Lottie tests [skip ci]

Tests/LottieMetalTest/LottieSwift/Sources/Private/MainThread/NodeRenderSystem/Nodes/OutputNodes/GroupOutputNode.swift

@@ -0,0 +1,77 @@
+//
+//  TransformNodeOutput.swift
+//  lottie-swift
+//
+//  Created by Brandon Withrow on 1/30/19.
+//
+
+import CoreGraphics
+import Foundation
+import QuartzCore
+
+class GroupOutputNode: NodeOutput {
+
+  // MARK: Lifecycle
+
+  init(parent: NodeOutput?, rootNode: NodeOutput?) {
+    self.parent = parent
+    self.rootNode = rootNode
+  }
+
+  // MARK: Internal
+
+  let parent: NodeOutput?
+  let rootNode: NodeOutput?
+  var isEnabled = true
+
+  private(set) var outputPath: CGPath? = nil
+  private(set) var transform: CATransform3D = CATransform3DIdentity
+
+  func setTransform(_ xform: CATransform3D, forFrame _: CGFloat) {
+    transform = xform
+    outputPath = nil
+  }
+
+  func hasOutputUpdates(_ forFrame: CGFloat) -> Bool {
+    guard isEnabled else {
+      let upstreamUpdates = parent?.hasOutputUpdates(forFrame) ?? false
+      outputPath = parent?.outputPath
+      return upstreamUpdates
+    }
+
+    let upstreamUpdates = parent?.hasOutputUpdates(forFrame) ?? false
+    if upstreamUpdates {
+      outputPath = nil
+    }
+    let rootUpdates = rootNode?.hasOutputUpdates(forFrame) ?? false
+    if rootUpdates {
+      outputPath = nil
+    }
+
+    var localUpdates = false
+    if outputPath == nil {
+      localUpdates = true
+
+      let newPath = CGMutablePath()
+      if let parentNode = parent, let parentPath = parentNode.outputPath {
+        /// First add parent path.
+        newPath.addPath(parentPath)
+      }
+      var xform = CATransform3DGetAffineTransform(transform)
+      if
+        let rootNode = rootNode,
+        let rootPath = rootNode.outputPath
+      {
+          if let xformedPath = rootPath.copy(using: &xform) {
+            /// Now add root path. Note root path is transformed.
+            newPath.addPath(xformedPath)
+          }
+      }
+
+      outputPath = newPath
+    }
+
+    return upstreamUpdates || localUpdates
+  }
+
+}

Tests/LottieMetalTest/LottieSwift/Sources/Private/MainThread/NodeRenderSystem/Nodes/OutputNodes/PassThroughOutputNode.hpp

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+#ifndef PassThroughOutputNode_hpp
+#define PassThroughOutputNode_hpp
+
+#include "Lottie/Private/MainThread/NodeRenderSystem/NodeProperties/Protocols/HasRenderUpdates.hpp"
+#include "Lottie/Private/MainThread/NodeRenderSystem/NodeProperties/Protocols/HasUpdate.hpp"
+#include "Lottie/Private/MainThread/NodeRenderSystem/Protocols/NodeOutput.hpp"
+
+namespace lottie {
+
+class PassThroughOutputNode: virtual public NodeOutput, virtual public HasRenderUpdates, virtual public HasUpdate {
+public:
+    PassThroughOutputNode(std::shared_ptr<NodeOutput> parent) :
+    _parent(parent) {
+    }
+    
+    virtual std::shared_ptr<NodeOutput> parent() override {
+        return _parent;
+    }
+    
+    virtual bool isEnabled() const override {
+        return _isEnabled;
+    }
+    virtual void setIsEnabled(bool isEnabled) override {
+        _isEnabled = isEnabled;
+    }
+    
+    virtual bool hasUpdate() override {
+        return _hasUpdate;
+    }
+    void setHasUpdate(bool hasUpdate) {
+        _hasUpdate = hasUpdate;
+    }
+    
+    virtual std::shared_ptr<CGPath> outputPath() override {
+        if (_parent) {
+            return _parent->outputPath();
+        }
+        return nullptr;
+    }
+    
+    virtual bool hasOutputUpdates(double forFrame) override {
+        /// Changes to this node do not affect downstream nodes.
+        bool parentUpdate = false;
+        if (_parent) {
+            parentUpdate = _parent->hasOutputUpdates(forFrame);
+        }
+        /// Changes to upstream nodes do, however, affect this nodes state.
+        _hasUpdate = _hasUpdate || parentUpdate;
+        return parentUpdate;
+    }
+    
+    virtual bool hasRenderUpdates(double forFrame) override {
+        /// Return true if there are upstream updates or if this node has updates
+        bool upstreamUpdates = false;
+        if (_parent) {
+            upstreamUpdates = _parent->hasOutputUpdates(forFrame);
+        }
+        _hasUpdate = _hasUpdate || upstreamUpdates;
+        return _hasUpdate;
+    }
+    
+private:
+    std::shared_ptr<NodeOutput> _parent;
+    bool _hasUpdate = false;
+    bool _isEnabled = true;
+};
+
+}
+
+#endif /* PassThroughOutputNode_hpp */

Tests/LottieMetalTest/LottieSwift/Sources/Private/MainThread/NodeRenderSystem/Nodes/OutputNodes/PassThroughOutputNode.swift

@@ -0,0 +1,47 @@
+//
+//  PassThroughOutputNode.swift
+//  lottie-swift
+//
+//  Created by Brandon Withrow on 1/30/19.
+//
+
+import CoreGraphics
+import Foundation
+
+class PassThroughOutputNode: NodeOutput {
+
+  // MARK: Lifecycle
+
+  init(parent: NodeOutput?) {
+    self.parent = parent
+  }
+
+  // MARK: Internal
+
+  let parent: NodeOutput?
+
+  var hasUpdate = false
+  var isEnabled = true
+
+  var outputPath: CGPath? {
+    if let parent = parent {
+      return parent.outputPath
+    }
+    return nil
+  }
+
+  func hasOutputUpdates(_ forFrame: CGFloat) -> Bool {
+    /// Changes to this node do not affect downstream nodes.
+    let parentUpdate = parent?.hasOutputUpdates(forFrame) ?? false
+    /// Changes to upstream nodes do, however, affect this nodes state.
+    hasUpdate = hasUpdate || parentUpdate
+    return parentUpdate
+  }
+
+  func hasRenderUpdates(_ forFrame: CGFloat) -> Bool {
+    /// Return true if there are upstream updates or if this node has updates
+    let upstreamUpdates = parent?.hasOutputUpdates(forFrame) ?? false
+    hasUpdate = hasUpdate || upstreamUpdates
+    return hasUpdate
+  }
+}

Tests/LottieMetalTest/LottieSwift/Sources/Private/MainThread/NodeRenderSystem/Nodes/OutputNodes/PathOutputNode.swift

@@ -0,0 +1,90 @@
+//
+//  PathNodeOutput.swift
+//  lottie-swift
+//
+//  Created by Brandon Withrow on 1/30/19.
+//
+
+import CoreGraphics
+import Foundation
+
+/// A node that has an output of a BezierPath
+class PathOutputNode: NodeOutput {
+
+  // MARK: Lifecycle
+
+  init(parent: NodeOutput?) {
+    self.parent = parent
+  }
+
+  // MARK: Internal
+
+  let parent: NodeOutput?
+
+  fileprivate(set) var outputPath: CGPath? = nil
+
+  var lastUpdateFrame: CGFloat? = nil
+  var lastPathBuildFrame: CGFloat? = nil
+  var isEnabled = true
+  fileprivate(set) var totalLength: CGFloat = 0
+  fileprivate(set) var pathObjects: [CompoundBezierPath] = []
+
+  func hasOutputUpdates(_ forFrame: CGFloat) -> Bool {
+    guard isEnabled else {
+      let upstreamUpdates = parent?.hasOutputUpdates(forFrame) ?? false
+      outputPath = parent?.outputPath
+      return upstreamUpdates
+    }
+
+    /// Ask if parent was updated
+    let upstreamUpdates = parent?.hasOutputUpdates(forFrame) ?? false
+
+    /// If parent was updated and the path hasn't been built for this frame, clear the path.
+    if upstreamUpdates && lastPathBuildFrame != forFrame {
+      outputPath = nil
+    }
+
+    if outputPath == nil {
+      /// If the path is clear, build the new path.
+      lastPathBuildFrame = forFrame
+      let newPath = CGMutablePath()
+      if let parentNode = parent, let parentPath = parentNode.outputPath {
+        newPath.addPath(parentPath)
+      }
+      for path in pathObjects {
+        for subPath in path.paths {
+          newPath.addPath(subPath.cgPath())
+        }
+      }
+      outputPath = newPath
+    }
+
+    /// Return true if there were upstream updates or if this node was updated.
+    return upstreamUpdates || (lastUpdateFrame == forFrame)
+  }
+
+  @discardableResult
+  func removePaths(updateFrame: CGFloat?) -> [CompoundBezierPath] {
+    lastUpdateFrame = updateFrame
+    let returnPaths = pathObjects
+    outputPath = nil
+    totalLength = 0
+    pathObjects = []
+    return returnPaths
+  }
+
+  func setPath(_ path: BezierPath, updateFrame: CGFloat) {
+    lastUpdateFrame = updateFrame
+    outputPath = nil
+    totalLength = path.length
+    pathObjects = [CompoundBezierPath(path: path)]
+  }
+
+  func appendPath(_ path: CompoundBezierPath, updateFrame: CGFloat) {
+    lastUpdateFrame = updateFrame
+    outputPath = nil
+    totalLength = totalLength + path.length
+    pathObjects.append(path)
+  }
+
+}

Tests/LottieMetalTest/LottieSwift/Sources/Private/MainThread/NodeRenderSystem/Nodes/OutputNodes/Renderables/FillRenderer.swift

@@ -0,0 +1,71 @@
+//
+//  FillRenderer.swift
+//  lottie-swift
+//
+//  Created by Brandon Withrow on 1/30/19.
+//
+
+import CoreGraphics
+import Foundation
+import QuartzCore
+
+extension FillRule {
+  var cgFillRule: CGPathFillRule {
+    switch self {
+    case .evenOdd:
+      return .evenOdd
+    default:
+      return .winding
+    }
+  }
+
+  var caFillRule: CAShapeLayerFillRule {
+    switch self {
+    case .evenOdd:
+      return CAShapeLayerFillRule.evenOdd
+    default:
+      return CAShapeLayerFillRule.nonZero
+    }
+  }
+}
+
+// MARK: - FillRenderer
+
+/// A rendered for a Path Fill
+final class FillRenderer: PassThroughOutputNode, Renderable {
+  var shouldRenderInContext = false
+
+  var color: CGColor? {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  var opacity: CGFloat = 0 {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  var fillRule: FillRule = .none {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  func render(_: CGContext) {
+    // do nothing
+  }
+
+  func setupSublayers(layer _: CAShapeLayer) {
+    // do nothing
+  }
+
+  func updateShapeLayer(layer: CAShapeLayer) {
+    layer.fillColor = color
+    layer.opacity = Float(opacity)
+    layer.fillRule = fillRule.caFillRule
+    hasUpdate = false
+  }
+
+}

Tests/LottieMetalTest/LottieSwift/Sources/Private/MainThread/NodeRenderSystem/Nodes/OutputNodes/Renderables/GradientFillRenderer.swift

@@ -0,0 +1,311 @@
+//
+//  GradientFillRenderer.swift
+//  lottie-swift
+//
+//  Created by Brandon Withrow on 1/30/19.
+//
+
+import Foundation
+import QuartzCore
+
+public var lottieSwift_getPathNativeBoundingBox: ((CGPath) -> CGRect)?
+
+// MARK: - GradientFillLayer
+
+extension CGPath {
+    var stringRepresentation: String {
+        var result = ""
+        
+        var indent = 1
+        self.applyWithBlock { element in
+            let indentString = Array<String>(repeating: " ", count: indent * 2).joined(separator: "")
+            switch element.pointee.type {
+            case .moveToPoint:
+                let point = element.pointee.points.advanced(by: 0).pointee
+                result += indentString + (NSString(format: "moveto (%10.15f, %10.15f)\n", point.x, point.y) as String)
+                indent += 1
+            case .addLineToPoint:
+                let point = element.pointee.points.advanced(by: 0).pointee
+                result += indentString + (NSString(format: "lineto (%10.15f, %10.15f)\n", point.x, point.y) as String)
+            case .addCurveToPoint:
+                let cp1 = element.pointee.points.advanced(by: 0).pointee
+                let cp2 = element.pointee.points.advanced(by: 1).pointee
+                let point = element.pointee.points.advanced(by: 2).pointee
+                result += indentString + (NSString(format: "curveto (%10.15f, %10.15f) (%10.15f, %10.15f) (%10.15f, %10.15f)\n", cp1.x, cp1.y, cp2.x, cp2.y, point.x, point.y) as String)
+            case .addQuadCurveToPoint:
+                let cp = element.pointee.points.advanced(by: 0).pointee
+                let point = element.pointee.points.advanced(by: 1).pointee
+                result += indentString + (NSString(format: "quadcurveto (%10.15f, %10.15f) (%10.15f, %10.15f)\n", cp.x, cp.y, point.x, point.y) as String)
+            case .closeSubpath:
+                result += indentString + "closepath\n"
+                indent -= 1
+            @unknown default:
+                break
+            }
+        }
+        
+        return result
+    }
+}
+
+private final class GradientFillLayer: CALayer, LottieDrawingLayer {
+
+  var start: CGPoint = .zero {
+    didSet {
+      setNeedsDisplay()
+    }
+  }
+
+  var numberOfColors = 0 {
+    didSet {
+      setNeedsDisplay()
+    }
+  }
+
+  var colors: [CGFloat] = [] {
+    didSet {
+      setNeedsDisplay()
+    }
+  }
+
+  var end: CGPoint = .zero {
+    didSet {
+      setNeedsDisplay()
+    }
+  }
+
+  var type: GradientType = .none {
+    didSet {
+      setNeedsDisplay()
+    }
+  }
+
+  override func draw(in ctx: CGContext) {
+    var alphaValues = [CGFloat]()
+    var alphaLocations = [CGFloat]()
+
+    var gradientColors = [Color]()
+    var colorLocations = [CGFloat]()
+    let colorSpace = ctx.colorSpace ?? CGColorSpaceCreateDeviceRGB()
+    for i in 0..<numberOfColors {
+      let ix = i * 4
+      if colors.count > ix {
+        gradientColors.append(Color(r: colors[ix + 1], g: colors[ix + 2], b: colors[ix + 3], a: 1.0))
+        colorLocations.append(colors[ix])
+      }
+    }
+
+    var drawMask = false
+    for i in stride(from: numberOfColors * 4, to: colors.endIndex, by: 2) {
+      let alpha = colors[i + 1]
+      if alpha < 1 {
+        drawMask = true
+      }
+      alphaLocations.append(colors[i])
+      alphaValues.append(alpha)
+    }
+      
+    if drawMask {
+        var locations: [CGFloat] = []
+        for i in 0 ..< min(gradientColors.count, colorLocations.count) {
+            if !locations.contains(colorLocations[i]) {
+                locations.append(colorLocations[i])
+            }
+        }
+        for i in 0 ..< min(alphaValues.count, alphaLocations.count) {
+            if !locations.contains(alphaLocations[i]) {
+                locations.append(alphaLocations[i])
+            }
+        }
+        
+        locations.sort()
+        if locations[0] != 0.0 {
+            locations.insert(0.0, at: 0)
+        }
+        if locations[locations.count - 1] != 1.0 {
+            locations.append(1.0)
+        }
+        
+        var colors: [Color] = []
+        
+        for location in locations {
+            var color: Color?
+            for i in 0 ..< min(gradientColors.count, colorLocations.count) - 1 {
+                if location >= colorLocations[i] && location <= colorLocations[i + 1] {
+                    let localLocation: Double
+                    if colorLocations[i] != colorLocations[i + 1] {
+                        localLocation = location.remap(fromLow: colorLocations[i], fromHigh: colorLocations[i + 1], toLow: 0.0, toHigh: 1.0)
+                    } else {
+                        localLocation = 0.0
+                    }
+                    let fromColor = gradientColors[i]
+                    let toColor = gradientColors[i + 1]
+                    color = fromColor.interpolate(to: toColor, amount: localLocation)
+                    
+                    break
+                }
+            }
+            
+            var alpha: CGFloat?
+            for i in 0 ..< min(alphaValues.count, alphaLocations.count) - 1 {
+                if location >= alphaLocations[i] && location <= alphaLocations[i + 1] {
+                    let localLocation: Double
+                    if alphaLocations[i] != alphaLocations[i + 1] {
+                        localLocation = location.remap(fromLow: alphaLocations[i], fromHigh: alphaLocations[i + 1], toLow: 0.0, toHigh: 1.0)
+                    } else {
+                        localLocation = 0.0
+                    }
+                    let fromAlpha = alphaValues[i]
+                    let toAlpha = alphaValues[i + 1]
+                    alpha = fromAlpha.interpolate(to: toAlpha, amount: localLocation)
+                    
+                    break
+                }
+            }
+            
+            var resultColor = color ?? gradientColors[0]
+            resultColor.a = alpha ?? 1.0
+            
+            /*resultColor.r = 1.0
+            resultColor.g = 0.0
+            resultColor.b = 0.0
+            resultColor.a = 1.0*/
+            
+            colors.append(resultColor)
+        }
+        
+        gradientColors = colors
+        colorLocations = locations
+    }
+
+    let cgGradientColors: [CGColor] = gradientColors.map { color -> CGColor in
+        return color.cgColorValue(colorSpace: colorSpace)
+    }
+      
+    guard let gradient = CGGradient(colorsSpace: colorSpace, colors: cgGradientColors as CFArray, locations: colorLocations)
+    else { return }
+    if type == .linear {
+      ctx.drawLinearGradient(gradient, start: start, end: end, options: [.drawsAfterEndLocation, .drawsBeforeStartLocation])
+    } else {
+      ctx.drawRadialGradient(
+        gradient,
+        startCenter: start,
+        startRadius: 0,
+        endCenter: start,
+        endRadius: start.distanceTo(end),
+        options: [.drawsAfterEndLocation, .drawsBeforeStartLocation])
+    }
+  }
+
+}
+
+// MARK: - GradientFillRenderer
+
+/// A rendered for a Path Fill
+final class GradientFillRenderer: PassThroughOutputNode, Renderable {
+
+  // MARK: Lifecycle
+
+  override init(parent: NodeOutput?) {
+    super.init(parent: parent)
+
+    maskLayer.fillColor = CGColor(colorSpace: CGColorSpaceCreateDeviceRGB(), components: [1, 1, 1, 1])
+    gradientLayer.mask = maskLayer
+
+    maskLayer.actions = [
+      "startPoint" : NSNull(),
+      "endPoint" : NSNull(),
+      "opacity" : NSNull(),
+      "locations" : NSNull(),
+      "colors" : NSNull(),
+      "bounds" : NSNull(),
+      "anchorPoint" : NSNull(),
+      "isRadial" : NSNull(),
+      "path" : NSNull(),
+    ]
+    gradientLayer.actions = maskLayer.actions
+  }
+
+  // MARK: Internal
+
+  var shouldRenderInContext = false
+
+  var start: CGPoint = .zero {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  var numberOfColors = 0 {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  var colors: [CGFloat] = [] {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  var end: CGPoint = .zero {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  var opacity: CGFloat = 0 {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  var type: GradientType = .none {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  func render(_: CGContext) {
+    // do nothing
+  }
+
+  func setupSublayers(layer: CAShapeLayer) {
+    layer.addSublayer(gradientLayer)
+    layer.fillColor = nil
+  }
+
+  func updateShapeLayer(layer: CAShapeLayer) {
+    hasUpdate = false
+
+    guard let path = layer.path else {
+      return
+    }
+
+    let frame = lottieSwift_getPathNativeBoundingBox!(path)
+    
+    let anchor = (frame.size.width.isZero || frame.size.height.isZero) ? CGPoint() : CGPoint(
+      x: -frame.origin.x / frame.size.width,
+      y: -frame.origin.y / frame.size.height)
+    maskLayer.path = path
+    maskLayer.bounds = frame
+    maskLayer.anchorPoint = anchor
+
+    gradientLayer.bounds = maskLayer.bounds
+    gradientLayer.anchorPoint = anchor
+
+    // setup gradient properties
+    gradientLayer.start = start
+    gradientLayer.end = end
+    gradientLayer.numberOfColors = numberOfColors
+    gradientLayer.colors = colors
+    gradientLayer.opacity = Float(opacity)
+    gradientLayer.type = type
+  }
+
+  // MARK: Private
+
+  private let gradientLayer = GradientFillLayer()
+  private let maskLayer = LottieCAShapeLayer()
+
+}

Tests/LottieMetalTest/LottieSwift/Sources/Private/MainThread/NodeRenderSystem/Nodes/OutputNodes/Renderables/GradientStrokeRenderer.swift

@@ -0,0 +1,66 @@
+//
+//  GradientStrokeRenderer.swift
+//  lottie-swift
+//
+//  Created by Brandon Withrow on 1/30/19.
+//
+
+import Foundation
+import QuartzCore
+
+// MARK: - Renderer
+
+final class GradientStrokeRenderer: PassThroughOutputNode, Renderable {
+
+  // MARK: Lifecycle
+
+  override init(parent: NodeOutput?) {
+    strokeRender = StrokeRenderer(parent: nil)
+    gradientRender = GradientFillRenderer(parent: nil)
+    strokeRender.color = CGColor(colorSpace: CGColorSpaceCreateDeviceRGB(), components: [1, 1, 1, 1])
+    super.init(parent: parent)
+  }
+
+  // MARK: Internal
+
+  var shouldRenderInContext = true
+
+  let strokeRender: StrokeRenderer
+  let gradientRender: GradientFillRenderer
+
+  override func hasOutputUpdates(_ forFrame: CGFloat) -> Bool {
+    let updates = super.hasOutputUpdates(forFrame)
+    return updates || strokeRender.hasUpdate || gradientRender.hasUpdate
+  }
+
+  func updateShapeLayer(layer _: CAShapeLayer) {
+    /// Not Applicable
+  }
+
+  func setupSublayers(layer _: CAShapeLayer) {
+    /// Not Applicable
+  }
+
+  func render(_ inContext: CGContext) {
+    guard inContext.path != nil && inContext.path!.isEmpty == false else {
+      return
+    }
+
+    strokeRender.hasUpdate = false
+    hasUpdate = false
+    gradientRender.hasUpdate = false
+
+    strokeRender.setupForStroke(inContext)
+
+    inContext.replacePathWithStrokedPath()
+
+    /// Now draw the gradient.
+    gradientRender.render(inContext)
+
+  }
+
+  func renderBoundsFor(_ boundingBox: CGRect) -> CGRect {
+    strokeRender.renderBoundsFor(boundingBox)
+  }
+
+}

Tests/LottieMetalTest/LottieSwift/Sources/Private/MainThread/NodeRenderSystem/Nodes/OutputNodes/Renderables/LegacyGradientFillRenderer.swift

@@ -0,0 +1,153 @@
+//
+//  LegacyGradientFillRenderer.swift
+//  lottie-swift
+//
+//  Created by Brandon Withrow on 1/30/19.
+//
+
+import Foundation
+import QuartzCore
+
+/// A rendered for a Path Fill
+final class LegacyGradientFillRenderer: PassThroughOutputNode, Renderable {
+
+  var shouldRenderInContext = true
+
+  var start: CGPoint = .zero {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  var numberOfColors = 0 {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  var colors: [CGFloat] = [] {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  var end: CGPoint = .zero {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  var opacity: CGFloat = 0 {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  var type: GradientType = .none {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  func updateShapeLayer(layer _: CAShapeLayer) {
+    // Not applicable
+  }
+
+  func setupSublayers(layer _: CAShapeLayer) {
+    // Not applicable
+  }
+
+  func render(_ inContext: CGContext) {
+    guard inContext.path != nil && inContext.path!.isEmpty == false else {
+      return
+    }
+    hasUpdate = false
+    var alphaColors = [CGColor]()
+    var alphaLocations = [CGFloat]()
+
+    var gradientColors = [CGColor]()
+    var colorLocations = [CGFloat]()
+    let colorSpace = CGColorSpaceCreateDeviceRGB()
+    let maskColorSpace = CGColorSpaceCreateDeviceGray()
+    for i in 0..<numberOfColors {
+      let ix = i * 4
+      if
+        colors.count > ix, let color = CGColor(
+          colorSpace: colorSpace,
+          components: [colors[ix + 1], colors[ix + 2], colors[ix + 3], 1])
+      {
+        gradientColors.append(color)
+        colorLocations.append(colors[ix])
+      }
+    }
+
+    var drawMask = false
+    for i in stride(from: numberOfColors * 4, to: colors.endIndex, by: 2) {
+      let alpha = colors[i + 1]
+      if alpha < 1 {
+        drawMask = true
+      }
+      if let color = CGColor(colorSpace: maskColorSpace, components: [alpha, 1]) {
+        alphaLocations.append(colors[i])
+        alphaColors.append(color)
+      }
+    }
+
+    inContext.setAlpha(opacity)
+    inContext.clip()
+
+    /// First draw a mask is necessary.
+    if drawMask {
+      guard
+        let maskGradient = CGGradient(
+          colorsSpace: maskColorSpace,
+          colors: alphaColors as CFArray,
+          locations: alphaLocations),
+        let maskContext = CGContext(
+          data: nil,
+          width: inContext.width,
+          height: inContext.height,
+          bitsPerComponent: 8,
+          bytesPerRow: inContext.width,
+          space: maskColorSpace,
+          bitmapInfo: 0) else { return }
+      let flipVertical = CGAffineTransform(a: 1, b: 0, c: 0, d: -1, tx: 0, ty: CGFloat(maskContext.height))
+      maskContext.concatenate(flipVertical)
+      maskContext.concatenate(inContext.ctm)
+      if type == .linear {
+        maskContext.drawLinearGradient(
+          maskGradient,
+          start: start,
+          end: end,
+          options: [.drawsAfterEndLocation, .drawsBeforeStartLocation])
+      } else {
+        maskContext.drawRadialGradient(
+          maskGradient,
+          startCenter: start,
+          startRadius: 0,
+          endCenter: start,
+          endRadius: start.distanceTo(end),
+          options: [.drawsAfterEndLocation, .drawsBeforeStartLocation])
+      }
+      /// Clips the gradient
+      if let alphaMask = maskContext.makeImage() {
+        inContext.clip(to: inContext.boundingBoxOfClipPath, mask: alphaMask)
+      }
+    }
+
+    /// Now draw the gradient
+    guard let gradient = CGGradient(colorsSpace: colorSpace, colors: gradientColors as CFArray, locations: colorLocations)
+    else { return }
+    if type == .linear {
+      inContext.drawLinearGradient(gradient, start: start, end: end, options: [.drawsAfterEndLocation, .drawsBeforeStartLocation])
+    } else {
+      inContext.drawRadialGradient(
+        gradient,
+        startCenter: start,
+        startRadius: 0,
+        endCenter: start,
+        endRadius: start.distanceTo(end),
+        options: [.drawsAfterEndLocation, .drawsBeforeStartLocation])
+    }
+  }
+}

Tests/LottieMetalTest/LottieSwift/Sources/Private/MainThread/NodeRenderSystem/Nodes/OutputNodes/Renderables/StrokeRenderer.swift

@@ -0,0 +1,166 @@
+//
+//  StrokeRenderer.swift
+//  lottie-swift
+//
+//  Created by Brandon Withrow on 1/30/19.
+//
+
+import Foundation
+import QuartzCore
+
+extension LineJoin {
+  var cgLineJoin: CGLineJoin {
+    switch self {
+    case .bevel:
+      return .bevel
+    case .none:
+      return .miter
+    case .miter:
+      return .miter
+    case .round:
+      return .round
+    }
+  }
+
+  var caLineJoin: CAShapeLayerLineJoin {
+    switch self {
+    case .none:
+      return CAShapeLayerLineJoin.miter
+    case .miter:
+      return CAShapeLayerLineJoin.miter
+    case .round:
+      return CAShapeLayerLineJoin.round
+    case .bevel:
+      return CAShapeLayerLineJoin.bevel
+    }
+  }
+}
+
+extension LineCap {
+  var cgLineCap: CGLineCap {
+    switch self {
+    case .none:
+      return .butt
+    case .butt:
+      return .butt
+    case .round:
+      return .round
+    case .square:
+      return .square
+    }
+  }
+
+  var caLineCap: CAShapeLayerLineCap {
+    switch self {
+    case .none:
+      return CAShapeLayerLineCap.butt
+    case .butt:
+      return CAShapeLayerLineCap.butt
+    case .round:
+      return CAShapeLayerLineCap.round
+    case .square:
+      return CAShapeLayerLineCap.square
+    }
+  }
+}
+
+// MARK: - StrokeRenderer
+
+/// A rendered that renders a stroke on a path.
+final class StrokeRenderer: PassThroughOutputNode, Renderable {
+
+  var shouldRenderInContext = false
+
+  var color: CGColor? {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  var opacity: CGFloat = 0 {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  var width: CGFloat = 0 {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  var miterLimit: CGFloat = 0 {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  var lineCap: LineCap = .none {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  var lineJoin: LineJoin = .none {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  var dashPhase: CGFloat? {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  var dashLengths: [CGFloat]? {
+    didSet {
+      hasUpdate = true
+    }
+  }
+
+  func setupSublayers(layer _: CAShapeLayer) {
+    // empty
+  }
+
+  func renderBoundsFor(_ boundingBox: CGRect) -> CGRect {
+    boundingBox.insetBy(dx: -width, dy: -width)
+  }
+
+  func setupForStroke(_ inContext: CGContext) {
+    inContext.setLineWidth(width)
+    inContext.setMiterLimit(miterLimit)
+    inContext.setLineCap(lineCap.cgLineCap)
+    inContext.setLineJoin(lineJoin.cgLineJoin)
+    if let dashPhase = dashPhase, let lengths = dashLengths {
+      inContext.setLineDash(phase: dashPhase, lengths: lengths)
+    } else {
+      inContext.setLineDash(phase: 0, lengths: [])
+    }
+  }
+
+  func render(_ inContext: CGContext) {
+    guard inContext.path != nil && inContext.path!.isEmpty == false else {
+      return
+    }
+    guard let color = color else { return }
+    hasUpdate = false
+    setupForStroke(inContext)
+    inContext.setAlpha(opacity)
+    inContext.setStrokeColor(color)
+    inContext.strokePath()
+  }
+
+  func updateShapeLayer(layer: CAShapeLayer) {
+    layer.strokeColor = color
+    layer.opacity = Float(opacity)
+    layer.lineWidth = width
+    layer.lineJoin = lineJoin.caLineJoin
+    layer.lineCap = lineCap.caLineCap
+    layer.lineDashPhase = dashPhase ?? 0
+    layer.fillColor = nil
+    if let dashPattern = dashLengths {
+      layer.lineDashPattern = dashPattern.map({ NSNumber(value: Double($0)) })
+    }
+  }
+}