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Fall back to the system browser when no web view engine is available #5298
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Merged
Gabriel Dufresne (GabrielDuf)
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fix/5285-webview2-missing-crash
Aug 19, 2026
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255 changes: 255 additions & 0 deletions
255
src/UniGetUI.Avalonia/Infrastructure/NativeWebViewSupport.cs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,255 @@ | ||
| using System; | ||
| using System.IO; | ||
| using System.Runtime.InteropServices; | ||
| using System.Runtime.Versioning; | ||
| using Microsoft.Win32; | ||
| using UniGetUI.Core.Logging; | ||
| using UniGetUI.Core.Tools; | ||
|
|
||
| namespace UniGetUI.Avalonia.Infrastructure; | ||
|
|
||
| /// <summary> | ||
| /// Tells whether the embedded browser (Avalonia's NativeWebView) can actually be hosted on | ||
| /// this machine, so the Help and Release Notes pages can show an "Open in browser" fallback | ||
| /// instead of embedding a control that blows up while initializing. | ||
| /// | ||
| /// #5285: Avalonia picks the WebView2 (Chromium) backend only when it finds the Edge WebView2 | ||
| /// runtime in the registry. When it doesn't, it silently falls back to the legacy EdgeHTML | ||
| /// backend (Windows.Web.UI.Interop.WebViewControl). That component was removed from Windows 10 | ||
| /// together with legacy Edge, so creating it throws InvalidOperationException (0x80131509, | ||
| /// "Unexpected HRESULT ... from a call to a COM component"). The throw happens inside an | ||
| /// `async void` continuation deep in NativeWebViewControlHost, so nothing at the call site can | ||
| /// catch it: it reaches the dispatcher as an unhandled exception and kills the process. | ||
| /// Portable (zip) installs are the usual victims, since the installer is what normally brings | ||
| /// the WebView2 runtime along. | ||
| /// | ||
| /// The detection below deliberately mirrors Avalonia's own ManagedWebView2Loader lookup, so | ||
| /// this class and Avalonia agree on which backend is about to be used. | ||
| /// </summary> | ||
| internal static class NativeWebViewSupport | ||
| { | ||
| private const string EDGE_UPDATE_CLIENTSTATE_KEY = @"Software\Microsoft\EdgeUpdate\ClientState"; | ||
| private const string BROWSER_FOLDER_OVERRIDE_VAR = "WEBVIEW2_BROWSER_EXECUTABLE_FOLDER"; | ||
|
|
||
| // EdgeUpdate channel identifiers, in the order Avalonia probes them. | ||
| private static readonly string[] CHANNEL_GUIDS = | ||
| [ | ||
| "{F3017226-FE2A-4295-8BDF-00C3A9A7E4C5}", // Stable | ||
| "{2CD8A007-E189-409D-A2C8-9AF4EF3C72AA}", // Beta | ||
| "{0D50BFEC-CD6A-4F9A-964C-C7416E3ACB10}", // Dev | ||
| "{65C35B14-6C1D-4122-AC46-7148CC9D6497}", // Canary | ||
| "{BE59E8FD-089A-411B-A3B0-051D9E417818}", // Internal | ||
| ]; | ||
|
|
||
| // Avalonia types that surface web view *initialization* failures: the two control hosts | ||
| // that await the adapter from an `async void`, the factory that picks the backend, and | ||
| // the Windows adapters themselves. The failing frames are the only reliable marker, since | ||
| // the exception is a plain InvalidOperationException/COMException with no web view | ||
| // specific type or message. | ||
| // | ||
| // Deliberately excludes plain `Avalonia.Controls.NativeWebView` frames: that class also | ||
| // raises NavigationStarted/NavigationCompleted, so matching it would silently swallow | ||
| // bugs in our own event handlers instead of letting them surface. | ||
| private static readonly string[] WEBVIEW_FRAME_MARKERS = | ||
| [ | ||
| "Avalonia.Controls.NativeWebViewControlHost", | ||
| "Avalonia.Controls.NativeWebViewCompositorHost", | ||
| "Avalonia.Controls.WebViewAdapter", | ||
| "Avalonia.Controls.Win.WebView1", | ||
| "Avalonia.Controls.Win.WebView2", | ||
| ]; | ||
|
|
||
| private static bool? _isAvailable; | ||
| private static bool _failedAtRuntime; | ||
|
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| /// <summary> | ||
| /// Raised (on the UI thread) when a web view that was believed to work failed to | ||
| /// initialize, so pages currently showing one can switch to their fallback content. | ||
| /// </summary> | ||
| public static event Action? BecameUnavailable; | ||
|
|
||
| /// <summary> | ||
| /// False when embedding a web view is known to fail, in which case callers must not add | ||
| /// a <see cref="Views.Controls.UniGetUiWebView"/> to the visual tree. | ||
| /// </summary> | ||
| public static bool IsAvailable | ||
| { | ||
| get | ||
| { | ||
| if (_isAvailable is { } cached) | ||
| return cached; | ||
|
|
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| bool available = DetectAvailability(); | ||
| _isAvailable = available; | ||
| return available; | ||
| } | ||
| } | ||
|
|
||
| /// <summary> | ||
| /// Message explaining why the embedded browser is unavailable, ready to show to the user. | ||
| /// </summary> | ||
| public static string UnavailableReason | ||
| { | ||
| get | ||
| { | ||
| // A runtime failure says nothing about what is or isn't installed, so it gets the | ||
| // generic wording rather than the (possibly wrong) "not installed" one. | ||
| if (!_failedAtRuntime) | ||
| { | ||
| if (OperatingSystem.IsLinux()) | ||
| return CoreTools.Translate("The built-in browser is not supported on Linux yet."); | ||
|
|
||
| if (OperatingSystem.IsWindows()) | ||
| return CoreTools.Translate("The built-in browser requires the Microsoft Edge WebView2 Runtime, which is not installed on this computer."); | ||
| } | ||
|
|
||
| return CoreTools.Translate("The built-in browser could not be loaded on this computer."); | ||
| } | ||
| } | ||
|
|
||
| /// <summary> | ||
| /// Records that the embedded browser cannot be used, so later navigations go straight to | ||
| /// the fallback instead of retrying a code path that is known to crash. | ||
| /// </summary> | ||
| public static void MarkUnavailable() | ||
| { | ||
| if (_isAvailable is false) | ||
| return; | ||
|
|
||
| _isAvailable = false; | ||
| _failedAtRuntime = true; | ||
|
|
||
| try | ||
| { | ||
| BecameUnavailable?.Invoke(); | ||
| } | ||
| catch (Exception ex) | ||
| { | ||
| // Called from the dispatcher's unhandled-exception handler: letting anything | ||
| // escape here would defeat the point of catching the failure in the first place. | ||
| Logger.Error("Could not switch the open page to its built-in-browser fallback"); | ||
| Logger.Error(ex); | ||
| } | ||
| } | ||
|
|
||
| /// <summary> | ||
| /// Whether <paramref name="exception"/> came out of web view initialization, and can | ||
| /// therefore be swallowed instead of taking the process down. | ||
| /// </summary> | ||
| public static bool IsWebViewFailure(Exception? exception) | ||
| { | ||
| for (Exception? current = exception; current is not null; current = current.InnerException) | ||
| { | ||
| if (current is AggregateException aggregate) | ||
| { | ||
| foreach (Exception inner in aggregate.Flatten().InnerExceptions) | ||
| { | ||
| if (HasWebViewFrame(inner)) | ||
| return true; | ||
| } | ||
| } | ||
|
|
||
| if (HasWebViewFrame(current)) | ||
| return true; | ||
| } | ||
|
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| return false; | ||
| } | ||
|
|
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| private static bool HasWebViewFrame(Exception exception) | ||
| { | ||
| if (exception.StackTrace is not { Length: > 0 } trace) | ||
| return false; | ||
|
|
||
| foreach (string marker in WEBVIEW_FRAME_MARKERS) | ||
| { | ||
| if (trace.Contains(marker, StringComparison.Ordinal)) | ||
| return true; | ||
| } | ||
|
|
||
| return false; | ||
| } | ||
|
|
||
| private static bool DetectAvailability() | ||
| { | ||
| // WKWebView is part of the OS and always available. | ||
| if (OperatingSystem.IsMacOS()) | ||
| return true; | ||
|
|
||
| // WebKitGTK/WPE are not shipped with UniGetUI, and the Linux pages have always | ||
| // offered the fallback instead. | ||
| if (!OperatingSystem.IsWindows()) | ||
| return false; | ||
|
|
||
| try | ||
| { | ||
| bool found = HasWebView2Runtime(); | ||
| if (!found) | ||
| { | ||
| Logger.Warn("The Edge WebView2 runtime was not found; the built-in browser will be replaced " + | ||
| "by a link to the system browser (see issue #5285)"); | ||
| } | ||
|
|
||
| return found; | ||
| } | ||
| catch (Exception ex) | ||
| { | ||
| // A failed probe must not be treated as "runtime present": embedding the web view | ||
| // is the crashing path, showing the fallback is not. | ||
| Logger.Warn("Could not determine whether the Edge WebView2 runtime is installed"); | ||
| Logger.Warn(ex); | ||
| return false; | ||
| } | ||
| } | ||
|
|
||
| [SupportedOSPlatform("windows")] | ||
| private static bool HasWebView2Runtime() | ||
| { | ||
| string? overrideFolder = Environment.GetEnvironmentVariable(BROWSER_FOLDER_OVERRIDE_VAR); | ||
| if (!string.IsNullOrEmpty(overrideFolder) && File.Exists(GetLoaderPath(overrideFolder))) | ||
| return true; | ||
|
|
||
| foreach (RegistryHive hive in (ReadOnlySpan<RegistryHive>)[RegistryHive.LocalMachine, RegistryHive.CurrentUser]) | ||
| { | ||
| foreach (string channelGuid in CHANNEL_GUIDS) | ||
| { | ||
| if (HasRuntimeInRegistry(hive, channelGuid)) | ||
| return true; | ||
| } | ||
| } | ||
|
|
||
| return false; | ||
| } | ||
|
|
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| [SupportedOSPlatform("windows")] | ||
| private static bool HasRuntimeInRegistry(RegistryHive hive, string channelGuid) | ||
| { | ||
| using RegistryKey root = RegistryKey.OpenBaseKey(hive, RegistryView.Registry32); | ||
| using RegistryKey? channel = root.OpenSubKey($@"{EDGE_UPDATE_CLIENTSTATE_KEY}\{channelGuid}"); | ||
| if (channel is null) | ||
| return false; | ||
|
|
||
| foreach (string valueName in channel.GetValueNames()) | ||
| { | ||
| if (channel.GetValue(valueName) is not string { Length: > 0 } value) | ||
| continue; | ||
|
|
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| bool pointsAtRuntime = valueName is "EBWebView" | ||
| || (value.Contains("EBWebView", StringComparison.Ordinal) && Directory.Exists(value)); | ||
|
|
||
| if (pointsAtRuntime && File.Exists(GetLoaderPath(value))) | ||
| return true; | ||
| } | ||
|
|
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| return false; | ||
| } | ||
|
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| private static string GetLoaderPath(string browserFolder) | ||
| => Path.Combine(browserFolder, "EBWebView", RuntimeInformation.ProcessArchitecture switch | ||
| { | ||
| Architecture.Arm => "arm", | ||
| Architecture.Arm64 => "arm64", | ||
| Architecture.X86 => "x86", | ||
| _ => "x64", | ||
| }, "EmbeddedBrowserWebView.dll"); | ||
| } | ||
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