Fixes/wpe script callbacks

src/Avalonia.Controls.WebView.Core/Android/AndroidWebViewAdapter.cs

@@ -30,7 +30,6 @@ namespace Avalonia.Controls.Android;
 internal class AndroidWebViewAdapter : IWebViewAdapterWithFocus, IWebViewAdapterWithInputRedirect,
     IWebViewAdapterWithCookieManager, IAndroidWebViewPlatformHandle, IWebViewWithPrintWithOptions
 {
-    private const string PostAvWebViewMessageName = "postAvWebViewMessage";
     private static bool s_canSetDataDirectorySuffix = true;
     private readonly JavaScriptInterface _jsInterface;
     private WebView? _webView;
@@ -93,7 +92,7 @@ public AndroidWebViewAdapter(global::Android.Content.Context parentContext, Andr
             _webView.Settings.LoadWithOverviewMode = true;
             _webView.Settings.UseWideViewPort = true;
         }
-        _webView.AddJavascriptInterface(_jsInterface, PostAvWebViewMessageName);
+        _webView.AddJavascriptInterface(_jsInterface, WebViewHelper.PostAvWebViewMessageName);
         _webView.SetWebViewClient(new AvaloniaWebViewClient(this));
         _webView.SetWebChromeClient(new WebChromeClient());
 
@@ -661,14 +660,7 @@ public override void OnPageFinished(WebView? view, string? url)
                 return;
 
             adapter._webView.EvaluateJavascript(
-                """
-                 function invokeCSharpAction(data)
-                 {
-                    var message = typeof data === 'object' ? JSON.stringify(data) : data;
-                    postAvWebViewMessage.postMessage(message);
-                 }
-                 """
-                , null);
+                WebViewHelper.BuildInvokeCSharpActionScript(WebViewHelper.PostAvWebViewMessageName, stringify: true), null);
 
             if (!_lastNavigationCompleted)
             {

src/Avalonia.Controls.WebView.Core/Gtk/GtkWebViewAdapter.cs

@@ -16,8 +16,6 @@ namespace Avalonia.Controls.Gtk;
 
 internal abstract class GtkWebViewAdapter : IWebViewAdapterWithFocus, IGtkWebViewPlatformHandle, IWebViewWithPrintWithOptions
 {
-    private const string PostAvWebViewMessageName = "postAvWebViewMessage";
-
     internal enum WebKitLoadEvent
     {
         Started,
@@ -111,17 +109,11 @@ protected GtkWebViewAdapter(GtkWebViewEnvironmentRequestedEventArgs args)
         _webViewHandle = webkit_web_view_new_with_context(context);
 
         var contentManager = webkit_web_view_get_user_content_manager(WebViewHandle);
-        _scriptMessageReceivedSignal = new GtkSignal(contentManager, $"script-message-received::{PostAvWebViewMessageName}", s_scriptMessageReceivedCallback, this);
-        webkit_user_content_manager_register_script_message_handler(contentManager, PostAvWebViewMessageName);
+        _scriptMessageReceivedSignal = new GtkSignal(contentManager, $"script-message-received::{WebViewHelper.PostAvWebViewMessageName}", s_scriptMessageReceivedCallback, this);
+        webkit_user_content_manager_register_script_message_handler(contentManager, WebViewHelper.PostAvWebViewMessageName);
 
         var script = webkit_user_script_new(
-            $$"""
-              function invokeCSharpAction(data)
-              {
-                var message = typeof data === 'object' ? JSON.stringify(data) : data;
-                window.webkit.messageHandlers.{{PostAvWebViewMessageName}}.postMessage(message);
-              }
-              """,
+            WebViewHelper.BuildWebKitInvokeCSharpActionScript(),
             0, 0, IntPtr.Zero, IntPtr.Zero);
         webkit_user_content_manager_add_script(contentManager, script);
 

src/Avalonia.Controls.WebView.Core/Linux/Interop/WpeInterop.cs

@@ -137,11 +137,27 @@ public static partial void webkit_web_view_set_background_color(
     [LibraryImport(LibWpeWebKit)]
     public static partial IntPtr webkit_web_view_get_user_content_manager(IntPtr webView);
 
+    [LibraryImport(LibWpeWebKit)]
+    public static partial IntPtr webkit_user_content_manager_get_type();
+
+    [LibraryImport(LibWpeWebKit)]
+    public static partial IntPtr webkit_user_content_manager_new();
+
     [LibraryImport(LibWpeWebKit, StringMarshalling = StringMarshalling.Utf8)]
     [return: MarshalAs(UnmanagedType.Bool)]
     public static partial bool webkit_user_content_manager_register_script_message_handler(
         IntPtr manager, string name, string? worldName);
 
+    [LibraryImport(LibWpeWebKit)]
+    public static partial void webkit_user_content_manager_add_script(IntPtr manager, IntPtr userScript);
+
+    [LibraryImport(LibWpeWebKit, StringMarshalling = StringMarshalling.Utf8)]
+    public static partial IntPtr webkit_user_script_new(
+        string source, int injectedFrames, int injectionTime, IntPtr allowList, IntPtr blockList);
+
+    [LibraryImport(LibWpeWebKit)]
+    public static partial void webkit_user_script_unref(IntPtr userScript);
+
     [LibraryImport(LibWpeWebKit, StringMarshalling = StringMarshalling.Utf8)]
     public static partial void webkit_settings_set_user_agent(IntPtr settings, string? userAgent);
 

src/Avalonia.Controls.WebView.Core/Linux/WpeWebViewAdapter.cs

@@ -33,6 +33,7 @@ internal sealed unsafe class WpeWebViewAdapter
     private IntPtr _exportable;
     private IntPtr _viewBackend;
     private IntPtr _networkSession;
+    private IntPtr _userContentManager;
     private IntPtr _cookieManager;
     private bool _exportableOwnedByWebKit; // true when webkit_web_view_backend_new took ownership
     private PixelSize _currentSize;
@@ -231,15 +232,32 @@ private void Initialize(LinuxWpeWebViewEnvironmentRequestedEventArgs args, Contr
         else
             _networkSession = WpeInterop.webkit_network_session_get_default();
 
+        _userContentManager = WpeInterop.webkit_user_content_manager_new();
+        if (_userContentManager == IntPtr.Zero)
+            throw new InvalidOperationException("webkit_user_content_manager_new failed.");
+
         var webViewType = WpeInterop.webkit_web_view_get_type();
         var wkBackendType = WpeInterop.webkit_web_view_backend_get_type();
         var networkSessionType = WpeInterop.webkit_network_session_get_type();
-        var keys = new[] { "backend", "network-session" };
-        var values = new[] { new GValue(wkBackendType, wkBackend), new GValue(networkSessionType, _networkSession) };
-        _webView = WpeInterop.g_object_new_with_properties(webViewType, 2, keys, values);
+        var contentManagerType = WpeInterop.webkit_user_content_manager_get_type();
+        var keys = new[] { "backend", "network-session", "user-content-manager" };
+        var values = new[]
+        {
+            new GValue(wkBackendType, wkBackend),
+            new GValue(networkSessionType, _networkSession),
+            new GValue(contentManagerType, _userContentManager)
+        };
+        _webView = WpeInterop.g_object_new_with_properties(webViewType, 3, keys, values);
         if (_webView == IntPtr.Zero)
             throw new InvalidOperationException("webkit_web_view_new failed.");
 
+        var viewContentManager = WpeInterop.webkit_web_view_get_user_content_manager(_webView);
+        if (viewContentManager != IntPtr.Zero && viewContentManager != _userContentManager)
+        {
+            WpeInterop.g_object_unref(_userContentManager);
+            _userContentManager = WpeInterop.g_object_ref(viewContentManager);
+        }
+
         // 5. Start GLib pump (WebKit needs it for internal IPC)
         WpeGLibIntegration.Start();
 
@@ -258,11 +276,17 @@ private void Initialize(LinuxWpeWebViewEnvironmentRequestedEventArgs args, Contr
         ConnectSignal(_webView, "decide-policy", Marshal.GetFunctionPointerForDelegate(_decidePolicyCallback), selfPtr);
         ConnectSignal(_webView, "create", Marshal.GetFunctionPointerForDelegate(_createCallback), selfPtr);
 
-        // 8. Register invokeCSharpAction message handler
-        var contentManager = WpeInterop.webkit_web_view_get_user_content_manager(_webView);
-        WpeInterop.webkit_user_content_manager_register_script_message_handler(contentManager, "invokeCSharpAction", null);
-        ConnectSignal(contentManager, "script-message-received::invokeCSharpAction",
+        // 8. Register the message handler, connecting before registering so that no message can arrive unhandled.
+        ConnectSignal(_userContentManager, $"script-message-received::{WebViewHelper.PostAvWebViewMessageName}",
             Marshal.GetFunctionPointerForDelegate(_scriptMessageCallback), selfPtr);
+        WpeInterop.webkit_user_content_manager_register_script_message_handler(
+            _userContentManager, WebViewHelper.PostAvWebViewMessageName, null);
+
+        // Inject the invokeCSharpAction wrapper into all frames at document start.
+        var bridgeScript = WpeInterop.webkit_user_script_new(
+            WebViewHelper.BuildWebKitInvokeCSharpActionScript(), 0, 0, IntPtr.Zero, IntPtr.Zero);
+        WpeInterop.webkit_user_content_manager_add_script(_userContentManager, bridgeScript);
+        WpeInterop.webkit_user_script_unref(bridgeScript);
 
         // 9. Apply settings
         var settings = WpeInterop.webkit_web_view_get_settings(_webView);
@@ -1019,6 +1043,12 @@ public void Dispose()
             _webView = IntPtr.Zero;
         }
 
+        if (_userContentManager != IntPtr.Zero)
+        {
+            WpeInterop.g_object_unref(_userContentManager);
+            _userContentManager = IntPtr.Zero;
+        }
+
         if (!_exportableOwnedByWebKit && _exportable != IntPtr.Zero)
         {
             WpeInterop.wpe_view_backend_exportable_fdo_destroy(_exportable);

src/Avalonia.Controls.WebView.Core/Macios/MaciosWebViewAdapter.cs

@@ -21,8 +21,6 @@ namespace Avalonia.Controls.Macios;
 internal class MaciosWebViewAdapter : IWebViewAdapterWithFocus, IWebViewAdapterWithInputRedirect,
     IWebViewAdapterWithCookieManager, IWebViewAdapterWithCommands, IWebViewWithPrint, IAppleWKWebViewPlatformHandle
 {
-    private const string DefaultPostAvWebViewMessageName = "postAvWebViewMessage";
-
     private readonly string _scriptHandlerMessageName;
     private readonly NSString _scriptHandlerMessageNameNative;
     private readonly WKWebViewConfiguration _config;
@@ -40,7 +38,7 @@ public MaciosWebViewAdapter(AppleWKWebViewEnvironmentRequestedEventArgs options)
         _scriptHandler = new WKScriptMessageHandler();
         _scriptHandler.DidReceiveScriptMessage += OnScriptHandlerOnDidReceiveScriptMessage;
 
-        _scriptHandlerMessageName = options.ScriptHandlerMessageName ?? DefaultPostAvWebViewMessageName;
+        _scriptHandlerMessageName = options.ScriptHandlerMessageName ?? WebViewHelper.PostAvWebViewMessageName;
         _scriptHandlerMessageNameNative = NSString.Create(_scriptHandlerMessageName);
         _config = new WKWebViewConfiguration { JavaScriptEnabled = true };
         _config.AddScriptMessageHandler(_scriptHandler, _scriptHandlerMessageNameNative);
@@ -297,7 +295,7 @@ private void OnDelegateOnDecidePolicyNavigation(object? _, WKNavigationDelegate.
 
     private async void OnDelegateOnDidFinishNavigation(object? sender, EventArgs args)
     {
-        _ = await InvokeScript($"function invokeCSharpAction(data){{window.webkit.messageHandlers.{_scriptHandlerMessageName}.postMessage(data);}}");
+        _ = await InvokeScript(WebViewHelper.BuildWebKitInvokeCSharpActionScript(_scriptHandlerMessageName, stringify: true));
 
         using var url = _webView.Url;
         NavigationCompleted?.Invoke(this, new WebViewNavigationCompletedEventArgs { Request = Uri.TryCreate(url!.AbsoluteString, UriKind.Absolute, out var uri) ? uri : null, IsSuccess = true });

src/Avalonia.Controls.WebView.Core/WebViewHelper.cs

@@ -4,8 +4,33 @@ namespace Avalonia.Controls;
 
 internal static class WebViewHelper
 {
+    internal const string PostAvWebViewMessageName = "postAvWebViewMessage";
+
     public static Uri EmptyPage { get; } = new("about:blank");
 
+    internal static string BuildWebKitInvokeCSharpActionScript(
+        string messageName = PostAvWebViewMessageName, bool stringify = true) =>
+        BuildInvokeCSharpActionScript("window.webkit.messageHandlers." + messageName, stringify: stringify);
+
+    /// <param name="postObject">Target object to send message to.</param>
+    /// <param name="postMethod">Method on the <see cref="postObject"/> that should be invoked to pass the message.</param>
+    /// <param name="stringify">
+    /// Defines if post data should be JSON serialized,
+    /// some backends do that automatically when marshall objects to the C# handlers.
+    /// </param>
+    internal static string BuildInvokeCSharpActionScript(string postObject,
+        string postMethod = "postMessage", bool stringify = true)
+    {
+        return stringify ?
+            "function invokeCSharpAction(data){" +
+            "var message = typeof data === 'object' ? JSON.stringify(data) : data;" +
+            $"{postObject}.{postMethod}(message);" +
+            "}" :
+            "function invokeCSharpAction(data){" +
+            $"{postObject}.{postMethod}(data);" +
+            "}";
+    }
+
     internal static bool IsAnchorNavigation(Uri? currentUrl, Uri? newUrl)
     {
         if (currentUrl is null || newUrl is null)

src/Avalonia.Controls.WebView.Core/Win/WebView1/WebViewCallbacks.cs

@@ -45,14 +45,8 @@ async void InitScript()
         {
             try
             {
-                var initScript =
-                    """
-                    window.invokeCSharpAction = function(data) {
-                        var message = typeof data === 'object' ? JSON.stringify(data) : data;
-                        window.external.notify(message);
-                    };
-                    """;
-                await adapter.InvokeScript(initScript);
+                await adapter.InvokeScript(WebViewHelper.BuildInvokeCSharpActionScript(
+                    "window.external", postMethod: "notify", stringify: true));
             }
             catch (Exception ex)
             {

src/Avalonia.Controls.WebView.Core/Win/WebView2/WebView2BaseAdapter.cs

@@ -297,7 +297,7 @@ public async Task InitializeAsync(WindowsWebView2EnvironmentRequestedEventArgs e
         var addScriptCompletion = new AddScriptToExecuteOnDocumentCreatedCompletedHandler();
         var webView = TryGetWebView2() ?? throw new InvalidOperationException("WebView2 is not initialized.");
         webView.AddScriptToExecuteOnDocumentCreated(
-            "function invokeCSharpAction(data){window.chrome.webview.postMessage(data);}", addScriptCompletion);
+            WebViewHelper.BuildInvokeCSharpActionScript("window.chrome.webview", stringify: false), addScriptCompletion);
         _ = await addScriptCompletion.Result.Task;
 
         controller.SetIsVisible(1);