feat: add terminal text measurer

- measure terminal display width for text and escape sequences

- truncate rendered lines to terminal columns

- add width and truncation examples

src/Example/Program.cs

@@ -5,14 +5,16 @@ using TinyTUI.Rendering;
 using TinyTUI.Runtime;
 using TinyTUI.Stdio;
 using TinyTUI.Stdout;
+using TinyTUI.Text;
 
 using var terminalInput = new ConsoleTerminalInput();
 var terminalOutput = new ConsoleTerminalOutput();
 var parser = new DefaultInputParser();
-var renderer = new FullScreenRenderer(terminalOutput);
+var textMeasurer = new TerminalTextMeasurer();
+var renderer = new FullScreenRenderer(terminalOutput, textMeasurer);
 using var runtime = new TuiRuntime(terminalInput, parser, renderer);
 
-var component = new EchoComponent(runtime);
+var component = new EchoComponent(runtime, textMeasurer);
 runtime.Add(component);
 runtime.SetFocus(component);
 
@@ -34,7 +36,7 @@ finally
 /// <summary>
 /// 用于手动验证 Runtime 的示例组件
 /// </summary>
-file sealed class EchoComponent(ITuiRuntime runtime) : IInputComponent
+file sealed class EchoComponent(ITuiRuntime runtime, ITextMeasurer textMeasurer) : IInputComponent
 {
     private readonly ManualResetEventSlim _done = new();
     private readonly List<string> _events = [];
@@ -54,6 +56,13 @@ file sealed class EchoComponent(ITuiRuntime runtime) : IInputComponent
             "- 调整窗口大小 验证 Resize 事件会进入焦点组件并触发重渲染",
             "- 按 Esc 退出",
             string.Empty,
+            "宽度示例:",
+            $"字符串 \"abc\" 的终端宽度 = {textMeasurer.GetWidth("abc")}",
+            $"字符串 \"中文\" 的终端宽度 = {textMeasurer.GetWidth("中文")}",
+            $"字符串 \"😀\" 的终端宽度 = {textMeasurer.GetWidth("😀")}",
+            $"截断前 \"abc中文😀xyz\" 的终端宽度 = {textMeasurer.GetWidth("abc中文😀xyz")}",
+            $"截断到 8 列后的结果 = \"{textMeasurer.Truncate("abc中文😀xyz", 8)}\"",
+            string.Empty,
             "最近事件:",
         };
 

src/TinyTUI/Rendering/FullScreenRenderer.cs

@@ -1,12 +1,15 @@
 using TinyTUI.Stdout;
+using TinyTUI.Text;
 
 namespace TinyTUI.Rendering;
 
 /// <summary>
 /// 每次渲染都清屏并重绘全部内容的基础渲染器
 /// </summary>
-public sealed class FullScreenRenderer(ITerminalOutput output) : IRenderer
+public sealed class FullScreenRenderer(ITerminalOutput output, ITextMeasurer? textMeasurer = null) : IRenderer
 {
+    private readonly ITextMeasurer _textMeasurer = textMeasurer ?? new TerminalTextMeasurer();
+
     /// <inheritdoc />
     public void Render(IReadOnlyList<string> lines, TerminalSize size)
     {
@@ -14,7 +17,7 @@ public sealed class FullScreenRenderer(ITerminalOutput output) : IRenderer
 
         foreach (var line in lines)
         {
-            output.Write(line);
+            output.Write(_textMeasurer.Truncate(line, size.Columns));
             output.Write("\r\n");
         }
 

src/TinyTUI/Text/TerminalTextMeasurer.cs

@@ -0,0 +1,166 @@
+using System.Buffers;
+using System.Globalization;
+using System.Text;
+
+namespace TinyTUI.Text;
+
+/// <summary>
+/// 基于常见终端字符单元规则的文本测量器
+/// </summary>
+public sealed class TerminalTextMeasurer : ITextMeasurer
+{
+    /// <inheritdoc />
+    public int GetWidth(string value)
+    {
+        var width = 0;
+
+        for (var index = 0; index < value.Length;)
+        {
+            if (TryReadEscape(value, index, out var escapeLength))
+            {
+                index += escapeLength;
+                continue;
+            }
+
+            var status = Rune.DecodeFromUtf16(value.AsSpan(index), out var rune, out var charsConsumed);
+            if (status != OperationStatus.Done)
+            {
+                index++;
+                continue;
+            }
+
+            width += GetRuneWidth(rune);
+            index += charsConsumed;
+        }
+
+        return width;
+    }
+
+    /// <inheritdoc />
+    public string Truncate(string value, int maxWidth)
+    {
+        if (maxWidth <= 0)
+        {
+            return string.Empty;
+        }
+
+        var builder = new StringBuilder();
+        var width = 0;
+
+        for (var index = 0; index < value.Length;)
+        {
+            if (TryReadEscape(value, index, out var escapeLength))
+            {
+                builder.Append(value.AsSpan(index, escapeLength));
+                index += escapeLength;
+                continue;
+            }
+
+            var status = Rune.DecodeFromUtf16(value.AsSpan(index), out var rune, out var charsConsumed);
+            if (status != OperationStatus.Done)
+            {
+                index++;
+                continue;
+            }
+
+            var runeWidth = GetRuneWidth(rune);
+            if (width + runeWidth > maxWidth)
+            {
+                break;
+            }
+
+            builder.Append(value.AsSpan(index, charsConsumed));
+            width += runeWidth;
+            index += charsConsumed;
+        }
+
+        return builder.ToString();
+    }
+
+    private static int GetRuneWidth(Rune rune)
+    {
+        if (Rune.IsControl(rune))
+            return 0;
+
+        var category = Rune.GetUnicodeCategory(rune);
+        if (category is UnicodeCategory.NonSpacingMark or UnicodeCategory.EnclosingMark or UnicodeCategory.Format)
+            return 0;
+
+        return IsWide(rune.Value) ? 2 : 1;
+    }
+
+    private static bool IsWide(int value) =>
+        value is
+            >= 0x1100 and <= 0x115f or
+            >= 0x2329 and <= 0x232a or
+            >= 0x2e80 and <= 0xa4cf or
+            >= 0xac00 and <= 0xd7a3 or
+            >= 0xf900 and <= 0xfaff or
+            >= 0xfe10 and <= 0xfe19 or
+            >= 0xfe30 and <= 0xfe6f or
+            >= 0xff00 and <= 0xff60 or
+            >= 0xffe0 and <= 0xffe6 or
+            >= 0x1f000 and <= 0x1faff;
+
+    private static bool TryReadEscape(string value, int start, out int length)
+    {
+        length = 0;
+
+        if (value[start] != '\e')
+            return false;
+
+        if (start + 1 >= value.Length)
+        {
+            length = 1;
+            return true;
+        }
+
+        return value[start + 1] switch
+        {
+            '[' => TryReadCsi(value, start, out length),
+            ']' or '_' or 'P' => TryReadStringEscape(value, start, out length),
+            _ => ReadSimpleEscape(value, start, out length),
+        };
+    }
+
+    private static bool TryReadCsi(string value, int start, out int length)
+    {
+        for (var index = start + 2; index < value.Length; index++)
+        {
+            var ch = value[index];
+            if (ch is >= '@' and <= '~')
+            {
+                length = index - start + 1;
+                return true;
+            }
+        }
+
+        length = value.Length - start;
+        return true;
+    }
+
+    private static bool TryReadStringEscape(string value, int start, out int length)
+    {
+        for (var index = start + 2; index < value.Length; index++)
+        {
+            switch (value[index])
+            {
+                case '\a':
+                    length = index - start + 1;
+                    return true;
+                case '\e' when index + 1 < value.Length && value[index + 1] == '\\':
+                    length = index - start + 2;
+                    return true;
+            }
+        }
+
+        length = value.Length - start;
+        return true;
+    }
+
+    private static bool ReadSimpleEscape(string value, int start, out int length)
+    {
+        length = Math.Min(2, value.Length - start);
+        return true;
+    }
+}