Fixes word boundaries when string starts with punctuation (toptensoftware#98)

Author: azeno

Topten.RichTextKit.Test/WordBoundaryTest.cs

@@ -91,6 +91,32 @@ public void Punctuation2()
             Assert.Equal(9, boundaries[2]);
         }
 
+        [Fact]
+        public void Punctuation3()
+        {
+            var str = ".Hello World";
+            var boundaries = WordBoundaryAlgorithm.FindWordBoundaries(new Utf32Buffer(str).AsSlice()).ToList();
+
+            Assert.Equal(3, boundaries.Count);
+            Assert.Equal(0, boundaries[0]);
+            Assert.Equal(1, boundaries[1]);
+            Assert.Equal(7, boundaries[2]);
+        }
+
+        [Fact]
+        public void Punctuation4()
+        {
+            var str = ".Hello.World.";
+            var boundaries = WordBoundaryAlgorithm.FindWordBoundaries(new Utf32Buffer(str).AsSlice()).ToList();
+
+            Assert.Equal(5, boundaries.Count);
+            Assert.Equal(0, boundaries[0]);
+            Assert.Equal(1, boundaries[1]);
+            Assert.Equal(6, boundaries[2]);
+            Assert.Equal(7, boundaries[3]);
+            Assert.Equal(12, boundaries[4]);
+        }
+
         [Fact]
         public void TestIsWordBoundary()
         {

Topten.RichTextKit/LineBreakAlgorithm/WordBoundaryAlgorithm.cs

@@ -77,6 +77,8 @@ public static IEnumerable<int> FindWordBoundaries(Slice<int> codePoints)
                         // Switch to a different word kind without a space
                         // just emit a word boundary here
                         yield return i;
+                        // Update wordGroup to the new boundary class
+                        wordGroup = bg;
                     }
                 }
             }