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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!



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needed to be relatively dark. Not so with CSS; all you need to do isadd a class to all anchors that need to be this shade of gray andmodify your styles accordingly, with the result seen in Figure 6-4:

BODY {color: black;}A:link {color: #808080;}      /* medium gray */A.external:link  {color: silver;}A:active {color: silver;}A:visited {color: #333333;}   /* a very dark gray */
Figure 6-4

Figure 6-4. Changing colors of hyperlinks

with a class of highlight to be yellow, as shownin
Figure 6-2:

Figure 6-2

Figure 6-2. Highlighting a table cell contents

6.1.1.1. BODY attributes

There are many uses forcolor, of course, the most basic of which is toreplace the BODY attributesTEXT, LINK ,simplest case for doing so:

H1 {margin-bottom: 0;}
P {margin-top: 0;}

This is, after all, one correct way to eliminate the space between succeeding elements. Navigator 4.x, however, will display the elements with the usual blank line between them, as you can see in Figure 7-26. This is because it's adding the zero values to its own default margins.

Remember that the containing block of an absolutely positioned element is not necessarily its parent element. In fact, it often is not, unless the author takes steps to correct this situation. Fortunately, that's easy to do. Just pick the element that you want to use as the containing block for the absolutely positioned element, and give it a position of relative with no offsets. Thus:

P.contain {position: relative;}

Consider the example in Figure 9-19. It shows two results from all browsers. Since no one can clearly say which is right, none of them can really be considered to be buggy -- at least, not until the specification is sufficiently clarified.

8.2.3. List Items

Speaking of list items, they have a few special rules in addition to everything discussed so far. List items are typically preceded by a