Book HomeCascading Style Sheets: The Definitive GuideSearch this book Monday 30th of May 2016 06:52:52 AM

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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H1 {color: white; background-color: rgb(20%,20%,20%);}
Figure 6-18

Figure 6-18. A nifty effect for H1 elements

This shows but one example of how displays can be dramatically changed with just a few styles. Of course, there are as many combinations as there are colors, but we can't exactly show them here -- being stuck in grayscale as we are -- however, we'll try to give you some idea of what you can do. Here are a few ideas to get you started.

This is a simple style sheet, as shown in Figure 6-19: element, or even to the browser window itself. The power of thisfeature is both obvious and surprising. It shouldn't be toosurprising to learn that this is the part of CSS2 that user agentsusually first attempt to support. Given that there were some verygood positioning implementations on the horizon as the book was beingcompleted, we felt it worthwhile to give readers a glimpse ofwhat's coming soon -- or, if you're reading this booka year or three after its publication, what can be done.

You may notice that, unlike other chapters, almost none of the SMALL {font-family: 'Zurich Light', sans-serif;}

Besides the obvious tedium of writing such a style sheet, it onlyworks if everyone has these fonts installed, and it's prettysafe bet that most people don't. It would make far more senseto specify a single font family for the whole document and thenassign weights to various elements. You can do this, in theory, usingthe various values for the property font-weight. Afairly obvious font-weight declaration is this:

B {font-weight: bold;}
which is <B STYLE="font-size: 24px;">boldfaced</B>and <SPAN STYLE="vertical-align: top;">tall</SPAN> and which is<BR>larger than the surrounding text.</P>

Now we're back to our earlier example, where the middle linebox is taller than the other line boxes. However, notice how the"tall" text is aligned in Figure 8-54.

Figure 8-54

Figure 8-54. Top-aligning text

What's happened here is that the top of the "tall"

Note that since horizontal margins do not collapse, the padding,borders, and margin of a parent element can affect its children. Thisis an indirect effect, of course, in that the margins (and so on) ofan element can induce an offset for child elements. Vertical marginsare still collapsed, as shown in Figure 8-18:

DIV {margin: 20px; padding: 20px;}P {margin: 10px; padding: 10px;}
Figure 8-18

Figure 8-18. Offset is implicit in the parent's margins and padding