Use TextHighlighter to implement background color for Span (#5025)

dotnet · Mar 3, 2022 · a840828 · a840828
1 parent b844082
commit a840828
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Showing 3 changed files with 32 additions and 18 deletions.
diff --git a/src/Compatibility/Core/src/Windows/LabelRenderer.cs b/src/Compatibility/Core/src/Windows/LabelRenderer.cs
@@ -350,7 +350,7 @@ void UpdateTextPlainText(TextBlock textBlock)
 					{
 						var span = formatted.Spans[i];
 
-						var run = span.ToRun(fontManager);
+						var run = span.ToRunAndColorsTuple(fontManager).Item1;
 						heights.Add(Control.FindDefaultLineHeight(run));
 						textBlock.Inlines.Add(run);
 					}

diff --git a/src/Controls/src/Core/Platform/Windows/Extensions/FormattedStringExtensions.cs b/src/Controls/src/Core/Platform/Windows/Extensions/FormattedStringExtensions.cs
@@ -1,4 +1,5 @@
 #nullable enable
+using System;
 using System.Collections.Generic;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Maui.Controls.Internals;
@@ -20,19 +21,38 @@ public static void UpdateInlines(this TextBlock textBlock, FormattedString forma
 			// Have to implement a measure here, otherwise inline.ContentStart and ContentEnd will be null, when used in RecalculatePositions
 			textBlock.Measure(new global::Windows.Foundation.Size(double.MaxValue, double.MaxValue));
 
-			var runs = formattedString.ToRuns(defaultLineHeight, defaultHorizontalAlignment, defaultFont, defaultColor, defaultTextTransform);
+			var runAndColorTuples = formattedString.ToRunAndColorsTuples(defaultLineHeight, defaultHorizontalAlignment, defaultFont, defaultColor, defaultTextTransform);
 
 			var heights = new List<double>();
-			foreach (var run in runs)
+			int currentTextIndex = 0;
+			foreach (var runAndColorTuple in runAndColorTuples)
 			{
+				Run run = runAndColorTuple.Item1;
+				Color textColor = runAndColorTuple.Item2;
+				Color background = runAndColorTuple.Item3;
 				heights.Add(textBlock.FindDefaultLineHeight(run));
 				textBlock.Inlines.Add(run);
+				int length = run.Text.Length;
+				if (background != null || textColor != null)
+				{
+					TextHighlighter textHighlighter = new TextHighlighter { Ranges = { new TextRange(currentTextIndex, length) } };
+					if (background != null)
+					{
+						textHighlighter.Background = background.ToPlatform();
+					}
+					if (textColor != null)
+					{
+						textHighlighter.Foreground = textColor.ToPlatform();
+					}
+					textBlock.TextHighlighters.Add(textHighlighter);
+				}
+				currentTextIndex += length;
 			}
 		}
 
-		public static IEnumerable<Run> ToRuns(this FormattedString formattedString, double defaultLineHeight = 0d, TextAlignment defaultHorizontalAlignment = TextAlignment.Start, Font? defaultFont = null, Color? defaultColor = null, TextTransform defaultTextTransform = TextTransform.Default, IFontManager? fontManager = null)
+		public static IEnumerable<Tuple<Run, Color, Color>> ToRunAndColorsTuples(this FormattedString formattedString, double defaultLineHeight = 0d, TextAlignment defaultHorizontalAlignment = TextAlignment.Start, Font? defaultFont = null, Color? defaultColor = null, TextTransform defaultTextTransform = TextTransform.Default, IFontManager? fontManager = null)
 		{
-			var runs = new List<Run>();
+			var runs = new List<Tuple<Run, Color, Color>>();
 
 			if (formattedString != null && formattedString.Spans != null)
 			{
@@ -41,27 +61,21 @@ public static IEnumerable<Run> ToRuns(this FormattedString formattedString, doub
 				for (var i = 0; i < formattedString.Spans.Count; i++)
 				{
 					var span = formattedString.Spans[i];
-					var run = span.ToRun(fontManager, defaultFont, defaultColor, defaultTextTransform);
+					var run = span.ToRunAndColorsTuple(fontManager, defaultFont, defaultColor, defaultTextTransform);
 					runs.Add(run);
 				}
 			}
 
 			return runs;
 		}
 
-		public static Run ToRun(this Span span, IFontManager fontManager, Font? defaultFont = null, Color? defaultColor = null, TextTransform defaultTextTransform = TextTransform.Default)
+		public static Tuple<Run, Color, Color> ToRunAndColorsTuple(this Span span, IFontManager fontManager, Font? defaultFont = null, Color? defaultColor = null, TextTransform defaultTextTransform = TextTransform.Default)
 		{
 			var transform = span.TextTransform != TextTransform.Default ? span.TextTransform : defaultTextTransform;
 
 			var text = TextTransformUtilites.GetTransformedText(span.Text, transform);
-
-			var run = new Run { Text = text ?? string.Empty };
 
-			var fgcolor = span.TextColor ?? defaultColor;
-			if (fgcolor is not null)
-				run.Foreground = fgcolor.ToPlatform();
-
-			// NOTE: Background is not supported in Run
+			var run = new Run { Text = text ?? string.Empty };
 
 			var font = span.ToFont();
 			if (font.IsDefault && defaultFont.HasValue)
@@ -77,7 +91,7 @@ public static Run ToRun(this Span span, IFontManager fontManager, Font? defaultF
 
 			run.CharacterSpacing = span.CharacterSpacing.ToEm();
 
-			return run;
+			return Tuple.Create(run, span.TextColor, span.BackgroundColor);
 		}
 	}
 }
diff --git a/src/Controls/tests/DeviceTests/Elements/FormattedStringTests.cs b/src/Controls/tests/DeviceTests/Elements/FormattedStringTests.cs
@@ -40,10 +40,10 @@ public async Task NativeFormattedStringContainsSpan()
 
 				result = spannable.ToString();
 #elif WINDOWS
-				var runs = formattedString.ToRuns(fontManager: fontManager);
+				var tuples = formattedString.ToRunAndColorsTuples(fontManager: fontManager);
 
-				foreach (var r in runs)
-					result += r.Text;
+				foreach (var t in tuples)
+					result += t.Item1.Text;
 #endif
 				return result;
 			});