[Webkit-unassigned] [Bug 133049] New: Child padding set in %, when the parent has padding as well

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=133049

           Summary: Child padding set in %, when the parent has padding as
                    well
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: PC
               URL: http://jsfiddle.net/Vd8YN/3/
        OS/Version: Windows 7
            Status: NEW
          Severity: Minor
          Priority: P2
         Component: CSS
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: listtad at rambler.ru


Steps to reproduce:

1. Create a parent div with left and right padding.
2. Place another div into the div from step 1.
3. Set the child's width and padding in percents - for example, 100%.
HTML:

<div class="parent padded"></div>
<div class="parent"></div>

CSS:

.parent{
    position:relative;
    width:200px;
    height:100px;
}
.parent.padded{
    padding:20px 30px;
}
.parent:after{
    position:absolute;
    bottom:0;
    left:0;
    box-sizing:border-box;
    width:50%;
    padding-bottom:50%;

    content:"";
}

Since CSS block's width and padding (all sides) depend on  the block's parent't width, both width and padding of the child div should be calculated based on a common formula: the parent width should either include padding or not. Ideally, this should depend on the box-sizing property.

So, width: 50% and padding:50% should calculate to equal values.

But the problem is: the child's padding (which is in percents) does not respect the parent's paddings, while the child's width does.

In Firefox (v12, v22), Opera (12.15), IE 9 this works as I expect.  If it's not a bug, I would love to be pointed at some explaination. Maybe the behavior described is the right one.

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