Fix WebView2 Initialization In Read-Only PerfView Installations

src/PerfView.Tests/GuiUtilities/WebBrowserWindowUserDataFolderTests.cs

@@ -0,0 +1,51 @@
+using System;
+using System.IO;
+using PerfView.GuiUtilities;
+using Xunit;
+
+namespace PerfViewTests.GuiUtilities
+{
+    public class WebBrowserWindowUserDataFolderTests
+    {
+        [Theory]
+        [InlineData(@"C:\Users\Test\AppData\Local", @"C:\Users\Test\AppData\Local\PerfView\WebView2")]
+        [InlineData(@"C:\Users\Test User\AppData\Local", @"C:\Users\Test User\AppData\Local\PerfView\WebView2")]
+        [InlineData("C:\\Users\\T\u00e9st\\AppData\\Local", "C:\\Users\\T\u00e9st\\AppData\\Local\\PerfView\\WebView2")]
+        [InlineData(@"C:\Users\Test\AppData\Local\", @"C:\Users\Test\AppData\Local\PerfView\WebView2")]
+        [InlineData(@"D:\LocalData", @"D:\LocalData\PerfView\WebView2")]
+        public void UserDataFolderIsUnderLocalApplicationData(string localApplicationData, string expected)
+        {
+            Assert.Equal(expected, WebBrowserWindow.GetUserDataFolder(localApplicationData));
+        }
+
+        [Fact]
+        public void UserDataFolderUsesWindowsLocalApplicationData()
+        {
+            string localApplicationData = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);
+
+            Assert.False(string.IsNullOrEmpty(localApplicationData));
+            Assert.Equal(
+                Path.Combine(localApplicationData, "PerfView", "WebView2"),
+                WebBrowserWindow.GetUserDataFolder(localApplicationData));
+        }
+
+        [Theory]
+        [InlineData(null)]
+        [InlineData("")]
+        [InlineData(" ")]
+        [InlineData("LocalData")]
+        [InlineData(@".\LocalData")]
+        [InlineData(@"..\LocalData")]
+        [InlineData(@"C:LocalData")]
+        [InlineData("C:")]
+        [InlineData(@"\LocalData")]
+        [InlineData("/LocalData")]
+        public void MissingOrRelativeLocalApplicationDataIsRejected(string localApplicationData)
+        {
+            var exception = Assert.Throws<InvalidOperationException>(
+                () => WebBrowserWindow.GetUserDataFolder(localApplicationData));
+
+            Assert.Contains("LocalApplicationData", exception.Message);
+        }
+    }
+}

src/PerfView/GuiUtilities/WebBrowser/WebBrowser.xaml.cs

@@ -6,7 +6,6 @@
 using System.Windows.Input;
 using Microsoft.Web.WebView2.Core;
 using Microsoft.Web.WebView2.Wpf;
-using Utilities;
 
 
 namespace PerfView.GuiUtilities
@@ -141,7 +140,8 @@ private void Browser_Loaded(object sender, RoutedEventArgs e)
                 return;
             }
 
-            var userDataFolder = Path.Combine(SupportFiles.SupportFileDir, "WebView2");
+            // Support files may be installed in a read-only directory; browser state must remain per-user.
+            var userDataFolder = GetUserDataFolder(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData));
             Directory.CreateDirectory(userDataFolder);
 
             var environmentAwaiter = CoreWebView2Environment
@@ -176,6 +176,19 @@ private void Browser_Loaded(object sender, RoutedEventArgs e)
             });
         }
 
+        internal static string GetUserDataFolder(string localApplicationData)
+        {
+            // On Windows, roots such as "C:" and "\" still depend on the current directory or drive.
+            if (string.IsNullOrWhiteSpace(localApplicationData) ||
+                !Path.IsPathRooted(localApplicationData) ||
+                Path.GetPathRoot(localApplicationData).Length < 3)
+            {
+                throw new InvalidOperationException("A fully qualified LocalApplicationData directory is required for PerfView's WebView2 browser data.");
+            }
+
+            return Path.Combine(localApplicationData, "PerfView", "WebView2");
+        }
+
         private const string CloseWindowMessage = "PerfView.CloseWindow";
         private const string CloseWindowMessageJson = "\"" + CloseWindowMessage + "\"";
         private const string CloseWindowOnEscapeScript = @"