Instance Method

addRelativeArc(center:radius:startAngle:delta:transform:)

Adds an arc of a circle to the path, specified with a radius and a difference in angle.

Declaration

func addRelativeArc(center: CGPoint, radius: CGFloat, startAngle: CGFloat, delta: CGFloat, transform: CGAffineTransform = .identity)

Parameters

center

The center of the arc, in user space coordinates.

radius

The radius of the arc, in user space coordinates.

startAngle

The angle to the starting point of the arc, measured in radians from the positive x-axis.

delta

The difference, measured in radians, between the starting angle and ending angle of the arc. A positive value creates a counter-clockwise arc (in user space coordinates), and vice versa.

transform

An affine transform to apply to the arc before adding to the path. Defaults to the identity transform if not specified.

Discussion

This method calculates starting and ending points using the radius and angles you specify, uses a sequence of cubic Bézier curves to approximate a segment of a circle between those points, and then appends those curves to the path.

The delta parameter determines both the length of the arc the direction in which the arc is created; the actual direction of the final path is dependent on the transform parameter and the current transform of a context where the path is drawn. In a flipped coordinate system (the default for UIView drawing methods in iOS), specifying a clockwise arc results in a counterclockwise arc after the transformation is applied.

If the path already contains a subpath, this method adds a line connecting the current point to the starting point of the arc. If the current path is empty, this method creates a new subpath whose starting point is the starting point of the arc. The ending point of the arc becomes the new current point of the path.

See Also

Constructing a Graphics Path

func move(to: CGPoint, transform: CGAffineTransform)

Begins a new subpath at the specified point.

func addLine(to: CGPoint, transform: CGAffineTransform)

Appends a straight line segment from the current point to the specified point.

func addLines(between: [CGPoint], transform: CGAffineTransform)

Adds a sequence of connected straight-line segments to the path.

func addRect(CGRect, transform: CGAffineTransform)

Adds a rectangular subpath to the path.

func addRects([CGRect], transform: CGAffineTransform)

Adds a set of rectangular subpaths to the path.

func addEllipse(in: CGRect, transform: CGAffineTransform)

Adds an ellipse that fits inside the specified rectangle.

func addRoundedRect(in: CGRect, cornerWidth: CGFloat, cornerHeight: CGFloat, transform: CGAffineTransform)

Adds a subpath to the path, in the shape of a rectangle with rounded corners.

func addArc(tangent1End: CGPoint, tangent2End: CGPoint, radius: CGFloat, transform: CGAffineTransform)

Adds an arc of a circle to the path, specified with a radius and two tangent lines.

func addCurve(to: CGPoint, control1: CGPoint, control2: CGPoint, transform: CGAffineTransform)

Adds a cubic Bézier curve to the path, with the specified end point and control points.

func addQuadCurve(to: CGPoint, control: CGPoint, transform: CGAffineTransform)

Adds a quadratic Bézier curve to the path, with the specified end point and control point.

func addPath(CGPath, transform: CGAffineTransform)

Appends another path object to the path.

func closeSubpath()

Closes and completes a subpath in a mutable graphics path.

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