Added an animated gif sample

samples/FormsSample/Core/DetailContentsPage.xaml.cs

@@ -23,12 +23,25 @@ namespace SkiaSharpSample.FormsSample
 			get { return sample; }
 			set
 			{
+				// clean up the old sample
+				if (sample != null)
+				{
+					sample.RefreshRequested -= OnRefreshRequested;
+					sample.Destroy();
+				}
+
 				sample = value;
+				Title = sample?.Title;
 
-				sample.Init(RefreshSamples);
+				// prepare the sample
+				if (sample != null)
+				{
+					sample.RefreshRequested += OnRefreshRequested;
+					sample.Init();
+				}
 
-				Title = sample.Title;
-				RefreshSamples();
+				// refresh the view
+				OnRefreshRequested(null, null);
 			}
 		}
 
@@ -120,6 +133,11 @@ namespace SkiaSharpSample.FormsSample
 			}
 		}
 
+		private void OnRefreshRequested(object sender, EventArgs e)
+		{
+			RefreshSamples();
+		}
+
 		private void RefreshSamples()
 		{
 			if (canvas.IsVisible)

samples/MacSample/MacSample/MainViewController.cs

@@ -18,6 +18,13 @@ namespace SkiaSharpSample.MacSample
 
 		public void SetSample(SampleBase newSample)
 		{
+			// clean up the old sample
+			if (sample != null)
+			{
+				sample.RefreshRequested -= OnRefreshRequested;
+				sample.Destroy();
+			}
+
 			sample = newSample;
 
 			// set the title
@@ -30,14 +37,18 @@ namespace SkiaSharpSample.MacSample
 			}
 
 			// prepare the sample
-			sample?.Init(() =>
+			if (sample != null)
 			{
-				// refresh the view
-				canvas.SetNeedsDisplayInRect(canvas.Bounds);
-				glview.SetNeedsDisplayInRect(glview.Bounds);
-			});
+				sample.RefreshRequested += OnRefreshRequested;
+				sample.Init();
+			}
 
 			// refresh the view
+			OnRefreshRequested(null, null);
+		}
+
+		private void OnRefreshRequested(object sender, EventArgs e)
+		{
 			canvas.SetNeedsDisplayInRect(canvas.Bounds);
 			glview.SetNeedsDisplayInRect(glview.Bounds);
 		}

samples/SkiaSharpSample.Shared/SampleBase.cs

@@ -36,7 +36,7 @@ namespace SkiaSharpSample
 
 		protected abstract void OnDrawSample(SKCanvas canvas, int width, int height);
 
-		public async void Init(Action callback = null)
+		public async void Init()
 		{
 			// reset the matrix for the new sample
 			Matrix = SKMatrix.MakeIdentity();
@@ -47,7 +47,17 @@ namespace SkiaSharpSample
 
 				IsInitialized = true;
 
-				callback?.Invoke();
+				Refresh();
+			}
+		}
+
+		public void Destroy()
+		{
+			if (IsInitialized)
+			{
+				OnDestroy();
+
+				IsInitialized = false;
 			}
 		}
 
@@ -56,6 +66,10 @@ namespace SkiaSharpSample
 			return Task.FromResult(true);
 		}
 
+		protected virtual void OnDestroy()
+		{
+		}
+
 		public void Tap()
 		{
 			if (IsInitialized)
@@ -120,6 +134,13 @@ namespace SkiaSharpSample
 				Title.IndexOf(searchText, StringComparison.OrdinalIgnoreCase) != -1 ||
 				Description.IndexOf(searchText, StringComparison.OrdinalIgnoreCase) != -1;
 		}
+
+		public event EventHandler RefreshRequested;
+
+		protected void Refresh()
+		{
+			RefreshRequested?.Invoke(this, EventArgs.Empty);
+		}
 	}
 
 	public enum GestureState

samples/SkiaSharpSample.Shared/Samples/DecodeGifFramesSample.cs

@@ -0,0 +1,85 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using SkiaSharp;
+
+namespace SkiaSharpSample.Samples
+{
+	[Preserve(AllMembers = true)]
+	public class DecodeGifFramesSample : SampleBase
+	{
+		private int currentFrame = 0;
+		private SKCodec codec = null;
+		private SKImageInfo info = SKImageInfo.Empty;
+		private SKBitmap bitmap = null;
+		private CancellationTokenSource cts;
+		private SKCodecFrameInfo[] frames;
+		private TaskScheduler scheduler;
+
+		[Preserve]
+		public DecodeGifFramesSample()
+		{
+		}
+
+		public override string Title => "Decode Gif Frames";
+
+		public override SampleCategories Category => SampleCategories.BitmapDecoding;
+
+		protected override async Task OnInit()
+		{
+			await base.OnInit();
+
+			var stream = new SKManagedStream(SampleMedia.Images.AnimatedHeartGif, true);
+			codec = SKCodec.Create(stream);
+			frames = codec.FrameInfo;
+
+			info = codec.Info;
+			info = new SKImageInfo(info.Width, info.Height, SKImageInfo.PlatformColorType, SKAlphaType.Premul);
+
+			bitmap = new SKBitmap(info);
+
+			cts = new CancellationTokenSource();
+
+			scheduler = TaskScheduler.Current;
+			var loop = Task.Run(async () =>
+			{
+				while (!cts.IsCancellationRequested)
+				{
+					var duration = frames[currentFrame].Duration;
+					if (duration <= 0)
+						duration = 100;
+
+					await Task.Delay(duration, cts.Token);
+
+					// next frame
+					currentFrame++;
+					if (currentFrame >= frames.Length)
+						currentFrame = 0;
+
+					new Task(Refresh).Start(scheduler);
+				}
+			}, cts.Token);
+		}
+
+		protected override void OnDestroy()
+		{
+			base.OnDestroy();
+
+			codec?.Dispose();
+			codec = null;
+
+			cts.Cancel();
+		}
+
+		protected override void OnDrawSample(SKCanvas canvas, int width, int height)
+		{
+			canvas.Clear(SKColors.Black);
+
+			var opts = new SKCodecOptions(currentFrame, false);
+			if (codec?.GetPixels(info, bitmap.GetPixels(), opts) == SKCodecResult.Success)
+			{
+				canvas.DrawBitmap(bitmap, 0, 0);
+			}
+		}
+	}
+}

samples/SkiaSharpSample.Shared/SkiaSharpSample.Shared.projitems

@@ -17,6 +17,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)SampleBase.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)SampleMedia.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Samples\BitmapAnnotationSample.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Samples\DecodeGifFramesSample.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Samples\BitmapSubsetDecoderSample.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Samples\ManipulatedBitmapShaderSample.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Samples\PathMeasureSample.cs" />

samples/TvSample/TvSample/ViewController.cs

@@ -69,11 +69,29 @@ namespace SkiaSharpSample.TvSample
 
 		private void OnSampleSelected(SampleBase sample)
 		{
+			// clean up the old sample
+			if (currentSample != null)
+			{
+				currentSample.RefreshRequested -= OnRefreshRequested;
+				currentSample.Destroy();
+			}
+
 			// update the selected sample
 			currentSample = sample;
-			currentSample?.Init(canvas.SetNeedsDisplay);
 
-			// refresh the canvas
+			// prepare the sample
+			if (sample != null)
+			{
+				sample.RefreshRequested += OnRefreshRequested;
+				sample.Init();
+			}
+
+			// refresh the view
+			OnRefreshRequested(null, null);
+		}
+
+		private void OnRefreshRequested(object sender, EventArgs e)
+		{
 			canvas.SetNeedsDisplay();
 		}
 	}

samples/UWPSample/UWPSample/MainPage.xaml.cs

@@ -163,20 +163,31 @@ namespace SkiaSharpSample.UWPSample
 
 		private void SetSample(SampleBase newSample)
 		{
+			// clean up the old sample
+			if (sample != null)
+			{
+				sample.RefreshRequested -= OnRefreshRequested;
+				sample.Destroy();
+			}
+
 			sample = newSample;
 
 			// set the title
 			titleBar.Text = sample?.Title ?? "SkiaSharp for Windows";
 
 			// prepare the sample
-			sample?.Init(() =>
+			if (sample != null)
 			{
-				// refresh the view
-				canvas.Invalidate();
-				glview.Invalidate();
-			});
+				sample.RefreshRequested += OnRefreshRequested;
+				sample.Init();
+			}
 
 			// refresh the view
+			OnRefreshRequested(null, null);
+		}
+
+		private void OnRefreshRequested(object sender, EventArgs e)
+		{
 			canvas.Invalidate();
 			glview.Invalidate();
 		}

samples/WPFSample/WPFSample/MainWindow.xaml.cs

@@ -176,20 +176,31 @@ namespace SkiaSharpSample.WPFSample
 
 		private void SetSample(SampleBase newSample)
 		{
+			// clean up the old sample
+			if (sample != null)
+			{
+				sample.RefreshRequested -= OnRefreshRequested;
+				sample.Destroy();
+			}
+
 			sample = newSample;
 
 			// set the title
 			Title = sample?.Title ?? "SkiaSharp for WPF";
 
 			// prepare the sample
-			sample?.Init(() =>
+			if (sample != null)
 			{
-				// refresh the view
-				canvas.InvalidateVisual();
-				glhost.Child?.Invalidate();
-			});
+				sample.RefreshRequested += OnRefreshRequested;
+				sample.Init();
+			}
 
 			// refresh the view
+			OnRefreshRequested(null, null);
+		}
+
+		private void OnRefreshRequested(object sender, EventArgs e)
+		{
 			canvas.InvalidateVisual();
 			glhost.Child?.Invalidate();
 		}

samples/WindowsSample/WindowsSample/Form1.cs

@@ -41,7 +41,6 @@ namespace SkiaSharpSample.WindowsSample
 				{
 					// create the sample item
 					var menuItem = new ToolStripMenuItem(sample.Title, null, OnSampleSelected) { Tag = sample };
-					menuItem.Click += OnSampleSelected;
 					menu.DropDownItems.Add(menuItem);
 				}
 				// add to the menu bar
@@ -157,20 +156,31 @@ namespace SkiaSharpSample.WindowsSample
 
 		private void SetSample(SampleBase newSample)
 		{
+			// clean up the old sample
+			if (sample != null)
+			{
+				sample.RefreshRequested -= OnRefreshRequested;
+				sample.Destroy();
+			}
+
 			sample = newSample;
 
 			// set the title
 			Text = sample?.Title ?? "SkiaSharp for Windows";
 
 			// prepare the sample
-			sample?.Init(() =>
+			if (sample != null)
 			{
-				// refresh the view
-				canvas.Invalidate();
-				glview.Invalidate();
-			});
+				sample.RefreshRequested += OnRefreshRequested;
+				sample.Init();
+			}
 
 			// refresh the view
+			OnRefreshRequested(null, null);
+		}
+
+		private void OnRefreshRequested(object sender, EventArgs e)
+		{
 			canvas.Invalidate();
 			glview.Invalidate();
 		}