I have a winforms application with a menu. The "New" item on the menu creates a new control which has a lot of sub-controls, so it takes about 300ms to construct the control.
When you click the "New" menu item, you see something like this for a brief moment:
As you can see, the menu disappears over some of the form, but over the toolbar, for example, you can still see it.
I tried this solution How to double buffer .NET controls on a form?, but it caused more problems than it solved (Laggy menus, crashes when window is not maximized).