[Webkit-unassigned] [Bug 67868] New: Optimize CSS rule handling for body and html for efficient CSS

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=67868

           Summary: Optimize CSS rule handling for body and html for
                    efficient CSS
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: CSS
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: sroussey at gmail.com


For quite some time, several frameworks, ExtJS for example, have used the html and body tags as a place to add classes so that they can target specific browsers or browser capabilities in css rules. For example a class "x-ie6" will be added in IE6 to the body element. You can see examples in the ext-all.css file[1]. And there are now a bunch of sites using Modernizr (and look at what they do to the html element!)[2].

Taking advantage of these classes on html and body makes it easy to target "fixes" or "features" for certain browsers. Typical would be using CSS3 to style a button with gradients and rounded borders and drop shadows, or in old versions of IE using image spriting instead.

Companies that use Sencha's ExtJS, for example, could reap some reward if Sencha changed its CSS to have:

body.x-ie6 .buttonClsExample {}

instead of 

.x-ie6 .buttonClsExample

And the browser could remove all the body.x-ie6 * rules. According to the Mozilla guide on efficient CSS[3], this would be a real gain.

I have also made a bug report for Mozilla[4].

[1] http://dev.sencha.com/deploy/ext-4.0.2a/resources/css/ext-all.css
[2] http://www.modernizr.com/
[3] https://developer.mozilla.org/en/Writing_Efficient_CSS
[4] https://bugzilla.mozilla.org/show_bug.cgi?id=678568

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