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initial implementation of path
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‎Sources/SwiftCrossUI/Backend/AppBackend.swift‎

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@@ -44,6 +44,7 @@ public protocol AppBackend {
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associatedtype Widget
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associatedtype Menu
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associatedtype Alert
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associatedtype Path
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/// Creates an instance of the backend.
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init()
@@ -527,6 +528,24 @@ public protocol AppBackend {
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gesture: TapGesture,
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action: @escaping () -> Void
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)
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// MARK: Paths
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/// Create a path. It will not be shown until ``renderPath(_:container:)`` is called.
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func createPath() -> Path
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/// Update a path. The updates do not need to be visible before ``renderPath(_:container:)``
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/// is called.
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/// - Parameters:
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/// - path: The path to be updated.
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/// - source: The source to copy the path from.
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/// - pointsChanged: If `false`, the ``Path/actions`` of the source have not changed.
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func updatePath(_ path: Path, _ source: SwiftCrossUI.Path, pointsChanged: Bool)
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/// Draw a path to the screen.
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/// - Parameters:
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/// - path: The path to be rendered.
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/// - container: The container widget that the path will render in. It has no other
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/// children.
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/// - environment: The environment values, including color.
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func renderPath(_ path: Path, container: Widget, environment: EnvironmentValues)
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}
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extension AppBackend {
@@ -843,4 +862,15 @@ extension AppBackend {
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) {
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todo()
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}
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// MARK: Paths
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func createPath() -> Path {
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todo()
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}
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func updatePath(_ path: Path, _ source: SwiftCrossUI.Path, pointsChanged: Bool) {
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todo()
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}
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func renderPath(_ path: Path, container: Widget, environment: EnvironmentValues) {
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todo()
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}
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}

‎Sources/SwiftCrossUI/Path.swift‎

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import Foundation // for sinf and cosf
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public enum StrokeCap {
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/// The stroke ends square exactly at the last point.
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case butt
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/// The stroke ends with a semicircle.
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case round
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/// The stroke ends square half of the stroke width past the last point.
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case square
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}
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public enum StrokeJoin {
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/// Corners are sharp, unless they are longer than `limit` times half the stroke width,
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/// in which case they are beveled.
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case miter(limit: Float)
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/// Corners are rounded.
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case round
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/// Corners are beveled.
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case bevel
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}
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public struct StrokeStyle {
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public var width: Float = 1.0
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public var cap: StrokeCap = .butt
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public var join: StrokeJoin = .miter(limit: 10.0)
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public static let none = StrokeStyle(width: 0.0)
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}
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/// An enum describing how a path is shaded.
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public enum FillRule {
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/// A region is shaded if it is enclosed an odd number of times.
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case evenOdd
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/// A region is shaded if it is enclosed at all.
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///
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/// This is also known as the "non-zero" rule.
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case winding
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}
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/// A type representing an affine transformation on a 2-D point.
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///
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/// Performing an affine transform consists of translating by ``translation`` followed by
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/// multiplying by ``linearTransform``.
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public struct AffineTransform: Equatable {
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/// The linear transformation. This is a 2x2 matrix stored in row-major order.
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///
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/// The four properties (`x`, `y`, `z`, `w`) correspond to the 2x2 matrix as follows:
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/// ```
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/// [ x y ]
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/// [ z w ]
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/// ```
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public var linearTransform: SIMD4<Float>
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/// The translation applied after the linear transformation.
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public var translation: SIMD2<Float>
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public init(linearTransform: SIMD4<Float>, translation: SIMD2<Float>) {
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self.linearTransform = linearTransform
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self.translation = translation
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}
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public static func translate(x: Float, y: Float) -> AffineTransform {
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AffineTransform(
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linearTransform: SIMD4(x: 1.0, y: 0.0, z: 0.0, w: 1.0),
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translation: SIMD2(x: x, y: y)
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)
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}
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public static func scale(by factor: Float) -> AffineTransform {
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AffineTransform(
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linearTransform: SIMD4(x: factor, y: 0.0, z: 0.0, w: factor),
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translation: .zero
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)
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}
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public static func rotate(
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radians: Float,
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center: SIMD2<Float> = .zero
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) -> AffineTransform {
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let sine = sinf(radians)
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let cosine = cosf(radians)
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return AffineTransform(
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linearTransform: SIMD4(x: cosine, y: -sine, z: sine, w: cosine),
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translation: SIMD2(
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x: -center.x * cosine - center.y * sine + center.x,
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y: center.x * sine - center.y * cosine + center.y
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)
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)
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}
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public static func rotate(
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degrees: Float,
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center: SIMD2<Float> = .zero
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) -> AffineTransform {
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rotate(radians: degrees * (.pi / 180.0), center: center)
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}
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public static let identity = AffineTransform(
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linearTransform: SIMD4(x: 1.0, y: 0.0, z: 0.0, w: 1.0),
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translation: .zero
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)
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}
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public struct Path {
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public struct Rect: Equatable {
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public var origin: SIMD2<Float>
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public var size: SIMD2<Float>
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public init(origin: SIMD2<Float>, size: SIMD2<Float>) {
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self.origin = origin
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self.size = size
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}
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public var x: Float { origin.x }
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public var y: Float { origin.y }
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public var width: Float { size.x }
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public var height: Float { size.y }
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public init(x: Float, y: Float, width: Float, height: Float) {
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origin = SIMD2(x: x, y: y)
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size = SIMD2(x: width, y: height)
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}
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}
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/// The types of actions that can be performed on a path.
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public enum Action: Equatable {
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case moveTo(SIMD2<Float>)
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case lineTo(SIMD2<Float>)
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case quadCurve(control: SIMD2<Float>, end: SIMD2<Float>)
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case cubicCurve(control1: SIMD2<Float>, control2: SIMD2<Float>, end: SIMD2<Float>)
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case rectangle(Rect)
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case circle(center: SIMD2<Float>, radius: Float)
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case arc(
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center: SIMD2<Float>,
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radius: Float,
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startAngle: Float,
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endAngle: Float,
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clockwise: Bool
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)
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case transform(AffineTransform)
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// case subpath([Action], FillRule)
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}
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/// A list of every action that has been performed on this path.
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///
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/// This property is meant for backends implementing paths. If the backend has a similar
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/// path type built-in (such as `UIBezierPath` or `GskPathBuilder`), constructing the
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/// path should consist of looping over this array and calling the method that corresponds
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/// to each action.
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public private(set) var actions: [Action] = []
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public private(set) var fillRule: FillRule = .evenOdd
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public private(set) var strokeStyle: StrokeStyle = .none
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public init() {}
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public consuming func move(to point: SIMD2<Float>) -> Path {
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actions.append(.moveTo(point))
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return self
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}
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public consuming func addLine(to point: SIMD2<Float>) -> Path {
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actions.append(.lineTo(point))
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return self
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}
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public consuming func addQuadCurve(
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control: SIMD2<Float>,
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to endPoint: SIMD2<Float>
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) -> Path {
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actions.append(.quadCurve(control: control, end: endPoint))
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return self
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}
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public consuming func addCubicCurve(
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control1: SIMD2<Float>,
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control2: SIMD2<Float>,
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to endPoint: SIMD2<Float>
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) -> Path {
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actions.append(.cubicCurve(control1: control1, control2: control2, end: endPoint))
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return self
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}
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public consuming func addRectangle(_ rect: Rect) -> Path {
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actions.append(.rectangle(rect))
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return self
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}
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public consuming func addCircle(center: SIMD2<Float>, radius: Float) -> Path {
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actions.append(.circle(center: center, radius: radius))
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return self
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}
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public consuming func addArc(
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center: SIMD2<Float>,
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radius: Float,
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startAngle: Float,
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endAngle: Float,
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clockwise: Bool
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) -> Path {
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actions.append(
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.arc(
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center: center,
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radius: radius,
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startAngle: startAngle,
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endAngle: endAngle,
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clockwise: clockwise
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)
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)
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return self
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}
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public consuming func transform(_ transform: AffineTransform) -> Path {
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actions.append(.transform(transform))
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return self
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}
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public consuming func stroke(style: StrokeStyle) -> Path {
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strokeStyle = style
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return self
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}
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public consuming func fillRule(_ rule: FillRule) -> Path {
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fillRule = rule
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return self
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}
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}

‎Sources/SwiftCrossUI/Views/Shapes/Circle.swift‎

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public struct Circle: Shape {
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public init() {}
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public func path(in bounds: Path.Rect) -> Path {
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Path().addCircle(
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center: SIMD2(x: bounds.x + bounds.width / 2.0, y: bounds.y + bounds.height / 2.0),
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radius: min(bounds.width, bounds.height) / 2.0
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)
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}
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public func size(fitting proposal: SIMD2<Int>) -> SIMD2<Int> {
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let minDim = min(proposal.x, proposal.y)
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return SIMD2(x: minDim, y: minDim)
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}
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}

‎Sources/SwiftCrossUI/Views/Shapes/Rectangle.swift‎

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public struct Rectangle: Shape {
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public init() {}
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public func path(in bounds: Path.Rect) -> Path {
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Path().addRectangle(bounds)
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}
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}

‎Sources/SwiftCrossUI/Views/Shapes/Shape.swift‎

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public protocol Shape: View
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where Content == EmptyView {
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/// Draw the path for this shape.
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func path(in bounds: Path.Rect) -> Path
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/// Determine the ideal size of this shape given the proposed bounds.
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///
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/// The default implementation returns the proposal unmodified.
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func size(fitting proposal: SIMD2<Int>) -> SIMD2<Int>
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}
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extension Shape {
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public var body: EmptyView { return EmptyView() }
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public func size(fitting proposal: SIMD2<Int>) -> SIMD2<Int> {
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return proposal
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}
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public func children<Backend: AppBackend>(
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backend _: Backend,
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snapshots _: [ViewGraphSnapshotter.NodeSnapshot]?,
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environment _: EnvironmentValues
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) -> any ViewGraphNodeChildren {
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ShapeStorage()
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}
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public func asWidget<Backend: AppBackend>(
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_ children: any ViewGraphNodeChildren, backend: Backend
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) -> Backend.Widget {
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let container = backend.createContainer()
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let storage = children as! ShapeStorage
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storage.backendPath = backend.createPath()
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storage.oldPath = nil
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return container
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}
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public func update<Backend: AppBackend>(
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_ widget: Backend.Widget, children: any ViewGraphNodeChildren, proposedSize: SIMD2<Int>,
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environment: EnvironmentValues, backend: Backend, dryRun: Bool
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) -> ViewUpdateResult {
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let storage = children as! ShapeStorage
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let size = size(fitting: proposedSize)
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let path = path(in: Path.Rect(x: 0.0, y: 0.0, width: Float(size.x), height: Float(size.y)))
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let pointsChanged = storage.oldPath?.actions != path.actions
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storage.oldPath = path
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let backendPath = storage.backendPath as! Backend.Path
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backend.updatePath(backendPath, path, pointsChanged: pointsChanged)
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if !dryRun {
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backend.setSize(of: widget, to: size)
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backend.renderPath(backendPath, container: widget, environment: environment)
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}
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return ViewUpdateResult.leafView(
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size: ViewSize(
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size: size,
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idealSize: SIMD2(x: 10, y: 10),
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minimumWidth: 0,
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minimumHeight: 0,
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maximumWidth: nil,
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maximumHeight: nil
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)
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)
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}
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}
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final class ShapeStorage: ViewGraphNodeChildren {
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let widgets: [AnyWidget] = []
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let erasedNodes: [ErasedViewGraphNode] = []
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var backendPath: Any!
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var oldPath: Path?
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}

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