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CSS CSS Presentation Transcript

  • CSS- Cascading Stylesheets Layout for web and XML
  • Cascading Stylesheets
    • A language to define how XML documents, html documents and XHTML documents should be rendered for screen, paper, TV, sound …
    • Reommendation from W3C
    • Not in itself XML-based, but operates on XML structures
  • CSS - Historical perspektive
    • html was built to structure text documetns with links, regardless of presentation medium.
    • The commercial success of the web drove a need to make more estetically pleasing content.
    • Logical elements (like <h3>) was used to get a certain graphical effect, instead of using it to indicate a logical content. New elements added without control.
    • Solution: Make an entirely new language for laout: CSS
  • Examples
    • Now
    • File b.css
    • p {
    • font-family: Helvetica, sans-serif;
    • }
    • File b.html
    • <?xml-stylesheet type=&quot;text/css&quot; href=&quot;b.css&quot;?>
    • […]
    • <p>
    • Text in helvetica
    • </p>
    • […]
    Before File a.html […] <p> <font face=&quot;Helvetica&quot;> Text in Helvetica </font> </p> […]
  • Internal or external CSS
    • A CSS can either be placed in the actual xml/html document, or as an external filef.
    • An internal CSS has the advantage that only one http request is required
    • However, the drawback is that copies of the CSS code must be placed in all documents using it, making updates more difficult.
  • Associating an XML-document ->CSS
    • type: MIME-typen text/css
    • href: URI to the css-file
    • charset: Character set
    • title: Title
    • media: The media for which the stylesheet should be used.An XML document can have several associated stylesheets. Which one(s) is used depends on the output medium: Screen, tty, tv, projection, handheld, print, braille, aural or all
    • To associate an XML document with a CSS, a processing instruction can be used.
    • Processin instruction in an XML-fil
    • <?xml-stylesheet
    • type=&quot;text/css&quot;
    • href=&quot;b.css&quot;
    • charset=&quot;ISO8859-1&quot;
    • title=”My Stylesheet&quot;
    • media=&quot;screen&quot;?>
  • Associating an HTML-document ->CSS
    • An internal CSS can be added using the style-element in the element head.
    • internal CSS in an HTML.-fil
    • <html>
    • <head>
    • <style type=&quot;text/css&quot;>
    • body { background-color: #ffffff; }</style>
    • </head>
    • <body>
    • </body>
    • </html>
    • To associate an html document with a CSS, you usually ad a link-element in the head-element.
    • External CSS + HTML-file
    • <html>
    • <head>
    • <link rel=&quot;stylesheet”
    • type=&quot;text/css&quot;
    • href=&quot;test.css”/>
    • </head>
    • <body>
    • </body>
    • </html>
  • Basic principle: Pattern -> Behaviour
    • The basic principle is to find different ”patterns” in the XML/html using ”selectors”, and then setting some property to some value.
    • A pattern can, for example, be a tag name.
    • A property can be a font-size.
    • Example:
    • p {
    • font-family: Helvetica, sans-serif;
    • }
    Selector: All p-elements Property Property value
  • Different selectors
    • There are a number of selectors that can be used to find different parts of an XML/html structure.
    • For example, you can find decendents, children, siblings and attributes.
    • Example:
    • * {
    • font-size: Medium
    • }
    • p a {
    • font-size: Medium
    • }
    Matches all elements matches all a-elements which are decendents to p-elements
  • Different selectors
    • Example:
    • p > a {
    • font-size: Medium
    • }
    • p + a {
    • font-size: Medium
    • }
    Matches a-elements which are children to p-elements. Matches all a-elements which directly follows a p-elements (siblings) Example: <p> <a></a> </p> <p> <strong> <a>Hej</a> </strong> </p> Matches Matches inte
  • Matching attributes
    • Example:
    • a-element wit href=&quot;a.html&quot;
    • a[href=&quot;a.html&quot;] {font-size: Medium}
    • a-element which has a href-attribut
    • a[href] {font-size: Medium}
    • a-element whose href contains the substring &quot;html&quot;
    • a[href~=&quot;html&quot;] {font-size: Medium}
    • Examples of attribute matches
      • if the attribute has a value
      • Substrings of attribute values
      • ID-values
  • Pseudo classes and pseudo elements
    • Example:
    • First child to a p-element
    • p:first-child {font-size: Medium}
    • First letter in a banana-element
    • banana:first-letter {font-size: Medium}
    • Before (or after) a banan-element
    • banana:before {content: ”A Banana!&quot;}
    • Pseudo classes and pseudo elements matches different types of meta information in the document.
    • Separated from elements/attributeses with a colon.
    • There are a number of properties to set height, lenght and sizes.
      • border-width, font-size, line-height, margin-left, margin-top, margin-right, margin-bottom, left, top, height, width
    • Most units used in typography can be used.
      • Absolute, t.ex. cm, in, pt
      • Relative.ex. em, ex, px
    • Example
    • banana {line-height: 2.2em}
    • tomato {font-size:14pt;line-height:3ex}
    Properties: Height/length/size Obs! Två properties till samma selektor, separerat med semikolon
  • Properties:Fonter
    • A number of properties for font handling.
      • font-family: i.e. Helvetica, sans-serif
      • font-style: i.e. italic, slanted
      • font-size: absolute values like 12pt or relative values like x-small
      • font-weight: bold, bolder, lighter or a scale of 100 - 900
      • font-stretch:wider, ultra-expanded, semi-condensed and so forth.
      • … and several other properties
  • Properties:Texts
    • Text-properties deals with indent, alignment and simple transformations.
      • Display: block, inline or none. Blocks start on a new-line and is followed by a new-line, inline does not disrupt the text flow, and ”none” hides the content.
      • text-indent: applicable only on elements with block-display.
      • text-align: left, right, center, justify
      • text-decoration: underline, overline, linethrough
      • text-transform: capitalize, uppercase, lowercase
      • white-space: pre to preserve linebreaks and whitespace.
  • Properties:Colours
    • The most important properties or colours are
      • Color (note: american spelling)
      • Background-color
      • Border-color
    • Pre-defined colours
      • Aqua, black, blue, fuchsia, gray, green, lime, maroon, navy, olive, purple, red, silver, teal, white, yellow
    • Or hexadecimala colours representations
      • p {color: # FF FF CC }
    • or
      • p {color:rgb( 100%, 100%, 70%}
  • Advanced 1: Counters
    • It is also possible to use ”variables” as counter, and insert the value of the counters in what is displayed.
    • p:before {
    • content: counter(banana) &quot;. &quot;;
    • counter-increment: banana
    • }
    • h1 {
    • counter-reset: banana
    • }
  • Advanced 2: Classes
    • If you want to set different properties just to some elements of a certain kind, you can use ”classes”.
    • p.tomato {
    • font-size:14pt
    • }
    • <p class=&quot;tomato&quot;>
    • Hello
    • </p>
  • Advanced 3: Pseudoclasses for links
    • It is common to want different colours on links, depending on whether they have been visited or not.
    • a:link {color: #FF0000} /* unvisited link */
    • a:visited {color: #00FF00} /* visited link */
    • a:hover {color: #FF00FF} /* mouse over link */
    • a:active {color: #0000FF} /* selected link */
  • Advanced 4: media types
    • A way to define different properties for diferent media types, i.e. print, screen and aural.
    • <html>
    • <head>
    • <style type=&quot;text/css&quot; media=&quot;screen&quot;>
    • @import &quot;/css/initial.css&quot;;
    • @import &quot;/css/screen.css&quot;;
    • </style>
    • <style type=&quot;text/css&quot; media=&quot;print&quot;>
    • @import &quot;/css/initial.css&quot;;
    • @import &quot;/css/print.css&quot;;
    • </style>
    • </head>
    • <body>
    • <p class=&quot;test&quot;>Hello</p>
    • </body>
    • </html>
  • Advanced 5: the print media type
    • A few properties exist only for the media type &quot;print&quot;. The most important are:
      • page-break-after
      • page-break-before
    • For more info, see http://www.w3schools.com/css/css_ref_print.asp
  • Advanced 6: mediatypen aural
    • An interesting possibility is to control the audio from a voice synthesizer. An example could be:
    • h1, h2, h3, h4
    • {
    • voice-family: male;
    • richness: 80;
    • cue-before: url(&quot;beep.au&quot;)
    • }
    • For more info, see http://www.w3schools.com/css/css_ref_aural.asp
  • Browsersupport
    • Today good support in all(most) modern browsers.
    • Opera probably best support
    • However: Don’t count on mobile phones to support CSS.
  • Limitations and possibilities
    • I CSS1: Only support for html-tags
    • I CSS2: Supports all XML documents, making it easier to separate content from presentation.
    • I CSS3: Support for columns, pagination, more powerful selectors and for non-european character sets.
    • A problem is that it is not possible to change the orders of elements, or to re-use an element several times.