Bug 282947 [CSS] ETabFolder does not draw right with border-visible: false
CTabFolders have always acted odd with respect to borders off and the first tab when selected. It just starts drawing top left. This behaviour seems to be confusing the ETabFolder draw code. It should draw the same curve regardless of whether borders are on or not.
bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/workbench/ui/renderers/swt/StackModelFactory.java
EList<MPart> kids = element.getParent().getChildren();
		for (Iterator iterator = kids.iterator(); iterator.hasNext();) {
			MPart mPart = (MPart) iterator.next();
			if (mPart == element)
				return index;
			if (mPart.isVisible())
				index++;
		}
		return index;
	}
	@Override
	public void childAdded(final MPart<?> parentElement, MPart<?> element) {
		super.childAdded(parentElement, element);
		if (element instanceof MItemPart<?>) {
			internalChildAdded(parentElement, element);
			
			
			Control ctrl = (Control) element.getWidget();
			if (ctrl != null) {
				showTab((MItemPart<?>) element);
				stylingEngine.style(ctrl);
			}
		}
	}
	private CTabItem findItemForPart(MPart<?> folder, MPart<?> part) {
		CTabFolder ctf = (CTabFolder) folder.getWidget();
		if (ctf == null)
			return null;
		CTabItem[] items = ctf.getItems();
		for (int i = 0; i < items.length; i++) {