Made MaxLength property consistent across all platforms (#5581)

src/Controls/tests/DeviceTests/Elements/Editor/EditorTests.cs

@@ -70,5 +70,30 @@ public async Task TextTransformUpdated(string text, TextTransform transform, str
 			var platformText = await GetPlatformText(handler);
 			Assert.Equal(expected, platformText);
 		}
+
+#if WINDOWS
+		// Only Windows needs the IsReadOnly workaround for MaxLength==0 to prevent text from being entered
+		[Fact]
+		public async Task MaxLengthIsReadOnlyValueTest()
+		{
+			Editor editor = new Editor();
+
+			await InvokeOnMainThreadAsync(() =>
+			{
+				var handler = CreateHandler<EditorHandler>(editor);
+				var platformControl = GetPlatformControl(handler);
+
+				editor.MaxLength = 0;
+				Assert.True(platformControl.IsReadOnly);
+				editor.IsReadOnly = false;
+				Assert.True(platformControl.IsReadOnly);
+
+				editor.MaxLength = 10;
+				Assert.False(platformControl.IsReadOnly);
+				editor.IsReadOnly = true;
+				Assert.True(platformControl.IsReadOnly);
+			});
+		}
+#endif
 	}
 }

src/Controls/tests/DeviceTests/Elements/Entry/EntryTests.cs

@@ -79,5 +79,30 @@ await InvokeOnMainThreadAsync(() =>
 			Assert.Equal(0, cursorPosition);
 #endif
 		}
+
+#if WINDOWS
+		// Only Windows needs the IsReadOnly workaround for MaxLength==0 to prevent text from being entered
+		[Fact]
+		public async Task MaxLengthIsReadOnlyValueTest()
+		{
+			Entry entry = new Entry();
+
+			await InvokeOnMainThreadAsync(() =>
+			{
+				var handler = CreateHandler<EntryHandler>(entry);
+				var platformControl = GetPlatformControl(handler);
+
+				entry.MaxLength = 0;
+				Assert.True(platformControl.IsReadOnly);
+				entry.IsReadOnly = false;
+				Assert.True(platformControl.IsReadOnly);
+
+				entry.MaxLength = 10;
+				Assert.False(platformControl.IsReadOnly);
+				entry.IsReadOnly = true;
+				Assert.True(platformControl.IsReadOnly);
+			});
+		}
+#endif
 	}
 }

src/Controls/tests/DeviceTests/Elements/SearchBar/SearchBarTests.cs

@@ -2,6 +2,7 @@
 using System.Threading.Tasks;
 using Microsoft.Maui.Controls;
 using Microsoft.Maui.Handlers;
+using Microsoft.Maui.Platform;
 using Xunit;
 
 namespace Microsoft.Maui.DeviceTests
@@ -28,5 +29,30 @@ public async Task TextTransformUpdated(string text, TextTransform transform, str
 			var platformText = await GetPlatformText(handler);
 			Assert.Equal(expected, platformText);
 		}
+
+#if WINDOWS
+		// Only Windows needs the IsReadOnly workaround for MaxLength==0 to prevent text from being entered
+		[Fact]
+		public async Task MaxLengthIsReadOnlyValueTest()
+		{
+			SearchBar searchBar = new SearchBar();
+
+			await InvokeOnMainThreadAsync(() =>
+			{
+				var handler = CreateHandler<SearchBarHandler>(searchBar);
+				var platformControl = GetPlatformControl(handler);
+
+				searchBar.MaxLength = 0;
+				Assert.True(MauiAutoSuggestBox.GetIsReadOnly(platformControl));
+				searchBar.IsReadOnly = false;
+				Assert.True(MauiAutoSuggestBox.GetIsReadOnly(platformControl));
+
+				searchBar.MaxLength = 10;
+				Assert.False(MauiAutoSuggestBox.GetIsReadOnly(platformControl));
+				searchBar.IsReadOnly = true;
+				Assert.True(MauiAutoSuggestBox.GetIsReadOnly(platformControl));
+			});
+		}
+#endif
 	}
 }

src/Core/src/Handlers/SearchBar/SearchBarHandler.Windows.cs

@@ -108,6 +108,7 @@ void OnLoaded(object sender, UI.Xaml.RoutedEventArgs e)
 				PlatformView?.UpdatePlaceholderColor(VirtualView);
 				PlatformView?.UpdateHorizontalTextAlignment(VirtualView);
 				PlatformView?.UpdateMaxLength(VirtualView);
+				PlatformView?.UpdateIsReadOnly(VirtualView);
 			}
 		}
 

src/Core/src/Platform/Android/EditTextExtensions.cs

@@ -92,6 +92,9 @@ public static void UpdateMaxLength(this EditText editText, int maxLength)
 
 		public static void SetLengthFilter(this EditText editText, int maxLength)
 		{
+			if (maxLength == -1)
+				maxLength = int.MaxValue;
+
 			var currentFilters = new List<IInputFilter>(editText.GetFilters() ?? new IInputFilter[0]);
 			var changed = false;
 
@@ -105,7 +108,7 @@ public static void SetLengthFilter(this EditText editText, int maxLength)
 				}
 			}
 
-			if (maxLength > 0)
+			if (maxLength >= 0)
 			{
 				currentFilters.Add(new InputFilterLengthFilter(maxLength));
 				changed = true;

src/Core/src/Platform/Windows/MauiAutoSuggestBox.cs

@@ -0,0 +1,34 @@
+#nullable enable
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Controls;
+
+namespace Microsoft.Maui.Platform
+{
+	public static class MauiAutoSuggestBox
+	{
+		public static void InvalidateAttachedProperties(DependencyObject obj)
+		{
+			OnIsReadOnlyPropertyChanged(obj);
+		}
+
+		// IsReadOnly
+
+		public static bool GetIsReadOnly(DependencyObject obj) =>
+			(bool)obj.GetValue(IsReadOnlyProperty);
+
+		public static void SetIsReadOnly(DependencyObject obj, bool value) =>
+			obj.SetValue(IsReadOnlyProperty, value);
+
+		public static readonly DependencyProperty IsReadOnlyProperty = DependencyProperty.RegisterAttached(
+			"IsReadOnly", typeof(bool), typeof(MauiTextBox),
+			new PropertyMetadata(true, OnIsReadOnlyPropertyChanged));
+
+		static void OnIsReadOnlyPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs? e = null)
+		{
+			var element = d as FrameworkElement;
+			var textBox = element?.GetDescendantByName<TextBox>("TextBox");
+			if (textBox != null)
+				textBox.IsReadOnly = true;
+		}
+	}
+}

src/Core/src/Platform/Windows/SearchBarExtensions.cs

@@ -94,15 +94,25 @@ public static void UpdateVerticalTextAlignment(this AutoSuggestBox platformContr
 
 		public static void UpdateMaxLength(this AutoSuggestBox platformControl, ISearchBar searchBar)
 		{
+			var maxLength = searchBar.MaxLength;
+
+			if (maxLength == -1)
+				maxLength = int.MaxValue;
+
+			if (maxLength == 0)
+				MauiAutoSuggestBox.SetIsReadOnly(platformControl, true);
+			else
+				MauiAutoSuggestBox.SetIsReadOnly(platformControl, searchBar.IsReadOnly);
+
 			var currentControlText = platformControl.Text;
 
-			if (currentControlText.Length > searchBar.MaxLength)
-				platformControl.Text = currentControlText.Substring(0, searchBar.MaxLength);
+			if (currentControlText.Length > maxLength)
+				platformControl.Text = currentControlText.Substring(0, maxLength);
 		}
-		
+
 		public static void UpdateIsReadOnly(this AutoSuggestBox platformControl, ISearchBar searchBar)
 		{
-			platformControl.IsEnabled = searchBar.IsReadOnly;
+			MauiAutoSuggestBox.SetIsReadOnly(platformControl, searchBar.IsReadOnly);
 		}
 
 		public static void UpdateIsTextPredictionEnabled(this AutoSuggestBox platformControl, ISearchBar searchBar)

src/Core/src/Platform/Windows/TextBoxExtensions.cs

@@ -128,6 +128,11 @@ public static void UpdateMaxLength(this TextBox textBox, ITextInput textInput)
 		{
 			var maxLength = textInput.MaxLength;
 
+			if (maxLength == 0)
+				textBox.IsReadOnly = true;
+			else
+				textBox.IsReadOnly = textInput.IsReadOnly;
+
 			if (maxLength == -1)
 				maxLength = int.MaxValue;