[Webkit-unassigned] [Bug 126336] New: [fragmentation] Transforms shouldn't affect layout

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=126336

           Summary: [fragmentation] Transforms shouldn't affect layout
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: CSS
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: krit at webkit.org
                CC: hyatt at apple.com, simon.fraser at apple.com,
                    achicu at adobe.com, mihnea at adobe.com, mibalan at adobe.com,
                    bjonesbe at adobe.com


Created an attachment (id=220155)
 --> (https://bugs.webkit.org/attachment.cgi?id=220155&action=review)
Continues painting - hover over content.

The title doesn't really describe the actual problem correctly. If you have an element that is fragmented, it is split into different border boxes. If you apply a transform on the fragmented element, it should appear as if each fragment was transformed individually by its own border box (transform-origin is affected as well of course).

For certain transforms, like rotation, more content can be visible up to the break. WebKit continues painting up to this break. This is incorrect. It seems as if the break is implemented as clipping rect and this clipping rect is not transformed as well. This leads to these weird effects that can be seen in the example.

There is a second weird thing happening. I assume it is related to the described problem. If there is a translate or scale, the content can leave the region or current column of multi-column layout. Right now this content is clipped to the boundaries of the column/region. Since transforms do not effect layout, this should not happen.

The attached example demonstrates both problems on multi-column. The same happens for regions as well of course. My assumption is that we should just transform the clipping region that is responsible for the breaking as well.

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