Add Support for Coordinate Conversion

Sources/SwiftPlot/GraphLayout.swift

@@ -22,7 +22,7 @@ public struct GraphLayout {
     /// The amount of (horizontal) space to reserve for markers on the Y-axis.
     var yMarkerMaxWidth: Float = 40
 
-    struct Results {
+    struct Results : CoordinateResolver {
         /// The size these results have been calculated for; the entire size of the plot.
         let totalSize: Size
 
@@ -51,6 +51,25 @@ public struct GraphLayout {
 
         var legendLabels: [(String, LegendIcon)] = []
         var legendRect: Rect?
+
+        func resolve(_ coordinate: Coordinate) -> Point {
+            let x = coordinate.point.x
+            let y = coordinate.point.y
+            switch(coordinate.coordinateSpace) {
+                case .figurePoints:
+                    return Point(x, y)
+                case .axesPoints:
+                    return Point(x, y) + plotBorderRect.origin
+                case .figureFraction:
+                    let maxX = plotBorderRect.origin.x + plotBorderRect.size.width
+                    let maxY = plotBorderRect.origin.y + plotBorderRect.size.height
+                    return Point(x * maxX, y * maxY)
+                case .axesFraction:
+                    let maxX = plotBorderRect.size.width
+                    let maxY =  plotBorderRect.size.height
+                    return Point(x * maxX, y * maxY) + plotBorderRect.origin
+            }
+        }
     }
 
     // Layout.
@@ -206,7 +225,7 @@ public struct GraphLayout {
         drawTitle(results: results, renderer: renderer)
         drawLabels(results: results, renderer: renderer)
         drawLegend(results.legendLabels, results: results, renderer: renderer)
-        drawAnnotations(renderer: renderer)
+        drawAnnotations(resolver: results, renderer: renderer)
     }
 
     private func drawTitle(results: Results, renderer: Renderer) {
@@ -379,9 +398,9 @@ public struct GraphLayout {
         }
     }
 
-    func drawAnnotations(renderer: Renderer) {
+    func drawAnnotations(resolver: CoordinateResolver, renderer: Renderer) {
         for var annotation in annotations{
-            annotation.draw(renderer: renderer)
+            annotation.draw(resolver: resolver, renderer: renderer)
         }
     }
 }

Sources/SwiftPlot/PlotStyleHelpers.swift

@@ -43,15 +43,30 @@ public struct PlotLegend {
     public init() {}
 }
 
+public struct Coordinate {
+    public enum CoordinateSpace {
+        case figurePoints
+        case figureFraction
+        case axesPoints
+        case axesFraction
+    }
+    public var coordinateSpace: CoordinateSpace = .figurePoints
+    public var point: Point = Point(0.0, 0.0)
+}
+
+public protocol CoordinateResolver {
+	func resolve(_ coordinate: Coordinate) -> Point
+}
+
 public protocol Annotation {
-    mutating func draw(renderer: Renderer)
+    mutating func draw(resolver: CoordinateResolver, renderer: Renderer)
 }
 
 struct Box: Annotation {
     public var color = Color.black
     public var location = Point(0.0, 0.0)
     public var size = Size(width: 0.0, height: 0.0)
-    public func draw(renderer: Renderer) {
+    public func draw(resolver: CoordinateResolver, renderer: Renderer) {
         renderer.drawSolidRect(Rect(origin: location, size: size),
                                fillColor: color,
                                hatchPattern: .none)
@@ -70,14 +85,14 @@ struct Text : Annotation {
     public var location = Point(0.0, 0.0)
     public var boundingBox: Box?
     public var borderWidth: Float = 5
-    public mutating func draw(renderer: Renderer) {
+    public mutating func draw(resolver: CoordinateResolver, renderer: Renderer) {
         if boundingBox != nil {
             var bboxSize = renderer.getTextLayoutSize(text: text, textSize: size)
             bboxSize.width += 2 * borderWidth
             bboxSize.height += 2 * borderWidth
             boundingBox?.location = Point(location.x - borderWidth, location.y - borderWidth)
             boundingBox?.size = bboxSize
-            boundingBox?.draw(renderer: renderer)
+            boundingBox?.draw(resolver: resolver, renderer: renderer)
         }
         renderer.drawText(text: text,
                           location: location,
@@ -107,7 +122,7 @@ struct Arrow : Annotation {
     public var isFilled: Bool = false
     public var startAnnotation: Annotation?
     public var endAnnotation: Annotation?
-    public mutating func draw(renderer: Renderer) {
+    public mutating func draw(resolver: CoordinateResolver, renderer: Renderer) {
         // Draws arrow body.
         renderer.drawPlotLines(points: [start, end],
                                strokeWidth: strokeWidth,
@@ -134,8 +149,8 @@ struct Arrow : Annotation {
         }
 
         //Draws start and end annotations if specified.
-        startAnnotation?.draw(renderer: renderer)
-        endAnnotation?.draw(renderer: renderer)
+        startAnnotation?.draw(resolver: resolver, renderer: renderer)
+        endAnnotation?.draw(resolver: resolver, renderer: renderer)
 
     }
     public init(color: Color = .black, start: Point = Point(0.0, 0.0), end: Point = Point(0.0, 0.0), strokeWidth: Float = 5, headLength: Float = 10, headAngle: Float = 20, isDashed: Bool = false, isFilled: Bool = false, startAnnotation: Annotation? = nil, endAnnotation: Annotation? = nil) {