CGLineJoin

CGLineJoin is an enumeration type defined in the Core Graphics framework of Apple’s operating systems, including macOS, iOS, watchOS, and tvOS. It specifies the style used to render the join between two connected line segments when forming a path. The enumeration provides three possible values: CGLineJoinMiter, CGLineJoinRound, and CGLineJoinBevel. Each value determines a distinct visual outcome when two line segments meet at an angle.

CGLineJoinMiter extends the outer edges of the connecting segments until they intersect, producing a sharp corner. However, if the angle between the segments is very small, the miter can become excessively long; to mitigate this, a maximum miter limit can be set via CGPathSetMiterLimit. CGLineJoinRound renders a smooth, rounded corner at the junction, blending the two segments with an arc whose radius extends half the line width. CGLineJoinBevel cuts off the corner, creating a straight, flattened join that blends the inside edges of the segments.

Developers configure a CGLineJoin value by setting the line join property of a CGContext or by specifying it in a CGPathDrawingOptions dictionary when creating or drawing paths. The default line join is CGLineJoinMiter. Selecting the appropriate join style is essential for achieving desired visual fidelity in vector graphics, user interface elements, and custom drawing routines.