[Webkit-unassigned] [Bug 16565] New: CG Path Handling Seems Inverted

[bugzilla-daemon at webkit.org]

http://bugs.webkit.org/show_bug.cgi?id=16565

           Summary: CG Path Handling Seems Inverted
           Product: WebKit
           Version: 525+ (Nightly build)
          Platform: PC
        OS/Version: Mac OS X 10.4
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebCore Misc.
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: bfulgham at gmail.com


The HTML5 specification indicates that arc is:
"void arc(in float x, in float y, in float radius, in float startAngle, in
float endAngle, in boolean anticlockwise);"

This was originally code with the boolean being labeled "clockwise", which
resulted in the Cairo back-end drawing 'flipped' arcs (see Bug#16558).

Review of the code indicates that this was simply a matter of improper label,
however the CoreGraphics backend has the following mysterious behavior:

The 'addArc' method takes a bool previously labeled 'clockwise', but which is
now known to actually mean 'anticlockwise' when triggered by a request to draw.
 This flag is passed (unchanged) to the "CGPathAddArc" function, which is
documented to expect this argument to mean 'clockwise' (not 'anticlockwise').

Consequently, I would expect the CG backend to be producing inverted drawings
(however it does seem to produce the expected output).

Either:
1.  The CGPathAddArc method is improperly documented in the Apple API docs.
2.  The CG drawing context is flipped when finally rendering, resulting in a
proper image.


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