Fix tab selection on move and enhance test coverage

Author: vogella

bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/StackRenderer.java

@@ -438,6 +438,8 @@ void subscribeTopicChildrenMoved(@UIEventTopic(UIEvents.ElementContainer.TOPIC_C
 		Font font = item.getFont();
 		Object data = item.getData();
 
+		boolean wasSelected = tabFolder.getSelection() == item;
+
 		item.dispose();
 
 		CTabItem newItem = new CTabItem(tabFolder, (showClose ? SWT.CLOSE : SWT.NONE), newIndex);
@@ -448,6 +450,9 @@ void subscribeTopicChildrenMoved(@UIEventTopic(UIEvents.ElementContainer.TOPIC_C
 		newItem.setData(data);
 		newItem.setData(OWNING_ME, movedElement);
 		newItem.setControl(control);
+		if (wasSelected) {
+			tabFolder.setSelection(newItem);
+		}
 	}
 
 	@Inject

tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/workbench/renderers/swt/StackRendererMoveTest.java

@@ -1,6 +1,7 @@
 package org.eclipse.e4.ui.workbench.renderers.swt;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotSame;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
@@ -84,7 +85,8 @@ public void testPartMoveUpdatesWidget() throws Exception {
 
 		// The old item1 should be disposed
 		assertTrue(item1.isDisposed(), "Old item for part1 should be disposed");
-		
+		assertFalse(item2.isDisposed(), "Item2 should not be disposed");
+
 		// part1 should have a NEW widget item, but the part's widget (content) should be preserved
 		assertNotSame(item1, newItem1);
 		assertEquals(part1, newItem1.getData(AbstractPartRenderer.OWNING_ME), "New item should have OWNING_ME set");