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red-star.jpgQuerying 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 red-a.jpg and then deliver the style sheet that best suits the environment.

0424a.jpg

Click to view larger image

red-a.jpg The general syntax for media queries.

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

ie.jpg

fi.jpg

sa.jpg

go.jpg

op.jpg

aspect-ratio

<ratio>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

max-aspect-ratio

<ratio>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

min-aspect-ratio

<ratio>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

device-aspect-ratio

<ratio>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

max-device-aspect-ratio

<ratio>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

min-device-aspect-ratio

<ratio>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

color

<integer>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

max-color

<integer>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

min-color

<integer>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

color-index

<integer>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

max-color-index

<integer>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

min-color-index

<integer>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

device-height

<length>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

max-device-height

<length>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

min-device-height

<length>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

device-width

<length>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

max-device-width

<length>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

min-device-width

<length>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

height

<length>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

max-height

<length>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

min-height

<length>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

monochrome

<integer>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

max-monochrome

<integer>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

min-monochrome

<integer>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

orientation

portrait, landscape

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

resolution

<resolution>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

max-resolution

<resolution>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

min-resolution

<resolution>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

scan

progressive, interlaced

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

width

<length>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

max-width

<length>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

min-width

<length>

bullet.jpg9

bullet.jpg

bullet.jpg

bullet.jpg

bullet.jpg

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).

    Create style sheets for the various media or specific devices for which you will be designing. Print is generally good to include (Code 4.17). You can call the sheet print.css, but you might also want to create style sheets specifically for tablets (Code 4.15) and for desktop computers (Code 4.16).

    Code 4.14. default.css—These styles are applied regardless of the screen size; but we are tailoring the styles for small devices, most likely mobile devices such as smart phones. We start with the small sizes first, and then tailor for larger sizes in the next two CSS files.

    /*** Default Screen Styles ***/
    body {
       color: charcoal;
       font: normal 1.5em/1 helvetica, arial, sans-serif;
       background: silver url('alice23c.gif') no-repeat center 0;
       padding: 120px 20px; }
    h1 { color: purple; font-size: 1.5em; }
    h2 { color: black; font-size: 1.25em; }
    p {   line-height: 2; font-size: 1em; }

    Code 4.15. medium.css—A custom view for medium-size screens. Generally, these styles will be used by tablet devices.

    /*** Medium Device Styles ***/
    
    body {
       color: dimgray;
       background-color: gray;
       font-size: 1.25em;
       padding: 200px 2em; }
    h1 { color: gold; }
    h2 { color: silver; }

    Code 4.16. large.css—The final style sheet will be used to serve a page tailored to larger computer screens.

    /*** Large Device Styles ***/
    
    body {
       color: silver;
       font: normal 1.1em/2 georgia,times,serif;
       background: black url('alice23b.gif') no-repeat 0 0;
       padding: 200px 175px; }
    h1 {
       color: red;
       font-style: italic; }
    h2 { color: gray; }

    Code 4.17. 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.

    /*** For Print ***/
    
    body {
       color: rgb(0,0,0);
       background: white url('alice23a.gif') no-repeat 0 0;
       padding: 200px 0 0 175px;
    }
    h1 { color: gray; }
    p { font: normal 12pt/2 Constantia, palatino, times, "times new roman", serif; }
  2. Add the viewport meta tag. In the head of your HTML document (Code 4.18), add a meta tag with a name equal to viewport and content, as shown.
    <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, minimum-scale=1, user-scalable=no" />

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

  3. Link to your default style sheet. In the head of your HTML document (Code 4.18), 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" >

    Code 4.18. The HTML code links to all three of the style sheets, which are displayed in default red-b.jpg, tablet red-c.jpg, smart phone red-d.jpg, and print red-e.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 identifies itself as a screen, not a handheld device.

    <!DOCTYPE html>
    <html lang="en">
    <head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1,
    → minimum-scale=1, user-scalable=no" />
    <title>Alice&#8217;s Adventures in Wonderland</title>
    <link rel="stylesheet" media="screen" href="14.css">
    <link rel="stylesheet" media="screen and (min-width: 740px) and (min-device-width: 740px),
    → (max-device-width: 800px) and (min-width: 740px) and (orientation:landscape)"
    → href="15.css">
    <link rel="stylesheet" media="screen and (min-width: 980px) and (min-device-width: 980px)"
    → href="16.css">
    <link rel="stylesheet" media="print" href="17.css">
    </head>
    <body>
    <hgroup>
    <h1>Alice&#8217;s Adventures In Wonderland</h1>
    <h2 id="ch01">Chapter 1 <span class="chaptertitle">Down the Rabbit-Hole</span></h2>
    </hgroup>
    <article>
    <p>Alice was beginning to get very tired of sitting by her sister on the bank, and of having
    → nothing to do: once or twice she had peeped into the book her sister was reading, but it had no
    → pictures or conversations in it, <q>and what is the use of a book,</q> thought Alice, <q>without
    → pictures or conversations?</q></p>
    </article>
    <footer><nav> Next:
    <a class="chaptertitle" href="AAIWL-ch02.html">The Pool of Tears</a>
    </nav></footer>
    </body>
    </html>
    0425c.jpg

    Click to view larger image

    red-b.jpg Code 4.18 output to a computer screen. This version uses a dark background and an inverted version of the Alice’s Adventures in Wonderland illustration. On an LCD screen, the lightly colored text will look fine.

    0426d.jpg

    Click to view larger image

    red-c.jpg Code 4.18 on a tablet device, in this case an iPad.

    0427e.jpg

    Click to view larger image

    red-d.jpg Code 4.18 on a mobile device, in this case an iPhone. A specially tailored version to fit the width of smaller devices uses a custom header of the Cheshire cat.

    0428f.jpg

    Click to view larger image

    red-e.jpg Code 4.18 output to a printer. The background is white, and the background image is no longer inverted. This works better in print.

  4. Use a media query to link to a style sheet. Immediately after the previous <link> tag, add more <link> tags that reference the style sheets for a specific media type and then add media queries (Table 4.8) in parentheses connecting multiple queries with and.
    <style type="text/css" media="screenand (min-width: 740px) and (min-device-width: 740px), (max-device-width: 800px)and (min-width: 740px) and (orientation:landscape)">@importurl("css/medium.css");</style>
    <style type="text/css" media="screenand (min-width: 980px) and (min-device-width: 980px)">@import url("css/medium.css"); @import url("css/large.css");</style>
  5. 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">

Using the @media rule

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

0429b.jpg

Click to view larger image

red-f.jpg The general syntax of the @media rule.

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 4.19).
  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) {...}

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

  3. Add other styles as necessary.
    body {...}

    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.

Code 4.19. The HTML code links to the various style sheets for different media types red-g.jpg and red-h.jpg.

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, minimum-scale=1, user-scalable=no" />
<title>Alice&#8217;s Adventures in Wonderland</title>

<style type="text/css">
   body {
      font: normal 12pt/2 times, "times new roman", serif;
      background: white url('alice23a.gif') no-repeat 0 0;
      padding: 200px 175px; }
    h1 { color: gray; }
    h2 { color: silver; }
    p { color: black; }
   @media screen and (max-width: 480px) {
      /*** Small screen Styles ***/
      body {
          -webkit-text-size-adjust:none;
          color: red;
         background: gray url('alice23c.gif') no-repeat center 0;
            padding: 120px 20px 20px 20px; }
      h1 {
         color: red;
         text-shadow: 0 0 5px black; }
      h2 { color: silver; }
      p {
         font-size: 1.5em;
         color: white;   }
   }
</style>
</head>
<body>
<hgroup>
<h1>Alice&#8217;s Adventures In Wonderland</h1>
<h2 id="ch01">Chapter 1 <span class="chaptertitle">Down the Rabbit-Hole</span></h2>
</hgroup>
<article>
<p>Alice was beginning to get very tired of sitting by her sister on the bank, and of having
→ nothing to do: once or twice she had peeped into the book her sister was reading, but it had no
→ pictures or conversations in it, <q>and what is the use of a book,</q> thought Alice, <q>without
→ pictures or conversations?</q></p>
</article>
<footer><nav> Next:
<a class="chaptertitle" href="AAIWL-ch02.html">The Pool of Tears</a>
</nav></footer>
</body>
</html>
0430g.jpg

Click to view larger image

red-g.jpg Code 4.19 on a computer screen.

0431h.jpg

Click to view larger image

red-h.jpg Code 4.19 on a mobile device screen. The styles and background have been modified based on the device width.

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