8366202: RichTextArea: wrong style used for typed text

Reviewed-by: lkostyra, zelmidaoui

Author: Andy Goryachev

modules/jfx.incubator.richtext/src/main/java/jfx/incubator/scene/control/richtext/model/RichTextModel.java

@@ -301,20 +301,20 @@ public int getTextLength() {
         }
 
         /**
-         * Retrieves the style attributes from the previous character (or next, if at the beginning).
+         * Retrieves the style attributes at the specified offset.
          * @param offset the offset
          * @return the style info
          */
         public StyleAttributeMap getStyleAttributeMap(int offset) {
-            int off = 0;
+            int pos = 0;
             int ct = size();
             for (int i = 0; i < ct; i++) {
                 RSegment seg = get(i);
                 int len = seg.getTextLength();
-                if (offset < (off + len) || (i == ct - 1)) {
+                pos += len;
+                if ((offset <= pos) || (i + 1 == ct)) {
                     return seg.getStyleAttributeMap();
                 }
-                off += len;
             }
             return StyleAttributeMap.EMPTY;
         }

modules/jfx.incubator.richtext/src/test/java/test/jfx/incubator/scene/control/richtext/RichTextAreaTest.java

@@ -79,6 +79,7 @@
 public class RichTextAreaTest {
     private RichTextArea control;
     private static final StyleAttributeMap BOLD = StyleAttributeMap.builder().setBold(true).build();
+    private static final StyleAttributeMap ITALIC = StyleAttributeMap.builder().setItalic(true).build();
 
     @BeforeEach
     public void beforeEach() {
@@ -474,6 +475,31 @@ public void hasNonEmptySelection() {
         assertTrue(control.hasNonEmptySelection());
     }
 
+    @Test
+    public void insertBetweenSegments() {
+        TextPos p = control.appendText("a", BOLD);
+        control.appendText("b", ITALIC);
+        control.appendText("c", BOLD);
+        control.select(p);
+        control.insertTab();
+        control.insertTab();
+        assertEquals("a\t\tbc", text());
+        control.select(TextPos.ofLeading(0, 2));
+        assertEquals(BOLD, control.getActiveStyleAttributeMap());
+        control.select(TextPos.ZERO);
+        assertEquals(BOLD, control.getActiveStyleAttributeMap());
+        control.select(TextPos.ofLeading(0, 1));
+        assertEquals(BOLD, control.getActiveStyleAttributeMap());
+        control.select(TextPos.ofLeading(0, 2));
+        assertEquals(BOLD, control.getActiveStyleAttributeMap());
+        control.select(TextPos.ofLeading(0, 3));
+        assertEquals(BOLD, control.getActiveStyleAttributeMap());
+        control.select(TextPos.ofLeading(0, 4));
+        assertEquals(BOLD, control.getActiveStyleAttributeMap());
+        control.select(TextPos.ofLeading(0, 5));
+        assertEquals(ITALIC, control.getActiveStyleAttributeMap());
+    }
+
     @Test
     public void insertLineBreak() {
         control.appendText("123");