Fix post undo/redo caret position (#915)

Author: Jugen

richtextfx/src/integrationTest/java/org/fxmisc/richtext/api/UndoManagerTests.java

@@ -44,19 +44,38 @@ public void incoming_change_is_not_merged_after_period_of_user_inactivity() {
         }
 
         @Test  // After undo, text insertion point jumps to the start of the text area #780
+               // After undo, text insertion point jumps to the end of the text area #912
         public void undo_leaves_correct_insertion_point() {
-            long periodOfUserInactivity = UndoUtils.DEFAULT_PREVENT_MERGE_DELAY.toMillis() + 300L;
-
-            write("abc def ");
-            sleep(periodOfUserInactivity);
-
-            write("xyz");
-            interact(area::undo);
 
-            write('g');
+            write("abc mno");
+            interact(() -> {
+                area.insertText(3," def");
+                area.appendText(" xyz");
+            });
 
-            sleep(periodOfUserInactivity);
-            assertTrue(area.getText().endsWith("g"));
+            assertEquals("abc def mno xyz",area.getText());
+
+            interact(area::undo); // removes " xyz"
+            assertEquals("abc def mno",area.getText());
+            //                       ^
+            assertEquals( area.getCaretPosition(), area.getSelection().getStart() );
+            assertEquals( 11, area.getSelection().getStart() );
+
+            interact(area::undo); // removes " def"
+            assertEquals("abc mno",area.getText());
+            //               ^
+            assertEquals( area.getCaretPosition(), area.getSelection().getStart() );
+            assertEquals( 3, area.getSelection().getStart() );
+
+            interact(area::redo); // restore " def"
+            assertEquals("abc def mno",area.getText());
+            //                   ^
+            assertEquals( area.getCaretPosition(), area.getSelection().getStart() );
+            assertEquals( 7, area.getSelection().getStart() );
+
+            interact(area::undo); // removes " def"
+            interact(() -> area.insertText(area.getCaretPosition()," ?"));
+            assertEquals("abc ? mno",area.getText());
         }
 
         @Test

richtextfx/src/main/java/org/fxmisc/richtext/util/UndoUtils.java

@@ -214,7 +214,10 @@ public static <PS, SEG, S> UndoManager<List<PlainTextChange>> plainTextUndoManag
      * by {@code area.replaceText(change.getPosition(), change.getRemovalEnd(), change.getInserted()}.
      */
     public static <PS, SEG, S> Consumer<PlainTextChange> applyPlainTextChange(GenericStyledArea<PS, SEG, S> area) {
-        return change -> area.replaceText(change.getPosition(), change.getRemovalEnd(), change.getInserted());
+        return change -> {
+            area.replaceText(change.getPosition(), change.getRemovalEnd(), change.getInserted());
+            moveToChange( area, change );
+        };
     }
 
     /**
@@ -223,7 +226,10 @@ public static <PS, SEG, S> Consumer<PlainTextChange> applyPlainTextChange(Generi
      */
     public static <PS, SEG, S> Consumer<RichTextChange<PS, SEG, S>> applyRichTextChange(
             GenericStyledArea<PS, SEG, S> area) {
-        return change -> area.replace(change.getPosition(), change.getRemovalEnd(), change.getInserted());
+        return change -> {
+            area.replace(change.getPosition(), change.getRemovalEnd(), change.getInserted());
+            moveToChange( area, change );
+        };
     }
 
     /**
@@ -238,6 +244,7 @@ public static <PS, SEG, S> Consumer<List<PlainTextChange>> applyMultiPlainTextCh
                 builder.replaceTextAbsolutely(c.getPosition(), c.getRemovalEnd(), c.getInserted());
             }
             builder.commit();
+            moveToChange( area, changeList.get( changeList.size()-1 ) );
         };
     }
 
@@ -253,7 +260,19 @@ public static <PS, SEG, S> Consumer<List<RichTextChange<PS, SEG, S>>> applyMulti
                 builder.replaceAbsolutely(c.getPosition(), c.getRemovalEnd(), c.getInserted());
             }
             builder.commit();
+            moveToChange( area, changeList.get( changeList.size()-1 ) );
         };
     }
 
+    /*
+     * Address #912 "After undo/redo, new text is inserted at the end".
+     * Without breaking PositionTests. (org.fxmisc.richtext.api.caret)
+     */
+    private static void moveToChange( GenericStyledArea area, TextChange chg ) {
+        int pos = chg.getPosition(), len = chg.getNetLength(); 
+        if ( len > 0 ) {
+           pos = Math.min( pos + Math.abs(len), area.getLength() );
+        }
+        area.moveTo( pos );
+    }
 }