LIS650 lecture 4Minor CSS, accessibility

Thomas Krichel2006-02-25

more on selectors

• We have seen three types of simple selectors.

• Here we are discussing some more advanced selectors. Most, but not all, of the selections that they achieve could also be done by appropriate class= use.

• CSS can be applied to any XML document, including, but not limited to XHTML documents.

• Remember that all selectors select elements in the XHTML or XML document.

ORing selectors

• When we write elementary several selectors separated by commas, we refer to all of them

• Example

h1, .heading {text-align: center}

will center all <h1> and all elements that are that are in the “heading” class.

more selectors• * selects any element.• E selects any element called <E>• E F selects any <F> element that is in the

contents of an <E> element, as a child, grand-child etc

• E > F selects any <F> element that is a direct child of an <E> element. This is more restrictive than the previous selector.

• E + F selects any <F> element immediately preceded by a sibling element <E>.

more selectors

• E:link selects an <E> element if it is a link.

• E:visited selects element <E> if <E> if it is in the contents of a link and the link has been visited.

• E:active, E:hover, E:focus selects element <E> during certain user actions with the mouse.

more selectors

• E:first-child selects <E> when <E> is the first child of its enclosing element

• E:first-letter selects the first letter in the content of element <E>

• E:first-word selects the first word in the contents of element <E>

more selectors

• E[a] selects any <E> element with an attribute a=, whatever the value

• E[a="v"] select any E element whose a= attribute value is exactly equal to "v".

• E[a~="v"] selects any element E whose a= attribute value is a list of space-separated values, one of which is exactly equal to "v". Useful for classes, because you can put an element into several classes, separated by blanks.

more selectors

• E:lang(c) selects element <E> if it is in the human language c.

• E[lang|="en"] selects any <E> element whose lang= attribute has a hyphen-separated list of values beginning (from the left) with `en’. This would select all en languages, be they en-us or en-gb

convenient shorthand

• We have already seen some.

• E.m is a convenient shorthand for E[class~="m"]

• E#myid is a convenient shorthand for E[id="myid"]

• .m is a convenient shorthand for *.m

E:before and E:after

• E:before or E:after can be used to add contents before or after a element <E>.

• We will deal come to these when we discuss generated contents properties.

• This will be coming up after the examples for selectors that we will discuss now.

examples

• h1, h2, h3 { font-family: sans-serif }

• h1 { color: red }

em { color: red }

h1 em { color: blue }

• p *[href] {font-family: monospace}

• body > p { line-height: 1.3 }

• ol > li {color: black}• h1 + p {text-indent: 0}

more example• h1 + h2 {margin-top: -5mm} • h1.opener + h2 {margin-top: -5mm}• h1[title] {color: blue} • span[class~="example"] {color: blue } • a[href="index.html"][title="Thomas"] { color: blue} • a[rel="copyright"] {color: red}• a[href="http://www.w3.org/"] {background-color:

grey}• *[lang="fr"] {display: none}

more examples

• *[lang|="en"] {color : red }

• .dialog .romeo {voice-family: "Lawrence Olivier", charles, male}

• a:link {color: red} /* unvisited links */

• a:visited {color: blue} /* visited links */

• a:hover {color: yellow} /* user hovers */

• a:active {color: lime} /* active links */

• a.external:visited {color: blue}

more examples

• html:lang(fr) { quotes: '« ' ' »' }

• html:lang(de) { quotes: '„' ‘”'}

• *:lang(fr) > q { quotes: '« ' ' »' }

• *:lang(de) > q { quotes: '„' ‘”'}

(quotation style depending on the surrounding language, not the language of the quote!)

more examples

• a[href="http://openlib.org/home/krichel"] {display: none}

• div > p:first-child {text-decoration: underline}

• a:focus:hover {color: red}

• div > * > div {font-family: sans-serif}

• img[class~="ny"][title="Albany town map"] {border-style: solid}

example: drop caps with uppercase

• CSSp { font-size: 12pt; line-height: 12pt }

p:first-letter { font-size: 200%; font-style: italic; font-weight: bold; float: left }

span { text-transform: uppercase }

• HTML<p><span>The first</span> few words of an article in

The Economist.</p>

generated contents properties I• generated contents is, for example, the bullet

appearing in front of a list item.

• {content:} can be used with the :before and :after selectors.The content can be– a text string

– a url(URL) where the contents is to be found

– a attr(att) where att is the name of the attribute, the content of which is being inserted

• Example

• p.note:before {content: "note"} will insert the string "note" before any paragraph in the class 'note'.

generated contents properties II

• Here are some counter properties– {counter-reset: counter} resets a counter counter– {counter-increment: counter} increments a counter– {counter(counter)} uses the counter

• Exampleh1:before {counter-increment: chapter_counter;counter-reset: section_counter;content: "Chapter " counter(chapter_counter) ":"}

and then we can use h2 for the sections, of course!

• browser support uncertain!

user interface properties I

• There is a {cursor:} property to change the shape of the cursor. It takes the following values– auto -- crosshair -- default

– pointer (something suggesting a link)

– e-resize –ne-resize –nw-resize –n-resize –se-resize

– sw-resize, --s-resize –w-resiz (Indicate that some edge is to be moved)

– text (usually as an I) --wait (watch or hourglass)

– help (question mark or balloon)

– url (with a uri to svg file, that has the graphic to show)

• use these to totally confuse your users

paged media support I

• CSS has the concept of a page box in which paged output should be placed into.

• @page rule can be used to specify the size of the page

• @page {size: 8.5in 11in}

• Valid values are one or two lengths and they words ‘portrait’ and ‘landscape’. The latter will depend on the default print sheet size, country-specific.

paged media support II

• You can add {margin: }, {margin-top: }, {margin-left: }, and {margin-right: } properties. They will add to the margins that the printer will set by default. The default printer margins are beyond your control.

• You can add a {marks: crop} property to add crop marks

• You can add a {mark: cross} property to create registration marks.

paged media support III

• You can use three pseudoclasses to specify special cases– :first for the first page

– :left for any left page

– :right for any right page

• Example– @page :first {margin-top: 3in}

named pages

• You can give a page rule an optional name. Example

@page rotated { size: landscape}

• Then you can use this with the ‘page’ property to specify specific ways to print things. Example

table {page: rotated}

will print the table on a landscape sheet. This comes in handy for bulky tables.

actual page breaking

• Pages will break if – the current page box flows over or if– a new page format is being used with a {page: }

property

• You can take some control with the {page-break-before: } and {page-break-after: } properties. They take the values– auto – always – avoid – left – right

The latter two make sure that the element is on a left or right page. Sometimes this will require two page breaks.

more examples

• I have made a stolen and simplified example available for three column layout, with flexible middle column, http://wotan.liu.edu/home/krichel/lis650/examples/css_layout/triple_column.html

• Unfortunately, this example relies a lot on dimensions that are fixed in pixels.

W3C tips on anchors

• When calling the user to action, use brief but meaningful link text that:– provides some information when read out of context

– explains what the link offers

– doesn't talk about mechanics

– is not a verb phrase

W3C tips on anchors

• Bad: “To download W3C's editor/browser Amaya, click here.”

• Bad: To download Amaya, go to the Amaya Website and get the necessary software.

• Good: “Get Amaya!”

• Bad: “Tell me more about Amaya”

• Good: “Tell me more about Amaya”

W3C tips for headings

• Use <h1> for your top heading.

• If it is too big a font in the most common browsers, you can scale it down.

• But then you have a scale down other headers correspondingly.

W3C tips for alt=

• If the image is simply decorated text , put the text in the alt attribute

• If the image is used to create bullets in a list, a horizontal line, or other similar decoration, it is fine to have an empty alt= , but it is better to use things like {list-style-image: } in CSS

• If the image presents a lot of important information, try to summarize it in a short line for the alt attribute and add a longdesc= link to a more detailed

accessibility• There are two versions of the Web Contents

Accessibility Guideline (WCAG) published by the W3C.

• Version 1 had 14 guidelines and each guideline has 1 or more checkpoints. It is stable.

• Version 2 is being developed right now supposed to be – easier to understand

– easier to implement

– easier to test

It still looks rather rough!

WCAG principles

• 4 principles– Content must be perceivable

– Interface elements in the content must be operable.

– Content and controls must be understandable

– Content must be robust enough to work with current and future Web technologies

• 3 implementation docs– 1 for HTML

– 1 for CSS (not published yet)

– 1 that is technology independent (not published yet)

WCAG HTML tasks

• Set a DTD using the DTD declaration• Set a <title>• Use the <address> to give a document's author,

e.g. <address>This page was written by <a href ="http://highgate.uk/~kmarx">Karl Marx </a> </address>

• Reveal the structure of the site through the <link rel="…"/> element. E.g, if you have a glossary, have it <link/>ed to with the rel="glossary" in the <head>.

WCAG

• Do not use redirects that are timed, only immediate redirects. (redirects are covered later)

• Do not refresh page contents by itself.

• Use <h1> to <h6> to give the structure of the document. Don't use them for visual effects.

• Use <html lang="…"/> to give the language for the document

WCAG

• Note changes of language with the lang= attribute. e.g. <span lang="fr">voiture</span> will avoid it being pronounced as "voter" by an English reading software.

• Use <strong> and <em> rather than <b> and <i>.

• Use <abbr> with the title= to explain an abbreviation eg <abbr title="incorporated"> inc. </abbr>. Same with <acronym> for acronyms.

WCAG

• Use <q> and <blockquote> for quotes, but don't use <blockquote> for formatting.

• Avoid <b> <i> <tt> <big> <small>.

• In nested lists, use compound counters.

• In tables, use the headers= and scope= attributes to explain the structure of your table.

• Avoid using tables for layout. If you must do it, only use <table>, <tr> and <td> elements and border= cellspacing= and cellpadding= attributes.

WCAG

• Provide useful link text. If you have an image and text for your link, combine them in the same <a>.

• You can use the accesskey= attribute with <a> to give users a key that is used to access a link.

• Hide the navigation links for challenged media.• Use alt="" for purely decorative images. • Avoid ASCII art.• Use emoticons judiciously.• Do not embed text in images.

WCAG

• Do not use background images.

• Whenever possible use markup and text, rather than images, to convey information.

• (there are other guidelines but they talk about things that we did not cover here, such as frames, forms, scripting.)

http://openlib.org/home/krichel

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