Bug 58934 – arc() should add a circle to the path when start and end angles are far enough apart

• Status: RESOLVED
• Resolution: FIXED
• Component: Canvas

[Matthew Delaney]

The spec says:

"If the anticlockwise argument is omitted or false and endAngle-startAngle is equal to or greater than 2π, or, if the anticlockwise argument is true and startAngle-endAngle is equal to or greater than 2π, then the arc is the whole circumference of this circle."
[http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#dom-context-2d-arc]

We don't currently check for this case. The test fast/canvas/canvas-largedraws.html appears to somewhat exercise this case.

[Matthew Delaney]

Created attachment 90359 [details]
Patch

Comment on attachment 90359 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=90359&action=review

> Source/WebCore/html/canvas/CanvasRenderingContext2D.cpp:856
> +    if (anticlockwise && sa - ea >= 2.0f * piFloat) {

The coding style guidelines says that you should just write this as 2 * piFloat.

> Source/WebCore/html/canvas/CanvasRenderingContext2D.cpp:859
> +        m_path.addArc(FloatPoint(x, y), r, sa, sa - piFloat, anticlockwise);
> +        m_path.addArc(FloatPoint(x, y), r, sa - piFloat, sa, anticlockwise);

This can be done as a single 2π arc.

[Matthew Delaney]

Created attachment 90402 [details]
Patch

[Matthew Delaney]

Created attachment 90411 [details]
Patch

[Maciej Stachowiak]

Comment on attachment 90411 [details]
Patch

r=me

[Matthew Delaney]

http://trac.webkit.org/changeset/84512