Use grapheme iteration in DrawHotString

Terminal.Gui/ViewBase/View.Drawing.Primitives.cs

@@ -106,16 +106,17 @@ public void DrawHotString (string text, Attribute hotColor, Attribute normalColo
         Rune hotkeySpec = HotKeySpecifier == (Rune)0xffff ? (Rune)'_' : HotKeySpecifier;
         SetAttribute (normalColor);
 
-        foreach (Rune rune in text.EnumerateRunes ())
+        foreach (string grapheme in GraphemeHelper.GetGraphemes (text))
         {
-            if (rune == new Rune (hotkeySpec.Value))
+            // The hotkey specifier is always a single simple character (e.g., '_')
+            if (grapheme.Length == 1 && new Rune (grapheme [0]) == new Rune (hotkeySpec.Value))
             {
                 SetAttribute (hotColor);
 
                 continue;
             }
 
-            AddRune (rune);
+            AddStr (grapheme);
             SetAttribute (normalColor);
         }
     }

Tests/UnitTestsParallelizable/ViewBase/Draw/DrawHotStringTests.cs

@@ -0,0 +1,61 @@
+using UnitTests;
+
+namespace ViewBaseTests.Drawing;
+
+public class DrawHotStringTests (ITestOutputHelper output) : TestDriverBase
+{
+    /// <summary>
+    ///     Verifies that <see cref="View.DrawHotString(string, Attribute, Attribute)" /> iterates by grapheme cluster,
+    ///     not by rune. When iterating by rune, combining marks (e.g., acute accent U+0301) are sent individually
+    ///     via AddRune and fail to compose with their base character. Iterating by grapheme and using AddStr
+    ///     ensures the combining mark stays attached to its base.
+    /// </summary>
+    [Theory]
+    [InlineData ("e\u0301", "é")] // e + combining acute → é
+    [InlineData ("n\u0303o", "ño")] // n + combining tilde + o → ño
+    [InlineData ("Les Mise\u0301rables", "Les Misérables")] // combining acute inside word
+    public void DrawHotString_CombiningMarks (string input, string expectedRendered)
+    {
+        // setup
+        IDriver driver = CreateTestDriver ();
+        driver.Clip = new Region (driver.Screen);
+        var view = new View
+        {
+            Driver = driver,
+            Width = 20, Height = 1
+        };
+
+        // execute
+        view.DrawHotString (input, Attribute.Default, Attribute.Default);
+
+        // verify
+        DriverAssert.AssertDriverContentsWithFrameAre (expectedRendered, output, driver);
+    }
+
+    /// <summary>
+    ///     Verifies that <see cref="View.DrawHotString(string, Attribute, Attribute)" /> correctly handles
+    ///     the hotkey specifier when combined with grapheme clusters. The hotkey specifier ('_') should
+    ///     switch to hot color, and subsequent grapheme clusters (including combining marks) should render
+    ///     correctly.
+    /// </summary>
+    [Fact]
+    public void DrawHotString_HotkeyWithCombiningMarks ()
+    {
+        // setup — "_Re\u0301sume\u0301" → hotkey on 'R', combining accents compose correctly
+        IDriver driver = CreateTestDriver ();
+        driver.Clip = new Region (driver.Screen);
+        var view = new View
+        {
+            Driver = driver,
+            Width = 20, Height = 1
+        };
+
+        // execute
+        var hotColor = new Attribute (Color.Red, Color.Black);
+        var normalColor = new Attribute (Color.White, Color.Black);
+        view.DrawHotString ("_Re\u0301sume\u0301", hotColor, normalColor);
+
+        // verify — the rendered text should show "Résumé" (without the underscore)
+        DriverAssert.AssertDriverContentsWithFrameAre ("Résumé", output, driver);
+    }
+}