feat: cache SVG previews in File Explorer

src/modules/previewpane/SvgPreviewHandler/SvgPreviewControl.cs

@@ -2,6 +2,7 @@
 // The Microsoft Corporation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.IO;
 using System.Net.Http;
 using System.Reflection;
 using System.Runtime.CompilerServices;
@@ -106,7 +107,7 @@ public override void DoPreview<T>(T dataSource)
                 return;
             }
 
-            CleanupWebView2UserDataFolder();
+            EnsureWebView2UserDataFolder();
 
             string svgData = null;
             bool blocked = false;
@@ -251,23 +252,27 @@ private void AddWebViewControl(string svgData)
                     _browser.CoreWebView2.AddWebResourceRequestedFilter("*", CoreWebView2WebResourceContext.All);
                     _browser.CoreWebView2.WebResourceRequested += CoreWebView2_BlockExternalResources;
 
-                    string generatedPreview = _previewGenerator.GeneratePreview(svgData);
+                    var cacheKey = SvgPreviewCacheHelper.BuildCacheKey(
+                        "v1",
+                        VirtualHostName,
+                        svgData,
+                        _settings.ColorMode.ToString(),
+                        _settings.ThemeColor.ToArgb().ToString(),
+                        _settings.SolidColor.ToArgb().ToString(),
+                        _settings.CheckeredShade.ToString());
 
-                    // WebView2.NavigateToString() limitation
-                    // See https://learn.microsoft.com/dotnet/api/microsoft.web.webview2.core.corewebview2.navigatetostring?view=webview2-dotnet-1.0.864.35#remarks
-                    // While testing the limit, it turned out it is ~1.5MB, so to be on a safe side we go for 1.5m bytes
-                    if (generatedPreview.Length > 1_500_000)
-                    {
-                        string filename = _webView2UserDataFolder + "\\" + Guid.NewGuid().ToString() + ".html";
-                        File.WriteAllText(filename, generatedPreview);
-                        _localFileURI = new Uri(filename);
-                        _browser.Source = _localFileURI;
-                    }
-                    else
+                    var cacheFolder = Path.Combine(_webView2UserDataFolder, "Cache");
+                    var cacheFilePath = SvgPreviewCacheHelper.GetCacheFilePath(cacheFolder, cacheKey);
+
+                    if (!File.Exists(cacheFilePath) || new FileInfo(cacheFilePath).Length == 0)
                     {
-                        _browser.NavigateToString(generatedPreview);
+                        string generatedPreview = _previewGenerator.GeneratePreview(svgData);
+                        File.WriteAllText(cacheFilePath, generatedPreview);
                     }
 
+                    _localFileURI = new Uri(cacheFilePath);
+                    _browser.Source = _localFileURI;
+
                     Controls.Add(_browser);
                 }
                 catch (Exception)
@@ -318,17 +323,11 @@ private void PreviewError<T>(Exception exception, T dataSource)
         /// <summary>
         /// Cleanup the previously created tmp html files from svg files bigger than 2MB.
         /// </summary>
-        private void CleanupWebView2UserDataFolder()
+        private void EnsureWebView2UserDataFolder()
         {
             try
             {
-                // Cleanup temp dir
-                var dir = new DirectoryInfo(_webView2UserDataFolder);
-
-                foreach (var file in dir.EnumerateFiles("*.html"))
-                {
-                    file.Delete();
-                }
+                Directory.CreateDirectory(_webView2UserDataFolder);
             }
             catch (Exception)
             {

src/modules/previewpane/SvgThumbnailProvider/SvgThumbnailProvider.cs

@@ -100,7 +100,7 @@ private static string AssemblyDirectory
         /// <param name="cx">The maximum thumbnail size, in pixels.</param>
         public Bitmap GetThumbnailImpl(uint cx)
         {
-            CleanupWebView2UserDataFolder();
+            EnsureWebView2UserDataFolder();
 
             if (cx == 0 || cx > MaxThumbnailSize)
             {
@@ -177,27 +177,24 @@ public Bitmap GetThumbnailImpl(uint cx)
                         }
                     };
 
-                    // WebView2.NavigateToString() limitation
-                    // See https://learn.microsoft.com/dotnet/api/microsoft.web.webview2.core.corewebview2.navigatetostring?view=webview2-dotnet-1.0.864.35#remarks
-                    // While testing the limit, it turned out it is ~1.5MB, so to be on a safe side we go for 1.5m bytes
                     SvgContentsReady.Wait();
                     if (string.IsNullOrEmpty(SvgContents) || !SvgContents.Contains("svg"))
                     {
                         thumbnailDone.Set();
                         return;
                     }
 
-                    if (SvgContents.Length > 1_500_000)
-                    {
-                        string filename = _webView2UserDataFolder + "\\" + Guid.NewGuid().ToString() + ".html";
-                        File.WriteAllText(filename, SvgContents);
-                        _localFileURI = new Uri(filename);
-                        _browser.Source = _localFileURI;
-                    }
-                    else
+                    var cacheKey = SvgPreviewCacheHelper.BuildCacheKey("v1", VirtualHostName, SvgContents);
+                    var cacheFolder = Path.Combine(_webView2UserDataFolder, "Cache");
+                    var cacheFilePath = SvgPreviewCacheHelper.GetCacheFilePath(cacheFolder, cacheKey);
+
+                    if (!File.Exists(cacheFilePath) || new FileInfo(cacheFilePath).Length == 0)
                     {
-                        _browser.NavigateToString(SvgContents);
+                        File.WriteAllText(cacheFilePath, SvgContents);
                     }
+
+                    _localFileURI = new Uri(cacheFilePath);
+                    _browser.Source = _localFileURI;
                 }
                 catch (Exception ex)
                 {
@@ -344,17 +341,11 @@ public void Dispose()
         /// <summary>
         /// Cleanup the previously created tmp html files from svg files bigger than 2MB.
         /// </summary>
-        private void CleanupWebView2UserDataFolder()
+        private void EnsureWebView2UserDataFolder()
         {
             try
             {
-                // Cleanup temp dir
-                var dir = new DirectoryInfo(_webView2UserDataFolder);
-
-                foreach (var file in dir.EnumerateFiles("*.html"))
-                {
-                    file.Delete();
-                }
+                Directory.CreateDirectory(_webView2UserDataFolder);
             }
             catch (Exception)
             {

src/modules/previewpane/UnitTests-SvgPreviewHandler/SvgPreviewHandlerHelperTests.cs

@@ -99,5 +99,31 @@ public void CheckBlockedElementsShouldReturnFalseIfSvgDataIsNullOrWhiteSpaces(st
             // Assert
             Assert.IsFalse(foundFilteredElement);
         }
+
+        [TestMethod]
+        public void BuildCacheKeyShouldReturnSameValueForSameInputs()
+        {
+            // Arrange
+            var firstKey = SvgPreviewCacheHelper.BuildCacheKey("v1", "svg-preview", "sample data");
+
+            // Act
+            var secondKey = SvgPreviewCacheHelper.BuildCacheKey("v1", "svg-preview", "sample data");
+
+            // Assert
+            Assert.AreEqual(firstKey, secondKey);
+        }
+
+        [TestMethod]
+        public void BuildCacheKeyShouldReturnDifferentValueForDifferentInputs()
+        {
+            // Arrange
+            var firstKey = SvgPreviewCacheHelper.BuildCacheKey("v1", "svg-preview", "sample data");
+
+            // Act
+            var secondKey = SvgPreviewCacheHelper.BuildCacheKey("v1", "svg-preview", "different data");
+
+            // Assert
+            Assert.AreNotEqual(firstKey, secondKey);
+        }
     }
 }

src/modules/previewpane/common/Properties/AssemblyInfo.cs

@@ -0,0 +1,5 @@
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("PowerToys.SvgPreviewHandler")]
+[assembly: InternalsVisibleTo("PowerToys.SvgThumbnailProvider")]
+[assembly: InternalsVisibleTo("Preview.SvgPreviewHandler.UnitTests")]

src/modules/previewpane/common/Utilities/SvgPreviewCacheHelper.cs

@@ -0,0 +1,33 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.IO;
+using System.Security.Cryptography;
+using System.Text;
+
+namespace Common.Utilities
+{
+    internal static class SvgPreviewCacheHelper
+    {
+        internal static string BuildCacheKey(params string[] cacheInputs)
+        {
+            var cacheKeyBuilder = new StringBuilder();
+
+            foreach (var input in cacheInputs)
+            {
+                cacheKeyBuilder.Append(input ?? string.Empty);
+                cacheKeyBuilder.Append('\n');
+            }
+
+            return Convert.ToHexString(SHA256.HashData(Encoding.UTF8.GetBytes(cacheKeyBuilder.ToString())));
+        }
+
+        internal static string GetCacheFilePath(string cacheRootFolder, string cacheKey)
+        {
+            Directory.CreateDirectory(cacheRootFolder);
+            return Path.Combine(cacheRootFolder, $"{cacheKey}.html");
+        }
+    }
+}