Some refactoring for the Skia Demos

Now to add a new demo method you only need to add it to the
SkiaSharp.Demos file and update the sampleList member at the bottom
of the file.

samples/SharedDemo/SkiaSharp.Demos.cs

@@ -1,9 +1,10 @@
 using System;
 using SkiaSharp;
+using System.Linq;
 
-namespace Skia.Forms.Demo
+namespace SkiaSharp
 {
-	public class DrawHelpers
+	public class Demos
 	{
 		#pragma warning disable 414
 		static readonly SKColor XamLtBlue = new SKColor (0x34, 0x98, 0xdb);
@@ -171,6 +172,38 @@ namespace Skia.Forms.Demo
 				}
 			}
 		}
+
+		[Flags]
+		public enum Platform
+		{
+			iOS = 1,
+			Android = 2,
+			OSX = 4,
+			All = 0xFFFF,
+		}
+
+		class Sample 
+		{
+			public string Title { get; set; }
+			public Action <SKCanvas, int, int> Method { get; set; }
+			public Platform Platform { get; set; }
+		}
+
+		public static string [] SamplesForPlatform (Platform platform)
+		{
+			return sampleList.Where (s => 0 != (s.Platform & platform)).Select (s => s.Title).ToArray ();
+		}
+
+		public static Action <SKCanvas, int, int> MethodForSample (string title)
+		{
+			return sampleList.Where (s => s.Title == title).First ().Method;
+		}
+
+		static Sample [] sampleList = new Sample[] {
+			new Sample {Title="Xamagon", Method = DrawXamagon, Platform = Platform.All},
+			new Sample {Title="Text Sample", Method = TextSample, Platform = Platform.All},
+			new Sample {Title="Gradient Sample", Method = DrawGradient, Platform = Platform.All},
+		};
 	}
 }
 

samples/Skia.Forms.Demo/Skia.Forms.Demo.cs

@@ -21,33 +21,18 @@ namespace Skia.Forms.Demo
 				BarTextColor = Xamarin.Forms.Color.White,
 			};
 
-			listView.ItemsSource = new [] {"Xamagon", "Text Sample", "Gradient Sample"};
+			listView.ItemsSource = Demos.SamplesForPlatform (Demos.Platform.iOS | Demos.Platform.Android);
 
 			listView.ItemSelected += (sender, e) => {
 				if (e.SelectedItem == null) return;
 				listView.SelectedItem = null;
 
 				navPage.PushAsync (new ContentPage {
-					Content = new SkiaView  (GetDrawHandler (e.SelectedItem.ToString ())),
+					Content = new SkiaView  (SkiaSharp.Demos.MethodForSample (e.SelectedItem.ToString ())),
 				});
 			};
 		}
 
-		Action <SKCanvas, int, int> GetDrawHandler (string selectedItem)
-		{
-			switch (selectedItem) {
-
-			case "Xamagon":
-				return DrawHelpers.DrawXamagon;
-			case "Text Sample":
-				return DrawHelpers.TextSample;
-			case "Gradient Sample":
-				return DrawHelpers.DrawGradient;
-			}
-
-			throw new NotImplementedException ();
-		}
-
 		protected override void OnStart ()
 		{
 			// Handle when your app starts

samples/Skia.Forms.Demo/Skia.Forms.Demo.csproj

@@ -32,9 +32,11 @@
   <ItemGroup>
     <Compile Include="Skia.Forms.Demo.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
-    <Compile Include="DrawHelpers.cs" />
     <Compile Include="ISkiaViewController.cs" />
     <Compile Include="SkiaView.cs" />
+    <Compile Include="..\SharedDemo\SkiaSharp.Demos.cs">
+      <Link>SkiaSharp.Demos.cs</Link>
+    </Compile>
   </ItemGroup>
   <Import Project="$(MSBuildExtensionsPath32)\Microsoft\Portable\$(TargetFrameworkVersion)\Microsoft.Portable.CSharp.targets" />
   <Import Project="packages\Xamarin.Forms.1.3.5.6335\build\portable-win+net45+wp80+MonoAndroid10+MonoTouch10+Xamarin.iOS10\Xamarin.Forms.targets" Condition="Exists('packages\Xamarin.Forms.1.3.5.6335\build\portable-win+net45+wp80+MonoAndroid10+MonoTouch10+Xamarin.iOS10\Xamarin.Forms.targets')" />

samples/Skia.OSX.Demo/Main.storyboard

@@ -85,9 +85,9 @@
                         <autoresizingMask key="autoresizingMask"/>
                         <subviews>
                             <popUpButton verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="mnJ-8z-WRI">
-                                <rect key="frame" x="334" y="17" width="129" height="26"/>
+                                <rect key="frame" x="258" y="17" width="205" height="26"/>
                                 <constraints>
-                                    <constraint firstAttribute="width" constant="124" id="3Ya-mE-NFc"/>
+                                    <constraint firstAttribute="width" constant="200" id="3Ya-mE-NFc"/>
                                     <constraint firstAttribute="height" constant="21" id="PW1-2o-QII"/>
                                 </constraints>
                                 <popUpButtonCell key="cell" type="push" bezelStyle="rounded" alignment="left" lineBreakMode="truncatingTail" borderStyle="borderAndBezel" imageScaling="proportionallyDown" inset="2" id="5te-c2-WKW">

samples/Skia.OSX.Demo/SkaiView.cs

@@ -14,13 +14,15 @@ namespace Skia.OSX.Demo
 
 		public SkaiView (IntPtr handle) : base (handle)
 		{
-			onDrawCallback = Skia.Forms.Demo.DrawHelpers.DrawXamagon;
 		}
 
 		public override void DrawRect (CoreGraphics.CGRect dirtyRect)
 		{
 			base.DrawRect (dirtyRect);
 
+			if (onDrawCallback == null)
+				return;
+
 			// Just not that sharp using the scale pixel scale only
 			// Going going 2x Pixel Scale
 			var screenScale = (int)NSScreen.MainScreen.BackingScaleFactor * 2;

samples/Skia.OSX.Demo/Skia.OSX.Demo.csproj

@@ -80,12 +80,12 @@
     <Compile Include="SkaiView.designer.cs">
       <DependentUpon>SkaiView.cs</DependentUpon>
     </Compile>
-    <Compile Include="..\Skia.Forms.Demo\DrawHelpers.cs">
-      <Link>DrawHelpers.cs</Link>
-    </Compile>
     <Compile Include="AppDelegate.designer.cs">
       <DependentUpon>AppDelegate.cs</DependentUpon>
     </Compile>
+    <Compile Include="..\SharedDemo\SkiaSharp.Demos.cs">
+      <Link>SkiaSharp.Demos.cs</Link>
+    </Compile>
   </ItemGroup>
   <ItemGroup>
     <InterfaceDefinition Include="Main.storyboard" />

samples/Skia.OSX.Demo/ViewController.cs

@@ -14,23 +14,14 @@ namespace Skia.OSX.Demo
 		public override void ViewDidLoad ()
 		{
 			base.ViewDidLoad ();
-			PopUpButton.AddItems (new [] {"Xamagon", "Text", "Gradient"});
+			PopUpButton.AddItems (SkiaSharp.Demos.SamplesForPlatform (SkiaSharp.Demos.Platform.OSX));
 			PopUpButton.SelectItem (0);
+			SkiaView.OnDrawCallback = SkiaSharp.Demos.MethodForSample (PopUpButton.SelectedItem.Title);
 		}
 
 		partial void PopUpButtonAction (NSObject sender)
 		{
-			switch (PopUpButton.SelectedItem.Title) {
-			case "Xamagon":
-				SkiaView.OnDrawCallback = Skia.Forms.Demo.DrawHelpers.DrawXamagon;
-				break;
-			case "Text":
-				SkiaView.OnDrawCallback = Skia.Forms.Demo.DrawHelpers.TextSample;
-				break;
-			case "Gradient":
-				SkiaView.OnDrawCallback = Skia.Forms.Demo.DrawHelpers.DrawGradient;
-				break;
-			}
+			SkiaView.OnDrawCallback = SkiaSharp.Demos.MethodForSample (PopUpButton.SelectedItem.Title);
 		}
 
 		public override NSObject RepresentedObject {