Fix Label Multiline Truncation

Co-authored-by: Javier Suárez <javiersuarezruiz@hotmail.com>

src/Controls/samples/Controls.Sample/Pages/Controls/LabelPage.xaml

@@ -231,6 +231,13 @@
             <Label
                 LineBreakMode ="TailTruncation"
                 Text="Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat." />
+            <Label
+                Text="TailTruncation (with 2 MaxLines)"
+                Style="{StaticResource Headline}" />
+            <Label
+                MaxLines="2"
+                LineBreakMode ="TailTruncation"
+                Text="Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat." />
             <Label
                 Text="CharacterWrap"
                 Style="{StaticResource Headline}" />

src/Controls/src/Core/Label/Label.Android.cs

@@ -36,7 +36,6 @@ private protected override void OnHandlerChangedCore()
 		public static void MapText(LabelHandler handler, Label label) => MapText((ILabelHandler)handler, label);
 		public static void MapLineBreakMode(LabelHandler handler, Label label) => MapLineBreakMode((ILabelHandler)handler, label);
 
-
 		public static void MapText(ILabelHandler handler, Label label)
 		{
 			Platform.TextViewExtensions.UpdateText(handler.PlatformView, label);

src/Controls/src/Core/Label/Label.Windows.cs

@@ -8,17 +8,16 @@ public partial class Label
 		public static void MapDetectReadingOrderFromContent(LabelHandler handler, Label label) => MapDetectReadingOrderFromContent((ILabelHandler)handler, label);
 		public static void MapText(LabelHandler handler, Label label) => MapText((ILabelHandler)handler, label);
 
-
 		public static void MapDetectReadingOrderFromContent(ILabelHandler handler, Label label) =>
 			Platform.TextBlockExtensions.UpdateDetectReadingOrderFromContent(handler.PlatformView, label);
 
 		public static void MapText(ILabelHandler handler, Label label) =>
 			Platform.TextBlockExtensions.UpdateText(handler.PlatformView, label);
 
 		public static void MapLineBreakMode(ILabelHandler handler, Label label) =>
-			handler.PlatformView?.UpdateLineBreakMode(label.LineBreakMode);
+			handler.PlatformView?.UpdateLineBreakMode(label);
 
 		public static void MapMaxLines(ILabelHandler handler, Label label) =>
 			handler.PlatformView?.UpdateMaxLines(label);
 	}
-}
+}

src/Controls/src/Core/Label/Label.iOS.cs

@@ -1,4 +1,4 @@
-#nullable disable
+#nullable disable
 using System;
 using Microsoft.Maui.Controls.Platform;
 

src/Controls/src/Core/Platform/Android/Extensions/TextViewExtensions.cs

@@ -2,6 +2,7 @@
 using System;
 using Android.Text;
 using Android.Widget;
+using AndroidX.AppCompat.Widget;
 using Microsoft.Maui.Controls.Internals;
 
 namespace Microsoft.Maui.Controls.Platform
@@ -31,14 +32,21 @@ public static void UpdateLineBreakMode(this TextView textView, Label label)
 
 		public static void UpdateMaxLines(this TextView textView, Label label)
 		{
-			// Linebreak mode also handles settng MaxLines
+			// Linebreak mode also handles setting MaxLines
 			textView.SetLineBreakMode(label.LineBreakMode, label.MaxLines);
 		}
 
 		internal static void SetLineBreakMode(this TextView textView, LineBreakMode lineBreakMode, int? maxLines = null)
 		{
 			if (!maxLines.HasValue || maxLines <= 0)
-				maxLines = int.MaxValue;
+			{
+				// Without setting the MaxLines property, to equalize behaviors across platforms
+				// we set the max to 1.
+				if (lineBreakMode == LineBreakMode.TailTruncation)
+					maxLines = 1;
+				else
+					maxLines = int.MaxValue;
+			}
 
 			bool singleLine = false;
 			bool shouldSetSingleLine = !OperatingSystem.IsAndroidVersionAtLeast(23);
@@ -67,12 +75,11 @@ internal static void SetLineBreakMode(this TextView textView, LineBreakMode line
 					break;
 				case LineBreakMode.TailTruncation:
 
-					// Leaving this in for now to preserve existing behavior
-					// Technically, we don't _need_ this for Labels; they will handle Ellipsization at the end just fine, even with multiple lines
-					// But we don't have a mechanism for setting MaxLines on other controls (e.g., Button) right now, so we need to force it here or
-					// they will potentially exceed a single line. Also, changing this behavior the for Labels would technically be breaking (though
-					// possibly less surprising than what happens currently).
-					maxLines = 1;
+					// We don't have a mechanism for setting MaxLines on other controls (e.g., Button) right now, so we need to force it here or
+					// they will potentially exceed a single line. 
+					if (textView is AppCompatButton)
+						maxLines = 1;
+
 					textView.Ellipsize = TextUtils.TruncateAt.End;
 					break;
 				case LineBreakMode.MiddleTruncation:

src/Controls/src/Core/Platform/Windows/Extensions/TextBlockExtensions.cs

@@ -12,44 +12,11 @@ namespace Microsoft.Maui.Controls.Platform
 	internal static class TextBlockExtensions
 	{
 		public static void UpdateLineBreakMode(this TextBlock textBlock, Label label) =>
-			textBlock.UpdateLineBreakMode(label.LineBreakMode);
+			textBlock.SetLineBreakMode(label.LineBreakMode, label.MaxLines);
 
 		public static void UpdateLineBreakMode(this TextBlock textBlock, LineBreakMode lineBreakMode)
 		{
-			if (textBlock == null)
-				return;
-
-			switch (lineBreakMode)
-			{
-				case LineBreakMode.NoWrap:
-					textBlock.TextTrimming = TextTrimming.Clip;
-					textBlock.TextWrapping = TextWrapping.NoWrap;
-					break;
-				case LineBreakMode.WordWrap:
-					textBlock.TextTrimming = TextTrimming.None;
-					textBlock.TextWrapping = TextWrapping.Wrap;
-					break;
-				case LineBreakMode.CharacterWrap:
-					textBlock.TextTrimming = TextTrimming.WordEllipsis;
-					textBlock.TextWrapping = TextWrapping.Wrap;
-					break;
-				case LineBreakMode.HeadTruncation:
-					// TODO: This truncates at the end.
-					textBlock.TextTrimming = TextTrimming.WordEllipsis;
-					DetermineTruncatedTextWrapping(textBlock);
-					break;
-				case LineBreakMode.TailTruncation:
-					textBlock.TextTrimming = TextTrimming.CharacterEllipsis;
-					DetermineTruncatedTextWrapping(textBlock);
-					break;
-				case LineBreakMode.MiddleTruncation:
-					// TODO: This truncates at the end.
-					textBlock.TextTrimming = TextTrimming.WordEllipsis;
-					DetermineTruncatedTextWrapping(textBlock);
-					break;
-				default:
-					throw new ArgumentOutOfRangeException();
-			}
+			textBlock.SetLineBreakMode(lineBreakMode, null);
 		}
 
 		static void DetermineTruncatedTextWrapping(TextBlock textBlock) =>
@@ -87,10 +54,8 @@ public static double FindDefaultLineHeight(this TextBlock control, Inline inline
 
 		public static void UpdateMaxLines(this TextBlock platformControl, Label label)
 		{
-			if (label.MaxLines >= 0)
-				platformControl.MaxLines = label.MaxLines;
-			else
-				platformControl.MaxLines = 0;
+			// Linebreak mode also handles setting MaxLines
+			platformControl.SetLineBreakMode(label.LineBreakMode, label.MaxLines);
 		}
 
 		public static void UpdateDetectReadingOrderFromContent(this TextBlock platformControl, Label label)
@@ -99,6 +64,46 @@ public static void UpdateDetectReadingOrderFromContent(this TextBlock platformCo
 				platformControl.SetTextReadingOrder(label.OnThisPlatform().GetDetectReadingOrderFromContent());
 		}
 
+		internal static void SetLineBreakMode(this TextBlock textBlock, LineBreakMode lineBreakMode, int? maxLines = null)
+		{
+			if (maxLines.HasValue && maxLines >= 0)
+				textBlock.MaxLines = maxLines.Value;
+			else
+				textBlock.MaxLines = 0;
+
+			switch (lineBreakMode)
+			{
+				case LineBreakMode.NoWrap:
+					textBlock.TextTrimming = TextTrimming.Clip;
+					textBlock.TextWrapping = TextWrapping.NoWrap;
+					break;
+				case LineBreakMode.WordWrap:
+					textBlock.TextTrimming = TextTrimming.None;
+					textBlock.TextWrapping = TextWrapping.Wrap;
+					break;
+				case LineBreakMode.CharacterWrap:
+					textBlock.TextTrimming = TextTrimming.WordEllipsis;
+					textBlock.TextWrapping = TextWrapping.Wrap;
+					break;
+				case LineBreakMode.HeadTruncation:
+					// TODO: This truncates at the end.
+					textBlock.TextTrimming = TextTrimming.WordEllipsis;
+					DetermineTruncatedTextWrapping(textBlock);
+					break;
+				case LineBreakMode.TailTruncation:
+					textBlock.TextTrimming = TextTrimming.CharacterEllipsis;
+					DetermineTruncatedTextWrapping(textBlock);
+					break;
+				case LineBreakMode.MiddleTruncation:
+					// TODO: This truncates at the end.
+					textBlock.TextTrimming = TextTrimming.WordEllipsis;
+					DetermineTruncatedTextWrapping(textBlock);
+					break;
+				default:
+					throw new ArgumentOutOfRangeException();
+			}
+		}
+
 		internal static void SetTextReadingOrder(this TextBlock platformControl, bool detectReadingOrderFromContent) =>
 			platformControl.TextReadingOrder = detectReadingOrderFromContent
 				? TextReadingOrder.DetectFromContent

src/Controls/src/Core/Platform/iOS/Extensions/TextExtensions.cs

@@ -72,8 +72,14 @@ public static void UpdateMaxLines(this UILabel platformLabel, Label label)
 		internal static void SetLineBreakMode(this UILabel platformLabel, Label label)
 		{
 			int maxLines = label.MaxLines;
+
 			if (maxLines < 0)
-				maxLines = 0;
+			{
+				if (label.LineBreakMode == LineBreakMode.TailTruncation)
+					maxLines = 1;
+				else
+					maxLines = 0;
+			}
 
 			switch (label.LineBreakMode)
 			{
@@ -97,7 +103,6 @@ internal static void SetLineBreakMode(this UILabel platformLabel, Label label)
 					break;
 				case LineBreakMode.TailTruncation:
 					platformLabel.LineBreakMode = UILineBreakMode.TailTruncation;
-					maxLines = 1;
 					break;
 			}
 

src/Controls/tests/DeviceTests/Elements/Label/LabelTests.Android.cs

@@ -66,6 +66,28 @@ public async Task VerticalTextAlignedWhenRtlIsFalse()
 			Assert.True(platformLabel.Gravity.HasFlag(GravityFlags.CenterVertical), "Label should only have the CenterVertical flag.");
 		}
 
+		// https://github.com/dotnet/maui/issues/18059
+		[Fact(DisplayName = "Using TailTruncation LineBreakMode with 2 MaxLines")]
+		public async Task UsingTailTruncationWith2MaxLines()
+		{
+			var label = new Label()
+			{
+				Text = "Lorem ipsum dolor sit amet, consectetur adipiscing elit",
+				LineBreakMode = LineBreakMode.TailTruncation,
+				MaxLines = 2
+			};
+
+			var handler = await CreateHandlerAsync<LabelHandler>(label);
+
+			var platformLabel = GetPlatformLabel(handler);
+
+			await InvokeOnMainThreadAsync((System.Action)(() =>
+			{
+				Assert.Equal(2, GetPlatformMaxLines(handler));
+				Assert.Equal(LineBreakMode.TailTruncation.ToPlatform(), GetPlatformLineBreakMode(handler));
+			}));
+		}
+
 		TextView GetPlatformLabel(LabelHandler labelHandler) =>
 			labelHandler.PlatformView;
 

src/Controls/tests/DeviceTests/Elements/Label/LabelTests.cs

@@ -1,4 +1,5 @@
-using System.Threading.Tasks;
+using System;
+using System.Threading.Tasks;
 #if __IOS__
 using Foundation;
 #endif
@@ -26,6 +27,37 @@ void SetupBuilder()
 				});
 			});
 		}
+
+		[Fact(DisplayName = "Does Not Leak")]
+		public async Task DoesNotLeak()
+		{
+			SetupBuilder();
+
+			WeakReference viewReference = null;
+			WeakReference platformViewReference = null;
+			WeakReference handlerReference = null;
+
+			await InvokeOnMainThreadAsync(() =>
+			{
+				var layout = new Grid();
+
+				var label = new Label
+				{
+					Text = "Test"
+				};
+
+				layout.Add(label);
+				var handler = CreateHandler<LayoutHandler>(layout);
+				viewReference = new WeakReference(label);
+				handlerReference = new WeakReference(label.Handler);
+				platformViewReference = new WeakReference(label.Handler.PlatformView);
+			});
+
+			await AssertionExtensions.WaitForGC(viewReference, handlerReference, platformViewReference);
+			Assert.False(viewReference.IsAlive, "Label should not be alive!");
+			Assert.False(handlerReference.IsAlive, "Handler should not be alive!");
+			Assert.False(platformViewReference.IsAlive, "PlatformView should not be alive!");
+		}
 
 		[Theory]
 		[ClassData(typeof(TextTransformCases))]
@@ -204,6 +236,32 @@ public async Task LineBreakModeDoesNotAffectMaxLines()
 			}));
 		}
 
+		[Fact(DisplayName = "LineBreakMode TailTruncation does not affect MaxLines")]
+		public async Task TailTruncationDoesNotAffectMaxLines()
+		{
+			var label = new Label()
+			{
+				Text = "Lorem ipsum dolor sit amet, consectetur adipiscing elit",
+				MaxLines = 3,
+				LineBreakMode = LineBreakMode.TailTruncation,
+			};
+
+			var handler = await CreateHandlerAsync<LabelHandler>(label);
+			var platformLabel = GetPlatformLabel(handler);
+
+			await InvokeOnMainThreadAsync(() =>
+			{
+				Assert.Equal(3, GetPlatformMaxLines(handler));
+				Assert.Equal(LineBreakMode.TailTruncation.ToPlatform(), GetPlatformLineBreakMode(handler));
+
+				label.LineBreakMode = LineBreakMode.CharacterWrap;
+				platformLabel.UpdateLineBreakMode(label);
+
+				Assert.Equal(3, GetPlatformMaxLines(handler));
+				Assert.Equal(LineBreakMode.CharacterWrap.ToPlatform(), GetPlatformLineBreakMode(handler));
+			});
+		}
+
 		[Fact(DisplayName = "MaxLines Initializes Correctly")]
 		public async Task MaxLinesInitializesCorrectly()
 		{

src/Controls/tests/DeviceTests/Elements/Label/LabelTests.iOS.cs

@@ -1,7 +1,4 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
+using System.Collections.Generic;
 using System.Threading.Tasks;
 using Microsoft.Maui.Controls;
 using Microsoft.Maui.Handlers;
@@ -12,6 +9,27 @@ namespace Microsoft.Maui.DeviceTests
 {
 	public partial class LabelTests
 	{
+
+		[Fact(DisplayName = "Using TailTruncation LineBreakMode changes MaxLines")]
+		public async Task UsingTailTruncationSetMaxLines()
+		{
+			var label = new Label()
+			{
+				Text = "Lorem ipsum dolor sit amet, consectetur adipiscing elit",
+				LineBreakMode = LineBreakMode.TailTruncation,
+			};
+
+			var handler = await CreateHandlerAsync<LabelHandler>(label);
+
+			var platformLabel = GetPlatformLabel(handler);
+
+			await InvokeOnMainThreadAsync((System.Action)(() =>
+			{
+				Assert.Equal(1, GetPlatformMaxLines(handler));
+				Assert.Equal(LineBreakMode.TailTruncation.ToPlatform(), GetPlatformLineBreakMode(handler));
+			}));
+		}
+
 		UILabel GetPlatformLabel(LabelHandler labelHandler) =>
 			(UILabel)labelHandler.PlatformView;