Prototype Tooltip - controlling "orientation"

As you can se开发者_StackOverflowe in this screenshot, the way the tooltip displays it is cut off by the viewport. If I can force the tooltip to display upwards, as opposed to downwards, then it wouldn't but cut off.

Any ideas on how I can display this in a more user-friendly way?

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If you're using prototip then you can hook it to your mouse and it will stay in the viewport. Also, (and I haven't tried this but the docs seem to indicate it), setting viewport=true without hooking will keep it in the viewport as well.