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A strange mix…
IE 5+ allows a strange mix of style and function called dynamic expressions. It alarms the purists, and intrigues the rule breakers.
It's a style, and it's a function. It's both.
Using CSS Dynamic Expressions:
1) Highlight the current page link.
Here's an example; it checks to see if the link matches the current page, and if so, returns a 'bold' font-weight.
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#TOC a {font-weight: expression(boldLink(this)); font-family: Verdana, Arial, sans-serif; font-size:10pt; color:navy;} |
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The style sheet calls the function boldLink();
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function boldLink(el) { if (el.href==window.location) { el.style.textDecoration = "none" return "bold" } }
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A mondo thanks and credit for the boldLink() script to: SiteExperts.com.
Another way to use dynamic expressions:
2) Expand the URL when printing.
It might be helpful to show the full, expanded URL of a link when printing a page. First, create the style that calls the function - this particular example uses the unique identifier #TOC, to narrow it's use to all links within that <DIV>.
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<STYLE> #TOC a {font-style: expression(showLink(this)); font-family: Verdana, Arial, sans-serif; font-size:10pt; color:navy;} </STYLE>
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Here is the function we call from the stylesheet:
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<script language="JavaScript1.2" type="text/javascript"> <!-- var pattern = "/%20/g"; function showLink(el) { var tmp = "";
var strInnerHTML = String(el.innerHTML);
if (strInnerHTML.indexOf(" (url: ") == -1) { tmp = " (url: " + el.href + ") "; tmp= tmp.replace(pattern," ") ; el.style.textDecoration = "none"; el.innerHTML = (el.innerHTML + tmp);
return "italic" } } //--> </script>
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Here is a simple link within a <DIV> tag.
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<div id="TOC"> Here is a link: <a href="thispage.htm">this page</a> <br> <br> A second link" <a href="thatpage.htm">that page</a> </div>
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By now, you have probably realized that these functions could be evoked just as easily from a regular JavaScript function when the page is printed.
The Dangers of Dynamic Expressions in CSS. . . ?
The entire concept of Dynamic Expressions built into a style sheet bothers a lot of IT professionals. Basically, it ignores the revered separation of content and format, form and function. The issues are twofold:
Security: now style sheets can pose the same security risks as scripts, and sites with user-submitted content are exposed to scripting risks.
Aesthetics: now active content exists where you least expect it. Style sheets now depend on scripts to display properly.
These issues are more of a concern for Internet management and web applications developers; it might not be as much of a concern to Help and ebook authors, and for users on company intranets.
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