Bug 282900 [CSS] ETabFolder should support setWebbyStyle()
And have field in CSS
bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/workbench/ui/renderers/swt/StackModelFactory.java
.get("activeChild")) != null && child != currentActive) { 
						currentActive = child;
					}
					
					if (currentActive == folderContext) {
						engine.setClassname(ctf, "active"); 
					} else {
						engine.setClassname(ctf, "inactive"); 
					}
				}
			});
		}
		return newWidget;
	}
	public void postProcess(MPart<?> part) {
		super.postProcess(part);
		if (!(part instanceof MStack))
			return;
		CTabFolder ctf = (CTabFolder) part.getWidget();
		MPart<?> selPart = ((MStack) part).getActiveChild();
		if (selPart == null)
			return;
		
		CTabItem selItem = findItemForPart(part, selPart);
		if (selItem != null) {
			ctf.setSelection(selItem);
		}
	}
	/*
	 * (non-Javadoc)