Bug 318498 Many toolbars on top of one another
I don't know how to reproduce this. I'll attach a screenshot.
bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/LazyStackRenderer.java
if (context.getParent() != newParentContext) {
					
					
					context.setParent(newParentContext);
				}
			}
		}
		
		if (element instanceof MPartStack && !element.isVisible()) {
			MWindow window = modelService.getTopLevelWindowFor(element);
			String trimId = element.getElementId() + "(minimized)"; 
			MPerspective persp = modelService.getPerspectiveFor(element);
			if (persp != null)
				trimId = element.getElementId() + '(' + persp.getElementId()
						+ ')';
			MToolControl trimCtrl = (MToolControl) modelService.find(trimId,
					window);
			if (trimCtrl != null)
				trimCtrl.setVisible(true);
		}
		
		if (element instanceof MWindow && element.getWidget() != null) {
			int visCount = 0;
			for (MUIElement kid : ((MWindow) element).getChildren()) {
				if (kid.isToBeRendered() && kid.isVisible())
					visCount++;
			}
			if (visCount > 0)
				element.setVisible(true);
		}