Circular arc approximation #72
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| import Foundation | ||
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| extension PathComponent { | ||
| public convenience init( |
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let's make the public interface on Path with an interface init(ellipseIn rect: CGRect). I'm trying to keep the API as similar to CGPath and SwiftUI's Path as much as possible which means it's desirable for the API to operate on Path objects instead of PathComponent objects where possible. For now I think that also means hiding the numberOfCurves parameter as well (we can expose it later on potentially, it's just harder to take public API functionality away than to add it).
| public convenience init( | ||
| arcCenter center: CGPoint, | ||
| radius: CGFloat, | ||
| startAngle: CGFloat, | ||
| endAngle: CGFloat, | ||
| clockwise: Bool, | ||
| numberOfCurves: Int = 4 |
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Let's make this private for now. In the future I'm going to add an API for the creation of Path objects that works similar to CGMutablePath. When that's ready we can use your code to add the functionality of CGMutablePath.addArc(center: CGPoint, radius: CGFloat, startAngle: CGFloat, endAngle: CGFloat, clockwise: Bool, transform: CGAffineTransform = .identity)
| CubicCurve(points: $0.points.map { | ||
| $0.applying(finalTransform) | ||
| }) |
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use copy(using: CGAffineTransform) -> Self instead of transforming the array of points.
| static let demo23 = Demo(title: "PathComponent(arcCenter: ...)", | ||
| quadraticControlPoints: [], | ||
| cubicControlPoints: [], | ||
| drawFunction: {(context: CGContext, demoState: DemoState) in | ||
| if demoState.quadratic { | ||
| return | ||
| } | ||
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| let pathComponent = PathComponent( | ||
| arcCenter: CGPoint(x: 100, y: 105), | ||
| radius: 100, | ||
| startAngle: .pi / 2, | ||
| endAngle: 2 * .pi, | ||
| clockwise: true | ||
| ) | ||
| Draw.drawPathComponent(context, pathComponent: pathComponent) | ||
| for curve in pathComponent.curves { | ||
| Draw.drawSkeleton(context, curve: curve) | ||
| } | ||
| }) |
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As I mentioned previously, I think we'll have to make the arc functionality private for now.
But when it's ready to be public it'd be cool to make this demo more interactive. Maybe we could drag the endpoints to set the start and end angle, for example?
| static let demo24 = Demo(title: "PathComponent(ovalIn rect: CGRect)", | ||
| quadraticControlPoints: [], | ||
| cubicControlPoints: [], | ||
| drawFunction: {(context: CGContext, demoState: DemoState) in | ||
| if demoState.quadratic { | ||
| return | ||
| } | ||
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| let pathComponent = PathComponent( | ||
| ovalIn: CGRect( | ||
| x: 0, y: 52.5, | ||
| width: 200, height: 100 | ||
| ) | ||
| ) | ||
| Draw.drawPathComponent(context, pathComponent: pathComponent) | ||
| Draw.setColor(context, color: Draw.pinkish) | ||
| Draw.drawBoundingBox(context, boundingBox: pathComponent.boundingBox) | ||
| }) |
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let's try to make this demo more interactive. We could let the user drag the origin and scale the oval perhaps
| let transform = CGAffineTransform.identity | ||
| .translatedBy(x: rect.origin.x, y: rect.origin.y) | ||
| .scaledBy( | ||
| x: rect.width / diameter, |
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I think that if the rect is zero sized this will cause a divide by zero. It's an edge case, but actually quite likely to occur in practice. We should check how CGPath(ellipseIn:) handles zero sized rects and use the same fallback behavior.
| ovalIn rect: CGRect, | ||
| numberOfCurves: Int = 4 | ||
| ) { | ||
| let diameter = min(rect.width, rect.height) |
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we should look at how this behaves with negative dimension rectangles. Core Graphics actually allows this and we should be sure to behave in the same way. We should also consider what happens if the caller passes CGRect.null for the rect parameter.
2 participants
This PR adds ability to create circles and ellipsis using pure BezierKit API and cubic curve arc approximation as described here.
P.S. I'm a total noob at writing tests thus sorry about this