowed. Percentage values on
the margin properties are relative to the dimensions of the page box; for left and right margins, they refer
to page box width while for top and bottom margins, they refer to page
box height. All other units associated with the respective CSS2CSS 2.1
properties are allowed.
Due to negative margin values (either on the page box or on
elements) or absolute
positioning content may end up outside the page box, but this
content may be "cut" --— by the user agent, the printer, or ultimately,
the paper cutter.
13.2.2 Page size :The 'size' property 'size' Value: <length> {1,2} | auto | portrait | landscape | inherit Initial: auto Applies to: computed value of box margins at the top or bottom of
the page context Inherited: N/A Percentages: N/A Media: visual , paged This property specifies the size and orientation of a page box. The size of a page box may either be "absolute" (fixed size) or "relative" (scalable, i.e., fitting available sheet sizes). Relative page boxes allow user agents to scale a document and make optimal use of the target size. Three values for the 'size' property create a relative page box: auto The page box will be set to the size and orientation of the target sheet. landscape Overrides the target's orientation. The page box is the same size as the target, and the longer sides are horizontal. portrait Overrides the target's orientation. The page box is the same size as the target, and the shorter sides are horizontal. Example(s): In the following example, the outer edges of the page box will align with the target. The percentage value on the 'margin' property is relative to the target size so if the target sheet dimensions are 21.0cm x 29.7cm (i.e., A4), the margins are 2.10cm and 2.97cm. @page { size: auto; /* auto is the initial value */ margin: 10%; } Length values for the 'size' property create an absolute page box. If only one length value is specified, it sets both the width and height of the page box (i.e., the box is a square). Since the page boxarea is the initial containing block , percentage values are not allowed for the 'size' property. Example(s): For example: @page { size: 8.5in 11in; /* width height */ } The above example set the width of the page box to be 8.5in and the height to be 11in. The page box in this example requires a target sheet size of 8.5"x11" or larger. User agents may allow users to control the transfer of the page box to the sheet (e.g., rotating an absolute page box that's being printed).zero.
If a page box does not fit the target sheet dimensions, the user agent may choose to:
The user agent should consult the user before performing these operations.
When the page box is smaller than the target size, the user agent is free to 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. 13.2.3 Crop marks : the 'marks' property 'marks' Value: [ crop || cross ] | none | inherit Initial: none Applies to: page context Inherited: N/A Percentages: N/A Media: visual , paged In high-quality printing, marks are often added outside the page box. This property specifies whether cross marks or crop marks or both should be rendered just outside the page box edge. Crop marks indicate where the page should be cut. Cross marks (also known as register marks or registration marks) are used to align sheets. Marks are visible only on absolute page boxes (seeuser agent
is free to place the 'size' property). In relativepage boxes,box anywhere on the sheet. However, it is
recommended that the page box willbe aligned with the target andcentered on the markssheet since this will
be outside the printable area. The size, style,align double-sided pages and positionavoid accidental loss of cross marks depend oninformation that
is printed near the user agent. 13.2.4edge of the sheet.
When printing double-sided documents, the page
boxes on left and right pages shouldmay be different. This can be
expressed through two CSS pseudo-classes that may be definedused in thepage context .selectors.
All pages are automatically classified by user agents into either the :left or :right pseudo-class.
@page :left { margin-left: 4cm; margin-right: 3cm; } @page :right { margin-left: 3cm; margin-right: 4cm; }
If different declarations have been given for left and right pages, the user agent must honor these declarations even if the user agent does not transfer the page boxes to left and right sheets (e.g., a printer that only prints single-sided).Authors may also specify style for the first page of a document
with the :first pseudo-class:
@page { margin: 2cm } /* All margins set to 2cm */ @page :first { margin-top: 10cm /* Top margin on first page 10cm */ }
Whether the first page of a document is :left or :right depends on the major writing direction of the document and is outside the scope of this document. However, to force a :left or :right first page, authors may insert a page break before the first generated box (e.g., in HTML, specify this for the BODY element).Properties specified in a :left (or :right)or :right @page rule override
those specified in an @page rule that has no pseudo-class specified.
Properties specified in a :first @page rule override those specified
in :left (or :right)or :right @page rules.
Note. AddingMargin declarations on left, right, and first pages may result in
different page area widths. To simplify
implementations, user agents may use a single page area width
on left, right, and first pages. In this case, the :left or :right pseudo-class does not influence whether the document comes outpage area width
of the printer double- or single-sided (which is outside the scope of this specification). Note. Future versions of CSS may include otherfirst page pseudo-classes. 13.2.5should be used.
When formatting content in the page model, some content may end up
outside the page box. For example, an element whose 'white-space' property has the
value 'pre' may generate a box that is wider than the page box. Also,
when boxes are positioned absolutely, they may end up in
"inconvenient" locations. For example, images may be placed on the
edge of the page box or 100,000 inchesmeters below the page box.
A specification forThe exact formatting of such elements lies outside the scope of
this document.specification. However, we recommend that authors and user agents
observe the following general principles concerning content outside
the page box:
The following sections explainThis section describes page formattingbreaks in CSS2.CSS 2.1. Five
properties indicate where the user agent may or should break pages,
and on what page (left or right) the subsequent content should resume.
Each page break ends layout in the current page
box and causes remaining pieces of the document tree to be laid out in a new
page box.
Value: | auto | always | avoid | left | right | inherit |
Initial: | auto |
Applies to: | block-level elements |
Inherited: | no |
Percentages: | N/A |
Media: | visual, paged |
Computed value: | as specified |
Value: | auto | always | avoid | left | right | inherit |
Initial: | auto |
Applies to: | block-level elements |
Inherited: | no |
Percentages: | N/A |
Media: | visual, paged |
Computed value: | as specified |
Value: | avoid | auto | inherit |
Initial: | auto |
Applies to: | block-level elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual, paged |
Computed value: | as specified |
Values for these properties have the following meanings:
Whether the first page of a document is :left or :right depends on the major writing direction of the document. A conforming user agent may interpret the values 'left' and 'right' as 'always'.
A potential page break location is typically under the influence of the parent element's 'page-break-inside' property, the 'page-break-after' property of the preceding element, and the 'page-break-before' property of the following element. When these properties have values other than 'auto', the values 'always', 'left', and 'right' take precedence over 'avoid'.
See the section on allowed page breaks for the exact rules on howThese properties may force or suppress a page break. 13.3.2 Using named pages: 'page' 'page' Value: <identifier> | auto Initial: auto Applies to: block-level elements Inherited: yes Percentages: N/A Media: visual , paged The 'page' property can be usedonly apply to specify a particular type ofnon-floating block-level elements.
Also, page where an element shouldbreaks cannot be displayed. Example(s): This example will put all tables on a right-hand side landscape page (named "rotated"): @page rotated {size: landscape}forced to occur inside table {page: rotated; page-break-before: right} The 'page' property works as follows: If a block box with inline content has a 'page' property that is different from the preceding block box with inline content, then one or two page breaks are inserted between them, and the boxes after the break are rendered on a page box of the named type. See "Forced page breaks" below. Example(s): In this example, the two tables are rendered on landscape pages (indeed, on the same page, if they fit),cells, absolutely positioned
boxes, and thefixed
positioned boxes. Page type "narrow" is not used at all, despite having beenbreaks set on the DIV: @page narrow {size: 9cm 18cm} @page rotated {size: landscape} DIV {page: narrow} TABLE {page: rotated} with this document:: <DIV> <TABLE>...</TABLE> <TABLE>...</TABLE> </DIV> 13.3.3before, inside, or after such
elements must be ignored.
The 'orphans' property specifies the minimum number of lines of a paragraph that must be left at the bottom of a page. The 'widows' property specifies the minimum number of lines of a paragraph that must be left at the top of a page. Examples of how they are used to control page breaks are given below.
For information about paragraph formatting, please consult the section on line boxes.
In the normal flow, page breaks can occur at the following places:
These breaks are subject to the following rules:
If the above doesn't provide enough break points to keep content from overflowing the page boxes, then rules B and D are dropped in order to find additional breakpoints.
If that still does not lead to sufficient break points, rules A and C are dropped as well, to find still more break points.
A page break must occur at (1) if, among the 'page-break-after' and 'page-break-before' properties of all the elements generating boxes that meet at this margin, there is at least one with the value 'always', 'left', or 'right'.
CSS2 does not define which of a set of allowed page breaks must be used; CSS2 does not forbid a user agent from breaking at every possible break point, or not to break at all. But CSS2 does recommend that user agents observe the following heuristics (while recognizing that they are sometimes contradictory):
Suppose, for example, that the style sheet
contains 'orphans :'orphans: 4', 'widows :'widows: 2', and
there are 20 lines (line boxes)
available at the bottom of the current page:
Now suppose that 'orphans' is '10', 'widows' is '20', and there are 8 lines available at the bottom of the current page:
Declarations in the page context obey the cascade just like normal CSS2 declarations.
Consider the following example:
@page { margin-left: 3cm; } @page :left { margin-left: 4cm; }
Due to the higher specificity of the pseudo-class selector, the left margin on left pages will be '4cm' and all other pages (i.e., the right pages) will have a left margin of '3cm'.