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10.8. Media Types and @-rules

Don't get too excited yet. We aren't talking about media types in the sense of things like audio and video authoring. Well, not exactly, anyway. We're talking about creating rules for presentation within various kinds of media. The defined types of media thus far are:

These are all values of @media, one of several new @-rules. Some others are:

10.8.1. Paged Media

Since I just brought up paged media, I should probably mention that there are some new properties that apply to such media. Five of them apply to page breaks and where they appear:

page-break-before
page-break-after
page-break-inside
orphans
widows 

The first two are used to control whether a page break should appear before or after a given element, and the latter two are common desktop publishing terms for the minimum number of lines that can appear at the end or beginning of a page. They mean the same thing in CSS2 as they do in desktop publishing.

page-break-inside (first proposed by this author, as it happens) is used to define whether or not page breaks should be placed inside a given element. For example, you might not want unordered lists to have page breaks inside them. You would then declare UL {page-break-inside: avoid;}. The rendering agent (your printer, for example) would avoid breaking unordered lists whenever possible.

There is also size, which is simply used to define whether a page should be printed in landscape or portrait mode and the length of each axis. If you plan to print your page to a professional printing system, you might want to use marks, which can apply either cross or crop marks to your page. Thus you might declare:

@page {size: 8.5in 11in; margin: 0.5in; marks: cross;}

This will set the pages to be U.S. letter-standard, 8.5 inches wide by 11 inches tall, and place cross marks in the corners of each page.

In addition, there are the new pseudo-classes :left , :right, and :first, all of which are applied only to the @page rule. Thus, you could set different margins for left and right pages in double-sided printing:

@page:left {margin-left: 0.75in; margin-right: 1in;}
@page:right{margin-left: 1in; margin-right: 0.75in;} 

The :first selector applies only to the first page of a document, so that you could give it a larger top margin or a bigger font size:

@page:first {margin-top: 2in; font-size: 150%;}

10.8.2. The Spoken Word

To round things out, we'll cover some of the properties in the area of aural style sheets. These are properties that help define how a speaking browser will actually speak the page. This may not be important to many people, but for the visually impaired, these properties are a necessity.

First off, there is

In CSS, it is possible to set an explicit height on any block-level element. If this is done, the resulting behavior is somewhat uncertain. Assume that the specified height is greater than that needed to display the content:

<P STYLE="height: 10em;">

In this case, then the extra height is treated somewhat like extra padding, as depicted in Figure 8-3.

Figure 8-3

Figure 8-3. Setting the height property for block-level elements

voice-family
, which is much the same as font-family in its structure: the author can define both a specific voice and a generic voice family. There are several properties controlling the speed at which the page is read (speech-rate), as well as properties for the pitch , pitch-range, stress, richness, and volume of a given voice. There are also properties that let you control how acronyms, punctuation, dates, numerals, and time are spoken. There are ways to specify audio cues, which can be played before, during, or after a given element (such as a hyperlink), ways to insert pauses before or after elements, and even the ability to control the apparent position in space from which a sound comes via the properties azimuth and elevation. With these last two properties, you could define a style sheet where the text is read by a voice "in front of" the user, whereas background music comes from "behind" and audio cues come from "above" the user!



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background-repeat: repeat-x; background-position: center;}
Figure 6-50

Figure 6-50. Centering with a horizontal repeat

Therefore, setting a large image in the center of the BODY and then letting it repeat will cause it to tile in all four directions: up, down, left, and right. The only difference background-position makes is in where the tiling starts. Figure 6-51 shows the difference between tiling from the center of the BODY, and from its top left corner. calculations, but will be applied to the right and left ends of theelement. If an inline element has both padding and a background, thebackground may be extended above and below the edges of the line-boxin which the inline element appears, but user agents are not requiredto support this behavior. There is also no defined behavior to saywhether the foreground content of a previous line appears above thebackground of a succeeding line, or is overwritten by thatbackground. Negative values are not permitted.

Example

A paragraph.</P></DIV><P>The next paragraph.</P>
Figure 8-23

Figure 8-23. The effects of a negative bottom margin

What's really happening in Figure 8-23 is thatthe elements following the DIV are placedaccording to the location of the bottom of the