[Webkit-unassigned] [Bug 76282] New: ForeignObject content is zoomed two times

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=76282

           Summary: ForeignObject content is zoomed two times
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: SVG
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: fmalita at google.com
                CC: zimmermann at kde.org, fmalita at google.com


Created an attachment (id=122441)
 --> (https://bugs.webkit.org/attachment.cgi?id=122441&action=review)
FO content zoomed twice

The zoom factor is applied twice to FO-embedded elements. This affects both SVG and HTML content, but for different reasons:

* When embedding foreign SVG content, we end up with two RenderSVGRoot nodes on the render path:
  RenderSVGRoot {svg}
    RenderSVGForeignObject {foreignObject}
      RenderSVGRoot {svg}
        RenderSVGRect {rect}
        ...

Each RenderSVGRoot::paint() applies the zoom factor to its current canvas context - hence the duplicate zooming: http://trac.webkit.org/browser/trunk/Source/WebCore/rendering/svg/RenderSVGRoot.cpp#L310 , http://trac.webkit.org/browser/trunk/Source/WebCore/rendering/svg/RenderSVGRoot.cpp#L355

* When embedding foreign HTML content, the CSS properties appear to be pre-scaled by the zoom factor (http://trac.webkit.org/browser/trunk/Source/WebCore/css/CSSStyleApplyProperty.cpp#L334), so the zoom introduced by RenderSVGRoot up the tree is compounding the effect.


See the attached test for an example; try zooming in/out a few times and observe how the FO content is scaled twice.
The test works correctly in FF8+.

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