[Webkit-unassigned] [Bug 75781] New: Rounding artefact in SVGTextNode.getBBox()

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Sat Jan 7 12:41:13 PST 2012


           Summary: Rounding artefact in SVGTextNode.getBBox()
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: UNCONFIRMED
          Severity: Major
          Priority: P2
         Component: SVG
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: selkovjr at gmail.com
                CC: zimmermann at kde.org

When the user space is transformed to small units, for example, when the entire world is smaller than [0 .. 1], the getBBox() method becomes unusable because it returns integer values (please see the attached test). It is also unusable with larger spaces, say, [0 .. 100], but the effect is less conspicuous.

It works correctly in Mozilla.

The test only demonstrates the effect on a bounding box for a text node, but I suspect the problem is more widespread in Webkit.

The rounding is also apparent in hit-testing. For example, when a set of nodes form a grid spaced 0.5 world units apart, the pointer events fire on all nodes, but only those nodes located at integer grid values are reported as targets of those events. That only happens when the co-ordinates are transformed using the viewBox attribute on the svg root node and does not happen when the transformation is defined as an attribute on a group, but I suspect the culprit is the same or similar. Apparently, parts of the code were only tested in pixel-minded applications.

I can provide a separate test for the viewBox artefact, if that will help.

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