Improve performance by projecting contents just once and caching result

Sources/GeoDrawer/GeoDrawer+CoreGraphics.swift

@@ -20,103 +20,111 @@ extension GeoDrawer {
 
   /// Draws the line into the current context
   public func draw(_ line: GeoJSON.LineString, strokeColor: CGColor, strokeWidth: Double = 2, in context: CGContext) {
-    for points in convertLine(line.positions) {
-
-      let path = CGMutablePath()
-      path.move(to: points[0].cgPoint)
-      for point in points[1...] {
-        path.addLine(to: point.cgPoint)
-      }
-
-      context.setStrokeColor(strokeColor)
-
-      context.setLineWidth(strokeWidth)
-      context.setLineCap(.round)
-      context.setLineJoin(.round)
-
-      context.addPath(path)
-      context.strokePath()
+    for line in project(line) {
+      draw(line, strokeColor: strokeColor, strokeWidth: strokeWidth, in: context)
     }
   }
 
   public func draw(_ polygon: GeoJSON.Polygon, fillColor: CGColor? = nil, strokeColor: CGColor? = nil, strokeWidth: Double = 2, frame: CGRect, in context: CGContext) {
-    // In some projections such as Azimuthal, we might need to colour a cut-out
-    // rather than the projected polygon.
-    let invert: Bool = invertCheck?(polygon) ?? false
+    for polygon in project(polygon) {
+      draw(polygon, fillColor: fillColor, strokeColor: strokeColor, strokeWidth: strokeWidth, frame: frame, in: context)
+    }
+  }
+
+  func drawCircle(_ position: GeoJSON.Position, radius: CGFloat, fillColor: CGColor, strokeColor: CGColor? = nil, strokeWidth: Double = 2, in context: CGContext) {
+    guard let center = converter(position)?.0 else { return }
+    drawCircle(center, radius: radius, fillColor: fillColor, strokeColor: strokeColor, strokeWidth: strokeWidth, in: context)
+  }
+
+  func draw(_ projectedLine: ProjectedLineString, strokeColor: CGColor, strokeWidth: Double, in context: CGContext) {
+    let points = projectedLine.points
+    let path = CGMutablePath()
+    path.move(to: points[0].cgPoint)
+    for point in points[1...] {
+      path.addLine(to: point.cgPoint)
+    }
 
-    for points in convertLine(polygon.exterior.positions) {
-
-      let path = CGMutablePath()
-      path.move(to: points[0].cgPoint)
-      for point in points[1...] {
-        path.addLine(to: point.cgPoint)
-      }
+    context.setStrokeColor(strokeColor)
+
+    context.setLineWidth(strokeWidth)
+    context.setLineCap(.round)
+    context.setLineJoin(.round)
+
+    context.addPath(path)
+    context.strokePath()
+  }
+
+  func draw(_ polygon: ProjectedPolygon, fillColor: CGColor?, strokeColor: CGColor?, strokeWidth: Double, frame: CGRect, in context: CGContext) {
+    let invert = polygon.invert
+
+    let points = polygon.exterior
+    let path = CGMutablePath()
+    path.move(to: points[0].cgPoint)
+    for point in points[1...] {
+      path.addLine(to: point.cgPoint)
+    }
+
+    // First we need to create a clip path, i.e., the area where we allowed to fill in the actual polygon.
+    // This is the whole frame *minus* the interior polygons.
+    // Useful example: https://samplecodebank.blogspot.com/2013/06/UIBezierPath-addClip-example.html
+    if !polygon.interiors.isEmpty {
+      let rect = CGMutablePath()
+      rect.move(to: frame.origin)
+      rect.addLine(to: CGPoint(x: frame.minX, y: frame.maxY))
+      rect.addLine(to: CGPoint(x: frame.maxX, y: frame.maxY))
+      rect.addLine(to: CGPoint(x: frame.maxX, y: frame.minY))
 
-      // First we need to create a clip path, i.e., the area where we allowed to fill in the actual polygon.
-      // This is the whole frame *minus* the interior polygons.
-      // Useful example: https://samplecodebank.blogspot.com/2013/06/UIBezierPath-addClip-example.html
-      if !polygon.interiors.isEmpty {
-        let rect = CGMutablePath()
-        rect.move(to: frame.origin)
-        rect.addLine(to: CGPoint(x: frame.minX, y: frame.maxY))
-        rect.addLine(to: CGPoint(x: frame.maxX, y: frame.maxY))
-        rect.addLine(to: CGPoint(x: frame.maxX, y: frame.minY))
-
-        for interior in polygon.interiors {
-          for interiorPoints in convertLine(interior.positions) {
-            rect.move(to: interiorPoints[0].cgPoint)
-            for point in interiorPoints[1...] {
-              rect.addLine(to: point.cgPoint)
-            }
-          }
+      for interiorPoints in polygon.interiors {
+        rect.move(to: interiorPoints[0].cgPoint)
+        for point in interiorPoints[1...] {
+          rect.addLine(to: point.cgPoint)
         }
-
-        context.addPath(rect)
-        context.clip(using: .evenOdd)
       }
 
-      // Then we can draw the polygon
-
-      context.addPath(path)
+      context.addPath(rect)
+      context.clip(using: .evenOdd)
+    }
+
+    // Then we can draw the polygon
+
+    context.addPath(path)
 
-      if let fillColor {
-        if invert {
-          // TODO: This doesn't actually invert. Would be nice to do that later.
-          context.setStrokeColor(fillColor)
-          context.setLineWidth(strokeWidth)
-          context.setLineCap(.round)
-          context.setLineJoin(.round)
-          context.strokePath()
-
-        } else {
-          context.setFillColor(fillColor)
-          context.setLineWidth(0)
-          context.fillPath()
-        }
-
-      }
-
-      if let strokeColor {
-        context.addPath(path)
-        context.setStrokeColor(strokeColor)
+    if let fillColor {
+      if invert {
+        // TODO: This doesn't actually invert. Would be nice to do that later.
+        context.setStrokeColor(fillColor)
         context.setLineWidth(strokeWidth)
         context.setLineCap(.round)
         context.setLineJoin(.round)
         context.strokePath()
+
+      } else {
+        context.setFillColor(fillColor)
+        context.setLineWidth(0)
+        context.fillPath()
       }
+
+    }
+
+    if let strokeColor {
+      context.addPath(path)
+      context.setStrokeColor(strokeColor)
+      context.setLineWidth(strokeWidth)
+      context.setLineCap(.round)
+      context.setLineJoin(.round)
+      context.strokePath()
     }
   }
+
 
-  func drawCircle(_ position: GeoJSON.Position, radius: CGFloat, fillColor: CGColor, strokeColor: CGColor? = nil, strokeWidth: Double = 2, in context: CGContext) {
-    guard let origin = converter(position) else { return }
-
-    context.addArc(center: origin.0.cgPoint, radius: radius / 2, startAngle: 0, endAngle: CGFloat(Double.pi * 2), clockwise: true)
+  func drawCircle(_ center: Point, radius: CGFloat, fillColor: CGColor, strokeColor: CGColor? = nil, strokeWidth: Double = 2, in context: CGContext) {
+    context.addArc(center: center.cgPoint, radius: radius / 2, startAngle: 0, endAngle: CGFloat(Double.pi * 2), clockwise: true)
 
     context.setFillColor(fillColor)
     context.fillPath()
 
     if let strokeColor {
-      context.addArc(center: origin.0.cgPoint, radius: radius / 2, startAngle: 0, endAngle: CGFloat(Double.pi * 2), clockwise: true)
+      context.addArc(center: center.cgPoint, radius: radius / 2, startAngle: 0, endAngle: CGFloat(Double.pi * 2), clockwise: true)
       context.setStrokeColor(strokeColor)
       context.setLineWidth(strokeWidth)
       context.strokePath()
@@ -181,7 +189,11 @@ extension GeoDrawer {
 extension GeoDrawer {
 
   public func draw(_ contents: [Content], mapBackground: CGColor? = nil, mapOutline: CGColor? = nil, mapBackdrop: CGColor? = nil, in context: CGContext) {
-
+    let projected = contents.compactMap(project)
+    draw(projected, mapBackground: mapBackground, mapOutline: mapOutline, mapBackdrop: mapBackdrop, in: context)
+  }
+
+  func draw(_ contents: [ProjectedContent], mapBackground: CGColor?, mapOutline: CGColor?, mapBackdrop: CGColor?, in context: CGContext) {
     let size = CGSize(width: self.size.width, height: self.size.height)
     let bounds = CGRect(origin: .zero, size: size)
 
@@ -201,10 +213,14 @@ extension GeoDrawer {
       switch content {
       case .circle:
         break // this will go above the outline, as they might go outside projection
-      case let .line(line, stroke, strokeWidth):
-        draw(line, strokeColor: stroke, strokeWidth: strokeWidth, in: context)
-      case let .polygon(polygon, fill, stroke, strokeWidth):
-        draw(polygon, fillColor: fill, strokeColor: stroke, strokeWidth: strokeWidth, frame: bounds, in: context)
+      case let .line(lines, stroke, strokeWidth):
+        for line in lines {
+          draw(line, strokeColor: stroke, strokeWidth: strokeWidth, in: context)
+        }
+      case let .polygon(polygons, fill, stroke, strokeWidth):
+        for polygon in polygons {
+          draw(polygon, fillColor: fill, strokeColor: stroke, strokeWidth: strokeWidth, frame: bounds, in: context)
+        }
       }
     }
 

Sources/GeoDrawer/GeoDrawer.swift

@@ -178,16 +178,72 @@ extension GeoDrawer {
 
 }
 
+// MARK: - Projected content
+
+extension GeoDrawer {
+
+  struct ProjectedLineString: Hashable {
+    let points: [Point]
+  }
+
+  struct ProjectedPolygon: Hashable {
+    let exterior: [Point]
+    let interiors: [[Point]]
+
+    // In some projections such as Azimuthal, we might need to colour a cut-out
+    // rather than the projected polygon.
+    let invert: Bool
+  }
+
+  enum ProjectedContent: Hashable {
+    case line([ProjectedLineString], stroke: Color, strokeWidth: Double)
+    case polygon([ProjectedPolygon], fill: Color, stroke: Color?, strokeWidth: Double)
+    case circle(Point, radius: Double, fill: Color, stroke: Color?, strokeWidth: Double)
+  }
+}
+
+extension GeoDrawer {
+  func project(_ line: GeoJSON.LineString) -> [ProjectedLineString] {
+    let lines = convertLine(line.positions)
+    return lines.map(ProjectedLineString.init(points:))
+  }
+
+  func project(_ polygon: GeoJSON.Polygon) -> [ProjectedPolygon] {
+    let invert: Bool = invertCheck?(polygon) ?? false
+    let interiors = polygon.interiors.flatMap { convertLine($0.positions) }
+    return convertLine(polygon.exterior.positions).map { points in
+      return .init(exterior: points, interiors: interiors, invert: invert)
+    }
+  }
+
+  func project(_ content: Content) -> ProjectedContent? {
+    switch content {
+    case let .line(line, stroke, strokeWidth):
+      return .line(project(line), stroke: stroke, strokeWidth: strokeWidth)
+    case let .polygon(polygon, fill, stroke, strokeWidth):
+      return .polygon(project(polygon), fill: fill, stroke: stroke, strokeWidth: strokeWidth)
+    case let .circle(center, radius, fill, stroke, strokeWidth):
+      guard let point = converter(center)?.0 else { return nil }
+      return .circle(point, radius: radius, fill: fill, stroke: stroke, strokeWidth: strokeWidth)
+    }
+  }
+}
+
 // MARK: - Line helper
 
 extension GeoDrawer {
 
-  private enum Grouping: Equatable {
+  enum Grouping: Equatable {
     case wrapped
     case notWrapped
     case notProjected
   }
 
+  /// - Returns: Typically returns a single element, but can return multiple, if the line wraps around
+  func convertLine(_ positions: [GeoJSON.Position]) -> [[Point]] {
+    Self.convertLine(positions, projection: projection, size: size, zoomTo: zoomTo, insets: insets, converter: converter)
+  }
+
   private static func projectLine(_ positions: [GeoJSON.Position], projection: Projection) -> [(Point, Point?)] {
 
     // 1. Turn degrees into radians
@@ -208,10 +264,11 @@ extension GeoDrawer {
   }
 
   /// - Returns: Typically returns a single element, but can return multiple, if the line wraps around
-  func convertLine(_ positions: [GeoJSON.Position]) -> [[Point]] {
+  private static func convertLine(_ positions: [GeoJSON.Position], projection: Projection?, size: Size, zoomTo: Rect?, insets: EdgeInsets, converter: (GeoJSON.Position) -> (Point, Bool)?) -> [[Point]] {
+
     guard let projection else {
       return [positions.compactMap {
-        self.converter($0)?.0
+        converter($0)?.0
       }]
     }
 

Sources/GeoDrawer/GeoMap+UIKit.swift

@@ -16,26 +16,32 @@ import GeoJSONKit
 
 public class GeoMapView: UIView {
   public var contents: [GeoDrawer.Content] = [] {
-    didSet { setNeedsDisplay(bounds) }
+    didSet {
+      _projected = nil
+      setNeedsDisplay(bounds)
+    }
   }
 
   public var projection: Projection = Projections.Equirectangular() {
     didSet {
       _drawer = nil
+      _projected = nil
       setNeedsDisplay(bounds)
     }
   }
 
   public var zoomTo: GeoJSON.BoundingBox? = nil {
     didSet {
       _drawer = nil
+      _projected = nil
       setNeedsDisplay(bounds)
     }
   }
 
   public var insets: GeoProjector.EdgeInsets = .zero {
     didSet {
       _drawer = nil
+      _projected = nil
       setNeedsDisplay(bounds)
     }
   }
@@ -56,10 +62,23 @@ public class GeoMapView: UIView {
   public override var frame: CGRect {
     didSet {
       _drawer = nil
+      _projected = nil
       setNeedsDisplay(bounds)
     }
   }
 
+
+  private var _projected: [GeoDrawer.ProjectedContent]!
+  private var projected: [GeoDrawer.ProjectedContent] {
+    if let _projected {
+      return _projected
+    } else {
+      let projected = contents.compactMap(drawer.project(_:))
+      _projected = projected
+      return projected
+    }
+  }
+
   private var _drawer: GeoDrawer!
   private var drawer: GeoDrawer {
     if let _drawer {
@@ -93,7 +112,7 @@ public class GeoMapView: UIView {
 
     // Use Core Graphics functions to draw the content of your view
     drawer.draw(
-      contents,
+      projected,
       mapBackground: mapBackground.cgColor,
       mapOutline: mapOutline.cgColor,
       mapBackdrop: background.cgColor,