[Webkit-unassigned] [Bug 107118] New: Bad rendering of quadratic curves with same endpoints

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=107118

           Summary: Bad rendering of quadratic curves with same endpoints
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: Canvas
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: youennf at gmail.com


Created an attachment (id=183169)
 --> (https://bugs.webkit.org/attachment.cgi?id=183169&action=review)
archive containing different tests

Some webkit back-end graphic libraries (cairo, qt...) seem to render incorrectly quadratic curves with same endpoints.

The canvas-quadratic-same-endpoint.html file in attachment highlights this at least with WebKitEFL (cairo 1.12.8) and WebKitQt (Qt5.0.0-r40), once the patch for https://bugs.webkit.org/show_bug.cgi?id=105650 is applied.
This test is passing on Firefox and Opera.

For WebKitQt, the line is drawn but the shape is not correct when the lineWidth is set to a large value.
This may be related to https://bugreports.qt-project.org/browse/QTBUG-27921

For WebKitEFL, a shape (similar to a point) is drawn but the curve itself (a line here) is not. 
This seems to happen with cairo 1.12.8 but not with some 1.10.x versions.

For Mac, the EWS buildbot marks the test as failed.

In attachment, the archive contains a set of files that illustrates the issue:
- canvas-quadratic-same-endpoint.html (to be placed in the LayoutTests/fast/canvas folder)
- cairo_test folder: direct cairo test that shows the issue with cairo 1.12.8
- qt_test folder: direct Qt test that shows the issue with Qt5.0.0-r40

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