fix #11 - Add thumbnail generator to images

NoFences/FenceWindow.cs

@@ -3,10 +3,8 @@
 using NoFences.Win32;
 using Peter;
 using System;
-using System.Diagnostics;
 using System.Drawing;
 using System.IO;
-using System.Threading.Tasks;
 using System.Windows.Forms;
 using static NoFences.Win32.WindowUtil;
 
@@ -44,6 +42,8 @@ public partial class FenceWindow : Form
 
         private readonly ShellContextMenu shellContextMenu = new ShellContextMenu();
 
+        private readonly ThumbnailProvider thumbnailProvider = new ThumbnailProvider();
+
         private void ReloadFonts()
         {
             var family = new FontFamily("Segoe UI");
@@ -61,6 +61,7 @@ public FenceWindow(FenceInfo fenceInfo)
             //DesktopUtil.PreventMinimize(Handle);
             this.titleHeight = fenceInfo.TitleHeight;
             this.MouseWheel += FenceWindow_MouseWheel;
+            thumbnailProvider.IconThumbnailLoaded += ThumbnailProvider_IconThumbnailLoaded;
             if (titleHeight < 16 || titleHeight > 100)
                 titleHeight = 35;
 
@@ -305,8 +306,8 @@ private void FenceWindow_Paint(object sender, PaintEventArgs e)
 
                 scrollOffset = Math.Min(scrollOffset, scrollHeight);
             }
-            
-            
+
+
 
             // Click handlers
             if (shouldUpdateSelection && !hasSelectionUpdated)
@@ -323,7 +324,7 @@ private void FenceWindow_Paint(object sender, PaintEventArgs e)
 
         private void RenderEntry(Graphics g, FenceEntry entry, int x, int y)
         {
-            var icon = entry.ExtractIcon();
+            var icon = entry.ExtractIcon(thumbnailProvider);
             var name = entry.Name;
 
             var textPosition = new PointF(x, y + icon.Height + 5);
@@ -484,6 +485,11 @@ private void FenceWindow_MouseWheel(object sender, MouseEventArgs e)
             Invalidate();
         }
 
+        private void ThumbnailProvider_IconThumbnailLoaded(object sender, EventArgs e)
+        {
+            Invalidate();
+        }
+
         private bool ItemExists(string path)
         {
             return File.Exists(path) || Directory.Exists(path);

NoFences/Model/FenceEntry.cs

@@ -4,6 +4,7 @@
 using System;
 using System.IO;
 using NoFences.Win32;
+using NoFences.Util;
 
 namespace NoFences.Model
 {
@@ -30,9 +31,19 @@ public static FenceEntry FromPath(string path)
             else return null;
         }
 
-        public Icon ExtractIcon()
+        public Icon ExtractIcon(ThumbnailProvider thumbnailProvider)
         {
-            return Type == EntryType.File ? Icon.ExtractAssociatedIcon(Path) : IconUtil.FolderLarge;
+            if (Type == EntryType.File)
+            {
+                if (thumbnailProvider.IsSupported(Path))
+                    return thumbnailProvider.GenerateThumbnail(Path);
+                else
+                    return Icon.ExtractAssociatedIcon(Path);
+            }
+            else
+            {
+                return IconUtil.FolderLarge;
+            }
         }
 
         public void Open()

NoFences/NoFences.csproj

@@ -72,6 +72,7 @@
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Util\Extensions.cs" />
     <Compile Include="Util\ThrottledExecution.cs" />
+    <Compile Include="Util\ThumbnailProvider.cs" />
     <Compile Include="Win32\BlurUtil.cs" />
     <Compile Include="Win32\DesktopUtil.cs" />
     <Compile Include="Win32\DropShadow.cs" />

NoFences/Util/ThumbnailProvider.cs

@@ -0,0 +1,78 @@
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Drawing;
+using System.IO;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace NoFences.Util
+{
+    public class ThumbnailProvider
+    {
+        // Supported .NET images as per https://docs.microsoft.com/en-us/dotnet/api/system.drawing.image.fromfile
+        private static readonly string[] SupportedExtensions =
+        {
+            ".bmp",
+            ".gif",
+            ".jpg",
+            ".jpeg",
+            ".png",
+            ".tiff",
+            ".tif"
+        };
+
+        private class ThumbnailState
+        {
+            public Icon icon;
+        }
+
+        // Only allow 4 concurrent images to be decoded to try and prevent OOM errors
+        private readonly SemaphoreSlim semaphore = new SemaphoreSlim(4);
+        private readonly IDictionary<string, ThumbnailState> iconCache = new Dictionary<string, ThumbnailState>();
+        public event EventHandler IconThumbnailLoaded;
+
+        public bool IsSupported(string path)
+        {
+            return SupportedExtensions.Any(ext => path.EndsWith(ext));
+        }
+
+        public Icon GenerateThumbnail(string path)
+        {
+            if (!iconCache.ContainsKey(path))
+            {
+                return SubmitGeneratorTask(path).icon;
+            }
+            else
+            {
+                return iconCache[path].icon;
+            }
+        }
+
+        private ThumbnailState SubmitGeneratorTask(string path)
+        {
+            var state = new ThumbnailState() { icon = Icon.ExtractAssociatedIcon(path) };
+            iconCache[path] = state;
+
+            Task.Run(() =>
+            {
+                semaphore.Wait();
+                using (MemoryStream ms = new MemoryStream(File.ReadAllBytes(path)))
+                {
+                    using (var img = Image.FromStream(ms))
+                    {
+                        var thumb = (Bitmap)img.GetThumbnailImage(32, 32, () => false, IntPtr.Zero);
+                        var icon = Icon.FromHandle(thumb.GetHicon());
+                        state.icon = icon;
+                        IconThumbnailLoaded(this, new EventArgs());
+                        semaphore.Release();
+                        return icon;
+                    }
+                }
+            });
+            return state;
+        }
+
+    }
+}