mchoe · garush13 · Oct 19, 2020
diff --git a/SwiftSVG.xcodeproj/project.pbxproj b/SwiftSVG.xcodeproj/project.pbxproj
@@ -138,6 +138,7 @@
 		E8235A6222F2686C00E8F1B3 /* Dictionary+JSON.swift in Sources */ = {isa = PBXBuildFile; fileRef = E8235A6022F2614000E8F1B3 /* Dictionary+JSON.swift */; };
 		E8235A6322F2687F00E8F1B3 /* cssColorNames.json in Resources */ = {isa = PBXBuildFile; fileRef = E8235A5E22F260E000E8F1B3 /* cssColorNames.json */; };
 		E8AFE31C22EBD6F600BD1672 /* Print.swift in Sources */ = {isa = PBXBuildFile; fileRef = E8AFE31B22EBD6F600BD1672 /* Print.swift */; };
+		FAB19BF0253E0632001A2C01 /* CenterParametrizedEllipticalArc.swift in Sources */ = {isa = PBXBuildFile; fileRef = FAB19BEF253E0632001A2C01 /* CenterParametrizedEllipticalArc.swift */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXContainerItemProxy section */
@@ -237,6 +238,7 @@
 		E8235A5E22F260E000E8F1B3 /* cssColorNames.json */ = {isa = PBXFileReference; lastKnownFileType = text.json; path = cssColorNames.json; sourceTree = "<group>"; };
 		E8235A6022F2614000E8F1B3 /* Dictionary+JSON.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "Dictionary+JSON.swift"; sourceTree = "<group>"; };
 		E8AFE31B22EBD6F600BD1672 /* Print.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Print.swift; sourceTree = "<group>"; };
+		FAB19BEF253E0632001A2C01 /* CenterParametrizedEllipticalArc.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CenterParametrizedEllipticalArc.swift; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -347,6 +349,7 @@
 				9E245B6A1AAE383200472F5A /* UIColor+Extensions.swift */,
 				66F9844A20EF511F00A2CBEF /* Unown.swift */,
 				E8235A5E22F260E000E8F1B3 /* cssColorNames.json */,
+				FAB19BEF253E0632001A2C01 /* CenterParametrizedEllipticalArc.swift */,
 			);
 			name = Helpers;
 			path = SVG/Helpers;
@@ -753,6 +756,7 @@
 				175093C11E6C669F00EF1853 /* SVGParserSupportedElements.swift in Sources */,
 				3807CCF01F29940A00E78314 /* Fillable.swift in Sources */,
 				387090361F0C134400F72660 /* ParsesAsynchronously.swift in Sources */,
+				FAB19BF0253E0632001A2C01 /* CenterParametrizedEllipticalArc.swift in Sources */,
 				381E99B11EF8AFE500839918 /* PathCommand.swift in Sources */,
 				3807CCF21F29940A00E78314 /* Stylable.swift in Sources */,
 				380FECF81F000AA000EDB255 /* FloatingPoint+DegreesRadians.swift in Sources */,

diff --git a/SwiftSVG.xcodeproj/project.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist b/SwiftSVG.xcodeproj/project.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist
@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEDidComputeMac32BitWarning</key>
+	<true/>
+</dict>
+</plist>
diff --git a/SwiftSVG/SVG/Helpers/CenterParametrizedEllipticalArc.swift b/SwiftSVG/SVG/Helpers/CenterParametrizedEllipticalArc.swift
@@ -0,0 +1,41 @@
+//
+//  CenterParametrizedEllipticalArc.swift
+//  SwiftSVG
+//
+//  Created by Garush Batikyan on 10/19/20.
+//  Copyright © 2020 Strauss LLC. All rights reserved.
+//  http://www.github.com/mchoe
+//  http://www.straussmade.com/
+//  http://www.twitter.com/_mchoe
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy
+//  of this software and associated documentation files (the "Software"), to deal
+//  in the Software without restriction, including without limitation the rights
+//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+//  copies of the Software, and to permit persons to whom the Software is
+//  furnished to do so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in
+//  all copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+//  THE SOFTWARE.
+
+import CoreGraphics
+
+struct CenterParametrizedEllipticalArc {
+    var cx: CGFloat
+    var cy: CGFloat
+    var rx: CGFloat
+    var ry: CGFloat
+    var theta: CGFloat
+    var dTheta: CGFloat
+    var psi: CGFloat
+    var fs: CGFloat
+}
+
diff --git a/SwiftSVG/SVG/Iterators/PathCommand.swift b/SwiftSVG/SVG/Iterators/PathCommand.swift
@@ -476,15 +476,14 @@ internal struct SmoothQuadraticCurveTo: PathCommand {
 
 /**
  The `PathCommand` that corresponds to the SVG `A` or `a` command
- - TODO: Still needs an implementation
  */
 internal struct EllipticalArc: PathCommand {
 
     /// :nodoc:
     internal var coordinateBuffer = [Double]()
 
     /// :nodoc:
-    internal let numberOfRequiredParameters = 2
+    internal let numberOfRequiredParameters = 7
 
     /// :nodoc:
     internal let pathType: PathType
@@ -494,8 +493,127 @@ internal struct EllipticalArc: PathCommand {
         self.pathType = pathType
     }
 
+    /// :nodoc:
+    internal func convertEndpointToCenterParameterization(
+        x1: CGFloat,
+        y1: CGFloat,
+        x2: CGFloat,
+        y2: CGFloat,
+        fa: CGFloat,
+        fs: CGFloat,
+        rx: CGFloat,
+        ry: CGFloat,
+        psiDeg: CGFloat) -> CenterParametrizedEllipticalArc
+    {
+        var rx = rx
+        var ry = ry
+        let psi = psiDeg * (CGFloat.pi / 180.0)
+        let xp = (cos(psi) * ((x1 - x2) / 2.0)) + (sin(psi) * ((y1 - y2) / 2.0))
+        let yp = (-1 * sin(psi) * ((x1 - x2) / 2.0)) + (cos(psi) * ((y1 - y2) / 2.0))
+        let lambda = (xp * xp) / (rx * rx) + (yp * yp) / (ry * ry)
+
+        if (lambda > 1) {
+            rx = rx * sqrt(lambda)
+            ry = ry * sqrt(lambda)
+        }
+
+        var f = sqrt(
+            (rx * rx * (ry * ry) - rx * rx * (yp * yp) - ry * ry * (xp * xp)) /
+                (rx * rx * (yp * yp) + ry * ry * (xp * xp))
+        )
+
+        if (fa == fs) {
+            f *= -1
+        }
+
+        if (f.isNaN) {
+            f = 0
+        }
+
+        let cxp = (f * rx * yp) / ry
+        let cyp = (f * -ry * xp) / rx
+
+        let cx = (x1 + x2) / 2.0 + cos(psi) * cxp - sin(psi) * cyp
+        let cy = (y1 + y2) / 2.0 + sin(psi) * cxp + cos(psi) * cyp
+
+        let vMag:(Array<CGFloat>) -> CGFloat = { v -> CGFloat in
+            return sqrt(v[0] * v[0] + v[1] * v[1])
+        }
+        let vRatio: (Array<CGFloat>,Array<CGFloat>) -> CGFloat = { u,v -> CGFloat in
+            return (u[0] * v[0] + u[1] * v[1]) / (vMag(u) * vMag(v));
+        };
+        let vAngle: (Array<CGFloat>,Array<CGFloat>) -> CGFloat = { u,v -> CGFloat in
+            return ((u[0] * v[1] < u[1] * v[0]) ? -1 : 1) * acos(vRatio(u, v))
+        };
+        let theta = vAngle([1, 0], [(xp - cxp) / rx, (yp - cyp) / ry])
+        let u = [(xp - cxp) / rx, (yp - cyp) / ry]
+        let v = [(-1 * xp - cxp) / rx, (-1 * yp - cyp) / ry]
+        var dTheta = vAngle(u, v)
+
+        if (vRatio(u, v) <= -1) {
+            dTheta = CGFloat.pi
+        }
+        if (vRatio(u, v) >= 1) {
+            dTheta = 0
+        }
+        if (fs == 0 && dTheta > 0) {
+            dTheta = dTheta - 2 * CGFloat.pi
+        }
+        if (fs == 1 && dTheta < 0) {
+            dTheta = dTheta + 2 * CGFloat.pi
+        }
+        return CenterParametrizedEllipticalArc(cx: cx,
+                                               cy: cy,
+                                               rx: rx,
+                                               ry: ry,
+                                               theta: theta,
+                                               dTheta: dTheta,
+                                               psi: psi,
+                                               fs: fs)
+    }
+
+    /// :nodoc:
+    internal func drawArc(parameters: CenterParametrizedEllipticalArc, to path: UIBezierPath)
+    {
+        let r = parameters.rx > parameters.ry ? parameters.rx : parameters.ry
+        let scaleX = parameters.rx > parameters.ry ? 1 : parameters.rx / parameters.ry
+        let scaleY = parameters.rx > parameters.ry ? parameters.ry / parameters.rx : 1
+        path.apply(CGAffineTransform(translationX: -parameters.cx, y: -parameters.cy))
+        path.apply(CGAffineTransform(rotationAngle: -parameters.psi))
+        path.apply(CGAffineTransform(scaleX: 1/scaleX, y: 1/scaleY))
+        let clockwise = (1 - parameters.fs) == 0
+        path.addArc(withCenter: .zero,
+                       radius: r,
+                       startAngle: parameters.theta,
+                       endAngle: parameters.theta + parameters.dTheta,
+                       clockwise: clockwise)
+        path.apply(CGAffineTransform(scaleX: scaleX, y: scaleY))
+        path.apply(CGAffineTransform(rotationAngle: parameters.psi))
+        path.apply(CGAffineTransform(translationX: parameters.cx, y: parameters.cy))
+    }
+
     /// :nodoc:
     internal func execute(on path: UIBezierPath, previousCommand: PreviousCommand? = nil) {
-        assert(false, "Needs Implementation")
+
+        let rx = CGFloat(self.coordinateBuffer[0])
+        let ry = CGFloat(self.coordinateBuffer[1])
+        let psi = CGFloat(self.coordinateBuffer[2])
+        let fa = CGFloat(self.coordinateBuffer[3])
+        let fs = CGFloat(self.coordinateBuffer[4])
+        let x1 = CGFloat(path.currentPoint.x)
+        let y1 = CGFloat(path.currentPoint.y)
+        let ap = CGPoint(x: coordinateBuffer[5], y: coordinateBuffer[6])
+        let rp = self.pointForPathType(ap, relativeTo: path.currentPoint)
+        let a = self.convertEndpointToCenterParameterization(x1: x1,
+                                                             y1: y1,
+                                                             x2: rp.x,
+                                                             y2: rp.y,
+                                                             fa: fa,
+                                                             fs: fs,
+                                                             rx: rx,
+                                                             ry: ry,
+                                                             psiDeg: psi)
+
+        drawArc(parameters: a, to: path)
     }
 }
diff --git a/SwiftSVG/SVG/Iterators/PathDLexer.swift b/SwiftSVG/SVG/Iterators/PathDLexer.swift
@@ -92,6 +92,8 @@ internal struct PathDConstants {
         DCharacter.q.rawValue: QuadraticCurveTo(pathType: .relative),
         DCharacter.T.rawValue: SmoothQuadraticCurveTo(pathType: .absolute),
         DCharacter.t.rawValue: SmoothQuadraticCurveTo(pathType: .relative),
+        DCharacter.A.rawValue: EllipticalArc(pathType: .absolute),
+        DCharacter.a.rawValue: EllipticalArc(pathType: .relative),
     ]
 
 }