[bfix][feat][conf]Darwin/CG fixes (#55)

* Small fixes for cross-(Darwin)-platform View hosting:
- Fixed availability annotations on QuartzRenderer, Color
- Add a method to QuartzRenderer to make a CGImage
- Improve fallback when converting Color -> CGColor

* Make it easier to flip to the portable-Darwin subset of products

* Simplified a BarChart method

Author: karwa

Package.swift

@@ -45,6 +45,8 @@ let platformProducts: [Product] =  [
   .library(name: "AGGRenderer", targets: ["AGGRenderer"]),
 ]
 
+// Building for iOS/tvOS/watchOS:
+// Change the condition below to "!os(macOS)".
 #elseif os(macOS)
 
 let platformTargets: [Target] = [
@@ -93,13 +95,7 @@ let platformProducts: [Product] =  [
   .library(name: "QuartzRenderer", targets: ["QuartzRenderer"])
 ]
 
-#elseif os(iOS) || os(tvOS) || os(watchOS)
-
-// Note: This isn't the correct way to do this, because
-// "#if os(...)" depends on the build OS, not the target OS.
-// But SwiftPM doesn't have platform-specific targets, so to make this work
-// on iOS/tvOS/watchOS, you have to comment out the AGG-related things on the macOS
-// configuration until it looks like this:
+#elseif os(iOS) || os(tvOS) || os(watchOS) || os(macOS)
 
 let platformTargets: [Target] = [
     .target(name: "SwiftPlot"),

Sources/QuartzRenderer/QuartzRenderer.swift

@@ -10,7 +10,7 @@ import AppKit
 import UIKit
 #endif
 
-@available(tvOS 13, watchOS 13, *)
+@available(tvOS 13.0, watchOS 6.0, *)
 public class QuartzRenderer: Renderer {
     static let colorSpace = CGColorSpaceCreateDeviceRGB()
     static let bitmapInfo = CGImageAlphaInfo.premultipliedFirst.rawValue
@@ -482,6 +482,10 @@ public class QuartzRenderer: Renderer {
             #endif
         }
     }
+    
+    public func makeCGImage() -> CGImage? {
+        context.makeImage()
+    }
 }
 
 // - Helpers
@@ -534,6 +538,7 @@ fileprivate extension NSImage {
     }
 }
 #elseif canImport(UIKit)
+@available(tvOS 13.0, watchOS 6.0, *)
 fileprivate extension UIImage {
     func writePng(to url: URL, options: Data.WritingOptions = .atomic) throws {
         guard let data = pngData() else { throw QuartzRenderer.WritePNGError.imageCouldNotBeRendered }

Sources/SwiftPlot/BarChart.swift

@@ -73,16 +73,9 @@ public class BarGraph<T:LosslessStringConvertible,U:FloatConvertible>: Plot {
                           color: Color = Color.lightBlue,
                           hatchPattern: BarGraphSeriesOptions.Hatching = .none,
                           graphOrientation: BarGraph.GraphOrientation = .vertical){
-        var values = [Pair<T,U>]()
-        for i in 0..<x.count {
-            values.append(Pair<T,U>(x[i], y[i]))
-        }
-        let s = Series<T,U>(values: values,
-                            label: label,
-                            color: color,
-                            hatchPattern: hatchPattern)
-        addSeries(s)
-        self.graphOrientation = graphOrientation
+        self.addSeries(values: zip(x, y).map { Pair($0.0, $0.1) },
+                       label: label, color: color, hatchPattern: hatchPattern,
+                       graphOrientation: graphOrientation)
     }
 }
 

Sources/SwiftPlot/Color.swift

@@ -32,22 +32,25 @@ public struct Color {
 
 #if canImport(CoreGraphics)
 import CoreGraphics
+
+fileprivate let RGBColorSpace = CGColorSpaceCreateDeviceRGB()
+
 public extension Color {
-    @available(tvOS 13, watchOS 13, *)
+    @available(tvOS 13.0, watchOS 6.0, *)
     var cgColor : CGColor {
-      if #available(OSX 10.15, iOS 13, *) {
-        return CGColor(srgbRed: CGFloat(r),
-                       green: CGFloat(g),
-                       blue: CGFloat(b),
-                       alpha: CGFloat(a))
-      } else {
-        #if !os(tvOS) && !os(watchOS) // Shouldn't be necessary, but it is.
-        return CGColor(red: CGFloat(r),
-                       green: CGFloat(g),
-                       blue: CGFloat(b),
-                       alpha: CGFloat(a))
-        #endif
-      }
+        if #available(OSX 10.15, iOS 13.0, *) {
+            return CGColor(srgbRed: CGFloat(r),
+                           green: CGFloat(g),
+                           blue: CGFloat(b),
+                           alpha: CGFloat(a))
+        } else {
+            var tuple = (CGFloat(r), CGFloat(g), CGFloat(b), CGFloat(a))
+            return withUnsafePointer(to: &tuple) { tupPtr in
+                return tupPtr.withMemoryRebound(to: CGFloat.self, capacity: 4) { floatPtr in
+                    return CGColor(colorSpace: RGBColorSpace, components:floatPtr)!
+                }
+            }
+        }
     }
 }
 #endif