From 0fb3035a0abae247b322e50167557acf70bfae8b Mon Sep 17 00:00:00 2001
From: Matthew Leibowitz <mattleibow@live.com>
Date: Tue, 4 Oct 2016 13:53:13 +0200
Subject: [PATCH] Added the Android Forms renderer

---
 .../SKGLViewRenderer.cs                       | 102 ++++++++++++++++++
 .../SkiaSharp.Views.Forms.Android.csproj      |   1 +
 2 files changed, 103 insertions(+)
 create mode 100644 source/SkiaSharp.Views.Forms/SkiaSharp.Views.Forms.Android/SKGLViewRenderer.cs

diff --git a/source/SkiaSharp.Views.Forms/SkiaSharp.Views.Forms.Android/SKGLViewRenderer.cs b/source/SkiaSharp.Views.Forms/SkiaSharp.Views.Forms.Android/SKGLViewRenderer.cs
new file mode 100644
index 000000000..c07070c9f
--- /dev/null
+++ b/source/SkiaSharp.Views.Forms/SkiaSharp.Views.Forms.Android/SKGLViewRenderer.cs
@@ -0,0 +1,102 @@
+using System;
+using System.ComponentModel;
+using Android.Content;
+using Android.Opengl;
+using Javax.Microedition.Khronos.Opengles;
+using Xamarin.Forms;
+using Xamarin.Forms.Platform.Android;
+
+using SKFormsView = SkiaSharp.Views.Forms.SKGLView;
+using SKNativeView = SkiaSharp.Views.SKGLSurfaceView;
+
+[assembly: ExportRenderer(typeof(SKFormsView), typeof(SkiaSharp.Views.Forms.SKGLViewRenderer))]
+
+namespace SkiaSharp.Views.Forms
+{
+	internal class SKGLViewRenderer : ViewRenderer<SKFormsView, SKNativeView>
+	{
+		protected override void OnElementChanged(ElementChangedEventArgs<SKFormsView> e)
+		{
+			if (e.OldElement != null)
+			{
+				var oldController = (ISKGLViewController)e.OldElement;
+
+				// unsubscribe from events
+				oldController.SurfaceInvalidated -= OnSurfaceInvalidated;
+			}
+
+			if (e.NewElement != null)
+			{
+				var newController = (ISKGLViewController)e.NewElement;
+
+				// create the native view
+				var view = new SKNativeView(Context);
+				view.SetRenderer(new Renderer(newController));
+				SetNativeControl(view);
+
+				// subscribe to events from the user
+				newController.SurfaceInvalidated += OnSurfaceInvalidated;
+
+				// start the rendering
+				SetRenderMode();
+			}
+
+			base.OnElementChanged(e);
+		}
+
+		protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
+		{
+			base.OnElementPropertyChanged(sender, e);
+
+			// refresh the render loop
+			if (e.PropertyName == SKFormsView.HasRenderLoopProperty.PropertyName)
+			{
+				SetRenderMode();
+			}
+		}
+
+		protected override void Dispose(bool disposing)
+		{
+			// detach all events before disposing
+			var controller = (ISKGLViewController)Element;
+			if (controller != null)
+			{
+				controller.SurfaceInvalidated -= OnSurfaceInvalidated;
+			}
+
+			base.Dispose(disposing);
+		}
+
+		// the user asked to repaint
+		private void OnSurfaceInvalidated(object sender, EventArgs eventArgs)
+		{
+			// if we aren't in a loop, then refresh once
+			if (!Element.HasRenderLoop)
+			{
+				Control.RequestRender();
+			}
+		}
+
+		private void SetRenderMode()
+		{
+			Control.RenderMode = Element.HasRenderLoop
+				? Rendermode.Continuously
+				: Rendermode.WhenDirty;
+		}
+
+		private class Renderer : SKNativeView.ISKRenderer
+		{
+			private readonly ISKGLViewController controller;
+
+			public Renderer(ISKGLViewController controller)
+			{
+				this.controller = controller;
+			}
+
+			public void OnDrawFrame(SKSurface surface, GRBackendRenderTargetDesc renderTarget)
+			{
+				controller.OnPaintSurface(new SKPaintGLSurfaceEventArgs(surface, renderTarget));
+			}
+		}
+	}
+}
diff --git a/source/SkiaSharp.Views.Forms/SkiaSharp.Views.Forms.Android/SkiaSharp.Views.Forms.Android.csproj b/source/SkiaSharp.Views.Forms/SkiaSharp.Views.Forms.Android/SkiaSharp.Views.Forms.Android.csproj
index 402476df2..d56ad5e04 100644
--- a/source/SkiaSharp.Views.Forms/SkiaSharp.Views.Forms.Android/SkiaSharp.Views.Forms.Android.csproj
+++ b/source/SkiaSharp.Views.Forms/SkiaSharp.Views.Forms.Android/SkiaSharp.Views.Forms.Android.csproj
@@ -84,6 +84,7 @@
   <ItemGroup>
     <Compile Include="Resources\Resource.designer.cs" />
     <Compile Include="SKCanvasViewRenderer.cs" />
+    <Compile Include="SKGLViewRenderer.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="packages.config" />