void (@NotNull ContentManagerEvent event) { Content content = event.getContent(); ContentTabLabel tab; if (content instanceof TabbedContent) { tab = new TabbedContentTabLabel((TabbedContent)content, this); } else { tab = new ContentTabLabel(content, this); } tabs.add(Math.min(event.getIndex(), tabs.size()), tab); contentToTabs.put(content, tab); DnDTarget target = getDnDTarget(content); if (target != null) { DnDSupport.createBuilder(tab) .setDropHandler(target) .setTargetChecker(target) .setCleanUpOnLeaveCallback(() -> target.cleanUpOnLeave()) .install(); } }