MyGWT has this inherently implemented should you be using that
interface but it doesn't sound like it. The roundabout way I usually
implement something like this:
1) Create a Widget. In the constructor, sinkEvents(Event.MOUSEEVENTS)
2) Override the onBrowserEvent(Event evt) method, and do a switch on
the DOM.eventGetType(evt) to find interesting events like ONMOUSEOVER
and ONMOUSEOUT. Use a combination of PopupPanel plus the knowledge of
where to popup at (you can get the event coordinates from the DOM and
adjust accordingly should your grid be falling off the screen) to show
a panel containing your grid. Show on mouse over, hide on mouse out.
3) Save the code for future use. :)
Hope that helps!
--
Carl Scott
Software Developer, Solertium Corporation