fix(wasm): Fix TextBox default alignment

src/Uno.UI/UI/Xaml/Controls/TextBox/TextBoxView.wasm.cs

@@ -49,7 +49,11 @@ namespace Microsoft.UI.Xaml.Controls
 		}
 
 		public TextBoxView(TextBox textBox, bool isMultiline)
-			: base(isMultiline ? "textarea" : "input")
+			// We need to use textarea regardless of isMultiline
+			// because "input" native HTML element can't have its text top-aligned.
+			// For PasswordBox, it must be input. So, for now we can't match WinUI and it will
+			// remain center-aligned instead of top-aligned.
+			: base(textBox is PasswordBox ? "input" : "textarea")
 		{
 			IsMultiline = isMultiline;
 			_textBox = textBox;
@@ -87,6 +91,11 @@ namespace Microsoft.UI.Xaml.Controls
 			HtmlInput += OnInput;
 			HtmlPaste += OnPaste;
 
+			if (!IsMultiline)
+			{
+				WindowManagerInterop.SetSingleLine(this);
+			}
+
 			SetTextNative(_textBox.Text);
 		}
 

src/Uno.UI/UI/Xaml/Window/WindowManagerInterop.wasm.cs

@@ -14,6 +14,7 @@ using Windows.UI;
 using Microsoft.UI.Xaml;
 
 using System.Runtime.InteropServices.JavaScript;
+using Microsoft.UI.Xaml.Controls;
 
 namespace Uno.UI.Xaml
 {
@@ -31,6 +32,9 @@ namespace Uno.UI.Xaml
 		internal static void SetBodyCursor(string value)
 			=> NativeMethods.SetBodyCursor(value);
 
+		internal static void SetSingleLine(TextBoxView textBoxView)
+			=> NativeMethods.SetSingleLine(textBoxView.HtmlId);
+
 		/// <summary>
 		/// This method has two purposes:
 		/// - Initializes the window size before launch
@@ -1111,6 +1115,9 @@ namespace Uno.UI.Xaml
 			[JSImport("globalThis.Uno.UI.WindowManager.setBodyCursor")]
 			internal static partial void SetBodyCursor(string value);
 
+			[JSImport("globalThis.Uno.UI.WindowManager.setSingleLine")]
+			internal static partial void SetSingleLine(IntPtr htmlId);
+
 			[JSImport("globalThis.Uno.UI.WindowManager.beforeLaunch")]
 			internal static partial string BeforeLaunch();
 

src/Uno.UI/WasmCSS/Uno.UI.css

@@ -264,7 +264,12 @@ embed.uno-frameworkelement.uno-unarranged {
 
 textarea {
   resize: none;
-  overflow: hidden; /* Scrolling is handled by the parent ScrollViewer */
+  scrollbar-width: none;
+}
+
+textarea::-webkit-scrollbar {
+  width: 0;
+  background: transparent;
 }
 
 input::-ms-reveal,

src/Uno.UI/ts/WindowManager.ts

@@ -183,6 +183,17 @@ namespace Uno.UI {
 			document.body.style.cursor = value;
 		}
 
+		static setSingleLine(htmlId: number): void {
+			const element = this.current.getView(htmlId);
+			if (element instanceof HTMLTextAreaElement) {
+				element.addEventListener("keydown", e => {
+					if (e.key === "Enter") {
+						e.preventDefault();
+					}
+				})
+			}
+		}
+
 		/**
 			* Reads the window's search parameters
 			*