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NEW IN CSS3: Querying the Media

In Chapter 3 you learned how to specify style sheets for a particular media type, allowing you to set styles depending on whether the HTML is output to a screen, print, TV, or a handheld or other device (Table 4.7). CSS3 adds an important new capability that allows you to set styles based on common interface properties such as width, height, aspect ratio, and number of available colors.

Table 4.7 Media Values

Value

Intended for

screen

Computer displays

tty

Teletypes, computer terminals, and older portable devices

tv

Television displays

projection

Projectors

handheld

Portable phones and PDAs

print

Paper

braille

Braille tactile readers

speech

Speech synthesizers

all

All devices

Media queries and the @media rule can be used to tailor your page, not just to a general device type but to the specific device your site visitor is using. This includes sizing for print, for mobile devices, or to best fit the size of the open browser window.

Media queries

If you want to know the current size of the browser window, why not just ask the browser? JavaScript gives you the ability to do this, but it’s a cumbersome way to get some basic facts about the Webbed environment your design is trying to fit into.

Media queries provide you with several common media properties that you can test circle-a.jpg and then delivers the style sheet that best suits the environment.

Although media queries have many properties (Table 4.8), they come in five basic flavors:

  • Aspect-ratio looks for the relative dimensions of the device expressed as a ratio: 16:9, for example.
  • Width and height looks for the dimensions of the display area. These can also be expressed as maximum and minimum values.
  • Orientation looks for landscape (height greater than width) or portrait (width greater than height) layout. This allows you to tailor designs for devices that can flip.
  • Color, Color-index, and monochrome finds the number of colors or bits per color. These allow you to tailor your design for black and white mobile devices.
  • Resolution looks at the density of pixels in the output. This is especially useful when you want to take advantage of display devices that have a higher resolution than 72 dpi.

Table 4.8 Media Query Properties

Property

Value

Compatibility

aspect-ratio

<ratio>

FF3.5, S1, C1, O9.5, CSS3

max-aspect-ratio

<ratio>

FF3.5, S1, C1, O9.5, CSS3

min-aspect-ratio

<ratio>

FF3.5, S1, C1, O9.5, CSS3

device-aspect-ratio

<ratio>

FF3.5, S1, C1, O9.5, CSS3

max-device-aspect-ratio

<ratio>

FF3.5, S1, C1, O9.5, CSS3

min-device-aspect-ratio

<ratio>

FF3.5, S1, C1, O9.5, CSS3

color

<integer>

FF3.5, S1, C1, O10, CSS3

max-color

<integer>

FF3.5, S1, C1, O10, CSS3

min-color

<integer>

FF3.5, S1, C1, O10, CSS3

color-index

<integer>

FF3.5, S1, C1, O10, CSS3

max-color-index

<integer>

FF3.5, S1, C1, O10, CSS3

min-color-index

<integer>

FF3.5, S1, C1, O10, CSS3

device-height

<length>

FF3.5, S1, C1, O9.5, CSS3

max-device-height

<length>

FF3.5, S1, C1, O9.5, CSS3

min-device-height

<length>

FF3.5, S1, C1, O9.5, CSS3

device-width

<length>

FF3.5, S1, C1, O9.5, CSS3

max-device-width

<length>

FF3.5, S1, C1, O9.5, CSS3

min-device-width

<length>

FF3.5, S1, C1, O9.5, CSS3

height

<length>

FF3.5, S1, C1, O9.5, CSS3

max-height

<length>

FF3.5, S1, C1, O9.5, CSS3

min-height

<length>

FF3.5, S1, C1, O9.5, CSS3

monochrome

<integer>

FF3.5, S1, C1, O10, CSS3

max-monochrome

<integer>

FF3.5, S1, C1, O10, CSS3

min-monochrome

<integer>

FF3.5, S1, C1, O10, CSS3

orientation

portrait, landscape

FF3.5, S1, C1, CSS3

resolution

<resolution>

FF3.5, S1, C1, O10, CSS3

max-resolution

<resolution>

FF3.5, S1, C1, O10, CSS3

min-resolution

<resolution>

FF3.5, S1, C1, O10, CSS3

scan

progressive, interlaced

FF3.5, S1, C1, O10, CSS3

width

<length>

FF3.5, S1, C1, O9.5, CSS3

max-width

<length>

FF3.5, S1, C1, O9.5, CSS3

min-width

<length>

FF3.5, S1, C1, O9.5, CSS3

By default, media queries are for the viewport (see Chapter 11 for details on the viewport) with the exception of those that specify device, in which case they are for the entire screen or output area. For example, width is the width of the visible browser viewport within the screen, whereas device-width is the width of the entire screen.

Using media queries to specify styles:

  1. Create your style sheets. Create a default media style sheet that captures all the general styles for your design and save it. I like to call mine default.css (Code 4.14).

    Code 4.14. default.css—These styles are applied regardless of the media type and include sans-serif fonts, a dark background, and light text.

    /*** Default Styles ***/
    
    body {
     background: black url('../_images/AAIW-illos/alice23b.gif') no-repeat 0 0;
     margin: 0 0;
     padding: 200px 0 0 175px; }
    h1 {
     color: white;
     font-style: italic; }
    h2 {
     color: rgb(153,153,153); }
    p {
     font: normal 100%/1.5 Corbel, Helvetica, Arial, Sans-serif;
     color: rgb(204,204,204); }

    Create style sheets for the various media or specific devices for which you will be designing. Print is generally good to include (Code 4.15). You can call the sheet print.css, but you might also want to create style sheets specifically for popular mobile devices such as the iPhone (Code 4.16), which you could name iphone.css.

    Code 4.15. print.css—These styles are tailored for the printed page, changing the background to white (assuming white paper), serif fonts, black text, and a different background image to match.

    /*** For Print ***/
    
    body {
     background: white url('../_images/AAIW-illos/alice23a.gif') no-repeat 0 0;
     padding: 200px 0 0 175px;
      }
    h1 {
     color: black; }
    p {
     font: normal 12pt/2 Constantia, palatino, times, "times new roman", serif;
     color: rgb(0,0,0); }

    Code 4.16. iphone.css—These styles are specific for use on an iPhone and are loosely based on that mobile device’s look and feel.

    /*** iPhone Styles ***/
    
    body {
     -webkit-text-size-adjust:none;
     background: rgb(102,102,102) url('../_images/AAIW-illos/alice23c.gif') no-repeat center 0;
     padding: 120px 20px 20px 20px; }
    h1 { color: rgb(153,125,125);
     text-shadow: 0 0 5px rgb(0,0,0); }
    p {
     font: normal 1em/1.25em "helvetica neue", Helvetica, Arial, Sans-serif;
     color: rgb(255,255,255); }
  2. Add the viewport meta tag. In the head of your HTML document (Code 4.17), add a meta tag with a name equal to viewport and content, as shown.
    <meta name="viewport" content="width=device-width; initial-scale=1.0; maximum-scale=1.0; user-scalable=0">

    This will prevent devices with smaller screens, most notably the iPhone, from resizing the page, overriding your styles to be set in step 5.

    Code 4.17. The HTML code links to all three of the style sheets, which are displayed in default circle-b.jpg, Print circle-c.jpg, and in the iPhone circle-d.jpg. The iPhone style sheet uses media queries to set a device’s width range in keeping with the iPhone. Notice that I used screen for the media type because the iPhone indentifies itself as a screen, not a handheld device.

    <!-- HTML5 -->
    <!DOCTYPE html>
    <html lang="en">
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <meta name="viewport" content="width=device-width; initial-scale=1.0; maximum-scale=1.0; user-scalable=0">
    <title>Alice's Adventure's In Wonderland</title>
    <link rel="stylesheet" media="all" href="default.css" >
    <link rel="stylesheet" media="print" href="print.css">
    <link rel="stylesheet" media="screen and (max-device-width: 480px) and (min-device-width: 320px)" href="iphone.css" >
    </head>
    <body>
    <h1>Alice&#8217;s Adventures In Wonderland</h1>
    <p class="byline">by <span class="author">Lewis Carroll</span></p>
    <article><!-- Article -->
    <header>
    <h2><strong>Chapter I.</strong> Down the Rabbit-Hole</h2>
    </header>
    <p>
    Alice was beginning to get very tired of sitting by her sister,...</p>
    </article>
    </body>
    </html>
  3. Link to your default style sheet. In the head of your HTML document, type a <link> tag that references the default version of the CSS and define media as all.
    <link rel="stylesheet" media="all" href="default.css" >
  4. Link to your print style sheet. Immediately after the <link> tag, add another <link> tag that references the print version of the CSS and define media as print.
    <link rel="stylesheet" media="print" href="print.css">
  5. Use a media query to link to a style sheet. Immediately after the previous <link> tag, add another <link> tag that references the style sheet for a specific media type and then add media queries (Table 4.8) in parentheses connecting multiple queries with and.
    <link rel="stylesheet" media="screen and (max-device-width: 480px) and (min-device-width: 320px)" href="iphone.css" >

Using the @media rule

Media queries allow you specify styles in the media property of <link> and <style> tags, but the @media rule circle-e.jpg allows you to embed media queries directly into a style sheet.

Using @media to specify styles:

  1. Create your style sheets. Create an external style sheet or embed a style sheet in the body of your document (Code 4.18).

    Code 4.18. screen.css—The iPhone code from Code 4.15 has been combined with more generic screen CSS.

    /*** Screen Styles ***/
    
    @media screen and (max-device-width: 480px) and (min-device-width: 320px) {
    
     /*** iPhone Styles ***/
    
     body {
      -webkit-text-size-adjust:none; color: red;
      background: rgb(102,102,102) url('../_images/AAIW-illos/alice23c.gif') no-repeat center 0;
       padding: 120px 20px 20px 20px; }
     h1 {
      color: rgb(153,125,125);
      text-shadow: 0 0 5px rgb(0,0,0); }
     p {
      font: normal 1em/1.25em "helvetica neue",
    Helvetica, Arial, Sans-serif;
      color: rgb(255,255,255); }
    }
    
    h2 strong {
     display: block;
     color: red;
     font-size: .75em;
     font-style: italic; }
  2. Use the @media rule to specify styles with media queries. In the head of your HTML document, type @ and media. Then specify the media type (Table 4.7) and any media queries (Table 4.8) for the styles.
    @media screen and (max-device-width: 480px) and (min-device-width: 320px) {...}

    For example, you might specify that these styles are for screens with a width between 320px and 480px. Finish with curly brackets. Add any media-specific styles between the curly brackets.

  3. Add other styles as necessary.
    h2 strong {...}

    You can add more @media rules or other nonmedia-specific rules. However, all CSS rules that are not in @rules (@media, @font-face, @import, and so on) must come after the @rules.

  4. Link to the style sheet from your HTML document. Place a link tag to add the external CSS file (Code 4.19).

Code 4.19. The HTML code links to the various style sheets for different media types. The big difference between this version and Code 4.16 is that the iPhone-specific code is now embedded in screen.css, so I’m not including media queries circle-f.jpg.

<!-- HTML5 -->
<!DOCTYPE html>
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<meta name="viewport" content="width=device-width; initial-scale=1.0; maximum-scale=1.0; user-scalable=0">
<title>Alice's Adventures In Wonderland</title>
<link rel="stylesheet" media="all" href="default.css" >
<link rel="stylesheet" media="print" href="print.css">
<link rel="stylesheet" media="screen" href="screen.css">
</head>
<body>
<h1>Alice&#8217;s Adventures In Wonderland</h1>
<p class="byline">by <span class="author">Lewis Carroll</span></p>
<article><!-- Article -->
<header>
<h2><strong>Chapter I.</strong> Down the Rabbit-Hole</h2>
</header>
<p>
Alice was beginning to get very tired of sitting by her sister,...</p>
</article>
</body>
</html>
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