Bug 26221 [Perspectives] Noticeable menubar "flash" when switching perspectives
Build 20021113 Note this is Windows XP. Open a Java Perspective. Open a Java Browsing Perspective. Switch back and forth between the two. On my XP machine I can visibly see the menu bar "shrink" as menu items are removed, then "expand" as menu items are added. It actually looks like it's animated. Anyway, very noticeable and somewhat strange since I'm switching between two perspectives that have the same base menus (i.e., the menu bar for each perspective is the same).
bundles/org.eclipse.jface/src/org/eclipse/jface/action/MenuManager.java
id = path.substring(0, separator);
		rest = path.substring(separator + 1);
	} else {
		return super.find(path);
	}
	IContributionItem item = super.find(id);
	if (item instanceof IMenuManager) {
		IMenuManager manager = (IMenuManager) item;
		return manager.findUsingPath(rest);
	}
	return null;
}
/**
 * Notifies any menu listeners that a menu is about to show.
 * Only listeners registered at the time this method is called are notified.
 *
 * @param manager the menu manager
 *
 * @see IMenuListener#menuAboutToShow
 */
private void fireAboutToShow(IMenuManager manager) {
	Object[] listeners = this.listeners.getListeners();
	for (int i = 0; i < listeners.length; ++i) {
		((IMenuListener) listeners[i]).menuAboutToShow(manager);
	}
}
/**
 * Returns the menu id.
 * The menu id is used when creating a contribution item 
 * for adding this menu as a sub menu of another.