Use Unicode 17 Indic extend data

Author: wieslawsoltes

src/RoyalTerminal.Unicode/Unicode/IndicConjunctBreakData.cs

@@ -2,9 +2,7 @@
 // Licensed under the MIT license. See LICENSE file in the project root for details.
 // Unicode 17.0 Indic_Conjunct_Break data used by UAX #29 rule GB9c.
 
-using System.Globalization;
 using System.Runtime.CompilerServices;
-using System.Text;
 
 namespace RoyalTerminal.Unicode;
 
@@ -32,31 +30,13 @@ public static IndicConjunctBreakClass Get(Codepoint codepoint)
             return IndicConjunctBreakClass.Consonant;
         }
 
-        // Include the non-mark members and Unicode 17 additions that may not
-        // yet have a mark category in the current .NET Unicode tables.
-        if (value is 0x200D or
-            >= 0x1ACF and <= 0x1ADD or
-            >= 0x1AE0 and <= 0x1AEB or
-            >= 0xFF9E and <= 0xFF9F or
-            >= 0x10EFA and <= 0x10EFB or
-            0x11B60 or
-            >= 0x11B62 and <= 0x11B64 or
-            0x11B66 or
-            >= 0x1F3FB and <= 0x1F3FF or
-            0x1E6E3 or
-            0x1E6E6 or
-            >= 0x1E6EE and <= 0x1E6EF or
-            0x1E6F5 or
-            >= 0xE0020 and <= 0xE007F)
-        {
-            return IndicConjunctBreakClass.Extend;
-        }
-
-        UnicodeCategory category =
-            Rune.GetUnicodeCategory(new Rune(checked((int)value)));
-        return category is UnicodeCategory.NonSpacingMark
-            or UnicodeCategory.SpacingCombiningMark
-            or UnicodeCategory.EnclosingMark
+        // Unicode 17's generated InCB=Extend set is the generated GCB Extend
+        // and ZWJ sets, excluding InCB Linkers (handled above) and ZWNJ.
+        // General Unicode mark categories are not equivalent: for example,
+        // U+0903 is a spacing combining mark but has InCB=None.
+        return value != 0x200C &&
+            codepoint.GraphemeBreakClass is GraphemeBreakClass.Extend
+                or GraphemeBreakClass.ZWJ
             ? IndicConjunctBreakClass.Extend
             : IndicConjunctBreakClass.None;
     }

tests/RoyalTerminal.Tests/UnicodeWidthTests.cs

@@ -72,6 +72,7 @@ public void ManagedGraphemeWidths_MatchPinnedGhosttyEdgeCases()
             [0x1F3F4, 0x200D, 0x2620, 0xFE0F],
             [0x1F1E6, 0x1F1E7, 0x1F1E8],
             [0x0915, 0x094D, 0x0937, (uint)'A'],
+            [0x0915, 0x094D, 0x0903, 0x0937],
             [0x0600, (uint)'A'],
             [0x0301, 0x0302],
             [0xD800, 0x0301],
@@ -166,6 +167,19 @@ public void FirstGraphemeWidth_ConsumesUnicode17IndicConjunct()
         Assert.Equal(2, width);
     }
 
+    [Fact]
+    public void FirstGraphemeWidth_StopsIndicConjunctAtIncbNoneSpacingMark()
+    {
+        uint[] codepoints = [0x0915, 0x094D, 0x0903, 0x0937];
+
+        int consumed = TerminalCellWidthCalculator.GetFirstGraphemeWidth(
+            codepoints,
+            out int width);
+
+        Assert.Equal(3, consumed);
+        Assert.Equal(2, width);
+    }
+
     [Fact]
     public void FirstGraphemeWidth_MatchesPinnedGhosttyForPrependCluster()
     {