Unexpected LineJoinStyle behavior when lines in path at 180 degrees

问题

I'm getting a clipped LineJoin in a UIBezierPath when one line comes back exactly over the previous line. If I adjust the second line by one pixel, the LineJoin behaves as expected. Here's the code:

UIBezierPath *path = [UIBezierPath bezierPath];
[path setLineWidth:10.0f];
[path setLineCapStyle:kCGLineCapRound];
[path setLineJoinStyle:kCGLineJoinRound];
[path moveToPoint:CGPointMake(100, 100)];
[path addLineToPoint:CGPointMake(200, 100)];
[path addLineToPoint:CGPointMake(150, 100)];
[path moveToPoint:CGPointMake(100, 120)];
[path addLineToPoint:CGPointMake(200, 120)];
[path addLineToPoint:CGPointMake(150, 121)];
[[UIColor redColor] setStroke];
[path stroke];

Here's what's displayed:

Is this a bug? If not, is there some way to get the top path LineJoin to be rounded? (without fudging the points)

This came up when I made a UIBezierPath from 'touch-input', and while scribbling around sometimes this happened.

回答1:

This is fixed in iOS 7. Open Radar also updated.

来源：https://stackoverflow.com/questions/13425765/unexpected-linejoinstyle-behavior-when-lines-in-path-at-180-degrees