xml - Adding namespace to a css should make the IDE validate the code? -

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in css file, using eclipse ide, adding header:

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");

should make eclipse check elements errors? (becouse it's not doing it).

if not, what's difference of adding header or not?

the @namespace module in css creating styles apply namespaces. it's useful applying css styles xml documents. can use xhtml , html5 well, apply styles documents , elements xml namespaces (defined xmlns attribute, in html tag).

for example, take @ following xhtml document:

<!doctype html public "-//w3c//dtd xhtml 1.0 transitional//en" "http://www.w3.org/tr/xhtml1/dtd/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > <head>     <title>@namespace examples</title>      <!-- stylesheet defines namespace prefix called "xhtml", , uses style p elements in namespace -->     <style type="text/css">         @namespace xhtml "http://www.w3.org/1999/xhtml";         xhtml|p          {             color: red;         }     </style>      <!-- stylesheet defines style apply imaginary "superhtml" namespace. shouldn't work xhtml elements -->     <style type="text/css">         @namespace "http://www.w3.org/20x6/superxhtml";         p          {             font-style: italic;                              }     </style>      <!-- stylesheet uses namespace url no namespace prefix, styles apply namespace. -->     <style type="text/css">         @namespace xhtml "http://www.w3.org/1999/xhtml";         p          {             text-decoration: underline;         }     </style>      <!-- stylesheet uses no namespace declaration, applies document includes it. -->     <style type="text/css">         p         {             font-size: 20pt;         }     </style>  </head> <body>      <p>if text red, underlined, , 20pt, you're using http://www.w3.org/1999/xhtml namespace.</p>  </body> </html>

load in firefox 4, , looks this:

http://i51.tinypic.com/295pt86.png

notice opening html tag: <html xmlns="http://www.w3.org/1999/xhtml" >. has xmlns attribute. because of that, css rules match namespace work in document. text red, underlined, , 20pt. notice however, text not italic. why? style rule italic paragraphs applied different namespace:

<!-- stylesheet defines style apply imaginary "superhtml" namespace. shouldn't work xhtml elements --> <style type="text/css">     @namespace "http://www.w3.org/20x6/superxhtml";     p      {         font-style: italic;                          } </style>

because html tag didn't have xmlns attribute pointed made-up namespace @ http://www.w3.org/20x6/superxhtml, style rule ignored.

now, might think changing xmlns in html tag value "http://www.w3.org/20x6/superxhtml" make paragraph black , italic. however, seems browsers support @namespace css declaration assume xhtml/html documents in http://www.w3.org/1999/xhtml namespace, , style them accordingly, if try change it.

because of this, @namespace might not seem useful, is useful if sharing stylesheet between multiple xml documents, or between xhtml document , xml document, , want have different styles each.

to demonstrate, i'll create 3 files:

first, namespacecss.css:

@namespace xhtml "http://www.w3.org/1999/xhtml"; @namespace article "http://www.example.com/namespaces/article";  xhtml|p {     color: red; }  article|p {     color: blue; }  p {     font-size: 20pt; }

next, namespacetest.html:

<!doctype html public "-//w3c//dtd xhtml 1.0 transitional//en" "http://www.w3.org/tr/xhtml1/dtd/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > <head>     <title>@namespace examples</title>     <link type="text/css" href="namespacecss.css" rel="stylesheet" /> </head> <body>      <p>if text red, you're using http://www.w3.org/1999/xhtml namespace.</p>  </body> </html>

finally, xml file, namespacetest.xml:

<?xml version="1.0"?> <?xml-stylesheet type="text/css" href="namespacecss.css"?> <document xmlns="http://www.example.com/namespaces/article">   <p>this should blue</p> </document>

now, load last 2 files firefox 4. namespacetest.html looks this:

http://i56.tinypic.com/2zeca44.png

and namespacetest.xml looks this:

http://i52.tinypic.com/foq5o3.png

the first style rule in namespacecss.css applies xhtml, xhtml paragraph red. second style rule applies our custom namespace, "article", paragraph in xml file blue. , third rule applies namespaces, text 20pt in both examples.

further reading:

thanks asking question! learned lot while answering it.


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