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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 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!

scrollbarsappearing or disappearing in a dynamic environment." Thus, evenif the element has sufficient space to display all of its content,the scrollbars would still appear. In addition, when printing a pageor otherwise displaying the document in a paged medium, the contentshould be displayed as though the value ofoverflow were declared to bevisible.

If the overflow is set to



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example, of course, the URL is relative. It could as easily have beensomething like http://www.style.org/sheet1.css.

Finally, there is theTITLE attribute. This attribute is notoften used, but it could become important in the future. Why? Itbecomes important when there is more than one LINKtag -- and there can be more than one. In these cases, however,only those LINK tags with a RELof stylesheet will be used in the initial displayFigure 8-57.

Figure 8-57

Figure 8-57. Inline borders and line-box layout

The borders are placed as they are because the border edge of inline elements is controlled by the font-size, not the line-height. In other words, if a SPAN element has a font-size of 12pt and a line-height of 36pt, its content area is 12pt high, and the content area is what will be surrounded with the width. Thus, if the sum of the seven properties must equal 400 pixels, and no padding or borders are set, and the right margin and width are set to 100px while the left margin is set to auto, then the left margin will be 200 pixels wide:

P {margin-left: auto; margin-right: 100px; width: 100px;} 

The results are shown in Figure 8-11.

Figure 8-11

Figure 8-11. Automatic left margin

In a sense, auto can be used to say, "makeelse.

The containingblock is the context in which formatting takesplace. For example, the containing block of a boldface element couldbe the paragraph in which it occurs, as demonstrated in Figure 9-1.

Figure 9-1

Figure 9-1. An example of a containing block

Not every element in CSS generates a containing block for itsdescendant elements. The rules for the establishment of a containing