Add surrogate pair (emoji) support via char-to-Rune migration

Migrate Cell.Character from char to System.Text.Rune across the entire
rendering pipeline to support Unicode characters outside the BMP,
including emoji (U+1F600+) and supplementary CJK ideographs.

Key changes:
- Cell.Character and ConsoleBuffer internal cell: char → Rune
- UnicodeWidth: add Rune-aware width functions with precise Unicode 15.0
  East_Asian_Width "W" ranges (not blanket emoji ranges)
- MarkupParser: Rune-aware iteration for Parse, StripLength, Truncate
- CharacterBuffer/ConsoleBuffer: Rune overloads for SetCell, WriteString
- ConsoleBuffer: pre-process continuation cells to prevent move artifacts
- Fix dropdown/bar graph controls using .Length instead of display width
- Add emoji to dropdown demo as visual test fixtures
- Add StringBuilderExtensions.AppendRune helper
- 50+ new wide char and emoji tests (1227 total passing)

Author: nickprotop

Examples/DemoApp/DemoWindows/DropdownWindow.cs

@@ -23,24 +23,24 @@ public static Window Create(ConsoleWindowSystem ws)
             .WithMargin(1, 1, 1, 0)
             .Build();
 
-        var header = Controls.Markup("[bold yellow]  Meal Planner[/]")
+        var header = Controls.Markup("[bold yellow]  \U0001F37D Meal Planner[/]")
             .StickyTop()
             .Build();
 
         var statusBar = Controls.Markup("[dim]Use \u2191\u2193 to browse | Type to search | Esc: Close[/]")
             .StickyBottom()
             .Build();
 
-        var cuisineLabel = Controls.Markup("[bold]Cuisine Type[/]").WithMargin(1, 1, 1, 0).Build();
+        var cuisineLabel = Controls.Markup("[bold]\U0001F35C Cuisine Type[/]").WithMargin(1, 1, 1, 0).Build();
         var cuisine = Controls.Dropdown("Choose cuisine...")
-            .AddItem(new DropdownItem("Japanese", "\u25cf", Color.Red) { Tag = "Japanese" })
-            .AddItem(new DropdownItem("Italian", "\u25cf", Color.Green) { Tag = "Italian" })
-            .AddItem(new DropdownItem("Mexican", "\u25cf", Color.Orange1) { Tag = "Mexican" })
-            .AddItem(new DropdownItem("Indian", "\u25cf", Color.Yellow) { Tag = "Indian" })
-            .AddItem(new DropdownItem("Thai", "\u25cf", Color.Magenta1) { Tag = "Thai" })
-            .AddItem(new DropdownItem("Chinese", "\u25cf", Color.Red) { Tag = "Chinese" })
-            .AddItem(new DropdownItem("French", "\u25cf", Color.Blue) { Tag = "French" })
-            .AddItem(new DropdownItem("Korean", "\u25cf", Color.Cyan1) { Tag = "Korean" })
+            .AddItem(new DropdownItem("\U0001F363 日本料理 Japanese", "\u25cf", Color.Red) { Tag = "Japanese" })
+            .AddItem(new DropdownItem("\U0001F355 Italian", "\u25cf", Color.Green) { Tag = "Italian" })
+            .AddItem(new DropdownItem("\U0001F32E Mexican", "\u25cf", Color.Orange1) { Tag = "Mexican" })
+            .AddItem(new DropdownItem("\U0001F35B Indian", "\u25cf", Color.Yellow) { Tag = "Indian" })
+            .AddItem(new DropdownItem("\U0001F958 Thai", "\u25cf", Color.Magenta1) { Tag = "Thai" })
+            .AddItem(new DropdownItem("\U0001F95F 中華料理 Chinese", "\u25cf", Color.Red) { Tag = "Chinese" })
+            .AddItem(new DropdownItem("\U0001F950 French", "\u25cf", Color.Blue) { Tag = "French" })
+            .AddItem(new DropdownItem("\U0001F356 한국 Korean", "\u25cf", Color.Cyan1) { Tag = "Korean" })
             .AddItem(new DropdownItem("Mediterranean", "\u25cf", Color.Green) { Tag = "Mediterranean" })
             .AddItem(new DropdownItem("Greek", "\u25cf", Color.Cyan1) { Tag = "Greek" })
             .AddItem(new DropdownItem("Vietnamese", "\u25cf", Color.Yellow) { Tag = "Vietnamese" })
@@ -49,32 +49,32 @@ public static Window Create(ConsoleWindowSystem ws)
             .WithMargin(1, 0, 1, 1)
             .Build();
 
-        var dietaryLabel = Controls.Markup("[bold]Dietary Restriction[/]").WithMargin(1, 0, 1, 0).Build();
+        var dietaryLabel = Controls.Markup("[bold]\U0001F96C Dietary Restriction[/]").WithMargin(1, 0, 1, 0).Build();
         var dietary = Controls.Dropdown("Choose diet...")
             .AddItems("None", "Vegetarian", "Vegan", "Gluten-Free", "Keto", "Paleo", "Pescatarian")
             .SelectedIndex(DefaultDietaryIndex)
             .WithMargin(1, 0, 1, 1)
             .Build();
 
-        var spiceLabel = Controls.Markup("[bold]Spice Level[/]").WithMargin(1, 0, 1, 0).Build();
+        var spiceLabel = Controls.Markup("[bold]\U0001F336 Spice Level[/]").WithMargin(1, 0, 1, 0).Build();
         var spice = Controls.Dropdown("Choose spice...")
-            .AddItem(new DropdownItem("Mild", "\u25cf", Color.Green))
-            .AddItem(new DropdownItem("Medium", "\u25cf", Color.Yellow))
-            .AddItem(new DropdownItem("Hot", "\u25cf", Color.Orange1))
-            .AddItem(new DropdownItem("Extra Hot", "\u25cf", Color.Red))
-            .AddItem(new DropdownItem("Inferno", "\u25cf", Color.DarkRed))
+            .AddItem(new DropdownItem("\U0001F7E2 Mild", "\u25cf", Color.Green))
+            .AddItem(new DropdownItem("\U0001F7E1 Medium", "\u25cf", Color.Yellow))
+            .AddItem(new DropdownItem("\U0001F7E0 Hot", "\u25cf", Color.Orange1))
+            .AddItem(new DropdownItem("\U0001F534 Extra Hot", "\u25cf", Color.Red))
+            .AddItem(new DropdownItem("\U0001F480 Inferno", "\u25cf", Color.DarkRed))
             .SelectedIndex(DefaultSpiceIndex)
             .WithMargin(1, 0, 1, 1)
             .Build();
 
-        var budgetLabel = Controls.Markup("[bold]Budget[/]").WithMargin(1, 0, 1, 0).Build();
+        var budgetLabel = Controls.Markup("[bold]\U0001F4B0 Budget[/]").WithMargin(1, 0, 1, 0).Build();
         var budget = Controls.Dropdown("Choose budget...")
             .AddItems("$ Budget", "$$ Moderate", "$$$ Premium", "$$$$ Luxury")
             .SelectedIndex(DefaultBudgetIndex)
             .WithMargin(1, 0, 1, 1)
             .Build();
 
-        var servingsLabel = Controls.Markup("[bold]Servings[/]").WithMargin(1, 0, 1, 0).Build();
+        var servingsLabel = Controls.Markup("[bold]\U0001F465 Servings[/]").WithMargin(1, 0, 1, 0).Build();
         var servings = Controls.Dropdown("Choose servings...")
             .AddItems("1 person", "2 people", "3 people", "4 people", "6 people", "8 people")
             .SelectedIndex(DefaultServingsIndex)

SharpConsoleUI.Tests/Controls/ImageControlTests.cs

@@ -1,3 +1,4 @@
+using System.Text;
 using SharpConsoleUI.Configuration;
 using SharpConsoleUI.Controls;
 using SharpConsoleUI.Imaging;
@@ -63,7 +64,7 @@ public void PaintDOM_WritesHalfBlockCharacters()
 		control.PaintDOM(charBuffer, bounds, bounds, Color.White, Color.Black);
 
 		var cell = charBuffer.GetCell(0, 0);
-		Assert.Equal(ImagingDefaults.HalfBlockChar, cell.Character);
+		Assert.Equal(new Rune(ImagingDefaults.HalfBlockChar), cell.Character);
 	}
 
 	#endregion

SharpConsoleUI.Tests/Drawing/BufferTextExtensionsWideCharTests.cs

@@ -0,0 +1,116 @@
+using Xunit;
+using SharpConsoleUI.Layout;
+using SharpConsoleUI.Drawing;
+using System.Text;
+
+namespace SharpConsoleUI.Tests.Drawing
+{
+	public class BufferTextExtensionsWideCharTests
+	{
+		[Fact]
+		public void WriteStringCentered_CjkText_CenteredByDisplayWidth()
+		{
+			// "中文" = 2 chars, each width 2 = 4 display columns
+			// In a 10-wide buffer, centered: (10 - 4) / 2 = 3 -> starts at column 3
+			var buffer = new CharacterBuffer(10, 5);
+			string cjk = "\u4E2D\u6587"; // 中文
+
+			buffer.WriteStringCentered(0, cjk, Color.White, Color.Black);
+
+			Assert.Equal(new Rune('\u4E2D'), buffer.GetCell(3, 0).Character);
+			// Column 4 is the wide continuation of 中
+			Assert.Equal(new Rune('\u6587'), buffer.GetCell(5, 0).Character);
+			// Column 6 is the wide continuation of 文
+		}
+
+		[Fact]
+		public void WriteStringCentered_MixedText_CenteredCorrectly()
+		{
+			// "Hi中文" = H(1) + i(1) + 中(2) + 文(2) = 6 display columns
+			// In a 12-wide buffer, centered: (12 - 6) / 2 = 3 -> starts at column 3
+			var buffer = new CharacterBuffer(12, 5);
+			string mixed = "Hi\u4E2D\u6587"; // Hi中文
+
+			buffer.WriteStringCentered(0, mixed, Color.White, Color.Black);
+
+			Assert.Equal(new Rune('H'), buffer.GetCell(3, 0).Character);
+			Assert.Equal(new Rune('i'), buffer.GetCell(4, 0).Character);
+			Assert.Equal(new Rune('\u4E2D'), buffer.GetCell(5, 0).Character);
+			// Column 6 is continuation of 中
+			Assert.Equal(new Rune('\u6587'), buffer.GetCell(7, 0).Character);
+			// Column 8 is continuation of 文
+		}
+
+		[Fact]
+		public void WriteStringRight_CjkText_AlignedByDisplayWidth()
+		{
+			// "中文" = 4 display columns
+			// In a 10-wide buffer, right-aligned: 10 - 4 = 6 -> starts at column 6
+			var buffer = new CharacterBuffer(10, 5);
+			string cjk = "\u4E2D\u6587"; // 中文
+
+			buffer.WriteStringRight(0, cjk, Color.White, Color.Black);
+
+			Assert.Equal(new Rune('\u4E2D'), buffer.GetCell(6, 0).Character);
+			// Column 7 is continuation of 中
+			Assert.Equal(new Rune('\u6587'), buffer.GetCell(8, 0).Character);
+			// Column 9 is continuation of 文
+		}
+
+		[Fact]
+		public void WriteStringRight_MixedText_AlignedCorrectly()
+		{
+			// "AB中" = A(1) + B(1) + 中(2) = 4 display columns
+			// In a 10-wide buffer, right-aligned: 10 - 4 = 6 -> starts at column 6
+			var buffer = new CharacterBuffer(10, 5);
+			string mixed = "AB\u4E2D"; // AB中
+
+			buffer.WriteStringRight(0, mixed, Color.White, Color.Black);
+
+			Assert.Equal(new Rune('A'), buffer.GetCell(6, 0).Character);
+			Assert.Equal(new Rune('B'), buffer.GetCell(7, 0).Character);
+			Assert.Equal(new Rune('\u4E2D'), buffer.GetCell(8, 0).Character);
+			// Column 9 is continuation of 中
+		}
+
+		[Fact]
+		public void WrapText_CjkText_WrapsAtDisplayWidth()
+		{
+			// "中文字体" = 4 chars, each width 2 = 8 display columns
+			// With width=4, each line fits 2 CJK chars (4 columns)
+			// Should wrap into 2 lines: "中文" and "字体"
+			var buffer = new CharacterBuffer(20, 5);
+			string cjk = "\u4E2D\u6587\u5B57\u4F53"; // 中文字体
+
+			buffer.WriteWrappedText(0, 0, 4, cjk, Color.White, Color.Black);
+
+			// First line: 中文
+			Assert.Equal(new Rune('\u4E2D'), buffer.GetCell(0, 0).Character);
+			Assert.Equal(new Rune('\u6587'), buffer.GetCell(2, 0).Character);
+
+			// Second line: 字体
+			Assert.Equal(new Rune('\u5B57'), buffer.GetCell(0, 1).Character);
+			Assert.Equal(new Rune('\u4F53'), buffer.GetCell(2, 1).Character);
+		}
+
+		[Fact]
+		public void WrapText_MixedText_WideCharDoesntSplitAcrossLines()
+		{
+			// With width=5, "Hello中文" should wrap:
+			// "Hello" (5 cols) on line 0, "中文" (4 cols) on line 1
+			// The wide char 中 should not be split across lines
+			var buffer = new CharacterBuffer(20, 5);
+			string mixed = "Hello \u4E2D\u6587"; // "Hello 中文"
+
+			buffer.WriteWrappedText(0, 0, 5, mixed, Color.White, Color.Black);
+
+			// First line: "Hello"
+			Assert.Equal(new Rune('H'), buffer.GetCell(0, 0).Character);
+			Assert.Equal(new Rune('o'), buffer.GetCell(4, 0).Character);
+
+			// Second line: "中文" - wide chars should not be split
+			Assert.Equal(new Rune('\u4E2D'), buffer.GetCell(0, 1).Character);
+			Assert.Equal(new Rune('\u6587'), buffer.GetCell(2, 1).Character);
+		}
+	}
+}

SharpConsoleUI.Tests/Helpers/TextTruncationHelperWideCharTests.cs

@@ -0,0 +1,84 @@
+using Xunit;
+using SharpConsoleUI.Helpers;
+using SharpConsoleUI.Parsing;
+
+namespace SharpConsoleUI.Tests.Helpers
+{
+	public class TextTruncationHelperWideCharTests
+	{
+		[Fact]
+		public void Truncate_CjkText_TruncatesByDisplayWidth()
+		{
+			// "中文字" = 3 CJK chars, each width 2 = 6 display columns
+			// maxWidth=5: ellipsis "..." = 3 cols, available for content = 2
+			// availableForContent (2) < MinContentCharsBeforeEllipsis (3),
+			// so falls back to MarkupParser.Truncate(text, 5)
+			// which fits "中文" (4 cols) but not "中文字" (6 cols), yielding "中文"
+			string cjk = "\u4E2D\u6587\u5B57"; // 中文字
+
+			string result = TextTruncationHelper.Truncate(cjk, 5);
+
+			// Should be truncated (original is 6 cols, maxWidth is 5)
+			int resultWidth = MarkupParser.StripLength(result);
+			Assert.True(resultWidth <= 5, $"Result width {resultWidth} exceeds maxWidth 5");
+			Assert.True(result.Length < cjk.Length || result != cjk,
+				"Result should be truncated");
+		}
+
+		[Fact]
+		public void Truncate_WideCharAtBoundary_TruncatesBefore()
+		{
+			// "A中文" = A(1) + 中(2) + 文(2) = 5 display columns
+			// maxWidth=4: ellipsis "..." = 3 cols, available for content = 1
+			// availableForContent (1) < MinContentCharsBeforeEllipsis (3),
+			// so falls back to MarkupParser.Truncate(text, 4) which gives "A中" (3 cols)
+			// The wide char 文 should not be partially included
+			string mixed = "A\u4E2D\u6587"; // A中文
+
+			string result = TextTruncationHelper.Truncate(mixed, 4);
+
+			int resultWidth = MarkupParser.StripLength(result);
+			Assert.True(resultWidth <= 4, $"Result width {resultWidth} exceeds maxWidth 4");
+			// The result should not split a wide character
+		}
+
+		[Fact]
+		public void Truncate_MixedText_CorrectEllipsisPosition()
+		{
+			// "Hello中文世界" = 5 + 8 = 13 display columns
+			// maxWidth=10: ellipsis "..." = 3, available for content = 7
+			// Truncated content should be 7 display cols + "..."
+			string mixed = "Hello\u4E2D\u6587\u4E16\u754C"; // Hello中文世界
+
+			string result = TextTruncationHelper.Truncate(mixed, 10);
+
+			int resultWidth = MarkupParser.StripLength(result);
+			Assert.True(resultWidth <= 10, $"Result width {resultWidth} exceeds maxWidth 10");
+			Assert.Contains("...", result);
+		}
+
+		[Fact]
+		public void Truncate_ExactFit_NoTruncation()
+		{
+			// "中文" = 4 display columns, maxWidth=4 -> exact fit, no truncation
+			string cjk = "\u4E2D\u6587"; // 中文
+
+			string result = TextTruncationHelper.Truncate(cjk, 4);
+
+			Assert.Equal(cjk, result);
+		}
+
+		[Fact]
+		public void Truncate_OneLessThanWide_Truncates()
+		{
+			// "中文" = 4 display columns, maxWidth=3 -> must truncate
+			string cjk = "\u4E2D\u6587"; // 中文
+
+			string result = TextTruncationHelper.Truncate(cjk, 3);
+
+			int resultWidth = MarkupParser.StripLength(result);
+			Assert.True(resultWidth <= 3, $"Result width {resultWidth} exceeds maxWidth 3");
+			Assert.NotEqual(cjk, result);
+		}
+	}
+}