Bug 36226 – [Qt] canvas arc element doesn't render correctly

• Status: RESOLVED
• Resolution: FIXED
• Component: Layout and Rendering

the endpoint of a canvas arc element renders with a jagged edge at the start point.

the easiest way i've found to see the effect is to install the Arora web browser and view the attached HTML file. Alternatively create a simple Qt web browser that points at the provided HTML file.

I have been unable to reproduce this error in any other WebKit based browser (tested Chrome, Safari, Konqueror) which makes me think it must be a Qt specific bug.

Created attachment 50952 [details]
html file that describes 2 canvas arc shapes

[Dirk Schulze]

This is a Qt-bug. If you create a new path, the starting point is set to 0,0. A workaround is setting moveTo after beginning a new path.

I changed:

ctx.beginPath();
ctx.lineWidth = 8;
ctx.strokeStyle = "#33CCCC";
ctx.arc(342, 212, 56.25714285714286, 6.997183637540902, 7.5683823018299545, false);
ctx.stroke();
ctx.closePath();

to:

ctx.beginPath();
ctx.moveTo(342, 212);
ctx.lineWidth = 8;
ctx.strokeStyle = "#33CCCC";
ctx.arc(342, 212, 56.25714285714286, 6.997183637540902, 7.5683823018299545, false);
ctx.stroke();
ctx.closePath();

with no results. What am I doing wrong?

[Andreas Kling]

@Dirk: I think you guys are talking about two separate issues :)
I've posted a patch for yours at https://bugs.webkit.org/show_bug.cgi?id=38526

@lonhutt: Jagged edge confirmed on ToT, will investigate.

[Andreas Kling]

This was indeed fixed with http://trac.webkit.org/changeset/59767