Colorbox: Show/simulate 'loading' animation for iframe content?

How can I show or simulate (using a fixed timespan) a loading animation for iframe content which is displayed using Colorbox?

What I'd like to achieve is actually a temporary overlay over the if开发者_如何学编程rame content, which disappears when the iframe-content is loaded. Is this somewhat possible?

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There is LoadMask plugin that can display an overlay. You will need to control when to show it and when to hide it manually though.