Handle preedit

src/Avalonia.Base/Input/TextInput/ITextInputMethodClient.cs

@@ -28,7 +28,7 @@ namespace Avalonia.Input.TextInput
         /// <summary>
         /// Sets the non-committed input string
         /// </summary>
-        void SetPreeditText(string text);
+        void SetPreeditText(string? text);
         /// <summary>
         /// Indicates if text input client is capable of providing the text around the cursor
         /// </summary>

src/Web/Avalonia.Web.Blazor/AvaloniaView.razor.cs

@@ -335,7 +335,23 @@ namespace Avalonia.Web.Blazor
 
         private void InputHelperOnCompositionEvent(object? sender, WebCompositionEventArgs e)
         {
-            Debug.WriteLine("Test");
+            if(_client == null)
+            {
+                return;
+            }
+
+            switch (e.Type)
+            {
+                case WebCompositionEventArgs.WebCompositionEventType.Start:
+                    _client.SetPreeditText(null);
+                    break;
+                case WebCompositionEventArgs.WebCompositionEventType.Update:
+                    _client?.SetPreeditText(e.Data);
+                    break;
+                case WebCompositionEventArgs.WebCompositionEventType.End:
+                    _client?.SetPreeditText(null);
+                    break;
+            }
         }
 
         private void OnRenderFrame()
@@ -417,6 +433,16 @@ namespace Avalonia.Web.Blazor
                 return;
             }
 
+            if(_client != null)
+            {
+                _client.SurroundingTextChanged -= SurroundingTextChanged;
+            }
+
+            if(client != null)
+            {
+                client.SurroundingTextChanged += SurroundingTextChanged;
+            }
+
             _inputHelper.Clear();
 
             _client = client;
@@ -434,6 +460,13 @@ namespace Avalonia.Web.Blazor
             }
         }
 
+        private void SurroundingTextChanged(object? sender, EventArgs e)
+        {
+            var surroundingText = _client.SurroundingText;
+
+            _inputHelper?.SetSurroundingText(surroundingText.Text, surroundingText.AnchorOffset, surroundingText.CursorOffset);
+        }
+
         public void SetCursorRect(Rect rect)
         {
         }